Lactic Acid in the Food Industry
Abstract
This Brief explores the importance of lactic acid and fermentation in the modern food industry. Although it is usually associated with milk and dairy products, lactic acid can also be found in many other fermented food products, including confectionery products, jams, frozen desserts, and pickled vegetables. In this work, the authors explain how lactic acid is produced from lactose by Lactobacillus and Streptococcus cultures, and they also emphasise its important role as pH regulator and preservative, helping to the inhibition of microbial growth in fermented foods. The Brief discusses a wide range of lactic acid’s applications as a natural additive, curing or gelling agent, flavour, food carrier, solvent, and discoloration inhibitor, among others. Readers will also find a brief overview of the current analytical methods for the quantitative and qualitative determination of lactic acid in foods.
Chapters (5)
The aim of this chapter is to give a brief and reliable overview of possible uses for lactic acid as additive in the current food industry. The importance of lactic acid in the food industry is apparently linked to microbial activity of certain life forms, in particular lactic acid bacteria. Consequently, fermentative bacteria are commonly employed in the food industry as starter cultures for industrial processing. On the other hand, lactic acid can be also used as food additive in the industry of edible products without the presence of lactic acid bacteria. This option can be extremely useful in various ambits. In spite of the main recommended use for this compound (intended as two optical isomers and the racemic mixture of them) as acidity regulator in many food products, several limitations should be considered in certain situations when speaking of maximum allowed amounts and the exclusive use of one isomer only. In addition, several different additives are chemically derived from lactic acid. For this reason, the application spectrum of lactic acid may be broader than the above-mentioned situation, with correlated exceptions and limitations.
The importance of lactic acid in the food industry is certainly correlated with its peculiar chemical and physical properties. According to the Joint FAO/WHO Food Standards Programme, lactic acid isomers and the racemic mixture can be used as acidity regulator in certain foods with the aim of contrasting certain acid-sensitive microorganisms. As a result, the description of food-related uses of lactic acid should involve also peculiar chemical and physical features. This chapter would give a brief and accurate overview of chemical and physical features of this additive. In addition, the chemical synthetic processes for the production of the so-called milk acid are described. Finally, fermentative pathways and related industrial strategies are discussed.
Since the discovery of lactic acid, this compound has been considered for many significant uses and applications in food, cosmetic, pharmaceutical, and chemical industries. Lactic acid occurs naturally in many edible products and also an important ingredient in the food industry. Also, lactic acid is non-toxic and consequently recognised and classified as ‘Generally Recognized as Safe’ substance by the United States Food and Drug Administration for wide use as an additive in the food industry. The notable range of legally allowed food applications depends on the demonstrated antimicrobial action against pathogens and the concomitant shelf life extension. In addition, this acid can serve as a flavouring substance in many food products such as pickles and fermented milk. This chapter discusses some practical and legally allowed examples of lactic acid uses in the production of fermented vegetables, cheeses, fermented milks, sourdough, fermented meats, and wines.
The aim of this chapter is to give a quick and sufficiently comprehensible overview of the current analytical methods for the quantitative and qualitative determination of lactic acid in foods. The importance of lactic acid in the world of food production is well known at present. At the same time, food technologists need accurate, fast, and reliable analytical methods for the determination of naturally present and/or added lactic acid (and related derivatives) in food products and in raw materials. The same thing can be affirmed when speaking of lactic acid as a normal food additive. Naturally, regulatory requirements represent an important demand for adequate and reliable analytical procedures. As a result, the ‘milk acid’ should be detected in foods in a reliable way, on condition that the food matrix and the desired function of lactic acid are well considered. For these reasons, this chapter discusses the practical advantages of several analytical procedures, including spectrophotometry, gas chromatography, capillary electrophoresis, and high-performance liquid chromatography, in relation to selected food categories.
Lactic acid bacteria are widely spread throughout the environment, being symbiotic to humans and among the most important microorganisms used in food fermentations. Despite being a heterogeneous group, lactic acid bacteria share common fermentative pathways, which lead primarily to the production of lactic acid. Their presence in food may be both beneficial and harmful, as their metabolic pathways may also lead to spoilage of certain foods. Furthermore, these microorganisms have gained particular attention due to production of substances of protein structure characterised by an antimicrobial activity (i.e. bacteriocins). These substances are being currently studied for their high potential in the application in food industry for biopreservation, being ‘Generally Recognised As Safe’. Therefore, the role of lactic acid bacteria in the food industry is evolving and promising an always increasing number of applications.
... Lactic acid is essential in various industries due to its versatility and wide applications. In the food industry, it serves as an acidulant and preservative, playing a crucial role in dairy product fermentation and the production of probiotic foods (Ameen & Caruso, 2017). In the pharmaceutical field, lactic acid is used in drug formulations and dermatological products (Daba & Elkhateeb, 2020;Ameen & Caruso, 2017). ...
... In the food industry, it serves as an acidulant and preservative, playing a crucial role in dairy product fermentation and the production of probiotic foods (Ameen & Caruso, 2017). In the pharmaceutical field, lactic acid is used in drug formulations and dermatological products (Daba & Elkhateeb, 2020;Ameen & Caruso, 2017). Furthermore, this compound is a fundamental component in the cosmetics industry, where its exfoliating and moisturizing properties are harnessed in skincare products. ...
... Furthermore, this compound is a fundamental component in the cosmetics industry, where its exfoliating and moisturizing properties are harnessed in skincare products. In the chemical industry, lactic acid is a raw material for producing biodegradable polymers and other compounds (Ameen & Caruso, 2017). It also finds applications related to the textile industry and the production of biodegradable packaging (Perin et al., 2020). ...
La fermentación ácido-láctica (FAL) de la papaya es una estrategia biotecnológica que, aunque tiene mucho potencial, ha sido poco estudiada. Sin embargo, puede ser de interés para una serie de oportunidades en diversas industrias, transformando este fruto en un recurso valioso. El objetivo de este artículo de revisión se enfoca en el impacto de la capacidad antioxidante, los beneficios para la salud y la valorización de los subproductos de la papaya a través de la FAL. La FAL es una estrategia para promover el incremento de la concentración de compuestos antioxidantes, como los compuestos fenólicos en la papaya. Las bacterias ácido lácticas (BAL) liberan y modifican estos compuestos durante la fermentación, lo que potencialmente mejora su capacidad antioxidante. Los productos generados de la FAL de la papaya han demostrado posibles efectos antihipercolesterolémicos, propiedades antivirales y la producción de hidrolizados de proteínas con potencial antioxidante. Las hojas, cáscaras y desechos de la papaya se pueden revalorizar, utilizando la FAL como proceso de extracción de compuestos bioactivos de interés para la industria farmacéutica, cosmética o alimentaria. La papaya es una buena fuente de fibra y azúcares simples y dada la gran diversidad de BAL, es factible el desarrollo de prebióticos y selección de posibles probióticos adaptados a medios vegetales. Si bien se han realizado avances significativos en la comprensión de sus beneficios para la salud y la valorización de los subproductos, se necesita más investigación para abarcar completamente su alcance y desarrollar productos específicos.
... Lactic acid LA is a hydroxycarboxylic acid that has a wide variety of uses in different industries, such as the food, pharmaceutical, cosmetic, and textile industries. In the food industry, it can be used as a preservative (antimicrobial agent), flavoring agent, or acidity regulator in a wide variety of foods, including bakery products, dairy products, confectionery, beverages, fermented meats, dressings, and ready meals (Ameen & Caruso, 2017;Komesu et al., 2017). In 2021, the global LA market was estimated to be worth USD 2.9 billion, and is forecast to expand to 5.8 billion by 2030 (Grand View Research, 2022). ...
... LA is also considered GRAS by the FDA in the United States (CFR, 2022), while in Europe, it has the E number E270 (FSAI, 2020). LA can be produced via microbial fermentation (using bacteria, yeasts, or fungi) or through chemical synthesis (e.g., hydrolysis of lactonitrile by a strong acid) (Ameen & Caruso, 2017;Komesu et al., 2017). However, in recent years there has been a move away from chemical methods due to increasing cost of raw materials and the associated negative environmental impact (Sharma et al., 2021). ...
... LAB are the most commonly used microorganisms for microbial LA production in the food industry (Hofvendahl & Hahn-Hägerdal, 2000;Komesu et al., 2017). Fermentation by LAB can occur as one of two main processes: homolactic fermentation, with LA as the primary product, or heterolactic fermentation, where the final product consists predominantly of LA but also contains a small amount of other side products, such as organic acids (e.g., acetic acid), CO 2 , and ethanol (Ameen & Caruso, 2017;Komesu et al., 2017). For efficient industrial production of LA, it is recommended to avoid byproduct formation if possible. ...
Permeates are generated in the dairy industry as byproducts from the production of high‐protein products (e.g., whey or milk protein isolates and concentrates). Traditionally, permeate was disposed of as waste or used in animal feed, but with the recent move toward a “zero waste” economy, these streams are being recognized for their potential use as ingredients, or as raw materials for the production of value‐added products. Permeates can be added directly into foods such as baked goods, meats, and soups, for use as sucrose or sodium replacers, or can be used in the production of prebiotic drinks or sports beverages. In‐direct applications generally utilize the lactose present in permeate for the production of higher value lactose derivatives, such as lactic acid, or prebiotic carbohydrates such as lactulose. However, the impurities present, short shelf life, and difficulty handling these streams can present challenges for manufacturers and hinder the efficiency of downstream processes, especially compared to pure lactose solutions. In addition, the majority of these applications are still in the research stage and the economic feasibility of each application still needs to be investigated. This review will discuss the wide variety of nondairy, food‐based applications of milk and whey permeates, with particular focus on the advantages and disadvantages associated with each application and the suitability of different permeate types (i.e., milk, acid, or sweet whey).
... The importance of lactic acid in the food industry is related to its peculiar physical and chemical properties (Table 26.3). This acid in two L and D isomers with the additional racemic mixture can be applied as regulator of acidity in certain foods such as smoked fish and smoke-flavored fish, and also, has been used as preservatives, baking additives, flavor enhancers, and pH buffering agents (Anyasi et al., 2015;Valli et al., 2006;Ameen and Caruso, 2017). ...
... In general, lactic acid can be synthesized by different chemical and microbiological methods such as fermentation. The commercial production at first is ascribed by Charles E. Avery in 1881 (Ameen and Caruso, 2017;Carr et al., 2002;Kelkar and Mahanwar, 2015). In the chemical synthesis, a racemic mixture of the two isomers is formed, which has various problems containing toxic raw substances, especially the incapability to produce the optically pure isomer and low conversion rates. ...
... In the chemical synthesis, a racemic mixture of the two isomers is formed, which has various problems containing toxic raw substances, especially the incapability to produce the optically pure isomer and low conversion rates. By discovery of Lactobacillus sp. by the French chemist Loius Pasteur in 1856, nearly 90% of lactic acid is made by fermentations using renewable resources, which is comparatively fast, economical, and able to supply an optically pure form of lactic acid (Quitmann et al., 2013;Ameen and Caruso, 2017;Salminen and Von Wright, 2004). Lactobacillus bacteria can produce lactic acid from carbohydrates, for example, glucose and lactose, and also they live in our gastrointestinal system (Ameen and Caruso, 2017;Carr et al., 2002). ...
... As hetero fermentation was carried out with Lactiplantibacillus ssp. in addition t main metabolite, which is lactic acid, it also provides carbon dioxide, thus measurement of the volume and composition of the fermentation gas can be use monitor the fermentation progress on an ongoing basis [39,40]. The measurement o volume of gas produced during lactic fermentation and the study of its composition l to conclusions about the course of the process. ...
... There was a significant decrea the volume of gas produced after 4 days in almost every fermenter (Figure 9). As hetero fermentation was carried out with Lactiplantibacillus ssp. in addition to the main metabolite, which is lactic acid, it also provides carbon dioxide, thus the measurement of the volume and composition of the fermentation gas can be used to monitor the fermentation progress on an ongoing basis [39,40]. The measurement of the volume of gas produced during lactic fermentation and the study of its composition leads to conclusions about the course of the process. ...
The content of polyphenols, lactic acid, and antioxidant properties in fermented juice increases more at 30 °C than at 35 °C during the lactic fermentation process in butanol extract and broccoli juice. The concentration of polyphenols is expressed by phenolic acid equivalents as gallic acid-Total Phenolic Content (TPC), ferulic acid (CFA), p-cumaric acid (CPA), sinapic acid (CSA), and caffeic acid (CCA). The polyphenols present in fermented juice exhibit antioxidant properties and the ability to reduce free radicals using total antioxidant capacity (TAC) assay, while also the percentage of the DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) cation radical scavenging activity. Lactic acid concentration (LAC), total flavonoid content as quercetin equivalents (QC), and acidity increases during the work of Lactiplantibacillus plantarum (previously Lactobacillus plantarum) in broccoli juice. The pH was monitored during the process of fermentation in both temperatures (30 °C and 35 °C). Densitometric measurements of lactic bacteria (LAB) showed increasing concentration at 30 °C and 35 °C after 100 h (~4 h), but the value concentration dropped after 196 h. The Gram staining showed only Gram-positive bacilli Lactobacillus plantarum ATCC 8014. The Fourier transform infrared (FTIR) spectrum for the fermented juice showed the characteristic carbon–nitrogen vibrations that may originate from glucosinolates or isothiocyanates. Among the fermentation gases, more CO2 was released from fermenters at 35 °C than at 30 °C. The biopreservation used Lactiplantibacillus plantarum to prevent the problem of food waste of plant origin. The probiotic bacteria used in fermentation have a very beneficial effect on health and the human body.
... Even though both of its isomeric forms are used in industry, L-(+)-LA is preferred for medical applications because it can be assimilated by the human body [41]. As a food additive, it is approved in many countries and used as a food preservative, curing agent, and flavoring agent (ingredient E270) [42]. However, to the best of our knowledge, the studies on the application of it, as well as other OAs, against Campylobacter biofilm cells are still very limited [43,44], although some previous studies have already shown the effectiveness of LA against planktonic or sometimes attached Campylobacter cells [19,30,31]. ...
Campylobacter spp. are prevalent foodborne bacterial enteric pathogens. Their inclusion in biofilms on abiotic surfaces is considered a strategy that facilitates their extraintestinal survival. Organic acid (OA) treatments could be used in a green approach to decontaminate various surfaces. This work aimed to evaluate the inhibitory and eradicative effects of L(+)-lactic acid (LA), a naturally occurring OA, on a dual-species biofilm formed on two food processing model surfaces (polystyrene and stainless steel) by three selected foodborne Campylobacter spp. isolates (two C. jejuni and one C. coli). The influence of aerobiosis conditions (microaerophilic, aerobic and CO 2 enriched) on the resistance of the established biofilms to the acid was also tested. In parallel, the predominant metabolites contained in the planktonic media of biofilm monocultures and mixed-culture biofilm were comparatively analyzed by an untargeted metabolomics approach. Results revealed that LA inhibited mixed-culture biofilm formation by more than 2 logs (>99%) on both surfaces when this was applied at its highest tested concentration (4096 µg/mL; 0.34% v/v). However, all the preformed mixed-culture biofilms (ca. 10 6−7 CFU/cm 2) could not be eradicated even when the acid was used at concentrations exceeding 5% v/v, denoting their extremely high recalcitrance which was still influenced by the abiotic substratum, and the biofilm-forming aerobiosis conditions. The metabolic analysis revealed a strain-specific metabolite production which might also be related to the strain-specific biofilm-forming and resistance behaviors and resulted in the distinct clustering of the different samples. Overall, the current findings provide important information on the effectiveness of LA against biofilm campylobacteria and may assist in mitigating their risk in the food chain.
... In general, LA exists as two pure optical isomers: L(+) lactic acid and D(−) lactic acid, or as a racemic mixture of both [3]. The D(−) lactic acid isomer, in doses exceeding 100 mg·kg body mass −1 ·day −1 , is harmful to the human body, as the digestive system only possesses the L-lactate dehydrogenase (L-LDH) enzyme, metabolizing L(+) lactic acid. ...
Lactic acid is widely used in the food industry. It can be produced via chemical synthesis or biotechnological pathways by using renewable resources as substrates. The main challenge of sustainable production lies in reaching productivities and yields that allow for their industrial production. In this case, the application of process engineering becomes a crucial tool to improve the performance of bioprocesses. In this work, we performed the solid-state fermentation of grape stalk using Rhizopus oryzae NCIM 1299 to obtain lactic acid, employing three different temperatures (22, 35, and 40 °C) and a relative humidity of 50%. The Logistic and First-Order Plus Dead Time models were adjusted for fungal biomass growth, and the Luedeking and Piret with Delay Time model was used for lactic acid production, obtaining higher R2 values in all cases. At 40 °C, it was observed that Rhizopus oryzae grew in pellet form, resulting in an increase in lactic acid productivity. In this context, the effect of temperature on the kinetic parameters was evaluated with a polynomial correlation. Finally, using this correlation, a smooth and continuous optimal temperature profile was obtained by a dynamic optimization method, improving the final lactic acid concentration by 53%.
... More specifically, betaine is a quaternary ammonium salt of natural origin that is used in cosmetic and skincare products for its moisturizing properties. Lactic acid is an alpha-hydroxy acid that finds applications in food and beverages as an acidifier and flavor enhancer as well as in personal care products as a pH adjustive agent, a moisturizing agent etc. [16,17]. Levulinic acid is a chemical building block for a wide variety of other compounds and is used among with its derivatives, like sodium levulinate in cosmetics and personal care products, fragrances, cleaning products, as well as in the pharmaceutical and food industry [18]. ...
In this work, a greener approach for the extraction of Greek propolis using ultrasound-assisted extraction method in combination with Natural Deep Eutectic Solvents (NADES) is presented. Propolis is a natural material of outmost interest as it possesses various biological and pharmacological activities and is therefore used for the manufacturing of extracts useful to various fields, such as pharmaceutics, cosmetics etc. Herein, five NADES were task-specifically selected as appropriate extraction solvents since they provide important assets to the final NADES-extracts, comparing to the conventionally used organic solvents. The screening study of the prepared solvents indicated the NADES L-proline/D,L-Lactic acid as the most effective medium for the raw propolis extraction due to the extract’s high total phenolic content as well as its’ significantly higher antioxidant activity. Then, the extraction using the selected NADES, was optimized by performing Experimental Design to study the effect of extraction time, propolis-to-solvent ratio and the %NADES content in the NADES-water system. All the extracts were characterized regarding their antioxidant activity and total phenolic content. The optimum NADES-extract as well as an extract derived by extraction using a conventional hydroethanolic solution were further characterized by performing LC/MS/MS analysis. The results showed that the NADES-extracts composition was similar or superior to the hydroethanolic extracts regarding the presence of valuable phytochemicals such as apigenin, naringenin etc. A disadvantage that is usually mentioned in the literature regarding the extractions using NADES is that the extracted bioactive compounds cannot be easily separated from the NADES in order to obtain dry extracts. However, this drawback can be converted to an asset as the task-specifically designed NADES that are used in this study add value to the end product and the optimum as-obtained NADES-extract has been successfully incorporated in a cosmetic cream formulation. In this work, The antioxidant activity and organoleptic characteristics of the cream formulation were also determined.
... The most precise ways to measure lactic acid involve various HPLC techniques, including ion, ion-pair, reversed-phase chromatography, and ion-exclusion [8]. Due to the difficulty of sample preparation, the requirement for costly equipment, and the need for trained workers, HPLC is not frequently utilized in ordinary practice. ...
The detection of biochemical performance and health parameters using wearable sensors have gained more attention. Lactic acid (LA) sensor was developed using the simple facile method for electrochemical detection in artificial sweat. The non-enzymatic LA sensing characteristics were assessed using cyclic voltammetry and amperometry response with a three-electrode system. The CuO nanoparticles were applied to a glassy carbon electrode (GCE) as a single-step modification using the Nafion matrix. In order to examine the CuO material used to modify the glassy carbon electrode, various analytical methods were used such as Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Visible), and X-ray powder diffraction (XRD). The minimum detectable concentration for lactic acid was found to be 0.05 × 103 mol/l. The present investigation provides an excellent pathway for the specific detection of LA biomolecule for medical purposes by a non-enzymatic approach.
... Recent studies in food science have focussed on the beneficial effects of lactic acid bacteria (LAB), which not only include enhancement of flavour, texture, and nutritional value of fermented foods, but also prevention of the growth of pathogens and spoilage microorganisms due to the production of antimicrobial compounds (Ameen & Caruso, 2017;Chen & Narbad, 2018). Besides lactic acid, they can produce other acids such as acetic and propionic, active against spoilage and pathogenic microorganisms (Mozzi, Raya, Vignolo, & Love, 2010). ...
Given the importance of lactic acid bacteria (LAB) in dairy products, this study assessed the antimicrobial properties of lactobacilli against some toxigenic Penicillium spp and pathogenic bacteria commonly found in cheese. Lactobacilli previously isolated from an artisanal Brazilian cheese (n = 32) were identified to species level by amplification and sequencing of the 16S rRNA gene and tested against Penicillium commune, Penicillium expansum, Penicillium nordicum and Penicillium roqueforti through an overlay method. The most resistant mould was P. commune-M35 and the major species that exhibited inhibition against all Penicillium spp. tested was Lactiplantibacillus plantarum. Cell free supernatants of two selected L. plantarum isolates (L119 and L49) were used to determine the antifungal and antibacterial activity using impedance and turbidimetric techniques, respectively. The antimicrobial activity showed inhibition beyond acid. Since L. plantarum-L49 and L119 have the ability to inhibit undesirable microorganisms, they could be candidates as novel protective cheese cultures.
... Lactic acid (LA) (CH 3 CH(OH)COOH) is a widely naturally occurring chiral hydroxycarboxylic acid, existing in two optical active isomeric forms. More specifically, there is the (S)-lactic acid or L (+)-lactic acid, which is the most essential one from a biological point of view, and the (R)-lactic acid or D (− )-lactic acid (Ameen and Caruso, 2017;Chen, 2010). LA has a wide range of applications such as in pharmaceutical industries, raw material in food, and as commodity chemical (Liang et al., 2014). ...
Lactic acid is a valuable compound used in several industrial processes such as polymers, emulsifiers manufacturing, pharmaceutical, and cosmetic formulations. The present study aims to evaluate the potential use of food waste to produce lactic acid through fermentation, both by indigenous microbiota and by the bio-augmentation with two lactic acid bacteria, namely Lactobacillus plantarum BS17 and Lactobacillus casei BP2. Fermentation was studied both in batch and continuously fed anaerobic reactors at mesophilic conditions and a Response Surface Methodology approach was used to optimize the bioprocess performance and determine the environmental parameters (namely pH and time) that lead to the enhancement of lactic acid production during the batch fermentation by indigenous microorganisms. Results revealed an optimum set of conditions for lactic acid production at a pH value of 6.5 and a fermentation period of 3.5 days at 37 °C. Under these conditions lactic acid production reached a value of 23.07 g/L, which was very similar to the mathematically predicted ones, thus verifying the accuracy of the experimental design. This optimum set of conditions was further employed to examine the production of lactic acid under continuous fermentation operation. Furthermore, concentrations of volatile fatty acids and ethanol were monitored and found to be relatively low, with ethanol being the dominant by-product of fermentation, indicating the presence of heterofermentative bacteria in the food wastes. A final step of downstream process was performed resulting in the successful recovery of lactic acid with purity over 90%.
... Quá trình lên men đã và đang được ứng dụng rất nhiều trong thực tiễn để sản xuất nhiều sản phẩm quan trọng phục vụ đời sống con người. Trong đó, lên men lactic là quy trình được ứng dụng nhiều nhất để tạo ra nhiều sản phẩm hữu ích ví dụ như sản xuất lactic acid và polylactic acid, sữa chua, các sản phẩm rau, củ, quả, thịt, cá muối chua [10]. Đó chính là lí do chúng tôi lựa chọn chủ đề lên men lactic trong nghiên cứu này. ...
STEM education is a teaching and learning approach that integrates all four disciplines (science, technology, engineering, and mathematics) into a single. STEM education gives students opportunities to see the connection between the content they are studying and the application of that content in the real-world. However, this is a new teaching philosophy that is not widely applied for teaching in Vietnam. In order to make STEM education become familiar with Biology teachers, in the present study we suggest 8 steps for preparing a biological subject and 7 steps for teaching the prepared subject oriented STEM education. We hope that this paper will be usefull for Vietnamese teachers, particularly teachers in Biology.
... Thus, the contribution of DLA in the PLA and other composites is credited with the structural stabilization and mechanical strength improvement. In addition to the polymer industry, DLA possess much wider applications in the other sectors of moderate economy like probiotics [10], animal nutrition [11], and food additives [12]. Traditional chemical methods like oxidation of glycerol/fatty acids into lactic acid yield racemic mixture of both D and L isomers in equal proportion at a cost of greater energy demand for fossil fuels [13]. ...
Valorization of cassava fibrous waste by lactic acid bacteria (LAB) into D-lactic acid (DLA) may assuage the massive supply chain for the synthesis of alternative bioplastics such as PLA. This investigation aims at developing a potential LAB cell factory say Lactobacillus delbrueckii, to synthesize DLA in a cost-effective biological route utilizing second-generation agricultural feedstock. Along with CFWEH (20 g/L), other complex nitrogen sources and yeast extract (YE)-based medium yielded 17.75 g/L of DLA. Further optimization based on one factor at a time approach (OFAT), YE at 5 g/L was found to be optimal for DLA production. At different initial CFWEH concentrations from 20 to 120 g/L, kinetic modeling of biomass and DLA formation and CFWEH consumption was carried out by weighted-average least square method. Predicted parameters show that the inhibitory concentration for substrate was above 99 g/L, also inhibition due to DLA synthesis occurred as high as 59 g/L for 120 g/L substrate loading. This research finding offers the knowledge of kinetic parameters, its transformation into operational parameters, which would be helpful for sustainable synthesis of DLA.
... This compound can be found in milk, dairy products, and many other fermented food products (pickled vegetables, jams, frozen desserts). This natural food additive is used e.g. as a preservative, pH regulator, flavor, solvent, and gelling agent (Ali, Anjum & Zahoor, 2009;Ameen & Caruso, 2017). Studies have demonstrated that BSG hydrolysate can be used as a substrate for lactic acid production by Lactobacillus delbrueckii, Lactobacillus pentosus, or Lactobacillus rhamnosus NBRC14710 (Cruz et al., 2007;Shindo & Tachibana, 2004). ...
Beer is the most popular low-alcohol beverage consumed in large amounts in many countries each year. The brewing industry is an important global business with huge annual revenues. It is profitable and important for the economies of many countries around the world. The brewing process involves several steps, which lead to fermentation of sugars contained in malt and conversion thereof into alcohol and carbon dioxide by yeasts. Beer brewing generates substantial amounts of by-products. The three main brewing industry wastes include brewer's spent grain, hot trub, and residual brewer's yeast. Proper management of these wastes may bring economical benefits and help to protect the environment from pollution caused by their excessive accumulation. The disposal of these wastes is cumbersome for the producers, however they are suitable for reuse in the food industry. Given their composition, they can serve as a low-cost and highly nutritional source of feed and food additives. They also have a potential to be a cheap material for extraction of compounds valuable for the food industry and a component of media used in biotechnological processes aimed at production of compounds and enzymes relevant for the food industry.
Tarihçe ve Gıda Mikrobiyolojisinin Gelişimi Aysun ORAÇ Gıdalarda Bulunan Mikroorganizmaların Özellikleri Şebnem ÖZTÜRKOĞLU BUDAK Ceren AKAL Gıdalardaki Önemli Mikroorganizma Grupları Kübra ERYAŞAR ÖRER Ercan SARICA Gıdalarda Bulunan Mikroorganizmaların Kaynakları Ezgi TELLİ Yusuf BİÇER Gıdalarda Mikrobiyal Gelişimi Etkileyen Faktörler Hale İnci ÖZTÜRK Gıdalarda Mikrobiyal Gelişme Kinetiği Sencer BUZRUL Starter Kültürler ve Gıdaların Fermentasyonunda Kullanılan Mikroorganizmalar Enes DERTLİ Fatma Nur DEMİRBAŞ Probiyotikler ve Yeni Nesil Probiyotikler Talha DEMİRCİ Mikrobiyal Orijinli Gıda Biyokoruyucuları Çiğdem KONAK GÖKTEPE Mikrobiyal Orijinli Gıda Bileşenleri Mehmet YÜKSEL Gıda Mikroorganizmalarının Tespiti ve TanımlanmasındaKullanılan Yöntemler Onur BULUT Gıdalarda Bozulmaya Neden Olan Mikroorganizmalar Ayça GEDİKOĞLU Hale İnci ÖZTÜRK Gıda Kaynaklı Mikrobiyal Hastalıklar Aysun ORAÇ Gıdalarda Mikrobiyal İnaktivasyon Sencer BUZRUL
Fungi provide ecological and environmental services to humans, as well as health and nutritional benefits, and are vital to numerous industries. Fermented food and beverage products from fungi are circulating in the market, generating billions of USD.
However, the highest potential monetary value of fungi is their role in blue carbon trading because of their ability to sequester
large amounts of carbon in the soil. There are no conclusive estimates available on the global monetary value of fungi, primarily because there are limited data for extrapolation. This study outlines the contribution of fungi to the global economy and provides a first attempt at quantifying the global monetary value of fungi. Our estimate of USD 54.57 trillion provides a starting point that can be analysed and improved, highlighting the significance of fungi and providing an appreciation of their value. This paper identifies the different economically valuable products and services provided by fungi. By giving a monetary value to all important fungal products, services, and industrial applications underscores their significance in biodiversity and conservation. Furthermore, if the value of fungi is well established, they will be considered in future policies for effective ecosystem management.
Degradation of the mycobacterial complex containing mycolic acids (MAs) by natural bioactive compounds is essential for producing safe and value-added foods with therapeutic activities. This study aimed to determine the degradation efficiency of natural organic acid extracts (i.e., citric, malic, tartaric, and lactic), quadri-mix extract from fruits and probiotics (i.e., lemon, apple, grape, and cell-free supernatant of Lactobacillus acidophilus), and synthetic pure organic acids (i.e., citric, malic, tartaric, and lactic), against MA in vitro in phosphate buffer solution (PBS) and Karish cheese models. The degradation effect was evaluated both individually and in combinations at different concentrations of degradants (1, 1.5, and 2%) and at various time intervals (0, 6, 12, 24, and 48 h). The results show that MA degradation percentage recorded its highest value at 2% of mixed fruit extract quadri-mix with L. acidophilus and reached 99.2% after 48 h both in PBS and Karish cheese, unlike other treatments (i.e., citric + malic + tartaric + lactic), individual acids, and sole extracts at all concentrations. Conversely, organic acid quadri-mix revealed the greatest MA degradation% of 95.9, 96.8, and 97.3% at 1, 1.5, and 2%, respectively, after 48 h. Citric acid was more effective in MA degradation than other acids. The fruit extract quadri-mix combined with L. acidophilus-fortified Karish cheese showed the highest sensorial characteristics; hence, it can be considered a novel food-grade degradant for MA and could be a promising biocontrol candidate against Mycobacterium tuberculosis (Mtb) in food matrices.
Lactic acid is a high-value-added chemical with large production, which is used in many industries including the production of pyruvic and acrylic acids. Lactic acid is largely obtained from the oxidation of glycerol, which is a prevalent by-product of biodiesel production. However, the oxidation of glycerol to lactic acid requires harsh reaction conditions such as high temperature and pressure as well as the use of a hefty strong base. In the presence of suitable catalysts, the production of lactic acid from glycerol can be achieved under mild conditions with 1 equivalent base per mole of glycerol. Herein, we review the reports of the catalytic conversion of glycerol to lactic acid in an aqueous alkaline medium considering the reaction conditions, catalytic activity for glycerol conversion and selectivity for lactic acid. We start first with the reports on the use of homogeneous catalysts that have high catalytic activity but miserable recovery. Next, we discuss the employment of colloidal metal(0) nanoparticles as catalysts in glycerol oxidation. The papers on the use of supported metal(0) nanoparticles are reviewed according to the type of support. We then review the polymetallic and metal/metal oxide nanocatalysts used for the conversion of glycerol to lactic acid in an alkaline medium. The catalysts tested for glycerol conversion to lactic acid without any additional bases are also discussed to emphasize the importance of a strong base for catalytic performance. The proposed mechanisms of glycerol oxidation to lactic acid in the presence or absence of catalysts as well as for the formation of side products are discussed. The available experimental kinetics data are shown to fit the mechanism with the formation of glyceraldehyde from glycerol alkoxide as the rate-determining step.
Acids have been widely used in food processing to enhance flavour, prevent the deterioration of food and eliminate or retard the growth of foodborne pathogens. The inhibition of foodborne pathogens can be due to disruption of outer structure of the microbial cell, inhibition of metabolic processes, or damage to the macro-cellular components such as nucleic acids and enzymes. However, some foodborne pathogens might survive, adapt, and develop tolerance to acid stress via a wide range of molecular mechanisms. Various intrinsic and extrinsic factors can affect the development of acid tolerance responses. In this chapter, we reviewed the acids commonly used in the food industry. We also discussed different modes of action of acids, the tolerance response induced in foodborne pathogens after being exposed to acid, and the various factors affecting the development of acid tolerance response.
The extraction of valuable phytochemicals from natural sources is an important and constantly evolving research area. Zingiber officinale Roscoe (ginger) contains high amounts of bioactive phytochemicals, which are desirable due to their significant properties. In this work, the ability of different natural deep eutectic solvents (NaDESs) to serve as green solvents for the preparation of high added value extracts from ginger is explored, in combination with ultrasound assisted extraction. The method was optimized by applying a response surface methodology using the NaDES Bet/La/W (1:2:2.5). Three independent variables, namely the extraction time, ultrasound power and NaDES-to-dry-ginger ratio, were investigated by employing a 17-run three-level Box–Behnken Design (BBD) in order to study the correlation between the extraction conditions and the quality of the obtained extracts. The optimum conditions (in order to achieve simultaneously maximum total phenolic content and antioxidant activity), were found to be 23.8 min extraction time, 60 Watt and NaDES/ginger 25:1 w/w. In the optimum conditions the DPPH radical scavenging ability of the extracts was found to reach IC50 = 18.16 mg/mL after 120 min, whereas the TPC was 20.10 ± 0.26 mg GAE/g of dry ginger. The green methodology was also compared with the extraction using conventional solvents. All the obtained extracts were evaluated for their antioxidant activity and their total phenolic content, while the extract derived by the optimum extraction conditions was further investigated for its ability to bind to calf thymus DNA (ctDNA).
Hand in hand with the flourish of the biodiesel industry, glycerol (GLY) as an inconvenient by-product has generated environmental and sustainability concerns. Devising measures for efficient transformation of GLY into value-added products is a promising solution. In this contribution, the transformation of GLY to lactic acid (LA) as a valuable chemical was investigated in a continuous process for industrial applications. In this regard, a catalytic method using heterogeneous Cu nanoparticles in NaOH solution was studied in a microreactor by a CFD simulation. A seven-inlet micromixer comprising an optimized mixing unit was incorporated for uniform distribution of the species. The effects of various parameters upon the process performance were considered and the optimum points were determined. Also, the extent of the influence of each variable on LA yield was evaluated using sensitivity analysis techniques. While higher LA yield could be obtained at extreme scenarios, optimum values of the Re and temperature for obtaining the maximum performance under sensible operating conditions were determined to be 0.108 and 510.1 K which led to the optimum yields of 67.8% and 59.5%, respectively. Moreover, the sensitivity analysis revealed that the molar ratio of OH⁻/GLY and temperature were the most and least significant parameters, respectively.
Only one crystalline phase of the metabolite, L -Lactic acid (LLA), has been described since its isolation from sour milk as long ago as 1780. Herein, we report the structures of...
All products present in a company can be a source of danger for workers and the environment, and this statement is particularly true for incoming products, manufactured products, waste, and chemicals. A large number of chemical products can become potentially dangerous and be sometimes at the origin of notable accidents or serious diseases. All companies, from the largest to the most modest enterprise, must take this aspect into consideration, including the sector of foods and beverages. Seven million people worldwide die each year because of certain diseases that are favoured by indoor and outdoor air pollution. This chapter is a general introduction to chemicals in the industry (food and non-food sectors) in relation to their importance, chemical risks, occupational exposure limits, pollution events, and toxicological evaluations.
Persons employed in microbiological laboratories constitute a group of employees who are particularly exposed to the wide spectrum of harmful biological agents. The work of a microbiologist requires extreme caution, as well as compliance with research procedures and health and safety regulations. The direct threat to the health of employees of microbiological laboratories are, among others, microbiological waste. Proper disposal as well as inactivation of these wastes has an impact on the quality of air inside laboratories. Therefore, it is extremely important to monitor the microbiological quality of air in laboratory rooms. This paper presents the results of measurements of concentrations of microbiological air pollutants in a laboratory storing and utilizing microbiological waste, located in the SilesianVoivodship. Bioaerosol samples were collected using a 6-stage Andersen impactor, with cut-off diameters of 7.0, 4.7, 3.3, 2.1, 1.1 and 0.65 μm (Thermo Fisher Scientific, Waltham, MA, USA). It has been shown that exposure to biological agents does not pose a direct threat to the health of workers in the laboratory under test, however, long-term inhalation of biological aerosols in this room may cause adverse health effects, especially in people sensitive to this type of air pollution. In order to ensure proper air quality in the analyzed laboratory, it is necessary to haveadequate ventilation and intensive ventilation of the room.Keywords: bioaerosol, bacterial aerosol, microbiological waste, indoor air quality (IAQ).
Osoby zatrudnione w laboratoriach mikrobiologicznych stanowią grupę pracowników, która w sposób szczególny narażona jestna działanie szerokiego spektrum szkodliwych czynników biologicznych. Praca mikrobiologa wymaga niezwykle dużej ostrożności, a także przestrzegania procedur badawczych oraz przepisów BHP. Bezpośrednie zagrożenie dla zdrowia pracowników laboratoriów mikrobiologicznych stanowią m.in. odpady mikrobio-logiczne. Odpowiednia utylizacja, a także inaktywacja tychże odpadów ma wpływ na jakość powietrza wewnątrz laboratoriów. Stąd też niezwykle istotne jest prowadzenie monitoringu jakości mikrobiologicznej powietrza w pomieszczeniach laboratoryjnych. W niniejszej pracy przedstawiono wyniki pomiarów stężeń zanieczyszczeń mikrobiologicznych powietrza wlaboratorium składującym i utylizującym odpady mikrobiologiczne, znajdującym się na terenie województwa śląskiego. Próbki bioaerozoli pobierano przy użyciu 6-stopniowego impaktora Andersena, ze średnicami odcięcia 7.0, 4.7, 3.3, 2.1, 1.1 i 0.65 μm (Thermo Fisher Scientific, Waltham, MA, USA). Wykazano,iż narażenie na czynniki biologiczne nie stwarza bezpośredniego zagrożenia dla zdrowia pracowników badanego laboratorium, jednak długotrwała inhalacja aerozoli biologicznych w tym pomieszczeniu może spowodować niekorzystne skutki zdrowotne, zwłaszcza u osób wrażliwych na tego typu zanieczyszczenia powietrza. W celu zapewnienia należytej jakości powietrza w analizowanym laboratorium niezbędna jest jego odpowiednia wentylacja oraz intensywne wietrzenie pomieszczenia.
Species of lactic
acid bacteria (LAB) represent as potential microorganisms and have been widely
applied in food fermentation worldwide. Milk fermentation process has been
relied on the activity of LAB, where transformation
of milk to good quality of fermented milk products made possible. The presence of LAB in milk fermentation can be
either as spontaneous or inoculated starter cultures. Both of them are
promising cultures to be explored in fermented milk manufacture. LAB have a role in milk
fermentation to produce acid which is important as preservative agents and generating flavour of the products. They also produce exopolysaccharides
which are essential as texture formation. Considering the existing reports on several health-promoting properties as
well as their generally recognized as safe
(GRAS) status of LAB, they can be widely used in the developing of new
fermented milk products.
Bacteriocins are a kind of ribosomal synthesized antimicrobial peptides produced by bacteria, which can kill or inhibit bacterial strains closely-related or non-related to produced bacteria, but will not harm the bacteria themselves by specific immunity proteins. Bacteriocins become one of the weapons against microorganisms due to the specific characteristics of large diversity of structure and function, natural resource, and being stable to heat. Many recent studies have purified and identified bacteriocins for application in food technology, which aims to extend food preservation time, treat pathogen disease and cancer therapy, and maintain human health. Therefore, bacteriocins may become a potential drug candidate for replacing antibiotics in order to treat multiple drugs resistance pathogens in the future. This review article summarizes different types of bacteriocins from bacteria. The latter half of this review focuses on the potential applications in food science and pharmaceutical industry.
Control of biofilms formed by microbial pathogens is an important subject for medical researchers, since the development of biofilms on foreign body surfaces often causes biofilm-associated infections in patients with indwelling medical devices. The present study examined the effects of different kinds of bacteriocins, which are ribosomally-synthesized antimicrobial peptides produced by certain bacteria, on biofilms formed by a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA). The activities and modes of action of three bacteriocins with different structures (nisin A, lacticin Q, and nukacin ISK-1) were evaluated. Vancomycin, a glycopeptide antibiotic used in the treatment of MRSA infections, showed bactericidal activity against planktonic cells, but not against biofilm cells. Among the tested bacteriocins, nisin A showed the highest bactericidal activity against both planktonic cells and biofilm cells. Lacticin Q also showed bactericidal activity against both planktonic cells and biofilm cells, but its activity against biofilm cells was significantly lower than that of nisin A. Nukacin ISK-1 showed bacteriostatic activity against planktonic cells and did not show bactericidal activity against biofilm cells. Mode-of-action studies indicated that pore formation leading to ATP efflux is important for the bactericidal activity against biofilm cells. Our results suggest that bacteriocins that form stable pores on biofilm cells are highly potent for the treatment of MRSA biofilm infections.
This work describes a simple, rapid, and reliable HPLC method for the determination of organic acids in fermented shrimp waste. Lactic, acetic and citric acids were quantified by HPLC with UV detection, on a 250×4.6 mm Extrasil ODS 5-μm column, mobile phase was ultrapure water adjusted with metaphosphoric acid to pH=2.1, flow rate 0.6 mL/min, column temperature 30 °C, and detection wavelength 210 nm. Under these conditions, the recovery (97.5 %) and the method repeatability (RSD=6.2 %) for lactic acid were of satisfying quality. Organic acids can preserve the quality and nutritive value of fermented shrimp waste.
The microbial profile of cheese is a primary determinant of cheese quality. Microorganisms can contribute to aroma and taste defects, form biogenic amines, cause gas and secondary fermentation defects, and can contribute to cheese pinking and mineral deposition issues. These defects may be as a result of seasonality and the variability in the composition of the milk supplied, variations in cheese processing parameters, as well as the nature and number of the non-starter microorganisms which come from the milk or other environmental sources. Such defects can be responsible for production and product recall costs and thus represent a significant economic burden for the dairy industry worldwide. Traditional non-molecular approaches are often considered biased and have inherently slow turnaround times. Molecular techniques can provide early and rapid detection of defects that result from the presence of specific spoilage microbes and, ultimately, assist in enhancing cheese quality and reducing costs. Here we review the DNA-based methods that are available to detect/quantify spoilage bacteria, and relevant metabolic pathways in cheeses and, in the process, highlight how these strategies can be employed to improve cheese quality and reduce the associated economic burden on cheese processors.
A great number of Gram (+) and Gram negative (-) bacteria produce during their growth, substances of protein structure (either proteins or polypeptides) possessing antimicrobial activities, called bacteriocins. Although bacteriocins could be categorized as antibiotics, they are not. The major difference between bacteriocins and antibiotics is that bacteriocins restrict their activity to strains of species related to the producing species and particularly to strains of the same species, antibiotics on the other hand have a wider activity spectrum and even if their activity is restricted this does not show any preferential effect on closely related strains. In addition, bacteriocins are ribosomally synthesized and produced during the primary phase of growth, though antibiotics are usually secondary metabolites. Among the Gram (+) bacteria, lactic acid bacteria (LAB) especially, Lactobacilli have gained particular attention nowadays, due to the production of bacteriocins. These substances can be applied in the food industry as natural preservatives. The use of LAB and of their metabolic products is generally considered as safe (GRAS, Grade One). The application of the produced antimicrobial compounds as a natural barrier against pathogens and food spoilage caused by bacterial agents has been proven to be efficient. Nisin is the only bacteriocin that has been officially employed in the food industry and its use has been approved worldwide. Bacteriocins can be applied on a purified or on a crude form or through the use of a product previously fermented with a bacteriocin producing strain as an ingredient in food processing or incorporated through a bacteriocin producing strain (starter culture).
Fermented foods are among the food products more often complained of having caused episodes of biogenic amines (BA) poisoning. Concerning milk-based fermented foods, cheese is the main product likely to contain potentially harmful levels of BA, specially tyramine, histamine, and putrescine. Prompted by the increasing awareness of the risks related to dietary uptake of high biogenic amine loads, in this review we report all those elaboration and processing technological aspects affecting BA biosynthesis and accumulation in dairy foods. Improved knowledge of the factors involved in the synthesis and accumulation of BA should lead to a reduction in their incidence in milk products. Synthesis of BA is possible only when three conditions converge: (i) availability of the substrate amino acids; (ii) presence of microorganisms with the appropriate catabolic pathway activated; and (iii) environmental conditions favorable to the decarboxylation activity. These conditions depend on several factors such as milk treatment (pasteurization), use of starter cultures, NaCl concentration, time, and temperature of ripening and preservation, pH, temperature, or post-ripening technological processes, which will be discussed in this chapter.
Fermented dairy products have long been an important component of nutritional diet. Historically, fermentation proc-ess involved unpredictable and slow souring of milk caused by the organisms inherently present in milk. However, modern microbiological processes have resulted in the production of different fermented milk products of higher nutri-tional value under controlled conditions. These products represent an important component of functional foods, and intense research efforts are under way to develop dairy products into which probiotic organisms are incorporated to make them more valuable. This article provides an overview of the different starter cultures and health benefits of fer-mented dairy products, which can be derived by the consumers through their regular intake.
Sugar concentration from sugarcane juice and yeast autolysate increased lactic acid production more than the other agro-industrial substrates tested. The concentrations of these two components were further optimized using the Plackett-Burman design and response surface method. A second-order polynomial regression model estimated that a maximal lactic acid production of 66.11 g/L would be obtained when the optimal values of sugar and yeast autolysate were 116.9 and 44.25 g/L, respectively. To validate the optimization of the medium composition, studies were carried out using the optimized conditions to confirm the result of the response surface analysis. After 48 h, lactic acid production using the shake-flask method was at 60.2 g/L.
This paper examines the synergistic action of carbon dioxide and nisin on Listeria monocytogenes Scott A wild-type and nisin-resistant (Nisr) cells grown in broth at 4°C. Carbon dioxide extended the lag phase and decreased the specific growth rate of both strains,
but to a greater degree in the Nisrcells. Wild-type cells grown in 100% CO2 were two to five times longer than cells grown in air. Nisin (2.5 μg/ml) did not decrease the viability of Nisr cells but for wild-type cells caused an immediate 2-log reduction of viability when they were grown in air and a 4-log reduction
when they were grown in 100% CO2. There was a quantifiable synergistic action between nisin and CO2 in the wild-type strain. The MIC of nisin for the wild-type strain grown in the presence of 2.5 μg of nisin per ml increased
from 3.1 to 12.5 μg/ml over 35 days, but this increase was markedly delayed for cultures in CO2. This synergism between nisin and CO2 was examined mechanistically by following the leakage of carboxyfluorescein (CF) from listerial liposomes. Carbon dioxide
enhanced nisin-induced CF leakage, indicating that the synergistic action of CO2 and nisin occurs at the cytoplasmic membrane. Liposomes made from cells grown in a CO2 atmosphere were even more sensitive to nisin action. Liposomes made from cells grown at 4°C were dramatically more nisin
sensitive than were liposomes derived from cells grown at 30°C. Cells grown in the presence of 100% CO2 and those grown at 4°C had a greater proportion of short-chain fatty acids. The synergistic action of nisin and CO2 is consistent with a model where membrane fluidity plays a role in the efficiency of nisin action.
A purified preparation of the nontoxic antimicrobial peptide, nisin (AMBICIN N), was used in the formulation of a germicidal sanitizer suitable for use on cow teats. The germicidal activity of the formulation against mastitis pathogens was measured on teat skin of live cows. The nisin-based formulation gave a mean log reduction of 3.90 against Staphylococcus aureus and 4.22 log reduction against Escherichia coli after exposure for 1 min to the germicide. This activity was comparable with that exhibited by a 1% iodophor teat dip but was significantly greater than that exhibited by the .1 and .5% iodophors and by the .5% chlorhexidine digluconate teat dips. The nisin-based formulation showed little or no potential for skin irritation after multiple application to skin, but iodophor and chlorhexidine digluconate teat dips showed significant potential for skin irritation in comparable studies.
This article details the basic concepts and the terminology of industrial fermentations. The two principal fermentation schemes - submerged culture and solid-state cultivation - are discussed. Operational practices such as batch, fed batch, and continuous culture are described. Common types of industrial fermenters - bubble columns, stirred tanks, airlift systems, trickle or packed beds, fluidized beds, and solid-state culture devices - are detailed. Factors that influence fermentations are outlined.
Although this chapter is devoted to milk and other dairy products, it begins with a discussion of fermentation because of the importance of this process to dairy products.
The formation of volatile compounds in fresh cheese by 32 wild strains of Lactococcus lactis was investigated, and compared to volatile compounds formed by six collection strains of lactococci. Hierarchical cluster analysis of the relative abundances of volatile compounds determined by GC-MS was used for the classification of strains. Seven compounds (1-propanol, 2-propanol, 2-methyl propanol, 3-methyl butanol, 3-methyl butanal, 2,3-heptanedione and isoamyl acetate) separated the strains into two main branches, one of which contained all collection strains. The standard addition method was used to quantify these seven compounds in cheeses. All but 1-propanol and 2-propanol were at levels exceeding their respective odour thresholds. Sensory evaluation by a trained panel was carried out on cheeses. Abnormal odours were detected in cheeses made with 27 out of the 32 wild L. lactis strains. Odour quality of cheeses was positively correlated to 2-propanol, α-pinene and descriptors butter, yoghurt and fresh cheese, whereas odour intensity was positively correlated to 13 volatile compounds (six alcohols, two aldehydes, four ketones and one ester) and descriptors branched-chain volatiles, fruity and roasted hazel nuts.
The presence of esterolytic activities in the intracellular extract of Lactococcus lactis subsp. lactis NCDO 763 was investigated. One major activity hydrolyzing β-naphthyl butyrate was detected. This activity was purified to homogeneity. The enzyme was a homotrimer; the molecular mass of the monomer was estimated by SDS-PAGE to be 29kDa; by mass spectrometry, it was 29655 ± 30 Da. The pI of the molecule was 4.5. The enzyme was active on para-nitrophenyl esters from C2 to C12 and on ortho-nitrophenyl butyrate, with a maximum activity on p-nitrophenyl butyrate. The optimum activity on this substrate was found at pH 8.0 and at 55 °C; kinetic parameters for this substrate were measured at 55 °C and were KM = 0.11 mM and Vmax = 8.17 μmol min−1. The enzyme was strongly inhibited by Pefabloc, diisopropyl fluoro-phosphate and 3,4-dichloroisocoumarin, demonstrating that it was a serine esterase. The amino-terminus of the enzyme was sequenced. The role of this enzyme in cheese ripening is discussed.
Metabolism of Lactobacillus bulgaricus ATCC 12278 and Lactobacillus belveticus ATCC 10797, associated with pink dis- coloration of cheese, was compared to that of Lactobacillus lactis ATCC 11061 which never caused the defect. Hydrogen peroxide was produced in various media by L. lactis but did not accumulate during growth of the other two strains. Cell suspensions of L. lactis consumed oxygen rapidly in the presence of glucose and lactate; the other strains were moder- ately active. Added tyrosine increased the ultimate intensity of pink discoloration in Romano cheese made with Lactobacillus bulgaricus and Lactobacillus belveticus; ascorbate, pyruvate, and fumarate ac- celerated rate of development of the defect. These additives did not induce the defect in cheese made with Lactobacillus lactis or Streptococcus tbermopbilus strain Mc which never were associated with the defect. Sodium thioglycolate and glutathione prevented the discolora- tion.
Solutions are urgently required for the growing number of infections caused by antibiotic-resistant bacteria. Bacteriocins, which are antimicrobial peptides produced by certain bacteria, might warrant serious consideration as alternatives to traditional antibiotics. These molecules exhibit significant potency against other bacteria (including antibiotic-resistant strains), are stable and can have narrow or broad activity spectra. Bacteriocins can even be produced in situ in the gut by probiotic bacteria to combat intestinal infections. Although the application of specific bacteriocins might be curtailed by the development of resistance, an understanding of the mechanisms by which such resistance could emerge will enable researchers to develop strategies to minimize this potential problem.
Lactic acid, the most widely occurring hydroxycarboxylic acid, is an enigmatic chemical. It was discovered a long time ago and its use in food preservation and processing and as a specialty chemical has grown over the years with current production of about 120 000 t yr−1. Its potential as a major chemical feedstock, derived from renewable carbohydrates by sustainable technologies, to make plastics, fibers, solvents and oxygenated chemicals, had also been recognized. Recently, new technologies have emerged that can overcome major barriers in separations and purification and processing. Advances in electrodialysis (ED) and bipolar membranes and one particular process configuration termed the `double ED' process, a specific combination of desalting ED followed by `water-splitting' ED with bipolar membranes, has given very promising results, showing a strong potential for an efficient and economic process for recovery and purification of lactic acid without generating a salt waste. For the production of polymers, several advances in catalysts and process improvements have occurred in the technology to produce dilactide and its polymerization to produce plastics and fibers by Natureworks LLC, which is the leader in lactic polymer technology and markets. Other advances in esterification technology with pervaporation and development of biosolvent blends also have a high potential for `green' solvents in many applications. Recently, a considerable amount of pioneering effort in technology, product development and commercialization has been expended by several companies. To overcome the barriers to replace long-established petroleum-derived products, further real support from consumer, regulatory and government organizations is also needed. Copyright © 2006 Society of Chemical Industry
To determine why reduced-fat (7% fat) Cheddar cheese does not develop full Cheddar flavour, volatiles from four manufactures of full-fat Cheddar (conventional and made by an ultrafiltration process) and reduced-fat Cheddars (1.5 and 2% salt, also made by the ultrafiltration process) were compared at intervals over a 26-week period of maturation. Molecular distillates and headspace volatiles were examined by gas chromatography/mass spectrometry. Headspace volatiles were also analysed for sulphur compounds by gas chromatography with a flame photometric detector. Full-fat cheeses consistently had more flavour than reduced-fat cheeses. For each type of cheese the rate of production of dimethyl sulphide became progressively less as the season advanced from lush spring pastures to dry summer pastures. Overall, there was a steady increase with time of maturation in the level of H2S while the concentration of methanethiol rose for the first 8 weeks and then levelled off. The concentration of sulphur compounds in the headspaces was greater generally for the reduced-fat cheeses than for the full-fat cheeses, but when partition coefficients are taken into consideration, the actual concentration of methanethiol in the reduced-fat cheese was about half that in the fullfat cheese. There was a correlation of 0.82 between the intensity of Cheddar flavour and the concentration of methanethiol in the cheeses, indicating that a lack of methanethiol in the reduced-fat cheeses was a major contributor to their lack of flavour. A combination of methanethiol and decanoic acid or butanoic acid in all cheeses gave a better correlation with Cheddar flavour than methanethiol alone.
A high-performance liquid chromatography method was developed for the simultaneous determination of dehydroascrobic, ascorbic, malic, citric, and oxalic acids in fruits, vegetables, and beverages. Separation of these compounds was accomplished by coupling reversed-phase and organic acid columns using 2% KH2PO4 (pH 2.3) as mobile phase with a flow rate of 0.4 mL/min. Detection was performed at 215 and 260 nm using a diode array detector interfaced with portable integrators and a chromatography data system. Selected fresh fruits, vegetables, and commercial orange juices were analyzed using this method.
Yogurt is a basic dairy product that has been consumed for centuries as a part of the diet, even when its beneficial effects were neither fully known nor scientifically proven. With time, yogurt has been continuously modified to obtain a product with better appeal and nutritional effects. The flavor components of yogurt are affected because of these modifications. The present review article is focused on the influence of the different parameters and modifications on aroma and taste components of yogurt. Extensive work has been done to explore the effect of chemical components as well as the microbial, processing, and storage aspects. The popularity of yogurt as a food component depends mainly on its sensory characteristics, of which aroma and taste are most important. This review also outlines the effects of the different modifications attempted in the composition of yogurt.
Composition, nutritional value, and other intrinsic factors make milk and milk products attractive for the growth of a variety of microorganisms. Due to microbiological food safety implications, the dairy industry is a highly regulated food industry in the United States, as well as throughout the developed world. In the United States, strict pasteurization and sanitation regulations are based upon the Grade A Pasteurized Milk Ordinance (PMO) which is adopted into state and local regulations, and is the regulatory standard under the National Conference on Interstate Milk Shipments a cooperative state/federal program. This chapter provides an overview of dairy product microbiology as well as sanitation, testing, and processing considerations related to these microorganisms. Microbiological contamination of milk and milk products can occur from a variety of sources. In addition, other factors will impact the growth of certain microorganisms, and contribute to the level of microorganisms in raw and/or pasteurized milk products.
The wide array of available dairy foods challenges the microbiologist, engineer, and technologist to find the best ways to
prevent the entry of microorganisms, destroy those that do get in along with their enzymes, and prevent the growth and activities
of those that escape processing treatments. Troublesome spoilage microorganisms include aerobic psychrotrophic Gram-negative
bacteria, yeasts, molds, heterofermentative lactobacilli, and spore-forming bacteria. Psychrotrophic bacteria can produce
large amounts of extracellular hydrolytic enzymes, and the extent of recontamination of pasteurized fluid milk products with
these bacteria is a major determinant of their shelf life. Fungal spoilage of dairy foods is manifested by the presence of
a wide variety of metabolic by-products, causing off-odors and flavors, in addition to visible changes in color or texture.
Antifungal activity of eleven selected bacterial cultures and five microfungi in different phases of their growth were investigated in respect of their activity against Penicillium expansum (Link.) Thom. The dynamics of linear growth and mycelium mass growth as well as the ability to produce patulin were examined. The results indicate that two bacteria Bacillius megaterium and Bacillus subtilis species and three strains of the genus Lactobacillus: L. casei, L. delbrueckii ssp. bulgaricus, and L. lactis ssp. cremoris are active against Penicillium expansum.
Over the last 2 decades, a variety of bacteriocins, produced by bacteria that kill or inhibit the growth of other bacteria, have been identified and characterized biochemically and genetically. This review article focuses on the ecology of bacteriocins, determination of bacteriocin activity, biosynthesis of bacteriocins, and mode of action. Bacteriocin production and modeling are discussed in the article. Nisin is discussed in some detail in this article since it is currently the only purified bacteriocin approved for food use in the U.S. and has been successfully used for several decades as a food preservative in more than 50 countries. For activity spectra and food applications, the review article focuses primarily on class I and class IIa bacteriocins produced by lactic acid bacteria (LAB) given their development as food preservatives.
Consumer demand for fresh-like products with little or no degradation of nutritional and organoleptic properties has led to the study of new technologies in food preservation. Pulsed electric fields (PEF) is a nonthermal preservation method used to inactivate microorganisms mainly in liquid foods. Microorganisms in the presence of PEF suffer cell membrane damage. Nisin is a natural antimicrobial known to disrupt cell membrane integrity. Thus the combination of PEF and nisin represents a hurdle for the survival of Listeria innocua in liquid whole egg (LWE). L. innocua suspended in LWE was subjected to two different treatments: PEF and PEF followed by exposure to nisin. The selected frequency and pulse duration for PEF was 3.5 Hz and 2 μs, respectively. Electric field intensities of 30, 40 and 50 kV/cm were used. The number of pulses applied to the LWE was 10.6, 21.3 and 32. The highest extent of microbial inactivation with PEF was 3.5 log cycles (U) for an electric field intensity of 50 kV/cm and 32 pulses. Treatment of LWE by PEF was conducted at low temperatures, 36°C being the highest. Exposure of L. innocua to nisin following the PEF treatment exhibited an additive effect on the inactivation of the microorganism. Moreover, a synergistic effect was observed as the electric field intensity, number of pulses and nisin concentration increased. L. innocua exposed to 10 IU nisin/ml after PEF exhibited a decrease in population of 4.1 U for an electric field intensity of 50 kV/cm and 32 pulses. Exposure of L. innocua to 100 IU nisin/ml following PEF resulted in 5.5 U for an electric field intensity of 50 kV/cm and 32 pulses. The model developed for the inactivation of L. innocua by PEF and followed by exposure to nisin proved to be accurate (p=0.05) when used to model the inactivation of the microorganism by PEF in LWE with 1.2 or 37 IU nisin/ml. The presence of 37 IU nisin/ml in LWE during the PEF treatment for an electric field intensity of 50 kV/cm and 32 pulses resulted in a decrease in the population of L. innocua of 4.4 U.
The prerequisites for any organism to be able to contribute to the secondary ripening processes in cheese are the availability of substrate(s), appropriate conditions for growth and enzyme activity (especially pH, salt concentration and temperature), and sufficient time to allow the biochemical reactions to take place. The role of deliberately added secondary microorganisms in the ripening of some varieties (e.g. the mould-ripened cheeses and the Emmental-type cheeses) is relatively clear. However, in many other varieties the contribution of secondary microorganisms to the development of cheese flavour during ripening remains a contentious topic. These secondary organisms may include both cultures added deliberately as adjuncts to blends of the primary acid-producing starter cultures and adventitious non-starter lactic acid bacteria (NSLAB) present as contaminants in the cheese.
A novel approach to controlling unwanted microbial adhesion in clinical environments is to inhibit the initial attachment of bacteria, rather than trying to remove them once they have adhered. Previous investigations have established that antimicrobial peptides such as nisin can adsorb to surfaces and still retain sufficient activity to inhibit pathogenic bacteria. We examined techniques of application of nisin in vitro to elucidate those most effective and practical for use on biomedical implants in vivo. Nisin adsorbed quickly on Polyvinyl chloride (PVC) suction catheter tubing, with only a slight gain in nisin activity as contact times increased from 10 s to 8 h. The activity of nisin adsorbed on PVC suction catheter tubing increased as solution concentrations increased from 0.01 to 2.0 mg/ml, and it decreased with aging in protein-free phosphate buffer for 48 h and with drying for up to 2 months. When exposed to three species of Gram-positive bacteria, nisin-treated PVC tubing demonstrated an ability to inhibit bacterial growth, while bacteria grew unchecked on catheter material that was untreated. We then examined the ability of nisin to retain its activity in vivo when placed on implants in blood vessels or the upper airway and whether nisin causes tissue reactions greater than untreated implants placed in sheep and ponies. Freshly prepared nisin was applied to Teflon® FEP intravenous catheters and to PVC tracheotomy tubes at the time of placement, using a concentration of 1.0 mg/ml and 10-s contact time. Tissue reactions in response to nisin adsorbed on intravenous catheters or tracheotomy tubes did not occur in sheep or ponies, respectively. Nisin activity was retained for more than 5 h but less than 1 week on intravenous catheters placed in the jugular veins of sheep, and the veins with short-term catheters showed fewer and less severe histologic abnormalities compared with controls, indicating a possible protective effect on vascular endothelium. Nisin activity was retained on PVC tracheotomy tubes maintained for 1–2 h in ponies, but not on tubes in place for 24 h. As the first preclinical trial of nisin-treated implantable materials, this study represents an important first step for developing the potentially broad use of protein antimicrobial films on implantable medical devices.
Most data dealing with the biopreservative activity of lactic acid bacteria (LAB) are focused on their antibacterial effects. Food spoilage by mould and the occurrence of their mycotoxins constitute a potential health hazard. Development of biological control should help improve the safety of products by controlling mycotoxin contamination. Data have actually shown that many LAB can inhibit mould growth and that some of them have the potential to interact with mycotoxins.This review summarizes these findings and demonstrates that LAB are promising biological agents for food safety.
Growth, metabolism, and bacteriocin production by seven Lactobacillus strains including five commercial probiotic strains were studied during fermentation in MRS medium and milk medium at constant pH 6.5. These strains were Lactobacillus acidophilus ACC, L. acidophilus IBB 801, L. casei Imunitas, L. casei YIT 9029, L. gasseri K7, L. johnsonii La1, and L. rhamnosus GG. Although the L. casei complex strains grew to higher cell levels than the L. acidophilus complex strains in MRS medium, monitored bacteriocin titres were higher for the L. acidophilus complex strains. L. johnsonii La1 and L. gasseri K7 grew in milk medium only when yeast extract was added. Addition of yeast extract (0.3–1.0% w/v) to milk medium enhanced both growth and bacteriocin production for all strains. Bacteriocin production was clearly observed in yeast extract supplemented milk medium for L. acidophilus IBB 801, L. johnsonii La1, and L. gasseri K7. L. acidophilus IBB 801, the only strain of dairy origin, displayed the best growth (10.5 log CFU mL−1) and bacteriocin production (3200 AU mL−1). These findings demonstrated that probiotic lactobacilli from an intestinal origin are difficult to cultivate in milk.
Antilisterial activity of nisin (Nisaplin), alone at concentrations of 400 and 800 IU/g and in combination with 2% sodium chloride was incorporated in raw buffalo meat mince. Samples of the raw meat mince were inoculated with 103 colony forming units (cfu)/g of L. monocytogenes and stored at 4°C for 16 days and at 37°C for 36 h. Initial estimates of pH, extract release volume, mesophilic and psychrophilic counts were found to be 5.74, 48 ml, 3.5×105 and 1.0×105 cfu/g of meat, respectively. The growth of L. monocytogenes in the treated groups was significantly (P<0.05) inhibited compared to the control group. The degree of inhibition increased with increasing concentration of nisin and decreasing storage temperature. Addition of 2% sodium chloride in combination with nisin increased the efficacy of nisin at both storage temperatures. The pH in the treated groups remained significantly lower (P<0.01) than in the control groups at both 4 and 37°C.
Sourdough technology is widely used; it is employed in bread making and for the production of cakes. Sourdough is characterized by a complex microbial ecosystem, mainly represented by lactic acid bacteria and yeasts, whose fermentation confers to the resulting bread its characteristic features such as palatability and high sensory quality. Investigation of the microbial composition of sourdough is relevant in order to determine the potential activities of sourdough microorganisms. This review focuses on the role of the most important group of sourdough fermenting bacteria that consists of lactobacilli; species that belong to the Lactobacillus genus are the main responsible of flavor development, improvement of nutritional quality as well as stability over consecutive refreshments of sourdough. Lactobacilli also establish some durable microbial associations. An overview of the tools for monitoring predominant species is also reported.
This paper reviews the history of the development of probiotics and the effect on the human gastrointestinal microecology. Furthermore, the application of probiotics to yogurt, commonly referred to as bio-yogurt and the effectiveness of yogurt as probiotic carrier food are also discussed. The paper also reviews the literature explaining, in essence, the concept of ‘therapeutic minimum’ levels and the importance of the survival of probiotic microorganisms in food products. The production of bio-yogurt, survival of probiotic species in yogurt during retail storage, technical considerations for incorporating probiotic microorganisms into yogurt, starter culture technology and enumeration of the probiotic organisms are also reviewed.
Food-borne fungi, both yeasts and moulds, cause serious spoilage of stored food. Moulds may also produce health-damaging mycotoxins, e.g. aflatoxins, trichothecenes, fumonisin, ochratoxin A and patulin. Consumer demands for minimally processed foods and reduced use of chemical preservatives have stimulated research on antifungal lactic acid bacteria as biopreservatives. Recently, a number of antifungal metabolites, e.g. cyclic dipeptides, phenyllactic acid, proteinaceous compounds, and 3-hydroxylated fatty acids have been isolated from lactic acid bacteria. This review summarizes these findings and suggests potential applications of antifungal lactic acid bacteria in the preservation of food and feeds.
Flavour development in dairy fermentations is the result of a series of chemical and biochemical processes during ripening. Starter lactic acid bacteria provide the enzymes involved in the formation of specific flavours. Amino acids, and in particular methionine, the aromatic and the branched-chain amino acids, are major precursors for volatile aroma compounds. The recent sequencing of complete genomes of several lactic acid bacteria (i.e. Lactococcus lactis, Lactobacillus plantarum, Streptococcus thermophilus) is beginning to provide insight into the full complement of proteins that may be involved in flavour-forming reactions, and hence the potential for formation of specific flavour compounds. Examples are given how bioinformatics tools can be used to search in genomes for essential components, such as proteinases, peptidases, aminotransferases, enzymes for biosynthesis of amino acids, and transport systems for peptides and amino acids.
Lactic acid is an industrially important product with a large and rapidly expanding market due to its attractive and valuable multi-function properties. The economics of lactic acid production by fermentation is dependent on many factors, of which the cost of the raw materials is very significant. It is very expensive when sugars, e.g., glucose, sucrose, starch, etc., are used as the feedstock for lactic acid production. Therefore, lignocellulosic biomass is a promising feedstock for lactic acid production considering its great availability, sustainability, and low cost compared to refined sugars. Despite these advantages, the commercial use of lignocellulose for lactic acid production is still problematic. This review describes the "conventional" processes for producing lactic acid from lignocellulosic materials with lactic acid bacteria. These processes include: pretreatment of the biomass, enzyme hydrolysis to obtain fermentable sugars, fermentation technologies, and separation and purification of lactic acid. In addition, the difficulties associated with using this biomass for lactic acid production are especially introduced and several key properties that should be targeted for low-cost and advanced fermentation processes are pointed out. We also discuss the metabolism of lignocellulose-derived sugars by lactic acid bacteria.
The principal pathways for the formation of flavour compounds in cheese (glycolysis, lipolysis and proteolysis) are reviewed. Depending on variety, microflora and ripening conditions, lactate may be metabolized by a number of pathways to various compounds which contribute to cheese flavour or off-flavours. Citrate metabolism by citrate-positive lactococci or Leuconostoc spp. is important in certain varieties (e.g., Dutch cheeses). Lipolysis results directly in the formation of flavour compounds by liberating free fatty acids (FFA). FFA may also be metabolized to alkan-2-ones and fatty acid lactones. Proteolysis of the caseins to a range of small-and intermediate-sized peptides and free amino acids (FAA) probably only contributes to the background flavour of most cheese varieties, but FAA are important precursors for a range of poorly-understood catabolic reactions which produce volatile compounds essential for flavour.
Lactic acid bacteria can produce a variety of antimicrobial compounds which may affect both the lactic acid bacteria themselves as well as undesirable or pathogenic strains. In this first section, we describe the biosynthesis, mode of action and activity spectra of these inhibitors. Metabolites of oxygen (hydrogen peroxide and free radicals) exhibit a bacteriostatic or bactericidal activity against lactic or non-lactic flora. When associated with the lactoperoxidase / thiocyanate system, hydrogen peroxide leads to the formation of inhibitory compounds which are bacteriostatic for lactic acid bacteria and bactericidal for Gram-negative bacteria. The antimicrobial activity of organic acids (lactic, acetic and formic) and of pH are closely linked. It appears that the non-dissociated fraction of these acids is the major inhibitory form. Thus, acetic acid whose pKa is higher than that of lactic acid exhibits the highest inhibitory activity. The antimicrobial activities of diacetyl, acetaldehyde and of the D isomers of amino acids are also described, although their effects are slight in usual lactic fermentations. Bacteriocins are the last type of inhibitory substance produced by some lactic acid bacteria. They will be described in a second section. Les bactéries lactiques sont capables de produire une variété de produits inhibiteurs dont les effets peuvent se répercuter sur la flore lactique elle-même mais aussi sur les flores indésirables ou pathogènes. Dans cette première partie, nous décrivons les mécanismes d'apparition, les modes d'action et les spectres d'activité de ces inhibiteurs. Les métabolites de l'oxygène (le peroxyde d'hydrogène et les radicaux libres) peuvent avoir des effets biologiques de nature bactériostatique ou bactéricide sur la flore lactique ou non lactique. Le peroxyde d'hydrogène associé au système lactoperoxydase / thiocyanate, catalyse la formation de produits inhibiteurs, bactériostatiques pour la flore lactique et bactéricides pour les bactéries Gram-négative. Les pouvoirs antibactériens des acides organiques et du pH sont intimement liés. Il semble que la fraction non dissociée de ces acides soit la forme inhibitrice majeure. De ce fait l'acide acétique de pKa supérieur au pKa de l'acide lactique, a un pouvoir inhibiteur supérieur. Les activités inhibitrices du diacétyle, de l'acétaldéhyde et des acides aminés de forme isomérique D sont décrites bien que leurs effets soient mineurs dans les fermentations lactiques habituelles. Les bactériocines produites par certaines bactéries lactiques seront décrites dans une seconde revue.
Yogurt is a simple ecosystem whose successful manufacture relies on interactions between two thermophilic lactic acid bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus). The present work studied the impact of co-culturing S. thermophilus with Lb. bulgaricus on bacterial growth in milk. To achieve this, we considered both sides of the bacterial association, by characterising proteolysis and quantifying formic acid in pure and mixed cultures of S. thermophilus and Lb. bulgaricus. In pure cultures, S. thermophilus CNRZ385 exhibited better growth than the two Lb. bulgaricus strains (1038 and CNRZ397). The S. thermophilus/Lb. bulgaricus association was positive for S. thermophilus growth with strain 1038, contrary to the association with strain 397. These effects were correlated with the different proteolytic capacities of the two Lb. bulgaricus strains. In contrast, the bacterial association had no significant effect on Lb. bulgaricus growth, possibly because of an insufficient production of formic acid by the S. thermophilus strain. We also showed that the S. thermophilus/Lb. bulgarius association affected the production of volatile molecules involved in flavour development.
Efficient L-lactic acid production from Jerusalem artichoke tubers by Lactobacillus casei G-02 using simultaneous saccharification and fermentation (SSF) in fed-batch culture is demonstrated. The kinetic analysis in the SSF signified that the inulinase activity was subjected to product inhibition, while the fermentation activity of G-02 was subjected to substrate inhibition. It was also found that the intracellularly NOX activity was enhanced by the citrate metabolism, which increased the carbon flux of Embden-Meyerhof-Parnas (EMP) pathway dramatically, and resulted more ATP production. As a result, when the SSF was carried out at 40 degrees after the initial hydrolysis of 1 h with supplemented sodium citrate of 10g/L, L-lactic acid concentration of 141.5 g/L was obtained in 30 h with a volumetric productivity of 4.7 g/L/h. The conversion efficiency and product yield were 93.6% of the theoretical lactic acid yield and 52.4 g lactic acid/100 g Jerusalem artichoke flour, respectively. Such a high concentration of lactic acid with high productivity from Jerusalem artichoke has not been reported previously, and hence G-02 could be a potential candidate for economical production of L-lactic acid from Jerusalem artichoke at a commercial scale.
Polylactic acid is receiving increasing attention as a renewable alternative for conventional petroleum-based plastics. In the present study, we constructed a metabolically-engineered Candida utilis strain that produces L-lactic acid with the highest efficiency yet reported in yeasts. Initially, the gene encoding pyruvate decarboxylase (CuPDC1) was identified, followed by four CuPDC1 disruption events in order to obtain a null mutant that produced little ethanol (a by-product of L-lactic acid). Two copies of the L-lactate dehydrogenase (L-LDH) gene derived from Bos taurus under the control of the CuPDC1 promoter were then integrated into the genome of the CuPdc1-null deletant. The resulting strain produced 103.3 g/l of L-lactic acid from 108.7 g/l of glucose in 33 h, representing a 95.1% conversion. The maximum production rate of L-lactic acid was 4.9 g/l/h. The optical purity of the L-lactic acid was found to be more than 99.9% e.e.
Maximum acetate produced aerobically by Streptococcus diacetilactis and Streptococcus cremoris was 14% of 1 to 7 mumol of glucose/ml in a partially defined medium that contained lipoic acid. Y (glucose) values were 35.3 (S. diacetilactis) and 31.4 (S. cremoris) with low concentrations (1 to 7 mumol/ml) of glucose in the medium and 21 (S. diacetilactis) with higher concentrations (6 to 15 mumol/ml). Y (adenosine 5'-triphosphate) values for the bacteria, determined by taking into account the end products produced, were 15.6 and 13.9 for S. diacetilactis and S. cremoris, respectively, in the partially defined medium containing 1 to 7 mumol of glucose/ml and higher (21.5 and 18.9, respectively) in a complex medium that contained 2 mumol of glucose/ml. Addition of citrate in addition to glucose did not result in higher molar growth yields.
Nisin, produced by Lactococcus lactis subsp. lactis, has a broad spectrum of activity against gram-positive bacteria and is generally recognized as safe in the United States for use in selected pasteurized cheese spreads to control the outgrowth and toxin production of Clostridium botulinum. This study evaluated the inhibitory activity of nisin in combination with a chelating agent, disodium EDTA, against several Salmonella species and other selected gram-negative bacteria. After a 1-h exposure to 50 micrograms of nisin per ml and 20 mM disodium EDTA at 37 degrees C, a 3.2- to 6.9-log-cycle reduction in population was observed with the species tested. Treatment with disodium EDTA or nisin alone produced no significant inhibition (less than 1-log-cycle reduction) of the Salmonella and other gram-negative species tested. These results demonstrated that nisin is bactericidal to Salmonella species and that the observed inactivation can be demonstrated in other gram-negative bacteria. Applications involving the simultaneous treatment with nisin and chelating agents that alter the outer membrane may be of value in controlling food-borne salmonellae and other gram-negative bacteria.
A simple and rapid method for the determination of organic acids in foods by high efficiency anion exchange chromatography is described. Separation of microequivalent amounts of up to 15 of the commonly occurring food acids can be completed in about 75 min. These acids include Krebs cycle acids (citric, isocitric, α-ketoglutaric, succinic, fumaric, malic, and oxalacetic), alicyclic acids (quinic, shikimic), and various other acids (acetic, galacturonic, lactic, malonic, oxalic, and tartaric). Separation of the predominant acids in particular food samples often requires only 20 to 40 min. A special precolumn injection system sharpens the acid peaks and makes possible the analysis of liquid samples (fruit juices, acidulated beverages, etc.) or aqueous extracts with little or no pretreatment. Use of a differential refractometer detector simplifies the quantitative measurements and facilitates collection of effluent samples for confirmation of identity.
Lactic acid bacteria perform an essential role in the preservation and production of wholesome foods. Generally the lactic acid fermentations are low-cost and often little or no heat is required in their preparation. Thus, they are fuel-efficient. Lactic acid fermented foods have an important role in feeding the world's population on every continent today. As world population rises, lactic acid fermentation is expected to become even more important in preserving fresh vegetables, fruits, cereals and legumes for feeding humanity.