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Role of ultrasound in assisted fermentation technologies for process enhancements
Abstract
Biological molecules are widely produced by fermentation technology using bacteria, fungi or yeast. Fermentation is a biochemical process wherein the rate of bioconversion is governed by the organisms involved. The growth of the organism is mainly limited by mass transfer rates of nutrients and gases that directly affect the product formation in fermentation. Attempts have been made to enhance the growth rate and yield using mutational, recombinant strain development approach at microbial level as well as fed batch and continuous processing approach at bioprocess level in the past. The growth rate of microbes can be accelerated by increased mass transfer rates and cell wall permeability with the use of controlled low frequency ultrasound irradiation. The present review provides insights into the application of acoustic cavitation in process intensification of fermentation approaches and the role of various factors involved are highlighted with typical examples.
... This method could be applied directly, via an ultrasonic probe, or indirectly using an ultrasonic bath and is now applicable for a variety of processes in biotechnology like fermentation, extraction, and different biological reaction catalysis. Besides, we can see this method's application in the food industry, pharmaceutical production, and waste disposal [18,19]. ...
... This phenomenon, named cativation, causes an increase in the temperature and pressure of the system. This temperature enhancement is usually controlled using recirculating cooling water to treat microorganisms in process temperatures under 40 ˚C [19][20][21]. Consequently, there will be an increase in cell membrane permeability, calcium channel activation, higher transportation of preferable nutrients, and finally, mass transfer enhancement between the inside of the cells and outside [19,22]. ...
... This temperature enhancement is usually controlled using recirculating cooling water to treat microorganisms in process temperatures under 40 ˚C [19][20][21]. Consequently, there will be an increase in cell membrane permeability, calcium channel activation, higher transportation of preferable nutrients, and finally, mass transfer enhancement between the inside of the cells and outside [19,22]. ...
Zinc (Zn) enriched Saccharomyces cerevisiae, was produced as a source of Zn. The impact of process variables on the bioaccumulation of Zn in yeast was studied by Plackett-Burmann and Box Behnken designs. For the first time impact of ultrasounds was investigated as a tool to stimulate Zn accumulation. The optimum growth condition was reported in which total Zn accumulation jumped by twice compared to similar conditions without ultrasounds stimulation. The results of this study revealed a suitable solution to overcome the deficiency problem of Zn is the production of Zn-yeast.
... The effects of the mechanisms described here are attributed to the enhancement of cell membrane permeability, increasing solubility of fairly soluble compounds, weakening the cell wall to promote efficient and selective transport and consequently, and enhancement of the mass transfer in and out the cells. 21,22 When nutrient transportation through the cell membrane is improved, the metabolite production is also favored. 23 It is already agreed in the literature that the application of US under controlled conditions has a beneficial effect on biological processes. ...
... Applying US at early phases of growth can damage premature cells, decreasing the production and release of metabolites. 22 Previous studies showed that exposure of microbial cultures to low frequency US at the proper time has major significance in the enhancement of productivity. 17,32,38 In this study, US treatment at 24 h of cultivation improved ⊎-1,3-glucanase and chitinase production at higher levels when compared to ultrasonication at earlier fermentation times. ...
... The US irradiation time has a remarkable effect on fermentation kinetics, which can be positive or negative for the process. 22 Figure 3 shows enzymatic activity profiles for ⊎-1,3-glucanase and chitinase with different ultrasonication times. Culture exposure to US for 5 min significantly enhanced the release of both enzymes to the fermentation media in comparison to the control fermentations. ...
BACKGROUND
Ultrasound (US) treatment was applied to increase the production of β‐1,3‐glucanase and chitinase by Beauveria bassiana (IBCB 66) cultivated in submerged fermentation. Application of US at different growth stages, US power outputs, time of ultrasonication, and duty cycles were the parameters evaluated.
RESULTS
The best strategy comprised ultrasonication during 5 min at 24 h of fermentation with a power output of 195 W (fixed frequency of 24 kHz) and a duty cycle of 0.5 s.s⁻¹ (0.5 s ON, 0.5 s OFF). The US treatment resulted in a production increase of 46% for β‐1,3‐glucanase and 42% for chitinase compared to the non‐sonicated control. Fragmentations of the mycelia in the sonicated samples were observed in Scanning Electron Microscopy (SEM) micrographs after the US application, supporting the idea of a better release of enzymes to outside the cell.
CONCLUSION
Ultrasound‐assisted fermentation was a promising tool to increase the production of β‐1,3‐glucanase and chitinase by Beauveria bassiana (IBCB 66). The combination of US parameters showed to be decisive in obtaining higher enzyme production when compared to the control non‐sonicated experiment. Therefore, this work brings a significant contribution to the field of stimulation of bioprocesses with ultrasound since it shows a strategy to obtain higher enzyme production when compared to traditional fermentation. © 2020 Society of Chemical Industry
... Recently, ultrasound-assisted fermentation has gained attention as a novel approach to enhance the fermentation process. The use of multifrequency ultrasound in the mono and co-culture fermentation of mulberry juice has yielded promising improvements in the metabolic, structural, micromorphological, and sensory qualities of the final product [35]. The application of multifrequency ultrasound has been shown to significantly boost the extraction of bioactive compounds, such as polyphenols and vitamins, from mulberry fruits, thereby enhancing the nutritional profile of the juice. ...
... The novelty of this study lies in the use of multi-frequency ultrasound (20/28/40 KHz) in conjunction with mono and co-cultures of LAB to enhance the metabolic, microstructural, and sensory properties of mulberry juice. While ultrasound and fermentation have each been studied independently for their effects on food products [31,35] their synergistic application in this study uniquely contributes to improving ...
The effect of multi-frequency ultrasound-assisted (20/28/40 KHz) lactic acid bacteria (LAB- Lacticaseibacillus casei, Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, Lactobacillus acidophilus, and Lactobacillus helveticus) fermentation (mono and co-cultures) on the metabolic, structural, micromorphological, and sensorial properties of mulberry juice were evaluated. Results indicated that multi-frequency ultrasound-assisted fermentation significantly modified the microstructure of mulberry juice powder, resulting in more porous and rougher surfaces with irregular indentations. Total phenolic content in the best-performing sample (S10) increased to 365.36 mg GAE/mL, while total flavonoid content rose to 139.20 mg RE/mL (p < 0.05). Antioxidant activity, as measured by DPPH and FRAP assays, also showed considerable improvement, with DPPH scavenging activity increasing to 87.45 % and FRAP-value to 3.27 mM TE/mL (p < 0.05). Additionally, HPLC-UV analysis revealed that the amendment in the concentrations of cyanidin-3-rutinoside (47.47 mg/L) and peonidin-3-O-glucoside (66.86 mg/L) in the S2-based sample. E-nose analysis demonstrated intense flavor profiles in fermented samples, particularly in sample S15. Sensory evaluation also highlighted that the fruity and floral aromas in co-culture fermented samples were enhanced, notably in S10, S7, and S14. Thus, combining multifrequency ultrasonication and fermentation significantly enhances the antioxidants capacity, flavor profile, micro-morphology, and overall quality of mulberry juice.
... Before fermentation, the pre-inoculum was sonicated (20 kHz, 140 W/l, 1 s ON and 10 s OFF) [15]. Ultrasonic irradiation was applied at two different power values (70 or 140 W/l), duty cycle (20 or 60%), and growth phase (lag or logarithmic phase), durations (0.5 or 2.5 h) at 30°C in 250 ml Erlenmeyer containing 100 ml fermentation medium [18]. ...
... Se accumulation also occurred in high sugar concentration (brix 35). This observation showed that ultrasound can improve the penetration of Se from medium through porous in the cellular membrane formed by sonication [18,19,20,21,22,23,24,25]. The maximum content of organic Se that was achieved in the screening step was 210.8 mg/L, while it was 586/765 mg/L in BBD. ...
Background
Ultrasonication was applied to stimulate the growth and Selenium biotransformation in Saccharomyces cerevisiae. Optimization study for maximal Se accumulation in S. cerevisiae was conducted using Plackett–Burman screening method and response surface methodology (RSM) for optimization of conditions. Screening of the variables influencing on Se biotransformation by yeast including duration and power of ultrasound, inoculum treatment with ultrasound, duty cycle, growth phase, time, shaking rate, inorganic salts concentration (Se, Zn, Mg, and K), nitrogen and carbon sources as well as their concentrations by using Plackett–Burman design.
Results
Main variables were carbon and Se concentration, as well as ultrasound power and duty cycle. The lack of fit was insignificant (P > 0.01). The optimum condition for Se accumulation was obtained at Se concentration of 60 µg/ml, carbon source brix of 15, ultrasound of 90 W/L, and duty cycle 40%.
Conclusions
The results showed that optimization of parameters and application of ultrasonication lead to a successful enhancement (2.78-fold) in the accumulation of selenium by S. cerevisiae. Such enriched yeast can be utilized in bread for increasing consumption of Se in diet of patient with Se deficiency.
... Furthermore, moderate ultrasonic treatment is proven to enhance mass transfer and cell wall permeability, thus improving both growth rates and yields [72]. For instance, the ultrasonic treatment of Phellinus igniarius at 0.28 W/cm 2 at 40 kHz increased the HA yield to 247.67 mg/L on the eighth day of fermentation [52]. ...
Hypocrellins (HYPs), naturally occurring 3,10-xylene-4,9-anthracene derivatives sourced from Shiraia bambusicola and Hypocrella bambusae, exhibit significant photobiological activities. Despite their capability for generating a high yield of reactive oxygen species, including singlet oxygen and superoxide anion radical, their application in photodynamic therapy (PDT) is constrained. This limitation is due to their low dark phototoxicity, weak absorption within the therapeutic window of PDT (600–900 nm), and inherent hydrophobicity, which hinder their immediate use in amphipathic PDT applications. This review comprehensively discusses the research advancements in the bioactivities and biosynthesis of HYPs, alongside the reported chemical and physical modifications that enhance their water solubility and extend their therapeutic window. Additionally, it explores potential strategies for developing pharmaceuticals, photocatalytic agents, and photosensitive pesticides based on HYPs.
... μg/mL, indicating that the phenolic content in the ultrasound-treated pineapple peel extract was lower than that in the non-ultrasound-treated extract. Ultrasound treatment has been utilized for extracting phenolic compounds from various food matrices, including citrus fruits and peels, to improve recovery rates and reduce extraction time [37]. High-intensity ultrasound treatment could effectively enhance the stability and increase the content of phenolic substances [38]. ...
This work investigated the effects of the combined use of thermosonication-preconditioned lactic acid bacteria (LAB) with the addition of ultrasound-assisted pineapple peel extracts (UU group) on the post-acidification potential, physicochemical and functional qualities of yogurt products, aimed at achieving prolonged preservation and enhancing functional attributes. Accordingly, the physical–chemical features, adhesion properties, and sensory profiles, acidification kinetics, the contents of major organic acids, and antioxidant activities of the differentially processed yogurts during refrigeration were characterized. Following a 14-day chilled storage process, UU group exhibited acidity levels of 0.5–2 oT lower than the control group and a higher lactose content of 0.07 mg/ml as well as unmodified adhesion potential, indicating that the proposed combination method efficiently inhibited post-acidification and delayed lactose metabolism without leading to significant impairment of the probiotic properties. The results of physicochemical analysis showed no significant changes in viscosity, hardness, and color of yogurt. Furthermore, the total phenolic content of UU-treated samples was 98 μg/mL, 1.78 times higher than that of the control, corresponding with the significantly lower IC50 values of DPPH and ABTS radical scavenging activities of the UU group than those of the control group. Observations by fluorescence inverted microscopy demonstrated the obvious adhesion phenomenon with no significant difference found among differentially prepared yogurts. The results of targeted metabolomics indicated the proposed combination strategy significantly modified the microbial metabolism, leading to the delayed utilization of lactose and the inhibited conversion into glucose during post-fermentation, as well as the decreased lactic acid production and a notable shift towards the formation of relatively weak acids such as succinic acid and citric acid. This study confirmed the feasibility of thermosonication-preconditioned LAB inocula, in combination with the use of natural active components from fruit processing byproducts, to alleviate post-acidification in yogurt and to enhance its antioxidant activities as well as simultaneously maintaining sensory features.
... The low-intensity US, on the other hand, promotes microbial development. Low-level sonoporation increases the permeability of cell membranes, that enhances the mass transfer of nutrients across the cell membrane and efficiently removes metabolic waste products, resulted in enhancing microbial growth [22]. ...
This study aimed to examine the impact of ultrasound on white finger millet-based probiotic beverages (WFMPB). The process variables such as amplitude and treatment time for ultrasound treatment were obtained using response surface methodology. Ultrasound (US) treatments were applied before and after the inoculation to trigger the culture growth. US-treated WFMPB were evaluated for total phenolic content, flavonoid content, antioxidant activity, reducing sugars, viable cell count, particle size, sugar analysis, and volatile organic compounds after the fermentation process and compared with the control (sterilized). The total phenol content, total flavonoid content, antioxidant activity, and reducing sugar content of US-treated samples were significantly increased. Glucose, fructose, sucrose, galactose, and maltose were observed to be the major sugars in WFMPB. The particle size of US-treated WFMPB was observed to be smaller than those in the non-sonicated WFMPB. Viable counts of US treatment before inoculation (8.56 log CFU/ mL) and after inoculation (8.31 log CFU/ mL) were higher than the control (7.76 log CFU/ mL). Collectively, the present study suggested that millet as a substrate for probiotic beverage production could overcome the concerns regarding high cholesterol content and lactose intolerance of dairy products in developed countries, as well as economic concerns in developing countries. In the future, the proliferation kinetics of probiotics during the fermentation and storage period can be studied. Thus, the fermented millet beverage with L. rhamnosus is a good and healthy probiotic-rich functional food.
... www.videleaf.com Without requiring very complex technology, fermentation is one of the oldest food processing techniques, which consists of the action of microorganisms, present or added to substrates, on the raw material in a biotransformation process in which carbohydrates are transformed into organic acids or alcohols [19,20]. There are numerous fermentation techniques -four main fermentation processes can be considered: acetic, alkaline, alcoholic, and lactic acid fermentation [21] -and microorganisms used in this process [22]. ...
The current consumer, with privileged access to information, can make more responsible and demanding choices, preferring healthy and environmentally friendly products. The food industry also takes advantage of technological and scientific advances to produce food and drinks that better adapt to consumer demand, with more sustainable and efficient production processes. The composition and functional and nutritional properties of fruit juice and fermented fruit drinks justify the development of various studies due to their proven effectiveness in the prevention of cardiovascular, cancer, and neurodegenerative diseases, among others. Non-thermal food processing has been highlighted in recent years and different emerging technologies are under study to evaluate their potential as an alternative to conventional heat treatments. The use of non-thermal processes minimizes undesirable changes in the food because involve methods by which fruit juices receive microbiological inactivation and enzymatic denaturation with or without the direct application of low heat, thereby lessening the adverse effects on the nutritional, bioactive, and flavor compounds of the treated fruit juices, extending their shelf-life.
... Such process concepts are sometimes called "sonobioreactors" (Chisti 2003), where the fermentation tank is subjected to ultrasonic irradiation (Yang et al. 2020). The mechanism by which low-intensity ultrasound enhances fermentation is not entirely clear; however, it has been postulated that the collapse of microbubbles on the cell wall causes microjets which weaken the cell wall, increase its permeability, and activate calcium channels (Avhad and Rathod 2014;Pawar and Rathod 2020). The increased transfer of materials across the cell membrane, including substrates and gene material, is called sonoporation. ...
There is a growing interest in using green technologies in the food industry. As a green processing technique, ultrasound has a great potential to be applied in many food applications. In this review, the basic mechanism of ultrasound processing technology has been discussed. Then, ultrasound technology was reviewed from the application of assisted food processing methods, such as assisted gelation, assisted freezing and thawing, assisted crystallization, and other assisted applications. Moreover, ultrasound was reviewed from the aspect of structure and property modification technology, such as modification of polysaccharides and fats. Furthermore, ultrasound was reviewed to facilitate beneficial food reactions, such as glycosylation, enzymatic cross-linking, protein hydrolyzation, fermentation, and marination. After that, ultrasound applications in the food safety sector were reviewed from the aspect of the inactivation of microbes, degradation of pesticides, and toxins, as well inactivation of some enzymes. Finally, the applications of ultrasound technology in food waste disposal and environmental protection were reviewed. Thus, some sonoprocessing technologies can be recommended for the use in the food industry on a large scale. However, there is still a need for funding research and development projects to develop more efficient ultrasound devices.
... Therefore, the study of HIUS processing times is essential to determine the processing duration that results in maximum results. Prolonged exposure may have detrimental effects on microbial cells, while low exposure times may not contribute to probiotic growth (Pawar & Rathod, 2020). ...
This study aimed to evaluate the effect of high‐intensity ultrasound (HIUS) application with different processing times (2.5, 5, 7.5 and 10 min) on the physicochemical, rheological and textural properties, antioxidant activity (AA) and probiotic survival in strawberry‐flavoured fermented probiotic strawberry drink during storage (7°C for 28 days). The application of HIUS resulted in products with lower fermentation times, higher organic acid stability during storage and improved texture (higher firmness and consistency) and functional properties (higher phenolic compounds content and/or AA). Using 2.5 min of processing time would be advisable due to the better probiotic survival to simulated gastrointestinal conditions (probiotic counts higher than 10⁶ CFU mL⁻¹), reduced fermentation times (reduction in 3 h), higher lactic acid content during storage and enhanced AA. The products showed a viable probiotic counts higher than 10⁶ CFU mL⁻¹ during the entire shelf life. HIUS may be considered as an adequate pre‐treatment in the development of probiotic fermented probiotic strawberry drink.
... Therefore, ultra- sonication as an emerging technology rather than conventional methods has influenced the fermentation yield, time of the process, physicochemical alterations, and the productivity of wine and other alcoholic beverages (Gavahian, Mathad, et al., 2021). In addition, fermentation products are formed by increasing mass transfer rates of nutrients and gases (such as carbon monoxide, and carbon dioxide), reported to be enhanced with ultrasonic exposure to sample for a few minutes (Pawar & Rathod, 2020). Raw materials (grapes, musts, and yeast) used during winemaking have also been treated with this technology to improve wine productivity in the winery industry. ...
Ultrasound is sound waves above 20 kHz that can be used as a nonthermal ‘‘green’’ technology for agri‐food processing. It has a cavitation effect, causing bubbles to form and collapse rapidly as they travel through the medium during ultrasonication. Therefore, it inactivates microorganisms and enzymes through cell membrane disruption with physicochemical and sterilization effects on foods or beverages. This emerging technology has been explored in wineries to improve wine color, taste, aroma, and phenolic profile. This paper aims to comprehensively review the research on ultrasound applications in the winery and alcoholic beverages industry, discuss the impacts of this process on the physicochemical properties of liquors, the benefits involved, and the research needed in this area. Studies have shown that ultrasonic technology enhances wine maturation, improves wine fermentation, accelerates wine aging, and deactivates microbes while enhancing quality, as observed with better critical aging markers such as phenolic compounds and color intensity. Besides, ultrasound enhances phytochemical, physicochemical, biological, and organoleptic properties of alcoholic beverages. For example, this technology increased anthocyanin in red wine by 50%. It also enhanced the production rate by decreasing the aging time by more than 90%. Ultrasound can be considered an economically viable technology that may contribute to wineries’ waste valorization, resource efficiency improvement, and industry profit enhancement. Despite numerous publications and successful industrial applications discussed in this paper, ultrasound up‐scaling and applications for other types of liquors need further efforts.
... For the directly ultrasonically treating strains prior to fermentation (pre-UT1/UT2), the viable counts of S. thermophilus were significantly lower than that of L. bulgaricus at 14 d of storage although the initial concentrations of S. thermophilus were higher than that of L. bulgaricus when the fermentation was accomplished. The more sharp decrease in the viable number of S. thermophilus responding to TS stress during storage was due to the association of the sensitivity to ultrasound treatment with the bacterial morphology (Pawar & Rathod, 2020), for which the larger surface area/volume of rod/bacillary bacteria are generally more susceptible to ultrasound stress pretreatments than spherical/spherical bacteria. ...
This study explored the feasibility of thermosonication (TS)-prestressed inoculum with different fermentation patterns for regulating microbial (post)-fermentation acidification kinetics. Through a Box-Behnken design, stimulative (20 min, 400 W, 33 kHz, 25 oC) and inhibitive (10 min, 600 W, 33 kHz, 20 oC) effects on the acidification capability of Lactobacillus plantarum A3 were achieved without observing greatly activated/inactivated strains growth, further confirmed by lactose fermentation performed by Streptococcus thermophilus and Lactobacillus bulgaricus. Lactic acid was the major contributing factor responsible for TS-induced acidification modifications corresponding to the potential fluctuations of CoA biosynthesis, fatty acid degradation and chain elongation pathways to TS prestress. Microscopy observations and quantitative extracellular substance assays showed palpable stress disturbance on microbes, but causing insignificant effects on products characteristics. This investigation demonstrated the potential of controlled sonication prestress strategies to achieve dual engineering effects on microbial metabolic behavior, for alleviating post-acidification problem or enhancing process efficiencies.
... High frequency ultrasonication generates smaller bubbles with low energy as there is less time for the bubble to grow when compared to ultrasonication with lower frequency (Leong et al., 2011). Larger the bubble size, more is the intensity generated on its implosion (Pawar and Rathod, 2020). Hence, the higher intensity achieved at a frequency of 25 kHz was more effective in weakening the adhesion of the gummy layer of the decorticated fiber. ...
In this study, we designed, developed, and optimized an enzymatic fiber degum-ming process. First, a Partially Purified Enzyme Solution (PPES) containing pectinase, cellulase and xylanase was co-produced via ultrasound-assisted fermentation of orange peels using Bacillus subtilis ABDR01. Then, degumming with PPES was optimized for pH, temperature, incubation time and PPES concentration. Finally, three sets of ultrasound-assisted degumming experiments-chemical, enzymatic, and coupled enzymatic-chemical degumming with reduced alkali concentration (0.5% NaOH, 30 min) were performed. Chemical degumming for 2 h with 1% NaOH at 98 • C resulted in residual gum content of 5.9%, whereas ultrasound-assisted (30 min, 25 kHz) chemical degumming reduced the gum content to 3.1%. At a pH of 7.5, temperature of 45 • C, 30 h incubation and 2% PPES, gum removal efficiency of >60% and fibers with <10% residual gum were produced. Coupling the ultrasound-assisted enzymatic degumming with reduced alkali chemical degumming resulted in gum content of <3%.
... Phosphatase activity in the pre-sonicated yogurt was significantly higher than that in the unsonicated group (0.31 U g −1 ); in particular, in the yogurt pre-treated with ultrasound for 30 min, the phosphatase activity was 74.2% higher than that in the unsonicated yogurt (Supporting Information Fig. S1). Therefore, the enhancement of pesticide degradation may be attributable to the following effects of ultrasound on L. plantarum: (1) the micro-turbulence generated by ultrasound disrupted cell clusters in the inoculum, enhancing nutrient and pesticide uptake and excretion of toxic substances produced by the degradation process; 30 (2) the cavitation effect of ultrasound increased the permeability of the microbial cell membrane, enhancing nutrient transport and promoting the growth and propagation of L. plantarum; 31 and (3) ultrasound promoted the activity of phosphatase in milk, which was the main mechanism for L. plantarum to degrade organophosphorus pesticides. 32 Effect of ultrasound on fermentation efficiency Changes in lactose concentration during fermentation are shown in Fig. 4(A). ...
BACKGROUND
Ultrasound has the potential to increase microbial metabolic activity, so this study explored the stimulatory effect of ultrasound pre‐treatment on the degradation of four common pesticides (fenitrothion, chlorpyrifos, profenofos, and dimethoate) during milk fermentation by Lactobacillus plantarum and its effect on yogurt quality.
RESULTS
Appropriate ultrasound pretreatment significantly enhanced the growth of L. plantarum. The degradation percentages of pesticides increased by 19–38% under ultrasound treatment. Ultrasonic intensity, pulse duty cycle, and duration time were key factors affecting microbial growth and pesticide degradation. Under optimal ultrasonic pre‐treatment conditions, the degradation rate constants of four pesticides were at least 3.4 times higher than those without sonication. In addition, such ultrasound pretreatment significantly shortened yogurt fermentation time, increased the water holding capacity, hardness and antioxidant activity of the yogurt, and improved the flavor quality of the yogurt.
CONCLUSION
Ultrasonic pretreatment significantly accelerated the degradation of the four pesticides during yogurt fermentation. In addition, such ultrasound pretreatment increased the efficiency of yogurt making and improved the quality of yogurt in terms of water holding capacity, firmness, antioxidant activity, and flavor. These findings provide a basis for the application of ultrasound to the removal of pesticide residues and quality improvement of yogurt. © 2022 Society of Chemical Industry.
... The effects of TPC and ATC of control and processed kiwifruit samples are shown in Figure 3. HIU-treated fresh-cut kiwifruit slices showed the highest phenolic compounds starting from the first day to the last day ( Figure 3). This might be caused by the release of the bound form of phenolic compounds as a result of the cell wall deformation thanks to ultrasonic cavitation (Pawar & Rathod, 2020). ...
In this study, high intensity ultrasound (HIU), antibrowning chemicals (calcium chloride and ascorbic acid), water bath were used to avoid the browning of kiwifruit pieces, and the shelf‐life of fresh‐cut was measured (two weeks). The treated fresh‐cut kiwi samples were evaluated in terms of color, enzyme activities, bioactive compounds, microbial and sensory studies. The study shown that HIU treatment restricted (p<0.05) the microbial growth (bacteria, yeats & mold) in fresh‐cut kiwi samples at 4 °C. Moreover, kiwi samples exposed to HIU exhibited significant (p<0.05) enhancements in bioactive metabolites as well as improvements in the physical features with the comparison of all other applications. Similarly, the lowest browning index (BI) values were observed for kiwifruit samples by HIU at the end of storage (180.04). Furthermore, the lowest scores for decay (0.5/3.0 and 0.9/3.0 in days 7 and 14, respectively) and off‐odor (1/7 and 2/7 in days 7 and 14, respectively) were determined for the fresh‐cut kiwifruit subjected to HIU. It has been proposed that HIU application is a possible choice to take the place of chemical and physical approaches to extend the product life and maintain quality characteristics in fresh‐cut kiwifruit at cold storage conditions.
... In the context of productivity enhancement in bioprocess intensification, ultrasound is generally limited to low power inputs to limit biocatalyst damage whilst still improving the mixing and mass transfer rates of the process. Much research effort has been directed at studying the effects of ultrasound and its cavitation impacts on whole cell fermentations and enzymatic reactions, many of which are discussed in detail in recently published reviews on these subjects [190][191][192][193][194]. A few pertinent and recent examples will be highlighted here to demonstrate the extent of intensification that can be realised by the ultrasound technique in bioprocessing. ...
With the current pressing need to rise to the ambition of net zero targets to mitigate carbon emissions and climate change impacts, sustainable processing has never been more critical. Bioprocessing has all the desirable attributes to respond to the sustainable processing challenge: use of cheap, renewable resources, nature-inspired, highly selective biocatalysts operating optimally under mild conditions and reduced energy consumption/carbon footprint. With bioprocessing productivity being far from ideal to meet the large-scale need for food, drugs, biofuels and bio-based chemicals, there has been tremendous interest of late in developing intensified bioprocesses, with significant advancement achieved in tailoring and utilising the technologies in the toolbox traditionally applied in chemical process intensification.
This review highlights the wide range of activities currently on-going in bioprocess intensification, focusing on upstream, bioreactor/fermentation and downstream separation steps. Great strides have been made in biocatalyst engineering and high density cell immobilisation for significant productivity enhancement, which, in conjunction with elegant process innovations such as novel bioreactor technologies and in-situ product separations, are enabling bioprocesses to become more competitive than ever before. The future prospects of bioprocess intensification are promising but there are still challenges that need to be overcome to fully exploit this technology.
... During cavitation, the microjets formed increase the cell porosity and helps to transfer the oxygen to interior cells enhancing the mass transfer [156]. Under these conditions, ultrasound enhances the growth of microorganisms due to increased cell membrane permeability for substrates, gases, and other nutrient components [157]. The mass transfer effects generated due to acoustic cavitation could also be used to simply enhance the rates of chemical reactions or chemical processes such as dairy fermentation. ...
Alternative methods for improving traditional food processing have increased in the last decades. Additionally, the development of novel dairy products is gaining importance due to an increased consumer demand for palatable, healthy, and minimally processed products. Ultrasonic processing or sonication is a promising alternative technology in the food industry as it has potential to improve the technological and functional properties of milk and dairy products. This review presents a detailed summary of the latest research on the impact of high-intensity ultrasound techniques in dairy processing. It explores the ways in which ultrasound has been employed to enhance milk properties and processes of interest to the dairy industry, such as homogenization, emulsification, yogurt and fermented beverages production, and food safety. Special emphasis has been given to ultrasonic effects on milk components; fermentation and spoilage by microorganisms; and the technological, functional, and sensory properties of dairy foods. Several current and potential applications of ultrasound as a processing technique in milk applications are also discussed in this review.
... Industrial and experimental applications of sonochemistry have been proven in nanotechnology, biotechnology and medicine [23,24]. Ultrasound-assisted techniques have been rapidly developed for a variety of chemical processes [25]. ...
One of the goals of green chemistry is to use environmentally friendly solvents or remove and reduce the volume of harmful spent solvents. In this study, a novel process for the synthesis of 5-substituted 1,3,4-oxadiazole-2-thiol derivatives was proposed via ultrasound-assisted reaction of aryl hydrazides with CS2 (1:1 molar ratio) in some drops of DMF in the absence of basic or acidic catalysts. They were produced in good to excellent yields under easy workup and purification conditions. In order to prove the usefulness of the prepared compounds, their antioxidant, antibacterial, and antifungal potentials were screened by DPPH free radical scavenging, serial twofold microdilution and streak plate methods. Acceptable to significant inhibitory activities were observed with synthesized heterocycles. The results showed that 5-(4-fluorophenyl)-1,3,4-oxadiazole-2-thiol (3c) is an broad-spectrum antimicrobial agent. Many of them displayed remarkable antioxidant properties comparable to standard controls (ascorbic acid and α-tocopherol). Synthesized 1,3,4-oxadiazoles are also potent candidates to treat cancer, Parkinson, inflammatory, and diabetes diseases.
Graphic Abstract
Eighteen 5-substituted 1,3,4-oxadiazole-2-thiol derivatives as potent antimicrobial and antioxidant agents were prepared via a new, efficient and green procedure.
Strategies to reduce cost and emission profiles are becoming increasingly important for the development of affordable and sustainable bio-based production. The overall objective of process intensification in different industries is to achieve substantial benefits in terms of cost, product concentration and quality, while eliminating waste and improving process safety. Intensification of bioprocesses could be a valuable tool for enhancing the efficiency and reducing resource consumption in bioproduction. In general, bioprocess intensification is defined as an increase in bioproduct output relative to cell concentration, time, reactor volume or cost. This brief overview provides a definition of process intensification in biotechnology, presents several general and specific examples, and addresses some of the current challenges.
Process industries such as textiles, leather and chemicals demand transformation from conventional methods to cope up with the challenges posed due to (i) environmental issues, (ii) adaptability to recent developments in manufacturing, and (iii) cost-competitive market environment. In this regard, potential use of process intensification tools such as ultrasound is being widely studied with broad interest. Ultrasound is useful in different unit operations and processes with benefits of improving process efficiency, optimum use of chemicals, process time reduction, pollution minimization and process-specific benefits. Ultrasound could be effective, in order to facilitate the cleaner/greener process. In the present paper, the application of ultrasound in leather processing, leather auxiliary’s preparation, diffusion through membranes, polymers, chemical reactions, textiles and wastewater treatment has been analyzed and reviewed along with the theory and practice of ultrasound with 200 references including recent publications. Use of ultrasound in leather processing steps is as follows: vegetable tanning, dyeing and fatliquoring provided significant enhancements and diffusion rate. In leather auxiliary’s preparation, solid–liquid extraction (vegetable tannins and natural dyes) from plant materials give improvements in mass transfer enhancement and %yield as an eco-friendly approach. 7E’s concept for balanced rationale for deployment of ultrasound system for process industries has been explained for the first time.
Efficient FAD/FADH2 regeneration is vital for enzymatic biocatalysis and metabolic pathway optimization. Here, we constructed an efficient and simple FAD/FADH2 regeneration system through a combination of l-amino acid deaminase (l-AAD) and halogenase (CombiAADHa), which was applied for catalyzing the conversion of an l-amino acid to halide and an α-keto acid. For cell-free biotransformation, the optimal activity ratio of l-AAD and halogenase was set between 1:50 and 1:60. Within 6 h, 170 mg/L of 7-chloro-tryptophan (7-Cl-Trp) and 193 mg/L of indole pyruvic acid (IPA) were synthesized in the selected mono-amino acid system. For whole-cell biotransformation, 7-Cl-Trp and IPA synthesis was enhanced by 15% (from 96 to 110 mg/L) and 12% (from 115 to 129 mg/L), respectively, through expression fine-tuning and the strengthening of FAD/FADH2 supply. Finally, ultrasound treatment was applied to improve membrane permeability and adjust the activity ratio, resulting in 1.6-and 1.4-fold higher 7-Cl-Trp and IPA yields. The products were then purified. This system could also be applied to the synthesis of other halides and α-keto acids.
Key points
• In this study, a whole cell FAD/FADH2 regeneration system co-expressing l-AAD and halogenase was constructed
• This study found that the activity and ratio of enzyme and the concentration of cofactors had a significant effect on the catalytic process for the efficient co-production of 7-chlorotryptophan and indole pyruvate
Recent social, economic, and technological evolutions have impacted consumption habits. The new consumer is more rational, more connected and demanding with products, more concerned with the management of the family budget, with the health, origin, and sustainability of food. The food industry over the last few years has shown remarkable technological and scientific evolution, with an impact on the development and innovation of new products using non-thermal processing. Non-thermal processing technologies involve methods by which fruit juices receive microbiological
inactivation and enzymatic denaturation with or without the direct application of low heat, thereby lessening the adverse effects on the nutritional, bioactive, and flavor compounds of the treated fruit juices, extending their shelf-life. The recognition of the nutritional and protective values of fruit juices and fermented fruit beverages is evident and is attributed to the presence of different bioactive compounds, protecting against chronic and metabolic diseases. Fermentation maintains the fruit's safety, nutrition, and shelf life and the development of new products. This review aims to summarize the chemical and sensory characteristics of fruit juices and fermented fruit drinks, the fermentation process, its benefits, and its effects.
Ultrasound (US) treatment of milk is one of several emerging technologies, often promoted as non-thermal, although a combination with heat appears to show greater potential. Bacteriocidal effects have been studied, as well as certain interesting chemical and physical changes occurring as a result of this treatment. Comparison of published results is confounded by the lack of standardised treatment parameters. US does not appear to offer advantages regarding microbiological quality, in comparison with conventional HTST pasteurisation (72 °C for 15 s). Most publications do not address possible sensory changes caused by US treatment but, according to some authors, some definitive changes do occur. To obtain knowledge that ensures that quality products are produced, research on US is needed that combines the aspects of the effect on microorganisms, product functionality and quality and the influence on flavour and sensory aspects of the milk or milk product.
Conventional fermentation processes need to be upgraded to produce a wide array of biomolecules to overcome lower product yield. The cost of production of biomolecules using the fermentation method could be reduced by increasing the product yield by various process enhancement methods. In this study, different innovative process enhancement methods were evaluated to increase the co-production of uricase and alkaline protease at the bioreactor level. Ultrasound-assisted fermentation (UAF), Extractive fermentation (ATPS), and Ultrasound-assisted extractive fermentation (UATPS) are the three innovative methods used for process enhancement. Maximum enzyme production was obtained in a combinatorial approach of ultrasound and extractive fermentation, i.e., ultrasound-assisted extractive fermentation where uricase and protease production enhanced by 2.5 fold and 1.9 fold, respectively, as compared to conventional fermentation.
Fruit and vegetable fermented beverages, a functional non-dairy fermented product, are popular worldwide due to their health-promoting attributes. It is reported that a variety of nutrients and chemical composition are found in fruit and vegetable fermented beverages, and health-promoting effects also have been reported. In addition, the quality and consumer acceptance of products is largely affected by probiotics starter, fermentation process, juice sterilization process and beverage enhancements. Considering the extensive reports on fruit and vegetable fermented beverages, the summary of these aspects is rare and not comprehensive enough. In view of this, we realized that it is necessary to update influencing factors of the quality and consumer acceptance of fruit and vegetable fermented beverages and some of the technologies involved, as well as nutrients, chemical properties and health benefits. Based on recent developments, it can be anticipated that fruit and vegetable fermented beverages will continue to be an important part of the functional food market.
Emerging technologies are being constantly improved, giving rise to new processes capable of promoting greater nutritional preservation and improved technological characteristics, in addition to the benefits related to energy efficiency. Ultrasound treatment has stood out among the non-thermal technologies, due to several benefits related to microstructural changes and microbial inactivation. The study of this technology is particularly important in dairy products, which represent one of the most important segments of the food industry and have a wide range of products developed from different processes. It has been shown that depending on the applied ultrasound treatment intensity (combination of frequency, power, processing time and sample volume) and the resulted temperature, the treatment may exert opposite effects on the food products, such as inactivation/stimulation of microorganisms and enzymes. Therefore, the purpose of this review was to contextualize the different applications and mechanism of action of ultrasound in milk and dairy products, approaching the technological benefits from the microbiological point of view.
Pretreatment and detoxification processes are essential for conventional cellulase production from lignocellulose. However, spent mushroom substrate (SMS) can be potentially used for cellulase production without these processes. In this study, lignocellulose contents in various generations of SMS used for cultivating Auricularia polytricha, Auricularia nigricans, and Pleurotus ostreatus were analyzed. The highest lignin degradation ability was observed in SMS used for cultivating A. polytricha, whereas the highest cellulose degradation ability was observed in SMS used for cultivating A. nigricans. The production of cellulase using the earlier generation of SMS was higher than that using the later generation, and the highest cellulase activity from the third-generation SMS used for A. polytricha was 3.51 U/mL. The study also demonstrates that the use of ultrasonic treatment in the fermentation process could improve the cellulase activity, as was evident by the increase of cellulase activity by 24.5% after ultrasonic treatment for 40 min at 0.8 duty cycle after 4 days of fermentation. This study not only provides a possible solution for SMS disposal, but also presents a substrate that can potentially be used for cellulase production without the need of pretreatment.
The conventional polymers (polyethylene, polypropylele, polystyrene, etc) are non-degradable and exhibits many hazardous effects on the environment. Due to their bio incompatibility and accumulation in nature, there is a need to produce environment-friendly biodegradable polymers. Polyhydroxybutyrate is one of the biodegradable biopolymers produced by a microorganism Cupriavidus necator in order to survive the stress condition. In this study, the effect of ultrasound to intensify the productivity of biopolymer was studied. Different ultrasound parameters, mainly the effect of ultrasound power, duty cycle, ultrasound irradiation time on the productivity of PHB were studied using the one-factor-at-a-time method. Intracellular PHB was extracted using chloroform as a solvent, and analysis was carried out using GC-MS, FT-IR analytical techniques for the detection of PHB. The highest productivity of 0.2155 ± 0.0049 g/100 mL (1.7 g PHB g⁻¹ dry cell wt⁻¹) is reported when a substrate was irradiated with ultrasound at 22 kHz frequency, 50 W power, 10% duty cycle and 10 min of irradiation time with a constant cycle time of 1 min.
Sonication (or ultrasound irradiation) has emerged as a potential technique for the intensification of diverse physical/chemical/biological processes. In recent years, sonication has been applied in the synthesis of liquid biofuels, such as biodiesel, and bioalcohols, such as ethanol. The process of bioalcohol synthesis comprises four steps, viz. acid pretreatment, alkaline delignification, enzymatic hydrolysis and fermentation. Significant literature has been published in the last decade on the application of ultrasound for the intensification of all the steps of bioalcohol synthesis. In this paper, a critical review and analysis of the literature on ultrasound-assisted bioalcohol synthesis has been presented. This review has addressed all four steps of bioalcohol synthesis. Essentially, the literature in the areas of ultrasound-assisted biomass pretreatment, delignification and hydrolysis has been reviewed, followed by an analysis of the literature on ultrasound-assisted fermentation. Finally, the mechanistic investigations of the various steps of bioalcohol synthesis have been reviewed, highlighting the synergistic links between the physical/chemical effects of ultrasound and cavitation and the basic physical/chemical mechanisms of the steps of bioalcohol synthesis. The critical analysis of the literature in this review has not only demonstrated the efficacy of ultrasound in the intensification of all the steps of bioalcohol synthesis, but has also brought to light the underlying mechanistic issues; this could provide guidelines for the design and optimization of commercial scale bioalcohol processes.
The non-destructive control by using ultrasound techniques has become of great importance in food industry. In this work, Ultrasound has been used for quality control and monitoring the fermentation stages of yogurt, which is a highly consumed product. On the contrary to the physico-chemical methods, where the measurement instruments are directly introduced in the sample, ultrasound techniques have the advantage of being non-destructive and contactless, thus reducing the risk of contamination. Results obtained in this study by using ultrasound seem to be in good agreement with those obtained by physico-chemical methods such as acidity measurement by using a PH-meter instrument. This lets us to conclude that ultrasound method may be an alternative for a healthy control of yoghurt fermentation process.
This study investigated the effects of high intensity ultrasound (temperature, amplitude, and time) on the inactivation of indigenous bacteria in pasteurized milk, Bacillus atrophaeus spores inoculated into sterile milk, and Saccharomyces cerevisiae inoculated into sterile orange juice using response surface methodology. The variables investigated were sonication temperature (range from 0 to 84°C), amplitude (range from 0 to 216 μm), and time (range from 0.17 to 5 min) on the response, log microbe reduction. Data were analyzed by statistical analysis system software and three models were developed, each for bacteria, spore, and yeast reduction. Regression analysis identified sonication temperature and amplitude to be significant variables on microbe reduction. Optimization of the inactivation of microbes was found to be at 84.8°C, 216 μm amplitude, and 5.8 min. In addition, the predicted log reductions of microbes at common processing conditions (72°C for 20 sec) using 216 μm amplitude were computed. The experimental responses for bacteria, spore, and yeast reductions fell within the predicted levels, confirming the accuracy of the models.
The present work illustrates ultrasound assisted production of a fibrinolytic enzyme at a 1 L bioreactor scale from Bacillus sphaericus MTCC 3672. To alleviate the shortcomings of one factor at a time method of optimization, central composite rotatable design of response surface methodology was employed for optimization of ultrasound assisted production. Different process parameters such as irradiation time, duty cycle and power of ultrasound were varied in 3 different levels in 11 experimental runs. For evaluating mass transfer enhancement effect of ultrasonication on production, control non sonicated fermentation was optimized by varying different agitation speed (300-500 rpm) and aeration rate (8.33-33.33 cc/s). Optimized ultrasonication protocol resulted in 1.48 fold increase in fibrinolytic enzyme yield as compared to non sonicated fermentation, which comprised of ultrasound irradiation at 25 kHz for 10 min with 40% duty cycle and 160 W power on 12 h of growth phase in 1 L bioreactor operated at 400 rpm agitation speed and 16.66 cc/s aeration rate. Declined glucose concentration from 0.1% w/v (non sonicated control run) to 0.05% w/v and breakage of cells cluster emphasized on increased substrate utilization potential and enhanced convection of ultrasound assisted fermentation in a bioreactor. Deliverables of current studies will provide significant insights for enhancement of productivity of various enzymes at a bioreactor level.
Extraction processes are largely used in many chemical, biotechnological and pharmaceutical industries for recovery of bioactive compounds from medicinal plants. To replace the conventional extraction techniques, new techniques as high-pressure extraction processes that use environment friendly solvents have been developed. However, these techniques, sometimes, are associated with low extraction rate. The ultrasound can be effectively used to improve the extraction rate by the increasing the mass transfer and possible rupture of cell wall due the formation of microcavities leading to higher product yields with reduced processing time and solvent consumption. This review presents a brief survey about the...
The present study is aimed at enhanced production of a fibrinolytic enzyme from Bacillus sphaericus MTCC 3672 under ultrasonic stimulation. Various process parameters viz; irradiation at different growth phases, ultrasonication power, irradiation duration, duty cycle and multiple irradiation were studied for enhancement of fibrinolytic enzyme productivity. The optimum conditions were found as follows, irradiation of ultrasonic waves to fermentation broth at 12h of growth phase with 25kHz frequency, 160W ultrasound power, 20% duty cycle for 5min. The productivity of fibrinolytic enzyme was increased 1.82-fold from 110 to 201U/mL compared with the non sonicated control fermentation. Drop in glucose concentration from 0.41% to 0.12% w/v in ultrasonicated batch implies that, ultrasonication increases the cell permeability, improves substrate intake and progresses metabolism of microbial cell. Microscopic images before and after ultrasonic stimulation clearly signifies the impact of duty cycle on decreasing biomass concentration. However, environmental scanning electron micrograph does not show any cell lysis at optimum ultrasonic irradiation. Offshoots of our results will contribute to fulfill the demand of enhancement of microbial therapeutic enzyme productivity, through ultrasonication stimulation.
Effects of ultrasound amplitude and duty cycle on cultures of Aspergillus terreus are reported in a 25l slurry bubble column sonobioreactor. Fermentations were carried out batchwise. A 2k-factorial design with added central points was used. Sonication at any cycle and amplitude level did not affect biomass growth
rate and yield relative to nonsonicated control, but did affect growth morphology. Ultrasound disrupted fungal pellets and
caused the biomass to grow mainly as dispersed hyphae. Production of lovastatin was reduced by medium- and high-cycle sonication.
Sonication affected broth rheology. In view of these results, sonication can be used to modify growth morphology and broth
rheology without affecting growth rate and yield of filamentous fungi.
Keywords
Aspergillus terreus
-Fungal rheology-Fungal morphology-Lovastatin-Sonobioreactors-Ultrasound
Hydrolytic enzymes, viz. α- and β-glucosidase, were produced from indigenous isolate, Lactobacillus acidophilus, isolated from fermented Eleusine coracana. Production of these enzymes was enhanced by optimizing media using one factor at a time followed by response surface methodology. The optimized media resulted in a 2.5- and 2.1-fold increase in α- and β-glucosidase production compared with their production in basal MRS medium. Localization studies indicated 80% of the total activity to be present in the cell membrane-bound fraction. Lack of sufficient release of these enzymes using various physical, chemical, and enzymatic methods confirmed their unique characteristic of being tightly cell membrane bound. Enzyme characterization revealed that both α- and β-glucosidase exhibited optimum catalytic activity at 50 °C and pH 6.0 and 5.0, respectively. K
m and V
max of α-glucosidase were 4.31 mM and 149 μmol min−1 mL−1 for p-nitrophenyl-α-d-glucopyranoside as substrate and 3.8 mM and 120 μmol min−1 mL−1 for β-glucosidase using p-nitrophenyl-β-d-glucopyranoside as the substrate.
An efficient intermittent ultrasonic treatment strategy was developed to improve laccase production from Trametes versicolor mycelia cultures. The optimized strategy consisted of exposing 2-day-old mycelia cultures to 5-min ultrasonic treatments for two times with a 12-h interval at the fixed ultrasonic power and frequency (120W, 40kHz). After 5days of culture, this strategy produced the highest extracellular laccase activity of 588.9U/L among all treatments tested which was 1.8-fold greater than the control without ultrasound treatment. The ultrasonic treatment resulted in a higher pellet porosity that facilitated the mass transfer of nutrients and metabolites from the pellets to the surrounding liquid. Furthermore, the ultrasonic treatment induced the expression of the laccase gene (lcc), which correlated with a sharp increase in both extracellular and intracellular laccase activity. This is the first study to find positive effects of ultrasound on gene expression in fungal cells. These results provide a basis for understanding the stimulation of metabolite production and process intensification by ultrasonic treatment in filamentous fungal culture.
This study aimed at utilizing ultrasound treatment to further enhance the growth of lactobacilli and their isoflavone bioconversion activities in biotin-supplemented soymilk. Strains of lactobacilli (Lactobacillus acidophilus BT 1088, L. fermentum BT 8219, L. acidophilus FTDC 8633, L. gasseri FTDC 8131) were treated with ultrasound (30 kHz, 100 W) at different amplitudes (20%, 60% and 100%) for 60, 120 and 180 s prior to inoculation and fermentation in biotin-soymilk. The treatment affected the fatty acids chain of the cellular membrane lipid bilayer, as shown by an increased lipid peroxidation (P<0.05). This led to increased membrane fluidity and subsequently, membrane permeability (P<0.05). The permeabilized cellular membranes had facilitated nutrient internalization and subsequent growth enhancement (P<0.05). Higher amplitudes and longer durations of the treatment promoted growth of lactobacilli in soymilk, with viable counts exceeding 9 log CFU/mL. The intracellular and extracellular β-glucosidase specific activities of lactobacilli were also enhanced (P<0.05) upon ultrasound treatment, leading to increased bioconversion of isoflavones in soymilk, particularly genistin and malonyl genistin to genistein. Results from this study show that ultrasound treatment on lactobacilli cells promotes (P<0.05) the β-glucosidase activity of cells for the benefit of enhanced (P<0.05) isoflavone glucosides bioconversion to bioactive aglycones in soymilk.
Sonication of implants has been shown to be a promising method for diagnosis of prosthetic infections due to its improved
sensitivity, simplicity, and low cost. The aim of the present study was to evaluate the effects of ultrasound performed under
different conditions regarding temperature, duration, and composition of sonication tubes on bacterial species often associated
with prosthetic infections. We found that ultrasound had an inhibitory effect on bacteria, of which gram-negative bacteria,
in particular Escherichia coli, were almost eradicated after 5 min of sonication at 35°C. Gram-positive bacteria were found to be resistant to the effect
of ultrasound. Four factors were important for the inhibitory effect of sonication: the type of microorganism, the temperature
of the sonication buffer, the duration of exposure to ultrasound (minutes), and the material and composition of the sonication
tube in which sonication is performed. On the basis of the results from the present study, we propose a protocol for sonication
and recovery of bacteria associated with biofilm on infected implants prior to conventional culture. From the present protocol,
we recommend sonication for 7 min at 22°C at the maximum effect which permits survival of gram-negative bacteria.
Some species of bacteria produce colonies and spores which agglomerate in spherical clusters (Bacillus subtilis) and this serves as a protection for the organisms inside against biocidal attack. Flocs of fine particles e.g. clay can entrap bacteria which can also protect them against the biocides. It is because of problems such as these that alternative methods of disinfecting water are under active investigation. One such method is the use of power ultrasound, either alone or in combination with other methods. Ultrasound is able to inactivate bacteria and deagglomerate bacterial clusters or flocs through a number of physical, mechanical and chemical effects arising from acoustic cavitation. The aim of this study was to investigate the effect of power ultrasound at different powers and frequencies on Bacillus subtilis. Viable plate count techniques were used as a measure of microbial activity. Results showed a significant increase in percent kill for Bacillus species with increasing duration of exposure and intensity of ultrasound in the low-kilohertz range (20 and 38 kHz). Results obtained at two higher frequencies (512 and 850 kHz) indicated a significant increase in bacteria count suggesting declumping. In assessing the bacterial kill with time under different sonication regimes three types of behaviour were characterized: High power ultrasound (lower frequencies) in low volumes of bacterial suspension results in a continuous reduction in bacterial cell numbers i.e. the kill rate predominates. High power ultrasound (lower frequencies) in larger volumes results in an initial rise in cell numbers suggesting declumping of the bacteria but this initial rise then falls as the declumping finishes and the kill rate becomes more important. Low intensity ultrasound (higher frequencies) gives an initial rise in cell numbers as a result of declumping. The kill rate is low and so there is no significant subsequent decrease in bacterial cell numbers.
We report in this study that the sonication of laccase from Trametes villosa and bovine serum albumin promotes the formation of protein aggregates with high molecular weight. The formation of aggregates leads to the deactivation of the enzyme, fact that was confirmed by the analysis of the enzyme stability (half-life time) upon ultrasound treatment. This inactivation was mainly caused by the radicals formed by the cavitation phenomenon. It was verified that the addition of polyvinyl alcohol to laccase had a protecting effect against enzyme inactivation. The performance of laccase in the decolourization of indigo carmine was studied. It was observed that the best results were attained when the dye solution was treated with ultrasound and enzyme stabilized with polyvinyl alcohol, where more than 65% of decolourization was achieved. This value is remarkably higher than that attained for the enzyme alone, which was only able to decolourize 20% of the dye solution within 1h of treatment. These results have important implications for the exploitation of sonication in textile industry, where the pollution caused by the release of dyes into effluents is one of the major concerns.
Low intensity ultrasound can produce various effects on biological materials, such as stimulating enzyme activity, cell growth, biosynthesis, etc., which may improve the efficiency of enhanced biological phosphorus removal (EBPR). We adopt total phosphorus (TP) and dehydrogenase activity (DHA) as indicators to confirm the feasibility of applying low intensity ultrasound in EBPR. Single-factor experiments and orthogonal test were conducted in batch anaerobic/oxic (A/O) process simulation to study the influence of ultrasonic intensity and exposure time in the EBPR process. The results showed that the optimal ultrasonic parameters were 0.2 W/cm2 and 10 min under which condition the TP concentration in the effluent was 35-50% lower than that of the control (without ultrasonic irradiation). Changes of sludge activities after ultrasonic irradiation were examined. The improvement of sludge activity by ultrasound took 4 h after irradiation to reach the peak level, when an increase above 50% of DHA has been achieved by ultrasonic irradiation, and the enhancing effects induced by ultrasound disappeared in 16 h after irradiation. A tentative mechanism of biological phosphorus removal enhancement stimulated by ultrasound was discussed based on these phenomena.
The enhanced β-glucosidase of Lactobacillus plantarum BCRC 10357 was investigated by a strategic ultrasound treatment on bacteria at different growth stages to induce biological stress response for biotransformation of isoflavones from glucosides to aglycones in okara. Without ultrasound, the highest β-glucosidase activity was occurred in 12-h incubation as 24.45 U/mL; while after ultrasound treatment at death phase, the highest β-glucosidase activity was greatly enhanced to 48.80 U/mL in 24-h re-incubation, showing the bacteria at early death phase behaving the highest resistance to stress than at other stages. With strategically ultrasound-treated L. plantarum BCRC 10357 to ferment okara in the broth at 37 °C, the fraction of bioactive aglycones (daidzein and genistein) in isoflavones was increased from 57% in 12 h to 89% in 36 h. The effective method to improve β-glucosidase released from L. plantarum was developed for the valorization of okara as potential functional ingredients in food.
Low energy ultrasound irradiation was used to enhance co-production of enzymes uricase and alkaline protease using Bacillus licheniformis NRRL 14209. Production of uricase and alkaline protease were evaluated for different ultrasound parameters such as ultrasound power, time of irradiation, duty cycle and growth stage of organisms at which irradiation is carried out. Maximum uricase production of 0.825 U/mL and alkaline protease of 0.646 U/mL have been obtained when fermentation broth was irradiated at 6 h of growth stage with 60 W power for 15 min of duration having 40% of duty cycle. The enzyme yield was found to be enhanced by a factor of 1.9 – 3.8 and 1.2 - 2.2 for uricase and alkaline protease respectively. Nevertheless, intracellular uricase was also observed in a fermentation broth after ultrasonic process intensification. The results indicate the effectiveness of low frequency ultrasound in improving enzyme yields with a vision of commercial applicability of the process.
Abstract
Aims: This research investigated the effect of sonication at frequencies of 20, 40 and 580 kHz and approximately the same acoustic intensity on the viability and declumping of two micro‐organisms (Escherichia coli and Klebsiella pneumonia).
Methods and Results: Two analytical methods were employed; viable plate counts (CFU ml−1) and flow cytometry to identify and quantify both live/viable and dead bacteria in the bulk liquid. Flow cytometry results for E. coli and Kl. pneumonia indicated a high sensitivity to 20 and 40 kHz frequency with a continuous decrease in the viable cells and an increase in dead cells during experiments. In contrast, results using the higher frequency of 580 kHz indicate predominantly deagglomeration of bacterial clumps rather than cell membrane disruption (Joyce et al. 2003). Results indicate a good correlation between flow cytometry and viable plate count methodology.
Conclusions: Sonication has two different effects on bacteria (i) inactivation and (ii) declumping; however, the scale of these effects is dependent on intensity and frequency. Flow cytometry provides a method to distinguish between and quantify the effects through the observation of two subpopulations: (i) live/viable and (ii) dead bacterial cells.
Significance and Impact of the study: Treatment using power ultrasound has been shown to have a significant impact on microbial activity. This is the first time a study has compared the influence of a range of different frequencies, but at similar power settings on the survival of bacteria in phosphate buffer saline (PBS). This work is of importance for applications where ultrasound has been considered for use in industry as a means of disinfection including the treatment and pretreatment of water and also for the sterilization of liquid foods.
Fermentation processes involve the participation of enzymes and organic catalysts, generated by range of microorganisms, to produce chemical transformations. Ultrasound can be used in such processes to either monitor the progress of fermentation or to influence its progress. High frequency ultrasound (> 2MHz) has been extensively reported as a tool for the measurement of the changes in chemical composition during fermentation providing real time information on reaction progress. Low frequency ultrasound (20 – 50 kHz) can influence the course of fermentation by improving mass transfer and cell permeability leading to improved process efficiency and production rates. It can also be used to eliminate micro-organisms which might otherwise hinder the process. This review summarises key applications of high and low frequency ultrasound in food fermentation applications.
The effect of a ‘bath type’ ultrasound on the fermentation of beer made from Korean six-row barley was studied. Beer samples were treated in an ultrasonication bath for 4 days during primary fermentation. The frequency of the ultrasound was 40 kHz, and the input power was adjusted to 120, 160 and 200 W. Ultrasonic treatment was performed for 2, 6 and 12 h for each input power. The physicochemical and sensory properties, as well as the quality of the beers were measured. Ultrasonication enhanced ethanol production by 13.18% at 160 W. Copyright © 2015 The Institute of Brewing & Distilling
This chapter first addresses the emergence of ultrasonic cleaning technology. The principles and mechanism of application are discussed, and an explanation of the benefits of ultrasonic cleaning is provided. Ultrasonic cleaning also has limitations, which are revealed, along with reasons for these shortfalls. This chapter serves as a practical guide for maximizing and monitoring the effectiveness of an ultrasonic cleaning system. Advances in ultrasonic technology are explored along with their impetus. Finally, this chapter speculates on the future of ultrasonic cleaning. An appendix on recent developments in ultrasonic washing of textiles also is included.
Objectives:
The aim of this study was to obtain valuable information about the effect of ultrasonic irradiation with a frequency of 30 kHz frequency and power of 100 W on the inactivation capability of two bacterial groups, namely, Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, in physiologic water samples.
Methods:
Ultrasonic irradiation of bacterial samples with different populations of 5 × 10(3), 1.5 × 10(4), and 3 × 10(4) colony-forming units/mL was performed at a constant frequency with various treatment times. The specific energy (γ) values were calculated for these different concentrations of E coli and S aureus. The rate constant for ultrasonic inactivation was estimated in the linear region of a plot representing a survival ratio logarithm versus sonication time.
Results:
Although a significant death rate for E coli was observed with ultrasound treatment, in contrary to expectations, an increase in S aureus populations was observed.
Conclusions:
Considering the widespread use of ultrasound for sterilization of tools and equipment used in hospitals, the results obtained in this study indicate that ultrasonic irradiation is not a suitable method for the elimination of the major hospital pathogen S aureus.
This paper presents a study of low-ultrasonic energy that can be affected to increase yeast growth. Forces of the ultrasonic stimulation in the yeast media broth, a liquid nutrient medium for the culture of yeast, produce change of liquid densities and surrounding pressure, which affect to the yeast growth. A utilized ultrasonic system including transducer of 20 kHz was varied powers and applied into the 200 ml. starter broth including Saccharomyces cerevisiae yeast. Those powers can be adjusted intensities, repetition times and durations to stimulate yeast cell. For monitoring the yeast growth, a cell direct-count with a Hemacytometer and an optical density using a Spectrophotometer were employed every 1 hour. Experiment results were shown enhancements of the yeast growth which were stimulated by the various ultrasonic powers compared with commonly used methods. Consequently, the ultrasonic can be applied to accelerate the yeast growth in fermentation to increase productivity and decrease the fermentation time.
The present endeavor encompasses process intensification approach for daunorubicin fermentation from Streptomyces peucetius MTCC 4332 using ultrasonic stimulus. One factor at a time design was employed to illustrate the effect of various process parameters of ultrasonic irradiation (irradiation at various growth phases, power, irradiation time and duty cycle) on enhancement of daunorubicin productivity. Ultrasonic irradiation on 4th day of bacterial culture growth at 25 kHz frequency with 160 W power and 40% duty cycle for 5 min shows 1.62 fold increase in daunorubicin production (from 46.96 to 76.42 mg/L) as compared to non sonicated batch fermentation. Higher duty cycle imparts detrimental effect on bacterial cell and decreases viability of cells. Environmental scanning electron microscopic analysis depicted structural integrity of bacterial cell after irradiation of optimized ultrasonic dose. Moreover, declined glucose concentration after ultrasonication from 1.16 to 0.46 gm/L after 7 days of incubation, implies that cellular uptake of substrate was increased and productivity of cell was also enhanced. Hence, proposed process intensification approach will be very useful to boost up the fermentation of various therapeutic molecules
A potent fibrinolytic protease (thrombinase) was isolated from marine actinomycetes which can be used for the treatment of myocardial infarction. Thrombinase producing actinomycetes were isolated from the marine water sample using fibrin plate assay. The spore morphology of the marine isolate was analyzed by light and scanning electron microscopy (SEM). Further the marine isolate was identified as Streptomyces venezuelae through biochemical tests and 16srRNA analysis. Effect of ultrasonication on cell concentration and enzyme activity was further determined and the maximum values 20.62 mg mL−1 and 6.24 FU mL−1, respectively were obtained under static condition. The maximum specific growth rate μm (h−1) of the marine isolate under static condition was evaluated as 0.554 h−1 with ultrasonication by modified gompertz model using Matlab 7.0. Moreover effect of salinity on cell concentration and enzyme activity was also analyzed, the maximum biomass, 22.42 mg mL−1 and maximum enzyme activity, 6.7 FU mL−1 at 6% (w/v) salinity. Optimization was done further by response surface methodology (RSM) using central composite design (CCD) and it was found pH 7, temperature 35 °C and salinity 6% (w/v) as optimum for maximum specific growth rate, 0.578 h−1 and thrombinase activity, 8.34 FU mL−1.
The effects of ultrasonic wave irradiation on cell growth and the formation of ethanol and other volatile components in the fermentation process were investigated. The fermentation periods were reduced to 50–64% in wine, beer, and sake made from saccharified rice solution when weak ultrasonic waves were irradiated at 30 mW/cm2; the total intensity was 590 mW. YEPD medium fermented by a combination of optimal thermal trajectory control and continuous ultrasonic irradiation yielded a concentration of isoamylacetate about 2.5 times greater than the maximum concentration under isothermal conditions (20°C). Irradiation had virtually no effect when the dissolved carbon dioxide concentration (DCO2) was maintained at a level lower than the experimental value of Bunsen's CO2 absorption coefficient. Therefore, it is suggested that irradiation accelerates the formation of ethanol and other components mainly by decreasing DCO2.
Microstructure changes and micro-damage behavior of some LAB under the impact of ultrasound shock (20 kHz for 5, 10, 15, 20, 25 and 30 minutes) was studied by optical microscope and Transmission Electron Microscope (TEM). Three kinds of micro damages are usually produced by ultrasound, micro-cracks, micro-voids and ruptures.Studies, by TEM showed that ultrasound can increase the cell wall permeability of the cells, which is important in the release of enzymes such as ß-galactosidas reduction of the coagulation time. The survival of LAB was very low in very long exposures of ultrasound.
Glycerol, the principal byproduct of biodiesel production, can be a valuable carbon source for bioconversion into diverse class of compounds. This paper attempts to investigate the mechanistic aspects of ultrasound mediated bioconversion of glycerol to ethanol and 1,3-propanediol (1,3-PDO) by immobilized Clostridium pasteurianum cells on silica support. Our approach is of coupling experimental results with simulations of cavitation bubble dynamics and enzyme kinetics. In addition, the statistical analysis (ANOVA) of experimental results was also done. The glycerol uptake by cells was not affected by either immobilization or with ultrasonication. Nonetheless, both immobilization and ultrasonication were found to enhance glycerol consumption. The enhancement effect of ultrasound on glycerol consumption was most marked (175%) at the highest glycerol concentration of 25 g/L (271.7 mM). The highest glycerol consumption (32.4 mM) was seen for 10 g/L (108.7 mM) initial glycerol concentration. The immobilization of cells shifted the metabolic pathway almost completely towards 1,3-PDO. No formation of ethanol was seen with mechanical shaking, while traces of ethanol were detected with ultrasonication. On the basis of analysis of enzyme kinetics parameters we attribute these results to increased substrate-enzyme affinity and decreased substrate inhibition for 1,3-PDO dehydrogenase in presence of ultrasound that resulted in preferential conversion of glycerol into 1,3-PDO. Biotechnol. Bioeng. © 2013 Wiley Periodicals, Inc.
We investigate the stability and rupture kinetics of planar lipid membranes covered with electrostatically adsorbed polyelectrolytes. After black lipid membranes were formed from negatively charged lipids, polylysines (PLs) of different molecular weights (MW) were added on one or on both sides of the membrane. The adsorption of PL was detected by recording changes of the transmembrane voltage. Rupture was induced by applying short voltage pulses across the membrane. The voltage causing breakdown of the membrane gives information on its mechanical stability. Adsorption of PL on one side of the membrane leads to an asymmetric transmembrane potential, which adds to the externally applied voltage. High MW PL decreases the critical breakdown voltage of the membrane significantly but also increases the delay time between the voltage pulse and pore formation. It is further shown that PL alters the time course of pore widening in a molecular weight-dependent manner. Low MW PL-decorated membranes and undecorated membranes show a fast rupture determined by inertia. In contrast, adsorption of high MW PLs causes a dramatic decrease of the rupture velocity. In this case, the rupture velocity is determined by viscosity. An analysis of the rupture kinetics allows an estimate of the 2D viscosity.
With significant growth of biodiesel industry in past few years, very large quantities of crude glycerol are available as side product of transesterification process. Effective conversion of glycerol to value added products can boost economy of biodiesel industry. The present study attempts to investigate ultrasound assisted bioconversion of glycerol to 1,3-propanediol (1,3-PDO) and ethanol (EtOH) from mechanistic. A dual approach of coupling experiments under ultrasound irradiation or mechanical shaking with simulations of cavitation bubble dynamics has been adopted. Effect of ultrasound on bioconversion has been assessed with the help of kinetic analysis of enzymatic reactions. The nature of convection generated by ultrasound irradiation at raised static or ambient pressure has dual character of oscillatory motion of liquid, accompanied by medium amplitude jerks by the acoustic or shock waves emitted by cavitation bubbles, which could contribute towards enhancement of the enzymatic reactions in metabolic pathway. In presence of ultrasound, the highest yield (0.06 mol/mol) of 1,3-PDO was obtained with lowest glycerol concentration (5 g/L) while highest ethanol yield (0.12 mol/mol) was observed at 10 g/L glycerol concentration. Yield of both products increases under ultrasound irradiation, but lesser enhancement is seen for 1,3 PDO than EtOH due to substrate inhibition. Maximum enhancement in yield (49%) of 1,3-PDO was seen for 10 g/L glycerol concentration. The role of ultrasound irradiation in enhancement of bioconversion of glycerol is found to be of physical nature, without any influence on biochemistry of glycerol conversion.
Reducing production costs for fermentation-based drugs (e.g., antibiotics) is crucial for the long-term sustainability of healthcare. In this study, we propose a novel low-intensity pulsed ultrasound (LIPUS) stimulation scheme using a nominal frequency of 1.5 MHz with a 20% duty cycle (200 μs ultrasound on and 800 μs ultrasound off) to increase production of fermentation-based drugs. We chose Penicillium brevicompactum as a model system to demonstrate the performance of our LIPUS system. Penicillium brevicompactum can produce mycophenolic acid (MPA), an immunosuppressive agent commonly used to prevent rejection after organ transplantation. We have stimulated Penicillium brevicompactum in 50 mL shake flasks using LIPUS during its fermentation. After a series of screening experiments to optimize ultrasound parameters (e.g., ultrasound intensities, treatment duration and treatment frequency per day), it was concluded that ultrasound stimulation can increase MPA production by as much as 60% when treated eight times a day for 10-min durations at an intensity (spatial peak temporal average) of 200 mW/cm(2). These findings elucidate a new approach to reduce the cost of producing fermentation-based drugs.
BACKGROUND: Fermentations of Aspergillus terreus are commercially used to produce lovastatin. How ultrasound might influence this fermentation is unknown. While high-intensity ultrasound is effective in disrupting microbial cells, ultrasound of low intensity is known to improve productivity of some fermentation processes without damaging cells. Mechanisms behind productivity improvements have not been clearly identified in earlier studies. This work reports on the effects of ultrasound on A. terreus fermentation for low (957 W m−3), medium (2870 W m−3) and high (4783 W m−3) values of sonication power input in a slurry bubble column sonobioreactor.
RESULTS: Sonication at any power level did not affect biomass growth profiles in comparison with negative controls. In contrast, medium- and high-intensity sonication greatly reduced production of lovastatin and substantially altered the growth morphology. At medium and high intensity, ultrasound disrupted fungal pellets and caused the biomass to grow mainly as dispersed hyphae. Sonication affected broth rheology because rheology depends on the morphology of the suspended biomass.
CONCLUSION: Sonication can be used to modify growth morphology and broth rheology without affecting growth of filamentous fungi. Sonication appears to influence the primary growth metabolism and secondary metabolism differently in different situations. Copyright
Ultrasound effects on the release and activity of invertase from Aspergillus niger cultivated in a medium containing sucrose and peptone and in another with sugar-cane molasses and peptone were investigated. Irradiation was conducted for periods of 2–10 min. with waves of amplitude 20 and 40 using an ultrasound processor of 20 kHz. Product formation was determined as reducing equivalents formed by time units using 3,5-dinitrosalicylic acid. Total and specific activities of the culture supernatants were compared in the presence and absence of sonication. Both amplitudes promoted a significant increase of total invertase activity in the time periods investigated and the highest values were obtained with an amplitude of 20. Ultrasound irradiation caused cell disruption, thus releasing invertase and, after 4 min, activation of the enzyme also occurred. The best conditions for production, extraction and activation of invertase were in molasses medium containing peptone and irradiation with ultrasound waves at 20 for 8 min. This method showed high efficiency for the extraction and activation of invertase from A. niger as well as a great potential for use in industrial processes.
Cavitation results in the generation of hot spots, highly reactive free radicals, and turbulence associated with liquid circulation currents, which can result in the intensification of various physical/chemical operations. The present work provides an overview of the applications of the cavitation phenomenon in the specific area of biochemical engineering/biotechnology, discussing the areas of application, the role of cavitation, the observed enhancement and its causes by highlighting some typical examples. The different methods of inducing cavitation and the dominance of one over the other, mostly with respect to energy requirements, in different areas of biotechnological application are discussed. The major applications discussed in the work include microbial cell disruption for the release or extraction of enzymes, microbial disinfection, wastewater treatment, crystallization, synthesis of biodiesel, emulsification, extraction of bio-components, freezing and gene transfer into cells or tissues. Some recommendations for optimal operating/geometric parameters have also been made. Overall, it appears that the combined efforts of physicists, chemists, biologists and chemical engineers are required to effectively use cavitational reactors for industrial applications.
The effects of ultrasound on the activities of alpha-amylase and amyloglucosidase toward starch and glycogen hydrolysis, and of invertase toward sucrose hydrolysis, were investigated using an ultrasound bath. A fixed-time assay was employed with product formation determined by reducing equivalents formed per unit time using the 3,5-dinitrosalicylate reagent (DNS). Reaction rates in the presence and absence of ultrasound were compared. Increases in rates were observed in the presence of ultrasound at most concentrations with a marked increase in invertase activity towards sucrose (37% at 0.9 m) and a reduction in the inhibition of sucrose hydrolysis observed at high substrate concentrations. Improvements in the efficiency of mixing and disruption of intra- and intermolecular substrate molecule interactions at high concentrations are possible explanations for the changes observed.
Sonolysis, enzyme treatment, and a combination of the two processes were tested for the degradation of phenol in aqueous medium. With sonolysis alone, 423 kHz ultrasound eliminated phenol molecules through hydroxyl radical reactions. In the presence of hydrogen peroxide, the enzyme horseradish peroxidase (HRP) catalyzed the oxidation of phenol to insoluble polymers which could be separated easily from the solution. In the combined system (HRP, H2O2, US-423 kHz) the degradation rate was accelerated, and the color of the solution changed to dark brown without any precipitate formation. The enhancement was more significant in the presence of additives such as polyethylene glycol (PEG). The higher rate induced through the use of ultrasound leads to the reduction of HRP dose requirements, which is of importance for the economic feasibility of this method. The enzyme solution alone did not show any inactivation up to 45 min sonication at 423 kHz. Investigation of phenol removal efficiency was mainly focused on enzyme, phenol and PEG concentrations, as well as the sequence and method of addition of reagents.
Production of ethanol from lactose by fermentation with the yeast Kluyveromyces marxianus (ATCC 46537) under various sonication regimens is reported. Batch fermentations were carried out at low-intensity sonication (11.8W cm(-2) sonication intensity at the sonotrode tip) using 10%, 20% and 40% duty cycles. (A duty cycle of 10%, for example, was equivalent to sonication for 1 s followed by a rest period (no sonication) of 10s.) Fermentations were carried out in a 7.5 L (3 L working volume) stirred bioreactor. The sonotrode was mounted in an external chamber and the fermentation broth was continuously recirculated between the bioreactor and the sonication chamber. The flow rate through the sonication loop was 0.2 L min(-1). All duty cycles tested improved ethanol production relative to control (no sonication). A 20% duty cycle appeared to be optimal. With this cycle, a final ethanol concentration of 5.20 +/- 0.68 g L(-1) was obtained, or nearly 3.5-fold that of the control fermentation. Sonication at 10% and 20% cycles appeared to stimulate yeast growth compared to the control fermentation, but 40% duty cycle had a measureable adverse impact on cell growth. Sonication at 10% and 20% cycles enhanced both the extracellular and the intracellular levels of beta-galactosidase enzyme. Although at the highest duty cycle sonication reduced cell growth, cell viability remained at >= 70% during most of the fermentation. Sonication at a controlled temperature can be used to substantially enhance productivity of bioethanol fermentations.
Ultrasound (US) has become a ubiquitous technological process in a large variety of scientific disciplines. However, little information exists on the use of ultrasound to enhance biological processes and/or processing and consequently this paper provides an overview of work reported to date on this topic. This review provides a brief introduction to ultrasound and the history of ultrasound as applied to bioprocesses. This is followed by a discussion of the influence of US on discrete enzyme systems, enzymes used in bioremediation, microbial fermentations and enzymatic hydrolysis of biopolymers. Augmentation of anaerobic digestion by US is then considered along with enhancement of enzymes in food science and technology. The use of ultrasonically stimulated enzymes in synthesis is then considered and other relevant miscellaneous topics are described. It is concluded that the precise mechanism of action of US in bio-processing remains to be elucidated though a variety of plausible suggestions are made.
Aims: This research investigated the effect of sonication at frequencies of 20, 40 and 580 kHz and approximately the same acoustic intensity on the viability and declumping of two micro-organisms (Escherichia coli and Klebsiella pneumonia).
Methods and Results: Two analytical methods were employed; viable plate counts (CFU ml−1) and flow cytometry to identify and quantify both live/viable and dead bacteria in the bulk liquid. Flow cytometry results for E. coli and Kl. pneumonia indicated a high sensitivity to 20 and 40 kHz frequency with a continuous decrease in the viable cells and an increase in dead cells during experiments. In contrast, results using the higher frequency of 580 kHz indicate predominantly deagglomeration of bacterial clumps rather than cell membrane disruption (Joyce et al. 2003). Results indicate a good correlation between flow cytometry and viable plate count methodology.
Conclusions: Sonication has two different effects on bacteria (i) inactivation and (ii) declumping; however, the scale of these effects is dependent on intensity and frequency. Flow cytometry provides a method to distinguish between and quantify the effects through the observation of two subpopulations: (i) live/viable and (ii) dead bacterial cells.
Significance and Impact of the study: Treatment using power ultrasound has been shown to have a significant impact on microbial activity. This is the first time a study has compared the influence of a range of different frequencies, but at similar power settings on the survival of bacteria in phosphate buffer saline (PBS). This work is of importance for applications where ultrasound has been considered for use in industry as a means of disinfection including the treatment and pretreatment of water and also for the sterilization of liquid foods.
This paper presents an analysis of lag phase phenomena in Saccharomyces cerevisiae growth as a function of ultrasonic irradiation.
Pulse irradiation treatments were performed by a 20 kHz ultrasonic transducer with different durations and energies. Data obtained from experiments were then employed to estimate growth parameters by specific transfer function. The significance of the different lag times in response to ultrasonic irradiation was analysed. The results showed that the yeast growth in lag phase responded to the irradiated ultrasonic of 20 min more than the 10 min. The ultrasonic energies between 330 and 360 W s m(-3) could decrease lag time up to 1 h compared to the sample without ultrasonic irradiation. Conversely, the treatments with energies higher than 850 W s m(-3) were able to extend the lag time and decrease the yeast growth.
The lag durations of S. cerevisiae were changed significantly by different ultrasonic irradiations, energies and durations. In particular, sufficient irradiation energies reduced the lag time, resulting in accelerated yeast growth. In contrast, high energy could inactivate growth by increasing the lag time. Significance and Impact of the Study: This work provides an alternative technique to either accelerate or inactivate the S.cerevisiae lag phase. The approach can be developed in experiment designed to control the yeast growth by ultrasonic irradiation as assistance in the environments.
A non-woven titanium dioxide (TiO(2)) fabric was applied to disinfection by ultrasound (US) irradiation, and the disinfection efficiency and lipid peroxidation of Escherichia coli (E. coli) cell membrane were evaluated to investigate the killing process. The addition of non-woven TiO(2) fabric enhanced hydroxyl (OH) radical generation and disinfection efficiency. Judging from the disinfection experiments using glutathione or t-butanol as a radical scavenger, the OH radical played a major role in cell killing in sonodynamic disinfection with non-woven TiO(2) fabric. Moreover, to understand the detailed killing process, damage to cell membrane was also evaluated using a diphenyl-1-pyrenylphosphine (DPPP) fluorescent probe, which detects the membrane's lipid peroxidation. The addition of non-woven TiO(2) fabric aggravated this peroxidation. This aggravation was caused by the OH radical according to an assay using a radical scavenger. From these results, it was concluded that non-woven TiO(2) fabric as a sonocatalyst promoted peroxidation of the polyunsaturated phospholipid component of the lipid membrane initially and induced a major disorder in the E. coli cell membrane under US irradiation.
The chemical effects of ultrasound in aqueous solutions are due to acoustic cavitation, which refers to the formation, growth, and collapse of small gas bubbles in liquids. The very high temperatures (several thousand K) and pressures (several hundred atmospheres) of collapsing gas bubbles lead to the thermal dissociation of water vapor into .OH radicals and .H atoms. Their formation has been confirmed by electron spin resonance (ESR) and spin trapping. The sonochemistry of aqueous solutions of gases and of volatile and nonvolatile solutes is reviewed. The similarities and differences between sonochemistry and radiation chemistry of aqueous solutions are explained. Some unusual characteristics of aqueous sonochemistry can be understood by considering the properties of supercritical water. By the use of rare gases with different thermal conductivities, it is possible to distinguish between temperature-dependent processes such as redox reactions initiated by .OH radicals and .H atoms and pressure-dependent processes which lead to polymer degradation and cell lysis. The evidence for free radical formation in aqueous solutions by pulsed ultrasound is discussed. This subject is of interest because it is related to the possible deleterious effects of ultrasonic diagnostic devices. The role of free radicals and of mechanical effects induced by ultrasound in DNA degradation, inactivation of enzymes, lipid peroxidation, and cell killing is reviewed.
The commercial production of ethanol from cellulose by simultaneous saccharification and fermentation (SSF) is prevented in part by the high cost of fungal cellulase enzymes. Intermittent exposure of SSF processes to ultrasonic energy under selected conditions (5 FPU of cellulase/g of substrate; 15 min of exposure/240 min cycle during the latter half of SSF) was found to increase ethanol production from mixed waste office paper by approximately 20%, producing 36.6 g/L ethanol after 96 h (70% of the maximum theoretical yield). Without ultrasound, 10 FPU of cellulase/g of substrate was required to achieve similar results. Continuous exposure of the organism to ultrasonic energy was bacteriostatic and decreased ethanol production but may be useful for the controlling bacterial growth in other processes.
Enhanced metabolic productivity of microbial, plant and animal cells in bioreactors can greatly improve the economics of biotechnology processes. Ultrasound is one method of intensifying the performance of live biocatalysts. Ultrasonication is generally associated with damage to cells but evidence is emerging for beneficial effects of controlled sonication on conversions catalyzed by live cells. This review focuses on the productivity enhancing effects of ultrasound on live biological systems and the design considerations for sonobioreactors required for ultrasound-enhanced biocatalysis.
Ultrasound was employed to increase the growth rate of bacterial cells attached to surfaces. Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli cells adhered to and grew on a polyethylene surface in the presence of ultrasound. It was found that low-frequency ultrasound (70 kHz) of low acoustic intensity (<2 W/cm(2)) increased the growth rate of the cells compared to growth without ultrasound. However, at high intensity levels, cells were partially removed from the surface. Ultrasound also enhanced planktonic growth of S. epidermidis and other planktonic bacteria. It is hypothesized that ultrasound increases the rate of transport of oxygen and nutrients to the cells and increases the rate of transport of waste products away from the cells, thus enhancing their growth.
The structure of the cell membrane of Ecemothecium ashbyii is considered to be one of the main obstacles in the improvement of riboflavin productivity, which impedes the release of riboflavin from the cell into the fermentation broth. The results of the present study show that stimulation on growth and riboflavin biosynthesis phase, the content of riboflavin was most obviously enhanced, as compared with the control and the total riboflavin quantity released by ultrasonic treatment. The optimal stimulation time was from 104 to 112 h and ultrasonic should be loaded every 1.5 h.
Gas-filled microbubbles have been successfully used as gene delivery reagents in combination with diagnostic ultrasound. Although shock wave exposure has been shown to transfect cells with naked DNA in vitro, it has not been tested whether the addition of microbubbles would augment DNA uptake under those conditions. Therefore, the aim of this study was to test the impact of microbubbles on transgene expression in vitro under shock wave exposure conditions. HEK 293 cells were treated with 60 or 120 pulses of shock waves at varying energy levels. Cells were mixed with either 100 μg/mL luciferase expressing plasmid DNA or with microbubbles that were produced with the same amount of this DNA. Cell death was evaluated after 1 h and transgene expression, after 24 h. In the presence of microbubbles, transgene expression was significantly higher (as much as 29-fold) relative to that obtained without microbubbles. Cells exposed to 120 pulses demonstrated higher transgene expression (as high as 2.7-fold) compared with cells exposed to 60 pulses. The use of microbubbles resulted in greater cell death, varying from 26% (low energy) to 78% (high energy). In conclusion, DNA-loaded microbubbles can significantly increase shock wave mediated gene transfer. However, this effect is associated with increased levels of cell destruction. (E-mail: [email protected]
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