Bioprocess and Biosystems Engineering

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Schematic representation of the improvement processes that the AGY001 yeast was submitted, from the parental strain SA-1
Evaluation of the influence of temperature on the relative activity (%) of the enzyme cocktail. Cellic®CTec2
Pareto chart—Assessment of the significance of each variable in the SSF process from the analysis of effects at a 90% confidence level
Contour curves—Optimal condition of process variables for optimization of the simultaneous saccharification and fermentation process
Article
The nonrenewable character and deleterious effects of fossil fuels foster the need for cleaner and more inexhaustible energy sources, such as bioethanol. Especially from lignocellulosic biomasses. However, the economic viability of this product in the market depends on process optimization and cost reduction. This research applied a sequential experimental project to investigate the process of enzymatic saccharification and simultaneous fermentation to produce ethanol with sugarcane bagasse. The differential of the work was the application of the strain of Saccharomyces cerevisiae AGY001 which was improved by evolutionary engineering to become thermotolerant and by a heterologous expression based on genomic integration by CRISPR/Cas9 to produce endoglucanase and β-glucosidase (AsENDO-AsBGL). The maximum ethanol yield found was 89% of the maximum theoretical yield (released sugars), obtained at temperature concentrations, sugarcane bagasse and inoculum at 40 °C, 16.5%, and 4.0 g/L, respectively (12.5 FPU/g bagasse). The mathematical model obtained can predict approximately 83% of the data set with 95% confidence. Therefore, these findings demonstrated the potential of sugarcane bagasse and S. cerevisiae AGY001 strain (CRISPR/Cas9 modified) in bioethanol production without the need for impractical selection media on an industrial scale, in addition to providing useful insights for the development of SSF processes.
 
Article
Chlorophenols are widely used in industry and are known environmental pollutants. The degradation of chlorophenols is important for environmental remediation. In this study, we evaluated the biodegradation of 2-chlorophenol using crude laccase produced by Myrothecium verrucaria. Atmospheric and room temperature plasma technology was used to increase laccase production. The culture conditions of the M-6 mutant were optimized. Our results showed that corn stover could replace glucose as a carbon source and promote laccase production. The maximum laccase activity of 30.08 U/mL was achieved after optimization, which was a 19.04-fold increase. The biodegradation rate of 2-chlorophenol using crude laccase was 97.13%, a positive correlation was determined between laccase activity and degradation rate. The toxicity of 2-CP was substantially reduced after degradation by laccase solution. Our findings show the feasibility of the use of corn stover in laccase production by M. verrucaria mutant and the subsequent biodegradation of 2-chlorophenol using crude laccase.
 
Concept of growth-associated target production based on a mutualistic co-culture
The designed metabolic pathway for growth-associated phenylalanine production: A FBA-predicted flux distribution of the ΔPYK ΔPPC ΔG6PDH2r ΔACALD strain at the optimal growth state. B Flux solution space of phenylalanine production in monoculture. C Flux solution space of phenylalanine production in co-culture of the L⁻ and F⁻ strains. The flux solution spaces were calculated with a constraint of oxygen consumption rate of 5 mmol g⁻¹ h⁻¹ (microaerobic conditions)
Fermentation profiles of the KF and KF-E strains
ALE experiment of co-culture using the KF and KL strains: A Changes in specific growth rate during the ALE experiment. B Changes in population ratio of the KF to KL strains)
Article
Combination of growth-associated pathway engineering based on flux balance analysis (FBA) and adaptive laboratory evolution (ALE) is a powerful approach to enhance the production of useful compounds. However, the feasibility of such growth-associated pathway designs depends on the type of target compound. In the present study, FBA predicted a set of gene deletions (pykA, pykF, ppc, zwf, and adhE) that leads to growth-associated phenylalanine production in Escherichia coli. The knockout strain is theoretically enforced to produce phenylalanine only at high growth yields, and could not be applied to the ALE experiment because of a severe growth defect. To overcome this challenge, we propose a novel approach for ALE based on mutualistic co-culture for coupling growth and production, regardless of the growth rate. We designed a synthetic mutualism of a phenylalanine-producing leucine-auxotrophic strain (KF strain) and a leucine-producing phenylalanine-auxotrophic strain (KL strain) and performed an ALE experiment for approximately 160 generations. The evolved KF strain (KF-E strain) grew in a synthetic medium (with glucose as the main carbon source) supplemented with leucine, while severe growth defects were observed in the parental KF strain. The phenylalanine yield of the KF-E strain was 2.3 times higher than that of the KF strain.
 
Side view schematic of the cylinder used in the study. Light gray is the supernatant, dark gray is the sediment
Microalgae sedimentation efficiencies at pH 3, 7, 9, and 11 and calcium concentration (Ca) of 1–5 mM (the mean values are shown, and the error bars are the standard deviations; n = 3)
Spatiotemporal variations in the chlorophyll a concentration (Chl. a). Measured and assumed values are indicated as crosses ( +) and circles (○), respectively. Seven sedimentation dynamic series are shown as the ln Chl. a concentrations found when systems with various pH and calcium concentrations (Ca, in mM) were used
Micrographs of the sediment produced at pH 7 and 11 and calcium concentrations (Ca) of 3 and 5 mM. The black areas are flocs, and the arrows indicate microalgae that have not formed flocs
a Calcium distribution after flocculation and b Calcium recovery from sediment after acid treatment (at pH 5, 3, and 1.5)
Article
The high cost of harvesting microalgae is a major hurdle for the microalgae industry, and an efficient pre-concentration method is required. In this study, the effects of using different pH values (between pH 3 and 11) and calcium (Ca²⁺) concentrations (between 0 and 5 mM) on Chlorella vulgaris sedimentation were investigated by evaluating the spacio-temporal distributions of microalgae cells. Fast and efficient sedimentation occurred (within 10 min) at a high Ca²⁺ concentration (5 mM) at pH 9 and 11. However, the sediment volume was lower at a Ca²⁺ concentration of 3 mM than at a Ca²⁺ concentration of 5 mM. This indicated that the Ca²⁺ concentration strongly affected the sediment volume. Fast sedimentation and a low sediment volume were found at pH 7 and a Ca²⁺ concentration of 5 mM, probably because of the neutral charge in the system (adhesion to calcium precipitates would have occurred at a high pH). The highest Ca²⁺ recovery (82%) was achieved when sediment produced at pH 11 and a Ca²⁺ concentration of 5 mM was acidified to pH 3.
 
Article
Perfusion bioreactors are commonly used for the continuous production of monoclonal antibodies (mAb). One potential benefit of continuous bioprocessing is the ability to operate under steady-state conditions for an extended process time. However, the process performance is often limited by the feedback control of feed, harvest, and bleed flow rates. If the future behavior of a bioprocess can be adequately described, predictive control can reduce set point deviations and thereby maximize process stability. In this study, we investigated the predictive control of biomass in a perfusion bioreactor integrated to a non-chromatographic capture step, in a series of Monte-Carlo simulations. A simple algorithm was developed to estimate the current and predict the future viable cell concentrations (VCC) of the bioprocess. This feature enabled the single prediction controller (SPC) to compensate for process variations that would normally be transported to adjacent units in integrated continuous bioprocesses (ICB). Use of this SPC strategy significantly reduced biomass, product concentration, and harvest flow variability and stabilized the operation over long periods of time compared to simulations using feedback control strategies. Additionally, we demonstrated the possibility of maximizing product yields simply by adjusting perfusion control strategies. This method could be used to prevent savings in total product losses of 4.5-10% over 30 days of protein production.
 
Article
Komagataella phaffii (K. phaffii) is a famous microbial cell of heterologous protein and value-added chemicals production because of its strict and strong promoter (alcohol oxidase 1 promoter, PAOX1). Formate is an attractive substitute of traditional inducer methanol because methanol is toxic and explosive. To obtain high level of Aspergillus niger ATCC1015 xylanase as a model of heterologous protein by K. phaffii at formate induction, insertion of three-copy cis-acting element W3A into PAOX1 additionally, and co-expression of transcription factor Mit1 under another PAOX1 were carried out separately and simultaneously. The yield of xylanase increased by 41% at formate induction when Mit1 was co-expressed. Furtherly, the yield of xylanase increased by 42% using sorbitol as supplemental carbon source with the result of 408.3 × 10³ U‧L⁻¹ xylanase. Therefore, a non-methanol needed and inducible heterologous protein expression system of Komagataella phaffii was developed successfully. Graphical abstract
 
Article
Thermobacillus xylanilyticus is a thermophilic and hemicellulolytic bacterium of interest for the production of thermostable hemicellulases. Enzymes’ production by this bacterium is challenging, because the proliferation of a cheating subpopulation of cells during exponential growth impairs the production of xylanase after serial cultivations. Accordingly, a strategy of successive cultivations with cells transfers in stationary phase and the use of wheat bran and wheat straw as carbon sources were tested. The ratio between subpopulations and their corresponding metabolic activities were studied by flow cytometry and the resulting hemicellulases production (xylanase, acetyl esterase and β-xylosidase) followed. During serial cultivations, the results pointed out an increase of the enzymatic activities. On xylan, compared to the first cultivation, the xylanase activity increases by 7.15-fold after only four cultivations. On the other hand, the debranching activities were increased by 5.88-fold and 57.2-fold on wheat straw and by 2.77-fold and 3.34-fold on wheat bran for β-xylosidase and acetyl esterase, respectively. The different enzymatic activities then stabilized, reached a plateau and further decreased. Study of the stability and reversibility of the enzyme production revealed cell-to-cell heterogeneities in metabolic activities which could be linked to the reversibility of enzymatic activity changes. Thus, the strategy of successive transfers during the stationary phase of growth, combined with the use of complex lignocellulosic substrates as carbon sources, is an efficient strategy to optimize the hemicellulases production by T. xylanilyticus, by preventing the selection of cheaters.
 
Kinetics of sodium maltobionate production at different concentrations of cells in the reaction medium
Contour curve for a bioconversion time, b mass productivity, c specific productivity, and d specific rate of product formation as a function of temperature and pH
Operational stability of the immobilized system in successive bioconversion cycles: a Mass productivity and b maximum concentration of sodium maltobionate and their respective residual values compared to the initial cycle
Storage stability of the immobilized system at a 22 ± 2 °C and b 4 ± 2 °C, expressed in mass productivity and residual productivity values compared to the initial cycle
Article
The purpose of this study was the production of maltobionic acid, in the form of sodium maltobionate, by Z. mobilis cells immobilized in polyurethane. The in situ immobilized system (0.125–0.35 mm) was composed of 7 g polyol, 3.5 g isocyanate, 0.02 g silicone, and 7 g Z. mobilis cell, at the concentration of 210 g/L. The bioconversion of maltose to sodium maltobionate was performed with different cell concentrations (7.0–9.0 gimobilized/Lreaction_medium), temperature (30.54–47.46 °C), pH (5.55–7.25), and substrate concentration (0.7–1.3 mol/L). The stability of the immobilized system was evaluated for 24 h bioconversion cycles and storage of 6 months. The maximum concentration of sodium maltobionate was 648.61 mmol/L in 34.34 h process (8.5 gdry_cell/Lreaction_medium) at 39 °C and pH 6.30. The immobilized system showed stability for 19 successive operational cycles of 24 h bioconversion and 6 months of storage, at 4 °C or 22 °C.
 
Article
Magnetic nanobiocatalysts (MNBCs) are a promising immobilization approach to ease enzyme recovery during bioprocessing. However, industrial adoption of MNBCs is unfeasible because MNBC-synthesis involves complex and potentially expensive processing steps including synthesis of silica-coated superparamagnetic iron oxide nanoparticles (Si-SPIONs). We developed a single-step process for Si-SPION synthesis using a tubular electrochemical system (TES) and investigated the effect of concentration of the Na2SiO3 coating agent on Si-SPION properties. The Si-SPIONs were used as a support for attachment of polymer-cellulase conjugate to make MNBCs. The spherical Si-SPIONs were 8–12 nm in diameter including a 2-nm silica coating. Na2SiO3 concentration in the reactor did not affect Si-SPION morphology, but increasing Na2SiO3 concentration reduced SPION productivity in the reactor. Protective properties of the SPION silica coatings were demonstrated by showing that they prevented dissolution of SPIONs in an acid solution for 48 h. Enzyme attachment was quantified as protein adsorption on Si-SPIONs which reached 55 μg/mg Si-SPION. The MNBCs were recovered and reused four times. The use of TES for Si-SPION synthesis is promising to reduce MNBC production complexity.
 
Article
The production of ε-poly-l-lysine (ε-PL) from cassava bagasse hydrolysate (CBH) by Streptomyces albulus US3-18 was investigated in this study. With 30 g/L glucose from CBH, 1.30 g/L ε-PL and 10.68 g/L biomass were obtained in shake flask fermentation. Interestingly, the two values were increased by 14.0% and 21.5%, respectively, compared to the control (1.14 g/L and 8.79 g/L). Simultaneously, the activities of four key enzymes of ε-PL synthesis during CBH fermentation were enhanced to varying degrees. In batch fermentation of 5-L bioreactor, 3.39 g/L ε-PL and 10.17 g/L DCW were harvested with 40 g/L glucose from CBH. The combination of fed-batch fermentation with two-stage pH strategy significantly increased ε-PL titer and biomass to 37.41 g/L and 41.0 g/L, respectively. Moreover, eleven volatile components were detected in CBH by GC–MS, and 6-pentyl-α-pyrone (6PP) was first identified as the most abundant volatile ingredient. The results in CBH fermentation demonstrated that S. albulus US3-18 exhibited high tolerance to these volatile byproducts. Using ICP–MS, the calcium concentration in CBH was determined as 195.0 mg/(kg hydrolyzate), and cobalt, copper, lead, chromium, mercury and arsenic were not detected. By adding 0.05 g/L CaCl2 to M3G medium, ε-PL yield was improved by 28.0%, indicating calcium was one of the factors for the enhanced ε-PL production. The study provides a reference for the efficient production of ε-PL from low-cost agricultural residues. Graphical abstract
 
Article
Perfusion cell culture technology has gained a lot of interest in recent years in the biopharmaceutical industry. One common application is N-1 perfusion which is used to intensify fed batch production processes and increase facility output. Upon running our perfusion process for the first time at manufacturing scale, unexpected cell damage was observed. Reducing the recirculation pump speed resulted in improvements in cell viability which implied the impact of pump shear stress on cell viability. In this study, we used polymethyl methacrylate (PMMA) nanoparticles to determine the shear stress inside two different sized rotary lobe pumps used in N-1 perfusion. The results were used to validate a computational fluid dynamics (CFD) model to predict the maximum shear under different operating conditions of the pump. The CFD model identified the radial and mesh clearance zones as regions that experience the maximum shear stress inside the pump. The model was then used to evaluate the impact of different geometry modifications in the pump lobes, and it predicted a 17% reduction in the maximum shear stress by increasing the mesh and radial clearances by 0.08 mm and 0.13 mm, respectively. The study indicates that CFD can be a useful tool to predict shear stress inside rotary pumps. The results can be used to optimize the pump operating conditions or even customize the pump geometry to save time and cost of process scaling to manufacturing without compromising the preset operating conditions or critical scale-up parameters.
 
Article
Enzymatic scouring of cotton has established itself (slowly) as a green alternative to alkaline scouring in the textile industry, mostly due to more environmentally friendly processing at lower pH and temperatures and its less aggressive action on the cotton fibers. However, among other limitations, enzyme costs have contributed to impeding its wide acceptance and use. For the first time, in this study, the recycling of the bioscouring bath was evaluated, unlike most current bioscouring that is performed using fresh enzyme solution. Bioscouring of raw knitted cotton fabric was carried out for 30 min with a commercial pectinase (BioPrep® 3000L) at 55 °C and pH 8.5. About 89% of the recovered pectate lyase-containing scouring bath was completed with 11% of fresh enzyme solution and reused in a new bioscouring process under the same conditions. Up to ten reuse cycles were possible maintaining the level of pectin removal and without significant loss in quality of subsequent dyeing. A detailed analysis of the pretreated fabrics is presented. Reusing the scouring bath, reducing the intensive consumption of input materials (enzyme, water, and chemicals) and wastewater generation can be possible, making bioscouring a more attractive and sustainable technique. The process demonstrated is promising and its industrial application is feasible.
 
Article
Menaquinone-7 (MK-7) offers significant health benefits; however, only the all-trans form is biologically active. MK-7 produced through fermentation can occur as all-trans and cis isomers, and the therapeutic value of the resulting MK-7 is exclusively determined by the quantity of the all-trans isomer. Therefore, this study aimed to investigate the effect of the media composition on the isomer profile obtained from fermentation and determine the optimum media combination to increase the concentration of the all-trans isomer and diminish the production of cis MK-7. For this purpose, design of experiments (DOE) was used to screen the most effective nutrients, and a central composite face-centred design (CCF) was employed to optimise the media components. The optimum media consisted of 1% (w/v) glucose, 2% (w/v) yeast extract, 2% (w/v) soy peptone, 2% (w/v) tryptone, and 0.1% (w/v) CaCl2. This composition resulted in an average all-trans and cis isomer concentration of 36.366 mg/L and 1.225 mg/L, respectively. In addition, the optimised media enabled an all-trans isomer concentration 12.2-fold greater and a cis isomer concentration 2.9-fold less than the unoptimised media. This study was the first to consider the development of an optimised fermentation media to enhance the production of the bioactive isomer of MK-7 and minimise the concentration of the inactive isomer. Furthermore, this media is commercially promising, as it will improve the process productivity and reduce the costs associated with the industrial fermentation of the vitamin.
 
Article
The under-treated wastewater, especially remaining carcinogenic aromatic compounds in wastewater discharge has been expansively reported, wherein the efficiency of conventional wastewater treatment is identified as the primary contributor source. Herein, the advancement of wastewater treatments has drawn much attention in recent years. In the current study, combined sequential and hybridized treatment of thermolysis and coagulation–flocculation provides a novel advancement for environmental emerging pollutant (EP) prescription. This research is mainly demonstrating the mitigation efficiency and degradation pathway of pararosaniline (PRA) hybridized and combined sequential wastewater treatment. Notably, PRA degradation dominantly via a linkage of reaction: thermal cleavage, deamination, silication and diazene reduction. Thermolysis acts as an initiator for the PRA decomposition through thermally induced bond dissociation energy (BDE) for molecular fragmentation whilst coagulation–flocculation facilitates the formation of organo-bridged silsesquioxane as the final degradation product. Different from conventional treatment, the hybridized treatment showed excellent synergistic degradability by removing 99% PRA and its EPs, followed by combined sequential treatment method with 86% reduction. Comprehensive degradation pathway breakdown of carcinogenic and hardly degradable aromatic compounds provides a new insight for wastewater treatment whereby aniline and benzene are entirely undetectable in effluent. The degradation intermediates, reaction derivatives and end products were affirmed by gas chromatography–mass spectrometry, Fourier transform infrared spectroscopy and ultraviolet–visible spectrophotometry (GC–MS, FTIR and UV–Vis). This finding provides valuable guidance in establishing efficient integrated multiple-step wastewater treatments. Graphical abstract
 
Article
The domination of high-cost organic acids over other 3-hydroxyvalerate (3HV) precursors due to the wide preference among polyhydroxyalkanoates (PHA)-producing bacteria has limited the development of diverse poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] production processes. 1-pentanol is a low-cost 3HV precursor but is rarely employed due to the relatively low tolerance among PHA-producing bacteria. This study demonstrated P(3HB-co-3HV) production with manipulable and reproducible 3HV composition and 3HV yield from palm olein and 1-pentanol. Cupriavidus malaysiensis USMAA2-4ABH16 is the transformant strain with acquired lipase genes that retains the high tolerance towards 1-pentanol of its wild-type, with a preference for 1-pentanol over valeric acid indicated by the sixfold higher 3HV yield than that from valeric acid. C. malaysiensis USMAA2-4ABH16 was able to tolerate up to 0.15 wt% C 1-pentanol. Upon optimization using response surface methodology, 0.41‒0.52 g/g P(3HB-co-3HV) yield and 72‒89 wt% PHA content was achieved for 7, 9, 12 and 16 mol% 3HV, with 3HV yields of 0.30 g/g, 0.26 g/g, 0.23 g/g and 0.23 g/g, respectively. Up-scaling batch production by adopting the optimized concentrations of substrates for 12 mol% 3HV resulted in reproducible 3HV composition and 3HV yield on a 120-fold larger scale. The P(3HB-co-12 mol% 3HV) produced displayed higher flexibility than polypropylene and P(3HB-co-3HV) produced from different carbon sources. C. malaysiensis USMAA2-4ABH16 could be practically applicable for sustainable and economically feasible P(3HB-co-3HV) production on an industrial scale from used palm olein with relatively similar oleic acid content with palm olein and 1-pentanol, with higher 3HV compositions achievable through fed-batch strategies owing to its high 1-pentanol tolerance.
 
Article
Kinases modulate the various physiological activities of microbial fermenting strains including the conversion of lignocellulose-derived phenolic aldehydes (4-hydroxyaldehyde, vanillin, and syringaldehyde). Here, we comprehensively investigated the gene transcriptional profiling of the kinases under the stress of phenolic aldehydes for ethanologenic Zymomonas mobilis using DNA microarray. Among 47 kinase genes, three genes of ZMO0003 (adenylylsulfate kinase), ZMO1162 (histidine kinase), and ZMO1391 (diacylglycerol kinase), were differentially expressed against 4-hydroxybenzaldehyde and vanillin, in which the overexpression of ZMO1162 promoted the phenolic aldehydes conversion and ethanol fermentability. The perturbance originated from plasmid-based expression of ZMO1162 gene contributed to a unique expression profiling of genome-encoding genes under all three phenolic aldehydes stress. Differentially expressed ribosome genes were predicted as one of the main contributors to phenolic aldehydes conversion and thus finally enhanced ethanol fermentability for Z. mobilis ZM4. The results provided an insight into the kinases on regulation of phenolic aldehydes conversion and ethanol fermentability for Z. mobilis ZM4, as well as the target object for rational design of robust biorefinery strains.
 
Article
Enzymatic hydrolysis of sugar beets for achieving liquefaction and sugar release is a critical step for beet-ethanol production. An enzyme recycling process was developed in this study to reduce the economic uncertainty raised by the high costs of enzymes by reducing the fresh enzyme usage. A mixture of cellulases and pectinases was used in the beet hydrolysis. The hydrolysate was centrifuged and then processed through a 50 kDa molecular weight cut-off polyethersulfone membrane to recover enzymes from the liquid. Liquid enzyme recycling with 50% fresh enzyme addition achieved a similar liquefaction extent and sugar yield compared to the positive control with 100% fresh enzyme. Solid enzyme recycling showed a lower liquefaction efficiency, requiring at least 75% of fresh enzyme addition for a comparable liquefaction extent. Five sequential batches of hydrolysis with liquid enzyme recycling were successfully conducted to hydrolyze sugar beets with similar liquefaction extents and sugar yields.
 
Article
An effective biosurfactant producer and extremophiles bacteria, Bacillus cereus KH1, was isolated from textile effluent and the biosurfactant was produced using molasses as the sole carbon source. Growth parameters such as pH, temperature, salinity and concentration of molasses were optimised for decolourising the textile effluent with 24-h incubation. The biosurfactant property of B. cereus KH1 was evaluated based on haemolytic activity, oil displacement technique, drop-collapsing test and emulsification index. The results of the produced biosurfactant showed a positive reaction in haemolytic activity, oil displacement technique, drop-collapsing test and exhibiting a 67% emulsification index. The cell-free broth was stable in 40 °C pH 7, 7% salinity and 7% molasses. Thin-Layer Chromatography and Fourier Transform Infrared Spectroscopy analysis revealed that the biosurfactant was a lipopeptide with a yield 2.98 g L⁻¹. These findings proved the synergistic action of B. cereus KH1 with lipopeptide biosurfactant may accelerated the decolourisation efficiency to 87%.
 
Article
The medium used for Chlorella vulgaris cultivation exerted obvious inhibitory effects on the growth of C. vulgaris after several culture-harvest cycles. The accumulated fatty acids secreted by C. vulgaris during their growth process were expected to be the cell inhibition components. In this work, the ultraviolet-driven photocatalytic oxidation technique was applied for the degradation of microalgae cell growth inhibition components in the aged cultivation medium, and the reaction parameters were optimized. The results indicated that the photocatalytic oxidation processes using 0.5 g/L [Formula: see text] NPs as the catalyst under the aeration condition showed as high as 74.61 ± 4.60% FA degradation efficiency after 20 min illumination, and the contents of -COOH, [Formula: see text] (α) and -COO-R functional groups in the aged C. vulgaris medium were significantly reduced. In addition, the modification of the photocatalyst further improved the ability of the degradation of FA. When the modified [Formula: see text]/AC and [Formula: see text]/Ag catalysts were applied, the FA degradation rates reached as high as 92.46 ± 0.37% and 93.91 ± 1.37%, respectively. In the recycled medium treated with [Formula: see text]/AC, the cell density in the stable phase reached 96.33 ± 1.83% of that in the fresh medium as the control. In summary, the photocatalytic oxidation with the modified [Formula: see text]/AC catalyst was proposed as the efficient strategy to realize the recycling of the aged C. vulgaris cultivation medium via the degradation of the FA as the cell growth inhibitors.
 
Article
The bioconversion of coal at ambient conditions is a promising technology for coal processing. However, there are few examples of the optimization of processes for industrial-scale use. In this work, the optimization of process parameters affecting lignite bioconversion by an isolated fungus WF8 using an artificial neural network (ANN) combined with a genetic algorithm (GA) was carried out for modeling of humic acids (HAs) yield and parameters. Kinetic models were used to understand the release characteristics of HAs from the bioconversion of lignite. The results of the present work indicate that the optimal process parameters (OPP) are 29 °C, initial pH of 7, 180 rpm, 0.6 mmol·L⁻¹ of CuSO4, 0.4 mmol L⁻¹ of MnSO4, and 6.4 μmol·L⁻¹ of veratryl alcohol (VA). The predicted experimental data obtained by ANN is similar to the actual and the significant correlation coefficient value (R²) of 0.99 indicates that ANN has good predictability. The actual yield of HAs are 5.17 mg·mL⁻¹. During bioconversion, the fungus WF8 could loosen and attack the structure of lignite. The release of HAs produced by bioconversion of lignite under the OPP via diffusion and swelling is fit to zero-order model independent on concentration. This provides support for the industrial bioconversion of lignite.
 
Article
This work investigates the possibility of using scales of sea bass Dicentrarchus labrax as a low-cost material for the adsorptive removal of methylene blue (MB) cationic dye in aqueous solutions. The physical–chemical characterizations of fish scales in natura (FS-in natura) revealed through thermogravimetry that they are composed of inorganic (hydroxyapatite) and organic (collagen) phases in relatively similar amounts. Spectroscopy analyses show that the interactions of MB with FS-in natura occur mainly in the organic phase layer of the adsorbent. The effects of initial MB concentration (5.0 × 10–4 and 5.0 × 10–3 mol L⁻¹) and temperature (25–55 °C) on the adsorption efficiency of FS-in natura were evaluated. FS-in natura at MB concentration (5.0 × 10–3 and 5.0 × 10–4 mol L⁻¹) exhibited the maximum adsorption capacities of 2.2 × 10–3 mol g⁻¹ at 25 °C and 2.8 × 10–5 mol g⁻¹ at 55 °C, respectively. The pseudo-second-order model represented the adsorption kinetics well, and the equilibrium isotherm data were better correlated using the Langmuir equation. The newly developed neural model demonstrated a high predictive capacity with an R-value greater than 0.99 and reduced values for mean squared error, root mean squared error, and mean absolute error equal to 0.003, 0.055, and 0.0348, respectively. The genetic algorithm was used to optimize the experimental conditions of the process. In conclusion, the sea bass scales have promising prospects as a low-cost alternative material for removing cationic dyes from aqueous solutions.
 
Article
Dental decay is known in the world as the most common human infectious disease. Ascending process of dental caries index in the world shows the failure of oral disease prevention. Streptococcus mutans bacteria cause acid damage and tooth decay by producing acid over time. Nanomaterials with suitable functionality, high permeability, extremely large surface area, significant reactivity, unique mechanical features, and non-bacterial resistance can be considered as promising agents for antimicrobial and antiviral applications. In this study, nickel oxide (NiO) nanoparticles with size range from 2 to 16 nm containing Stevia natural sweetener were eco-friendly synthesized via a simple method. Additionally, their various concentrations were evaluated on S. mutans bacteria by applying the broth dilution method. The results demonstrated that these spherical NiO nanoparticles had efficient bacteriostatic activity on this gram-positive coccus. Graphical abstract
 
Article
Aerobic composting is an efficient and environmentally friendly method of converting organic waste into nontoxic fertilizers or soil quality enhancers. The quality of the resultant compost depends greatly upon the composition of the substrate used. The initial carbon-to-nitrogen (C/N) ratio of the substrate is an important factor affecting the composting process. This study elucidated how initial C/N ratios affect the biodegradation of lignocellulose, due to changes in microbial community structure. Four different C/N ratios (20:1, 25:1, 30:1, and 35:1) were examined during a 35-day composting process. The degradation of cellulose, hemicellulose, and lignin was highest (35.7%, 30.6%, and 19.1% respectively) at a 30:1 C/N ratio; after 30 days, the 25:1 C/N ratio ranked second in terms of lignocellulosic degradation rate. The 30:1 C/N ratio further promoted the growth of functional microorganisms responsible for lignocellulose degradation (Luteimonas, Sphingobium, Trichoderma, Chaetomium, and Rosellinia), while the growth of dominant pathogenic microbes (Erwinia and Ulocladium) decreased significantly. These results confirm that the initial C/N ratio of the substrate has a significant effect on the microbial community and degradation of organic matter, during walnut branch composting. This process could therefore offer an alternative means of efficient recycling and recovery of waste branches.
 
Article
Solid-phase microbial fuel cell (SMFC) can accelerate the removal of organic pollutants through the electrons transfer between microorganisms and anodes in the process of generating electricity. Thus, the characteristics of the anode material will affect the performance of SMFCs. In this study, corn stem (CS) is first calcined into a 3D macroporous electrode, and then modified with carbon nanotubes (CNTs) through electrochemical deposition method. Scanning electron microscope analysis showed the CS/CNT anode could increase the contact area on the surface. Furthermore, electrochemical impedance spectroscopy and cyclic voltammetry analysis indicated the electrochemical double-layer capacitance of the CS/CNT anode increased while its internal resistance decreased significantly. These characteristics are crucial for increasing bacterial adhesion capability and electron transfer rate. The maximum output voltage of the SMFC with CS/CNT anode was 158.42 mV, and the removal rate of petroleum hydrocarbon (PH) reached 42.17%, 2.72 times that of unmodified CS. In conclusion, CNT-modified CS is conducive to improve electron transfer rate and microbial attachment, enhancing the removal efficiency of PH in soil. Graphical abstract
 
Flow chart of preparing barley malt kvass
Phylogenetic tree of LABs (A), yeasts (B), and AABs (C) isolated from homemade bread kvass based on 16 sRNA or 26 sRNA sequences
The effect of wort concentration (A), fermentation temperature (B), fermentation time (C), inoculum size (D), and strain ratio (E) on the alcohol content and sensory evaluation score of barley malt fermented kvass
Three-dimensional plots and corresponding contour plots of the independent variables on the sensory evaluation score of barley malt fermented kvass. A Effect of wort concentration and fermentation time for a fermentation temperature of 29 ℃. B Effect of wort concentration and fermentation temperature for a fermentation time of 24 h. C Effect of fermentation temperature and fermentation time for a wort concentration of 7°Brix
Properties comparison of barley malt kvass and commercial kvass products. PCA biplot of different kvass on E-tongue measurements (A) and E-nose measurements (B). The DPPH (C) and ABTS (D) radical scavenging activity of different kvass in vitro. E Sensory evaluation score of barley malt fermented kvass compared with commercial products
Article
Kvass is a popular low-alcohol beverage produced by the natural fermentation of dark rye bread or malt with complex microbial flora. However, few pieces of research focus on the microflora of traditional bread kvass, and the industrial kvass based on malt concentrate has some disadvantages, including the lack of viable probiotics and containing multiple artificial additives. Therefore, in the present study, based on the different homemade traditional bread kvass, the predominant species including Lacticaseibacillus paracasei, Acetobacter pasteurianus, and Saccharomyces cerevisiae were screened and identified. In addition, barley malt was used instead of bread for kvass production, and the co-fermentation conditions with three different strains were optimized as wort concentration of 7.4°Brix, cell ratio of 2/2/1 (S. cerevisiae/L. paracasei/A. pasteurianus), inoculum amount of 8%, fermentation temperature of 29.5 °C and fermentation time of 24.6 h. Moreover, the physicochemical (pH, total soluble solids, color, and alcohol content) and probiotic (microorganisms counting and antioxidant activity) properties of the barley malt kvass prepared at optimal conditions were symmetrically evaluated. Besides, compared with the commercial kvass products, the produced barley malt kvass exhibited better taste and more desirable antioxidant activity, and also maintained around 6–7 log CFU/mL of viable probiotic microorganisms during a week of storage. The present study not only enriched the biological resource of the traditional kvass, but also promoted the development of the kvass as a live-bacteria beverage.
 
Article
Lipases (E.C. 3.1.1.3) have buried active sites and used access tunnels in the transport of substrates and products for biotransformation processes. Computational methods are used to predict the trajectory and energy profile of ligands through these tunnels, and they complement the experimental methodologies because they filter data, optimizing laboratory time and experimental costs. Access tunnels of Burkholderia cepacia lipase (BCL), Candida rugosa lipase (CRL), and porcine pancreas lipase (PPL) and the transport of fatty acids, alcohols and esters through the tunnels were evaluated using the online server CaverWeb V1.0, and server calculation results were compared with experimental data (productivity). BCL showed higher productivity with palmitic acid-C16:0 (4029.95 µmol/h mg); CRL obtained productivity for oleic acid-C18:1 (380.80 µmol/h mg), and PPL achieved productivity for lauric acid-C12:0 (71.27 µmol/h mg). The highest probability of transport for BCL is through the tunnels 1 and 2, for CRL through the tunnel 1, and for PPL through the tunnels 1, 2, 3 and 4. Thus, the best in silico result was the transport of the substrates palmitic acid and ethanol and product ethyl palmitate in tunnel 1 of BCL. This result corroborates with the best result for the productivity data (higher productivity for BCL with palmitic acid-4029.95 µmol/h mg). The combination of in silico evaluation and experimental data gave similar results, demonstrating that in silico approaches are a promising alternative for reducing screening tests and minimizing laboratory time in the bio-catalysis area by identifying the lipases with the greatest reaction potential, as in the case of this proposal.
 
Article
Many operating parameters of ultrafiltration (UF) are playing a crucial role when using a polyethersulfone membrane to separate xylose reductase (XR) enzyme from reaction mixtures during xylitol synthesis. The present study focuses on the separation of XR enzyme using a cross-flow ultrafiltration (UF) membrane. The filtration process was analyzed using the three effective variables such as filtration time, cross-flow velocity (CFV), and the transmembrane pressure (TMP), which were ranging from 0 to 100 min, 0.52 to 1.2 cm/s and 1–1.6 bar, respectively. Then, using the resistance in series model, the hydraulic resistance for alkali chemical cleaning during XR separation was estimated. During separation, increased TMP showed a positive-flux effect as a driving force, however, fouling and polarized layer were more prominent under higher TMP. Increased CFV, on the other hand, was found more efficient in fouling control. In terms of the membrane cleaning techniques, an alkaline solution containing 0.1 M sodium hydroxide was shown to be the most effective substance in removing foulants from the membrane surface in this investigation. Cleaning with an alkaline solution resulted in a maximum flux recovery of 93% for xylose reductase separation. This work may serve as a useful guide to better understand the optimization parameters during XR separation and alleviating UF membrane fouling induced during XR separation.
 
Article
γ-Aminobutyric acid (GABA) is a non-protein amino acid with a variety of physiological functions. Recently, yeast Kluyveromyces marxianus strains involved in the catabolism and anabolism of GABA can be used as a microbial platform for GABA production. Okara, rich in nutrients, can be used as a low-cost fermentation substrate for the production of functional materials. This study first proved the advantages of the okara medium to produce GABA by K. marxianus C21 when l-glutamate (l-Glu) or monosodium glutamate (MSG) is the substrate. The highest production of GABA was obtained with 4.31 g/L at optimization condition of culture temperature 35 °C, fermentation time 60 h, and initial pH 4.0. Furthermore, adding peptone significantly increased the GABA production while glucose and vitamin B6 had no positive impact on GABA production. This research provided a powerful new strategy of GABA production by K. marxianus C21 fermentation and is expected to be widely utilized in the functional foods industry to increase GABA content for consumers as a daily supplement as suggested. Graphical abstract
 
General structure of PFASs where X represents a hydrophilic functional group such as sulfonates (–SO3⁻) and carboxylates (–COO⁻)
Transport and bioaccumulation of PFASs in plant
Bioaccumulation factors of aquatic plants for different types of PFCs [29]
The mechanisms of PFCs breakdown by fungi
Reductive defluorination in bacteria (https://sfamjournals.onlinelibrary.wiley.com/doi/10.1111/1751-7915.13928) [48]
Article
Perfluorochemicals are widely found in the environment due to their versatile uses and persistent nature. Perfluorochemicals have also been detected in human and animals due to direct or indirect exposures, giving rise to health concerns. This review aims to examine the bioremediation of perfluorochemicals with plants, bacteria and fungi, including their efficiency and limitations. It also aims to propose the future prospects of bioremediation of perfluorochemicals. This review retrieved peer-reviewed journal articles published between 2010 and 2021 from journal databases consisting of Web of Science, Scopus and ScienceDirect. This review shows that multiple Pseudomonas species could degrade perfluorochemicals particularly perfluoroalkyl acids under aerobic condition. Acidimicrobium sp. degraded perfluoroalkyl acids anaerobically in the presence of electron donors. A mixed Pseudomonas culture was more effective than pure cultures. Multiple plants were found to bioconcentrate perfluorochemicals and many demonstrated the ability to hyperaccumulate perfluoroalkyl acids, particularly Festuca rubra, Salix nigra and Betula nigra. Fungal species, particularly Pseudeurotium sp. and Geomyces sp., have the potential to degrade perfluorooctanoic acid or perfluorooctane sulphonic acid. Perfluorochemicals bioremediation could be advanced with identification of more candidate species for bioremediation, optimization of bioremediation conditions, mixed culturing, experiments with environmental media and studies on the biochemical pathways of biotransformation. This review provides comprehensive insight into the efficiency of different bacterial, plant and fungal species in perfluorochemicals bioremediation under different conditions, their limitations and improvement.
 
Article
Manganese peroxidase (Mn P) is capable of effectively degrading anionic polyacrylamide (HPAM). However, the interaction of Mn P with HPAM at molecular level is lacking until now. Here, the HPAM model compounds, HPAM-2, HPAM-3, HPAM-4, and HPAM-5, were selected to reveal their binding mechanisms with Mn P. The results showed that the most suitable substrate for Mn P was HPAM-5, and the main reason for MnP-HPAM-5 with maximal affinity was strong hydrogen bond. LYS96 was the important key residue in all complexes, and the number of key residue was largest in MnP-HPAM-5. The optimal THR27ILE mutant may enhance the affinity of Mn P to HPAM-4. The stability of Mn P binding to HPAM-4 was the optimal. These results were helpful in designing highly efficient Mn P against HPAM to protect the ecological environment.
 
The appearance of J. curcas plants in treatment A and treatment B during 4-week treatment
Aluminium removal by J. curcas during 4-week treatment
Bioconcentration factor of J. curcas for 4-week treatment
Article
Bauxite wastewater creates soil contamination and produces toxic effects on human health such as respiratory and skin rash problems. In this study, we investigated the phytoremediation ability of Jatropha curcas to remove bauxite wastewater from soil. Pot experiments were conducted to investigate the bauxite wastewater on the phytoremediation potential of J. curcas grown in contaminated soils. J. curcas exhibited a significant increase in plant growth leaf, root activity, plant height, and plant shoot when grown in bauxite contaminated soils compared with J. curcas grown in uncontaminated soils after 30 d treatment. Under bauxite exposure, a higher aluminium removal (88.5%) was observed in soils planted with J. curcas than unplanted soils (39.6%). The bioconcentration factor was also found to be 5.62, indicating that J. curcas have great tolerance and hyperaccumulator of aluminium under high aluminium concentrations and are capable of phytoextraction of soil contaminated with bauxite wastewater.
 
Article
The growing interest in the use of lentiviral vectors (LVs) for various applications has created a strong demand for large quantities of vectors. To meet the increased demand, we developed a high cell density culture process for production of LV using stable producer clones generated from HEK293 cells, and improved volumetric LV productivity by up to fivefold, reaching a high titer of 8.2 × 10 ⁷ TU/mL. However, culture media selection and feeding strategy development were not straightforward. The stable producer clone either did not grow or grow to lower cell density in majority of six commercial HEK293 media selected from four manufacturers, although its parental cell line, HEK293 cell, grows robustly in these media. In addition, the LV productivity was only improved up to 53% by increasing cell density from 1 × 10 ⁶ and 3.8 × 10 ⁶ cells/mL at induction in batch cultures using two identified top performance media, even these two media supported the clone growth to 5.7 × 10 ⁶ and 8.1 × 10 ⁶ cells/mL, respectively. A combination of media and feed from different companies was required to provide diverse nutrients and generate synergetic effect, which supported the clone growing to a higher cell density of 11 × 10 ⁶ cells/mL and also increasing LV productivity by up to fivefold. This study illustrates that culture media selection and feeding strategy development for a new clone or cell line can be a complex process, due to variable nutritional requirements of a new clone. A combination of diversified culture media and feed provides a broader nutrients and could be used as one fast approach to dramatically improve process performance.
 
Different stages of experimental sections. A NPW after initial stages of size reduction. B NPW after acid-alkaline pretreatment process. C Final inoculum development for Trichoderma reesei (MTCC 164) in the presence of 3 g/L of pretreated paper waste inducer. D After fermentative production of cellulase from pretreated NPW
Physicochemical characterization of newspaper sample at different stages of pretreatment: A SEM image of native newspaper material at 1000 × magnification B SEM image of native newspaper material at 2000 × magnification C SEM image of acid-alkaline pretreated newspaper material at 1000 × magnification D SEM image of acid-alkaline pretreated newspaper material at 2000 × magnification E FTIR spectra of untreated and acid-alkaline pretreated newspaper material
Analysis section of response surface methodology. A Distribution of predicted response vs. actual response values. B Response surface plot showing combined effect lactose and newspaper waste on cellulase production. C Response surface plot showing combined effect of peptone and newspaper waste on cellulase production. D Response surface plot showing combined effect of peptone and lactose on cellulase production
Model predicted and experimental results of cellular growth, substrate consumption and cellulase production at three different conditions of fermentation (A) with 1.5% (wv⁻¹) pretreated PW concentration (B) with 3.29% (wv⁻¹) pretreated PW concentration (C) with 4% (wv⁻¹) pretreated PW concentration
Article
A systematic evaluation of microorganism’s potential towards biosynthesis of cellulases from inexpensive lignocellulosic feedstock through appropriate kinetic modelling facilitates understanding, optimization and designing of an effective industrial cellulase enzyme production process. The present study aims to optimize a submerged fungal cultivation strategy for cellulase production from abundantly available newspaper wastes (NPW). A combined pretreatment strategy consisting diluted, 1% (v v⁻¹) H2SO4 followed by 2% (wv⁻¹) NaOH treatment was highly effective to convert newspaper waste to an effective cellulose-enriched inducer for the production of cellulase. In addition, the composition of the most influential nutrient components like peptone and lactose was optimized with the help of response surface methodology for enhanced cellulase production with maximum activity levels. Maximum cellulase production of 8.64 g L⁻¹ with 7.82 FPU mL⁻¹ total activity levels was achieved from optimized composition of pretreated NPW 3.29% (w v⁻¹), lactose 2.94% (w v⁻¹) and peptone 1.53% (w v⁻¹). To analyse intrinsic inhibition effect of the substrate concentration on cellulase production, modified Luedeking–Piret model simulated experiments were further conducted with 1.5% (w/v), 3.29% (w/v) and 4% (w/v) NPW concentrations. The developed kinetic model perfectly captured the trends of biomass production, substrate consumption and adsorption characteristic of cellulase enzyme on its activity during production. The rate constant for cellulase synthesis was evaluated to be increased to 0.040 IU g⁻¹ h ⁻¹ at 3.29% (w v⁻¹) of NPW concentration; however, it was further reduced to 0.024 IU g⁻¹ h ⁻¹ at higher NPW concentration of 4% (w v⁻¹).
 
Article
In the scenario of alarming increase in greenhouse and toxic gas emissions from the burning of conventional fuels, it is high time that the population drifts towards alternative fuel usage to obviate pollution. Hydrogen is an environment-friendly biofuel with high energy content. Several production methods exist to produce hydrogen, but the least energy intensive processes are the fermentative biohydrogen techniques. Dark fermentative biohydrogen production (DFBHP) is a value-added, less energy-consuming process to generate biohydrogen. In this process, biohydrogen can be produced from sugars as well as complex substrates that are generally considered as organic waste. Yet, the process is constrained by many factors such as low hydrogen yield, incomplete conversion of substrates, accumulation of volatile fatty acids which lead to the drop of the system pH resulting in hindered growth and hydrogen production by the bacteria. To circumvent these drawbacks, researchers have come up with several strategies that improve the yield of DFBHP process. These strategies can be classified as preliminary methodologies concerned with the process optimization and the latter that deals with pretreatment of substrate and seed sludge, bioaugmentation, co-culture of bacteria, supplementation of additives, bioreactor design considerations, metabolic engineering, nanotechnology, immobilization of bacteria, etc. This review sums up some of the improvement techniques that profoundly enhance the biohydrogen productivity in a DFBHP process. Graphical abstract
 
Article
A series of nickel-incorporated SBA-15 mesoporous molecular sieves (Ni-SBA-15) were prepared as support for the immobilization of his-tagged recombinant Microbacterium esterase. The Ni-SBA-15 could strongly and specific absorb the his-tagged esterase from cell disrupted supernatant. It was found that the nickel amount in Ni-SBA-15 has dramatic influence on the activity and thermo-stability of immobilized enzyme, while the kinds of nickel precursor had little effect on enzyme stability. The morphology, chemical composition and structure of the best support NiCl2-SBA-15 (Ni-SBA-15 prepared from NiCl2 precursor) were characterized by various spectroscopy techniques. The immobilized esterase retained full activity of free esterase and showed high immobilized yield (> 90%) with higher thermo-stability, pH stability and organic solvent resistance compared with free enzyme. The optimum reaction temperature increased from 35 to 40 °C and the optimal reaction pH moved from 10.0 to 8.0 after enzyme immobilization. The immobilized esterase exhibited excellent storage stability and keeping 92% of the initial activity after 30 days’ storage at 25 °C. In addition, the immobilized esterase had excellent reusability for the synthesis of key chiral intermediate of d-biotin and the substrate conversion could still keep 100% after 13 cycles continuously. Finally, optical pure (4S, 5R)-hemiester was obtained in 80.8% isolated yield and 99% purity in the gram preparative scale.
 
Article
The formation of electroactive biofilm from activated sludge on electrode surface is a key step to construct a bio-electrochemical system, yet it is greatly limited by the poor affinity between the bacteria and the electrode interface. Herein, we report a new method to promote the formation of electroactive biofilm by regulating the extracellular polymeric substance (EPS) content in activated sludge with lysozyme. The investigation of the effect of lysozyme treatment on the content of extracellular polymers and the biofilm formation of electroactive bacteria suggests that lysozyme can improve the permeability of the positive bacterial cell membrane and thus increase the EPS content in the activated sludge. The characterizations of electrochemical activity, surface morphology and community structure of the anode biofilm indicate that increasing EPS content promotes the adhesion of the mixed bacteria in the activated sludge on the electrode and results in denser biofilms with better conductivities. The microbial fuel cell (MFC) inoculated with the sludge of high EPS content exhibits the power density up to 2.195 W/m², much higher than that inoculated with the untreated sludge (1.545 W/m²). The strategy of adjusting EPS content in activated sludge with a biological enzyme can effectively enhance the ability of the bacterial community to form biofilms and exhibits great application potentials in the construction of high efficiency bio-electrochemical systems.
 
The effect of pH on TF synthesis
The effect of substrate concentration on TFs synthesis
The effect of reaction time on TF synthesis
The effect of reaction temperature on TF synthesis
The dynamic changes of the enzymatic reaction system. a The dynamic change of the catechin content in the reaction system; b the dynamic change of the TF content in the reaction system
Article
Theaflavin (TF), a chemical component important in measuring the quality of fermented tea, has a strong natural antioxidant effect and many pharmacological functions. Enzymatic oxidation has become a widely used method for preparing TFs at the current research stage. Using plant exogenous polyphenol oxidase (PPO) to enzymatically synthesize TFs can significantly increase yield and purity. In this study, tea polyphenols were used as the reaction substrate to discuss the optimal synthesis conditions of potato PPO enzymatic synthesis of theaflavins and the main products of enzymatic synthesis of TFs. The optimal enzymatic synthesis conditions were as follows: pH of the reaction system was 5.5, reaction time was 150 min, substrate concentration was 6.0 mg/mL, reaction temperature was 20 °C, and the maximum amount of TFs produced was 651.75 μg/mL. At the same time, high-performance liquid chromatography was used to determine the content of theaflavins and catechins in the sample to be tested, and the dynamic changes and correlations of the main catechins and theaflavins in the optimal enzymatic system were analyzed. The results showed that epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG) are all the main substrates synthesis of TFs. The main substrate of TFs and its strongest enzymatic catalytic effect on EGCG make theaflavin-3,3′-digallate (TFDG) the most important synthetic monomer. In this study, theaflavins were synthesized by polyphenol oxidase catalysis, which laid a foundation for industrialization of theaflavins.
 
Cellobiose-oxidizing activity and CBA production in original P. taetrolens and P. taetrolens [pDSK-GDH] strains. The bars in the graph represent intracellular cellobiose-oxidizing activity (blank) and CBA production (filled) at 12-h culture time. The error bars represent the standard deviation from three independent experiments
Effect of reaction temperature on CBA production. The WCB of P. taetrolens [pDSK-GDH] was incubated at different temperatures in a 300-mL baffled flask containing 50 mL of reaction medium. The time-course profiles of cellobiose consumption (A) and CBA production (B) are analyzed and the standard deviations of three independent experiments are expressed as error bars
Effect of cell density of WCB on CBA production. Different amounts of WCB of P. taetrolens [pDSK-GDH] were used at 35 °C in a 300-mL baffled flask containing 50 mL of the reaction medium. The time-course profiles of a change of cell density in the reaction medium (A), cellobiose consumption (B), and CBA production (C) are obtained. The error bars represent the standard deviation from three independent experiments
Effect of the growth phase of P. taetrolens cells on CBA production. The WCB samples of P. taetrolens [pDSK-GDH] were prepared from the cells harvested at the different culture times. Each WCB sample was incubated at the final cell density of 10 of OD600nm in a 300-mL baffled flask containing 50 mL of the reaction medium. The time-course profiles of cell growth during fermentation (A), cellobiose consumption (B), and CBA production (C) were analyzed. Arrows in (A) indicate the time points at which cells were harvested during fermentation. The error bars represent the standard deviation from three independent experiments
CBA production of the WCB of P. taetrolens [pDSK-GDH] during repeated reaction cycles. The WCB of P. taetrolens [pDSK-GDH] recovered through centrifugation and washing process was repeatedly applied to the reaction. CBA concentration was analyzed three times for each cycle of the reaction. The error bars represent the standard deviation from three independent experiments
Article
Pseudomonas taetrolens has previously been shown to convert cellobiose to cellobionic acid (CBA), which can potentially be used in cosmetics, food, and pharmaceutical industries. The cellobiose-oxidizing activity of the P. taetrolens strain, which expressed the homologous quinoprotein glucose dehydrogenase (GDH), was increased by approximately 50.8% compared to the original strain. Whole-cell biocatalyst (WCB) of the genetically modified P. taetrolens strain [pDSK-GDH] was prepared simply by fermentation and washing processes. Reaction conditions for the proper use of WCB, such as reaction temperature, cell density to be added, and cell harvest time for preparing WCB, were investigated. The highest CBA productivity (18.2 g/L/h) was achieved when WCB prepared in the late-exponential phase of cell culture was used at 35 °C with cell density of 10 at OD600nm. Under these conditions, 200 g/L of cellobiose was all converted to CBA in 11 h, and the WCB of P. taetrolens [pDSK-GDH] maintained the maximum catalytic activity during at least six cycles without a significant decline in the productivity. Our results suggest that the manufacture of WCB based on genetically engineered P. taetrolens and its optimized use could be further developed as an economically viable option for the large-scale production of CBA.
 
Article
In this study, blend nanofibrous scaffolds were electrospun from polycaprolactone/gelatin (PCL/Gel) blend solutions reinforced by bone morphogenetic protein (BMP)-modified graphene oxide (GO). SEM results showed that uniform and bead-less nanofibers with 270 nm average diameter were obtained from electrospun of PCL/Gel blend solutions. Tensile strength test and contact angle measurement demonstrated that addition of PCL led to higher mechanical and physical properties of the resulting nanofibers. The addition of PCL as well as GO in the blend supports the suitable mechanical strength in the body media. The loading of BMP-modified graphene in the Gel/PCL structure caused the formation of nanofibrous substrate with great resemblance to bone tissue. Gel/PCL-G hybrid nanofibers revealed good biocompatibility in the presence of human osteosarcoma cells, and no trace of cellular toxicity was observed. The cells grown on the scaffolds exhibited a spindle-like and broad morphology and almost uniformly covered the entire nanofiber scaffold. Graphical abstract Gel/PCL nanofibers reinforced by graphene oxide-immobilized bone morphogenetic protein was prepared as a promising safe and biocompatible nanofiber with high antibacterial activity for bone tissue engineering.
 
Batch fermentation of SBH for xylitol production: a production profile; b relation between xylitol yield vs XR activity; c relation between xylitol yield vs XR/XDH ratio; d purification profile; e semi-purified xylitol crystals; f. purified crystals
Characterization of purified xylitol crystals a XRD; b FT-IR, c GC–MS, and d NMR
Regeneration profile of adsorbent with acetic acid and its reuse. CAC commercial fresh carbon; SpC spent carbon; CAW chromic acid wash; DwW distilled water wash; AW acid/acetic acid wash; R1–R7 regenerated carbons in successive cycles; CL carbon loss; IN iodine number; DRC dye removal capacity; BD broth decolorization; XLTR xylitol recovered; PRC phenolics removal capacity; FRC furfural removal capacity
Xylitol recovery and adsorbent regeneration
Article
Xylitol is a well-known sugar alcohol with exponentially rising market demand due to its diverse industrial applications. Organic agro-industrial residues (OAIR) are economic alternative for the cost-effective production of commodity products along with addressing environmental pollution. The present study aimed to design a process for xylitol production from OAIR via microbial fermentation with Pseudomonas gessardii VXlt-16. Parametric analysis with Taguchi orthogonal array approach resulted in a conversion factor of 0.64 g xylitol/g xylose available in untreated sugarcane bagasse hydrolysate (SBH). At bench scale, the product yield increased to 71.98/100 g (0.66 g/L h). 48.49 g of xylitol crystals of high purity (94.56%) were recovered after detoxification with 2% activated carbon. Cost analysis identified downstream operations as one of the cost-intensive parts that can be countered by adsorbent recycling. Spent carbon, regenerated with acetic acid washing can be reused for six cycles effectively and reduced downstream cost by about ≈32%. The strategy would become useful in the cost-effective production of several biomass-dependent products like proteins, enzymes, organic acids, as well. Graphical abstract
 
Article
The selection of highly recombinant protein (RP)-productive Chinese hamster ovary (CHO) cell lines is widely carried out in shake flasks. It is assumed that increases in the operating parameters in shake flasks lead to impairments in cell growth and RP production. These effects in cells metabolism are widely associated with high mass transfers and hydrodynamic stress. This study examined the impact of commonly used operational parameters on growth and specific productivity (qP) of two CHO cell lines differentially secreting a humanized anti-hIL8 monoclonal antibody (mAb) and cultured in 250 ml flasks. The evaluated parameters are filling volume (10, 15, and 20%), shaking frequency (60 and 120 revolutions per minute -rpm-), and orbital diameter (25.4 and 19 mm). The analysis of the oxygen transfer was done in terms of the measured volumetric mass transfer coefficient (kLa) and of the hydrodynamics in terms of power input per unit volume of liquid (P/V), the turbulent eddy length scale measured by the Kolmogorov’s microscale of turbulence, the energy dissipation rate, the average shear stress, and the shear rate. Though almost all measured kinetic and stoichiometric parameters remained unchanged, mAb titer included, significant differences were found in maximum cell concentration, 10–45% higher in conditions with lower values of kLa and P/V. Changes in glucose metabolism contributing to qP were only shown in the higher producer cell line. Non-lethal responses to elevated oxygen transfer and shear stress might be present and must be considered when evaluating CHO cell cultures in shake flasks.
 
A schematic flow diagram showing enzymatic hydrolysis residue (EHR) fractionation by p-toluenesulfonic acid (p-TsOH) to produce fermentable sugars and LNPs adsorbent.
Time course of glucose yield (A) and xylose yield (B) of EHR and p-TsOH fractionated EHR at different p-TsOH concentration. p-TsOHp-Toluenesulfonic acid, EHR enzymatic hydrolysis residue, P15, P35, P55, and P75, refers to the solid residue obtained after p-TsOH fractionation at p-TsOH concentration of 15%, 35%, 55%, and 75% at 90 °C for 120 min, respectively.
Transmission electron microscopy (TEM) analyses of LNPs from p-TsOH fractionated EHR at different p-TsOH concentration and LNPs particle diameter distribution. (A, a) P15, (B, b) P35, (C, c) P55, (D, d) P75, (E, e) untreated EHR. LNPs lignin nanoparticles, p-TsOH p-Toluenesulfonic acid, EHR enzymatic hydrolysis residue, P15, P35, P55, and P75, refers to the solid residue obtained after p-TsOH fractionation at p-TsOH concentration of 15%, 35%, 55%, and 75% at 90 °C for 120 min, respectively.
Effect of different concentrations of EHR or LNPs on the removal of main inhibitors in the xylose-rich prehydrolyzate. EHR enzymatic hydrolysis residue, LNPs lignin nanoparticles, HMF 5-hydroxymethylfurfural.
Article
This study proposed a recyclable p-toluenesulfonic acid (p-TsOH) fractionation process for co-producing lignin nanoparticles (LNPs) and fermentable sugars from lignocellulosic biorefinery biowaste (enzymatic hydrolysis residue (EHR)). The prepared LNPs were used to detoxify the inhibitors in the xylose-rich prehydrolyzate for improving ethanol production. Results showed that the EHR was fractionated into a cellulose-rich water-insoluble solid (WIS) fraction and a lignin-rich spent liquor (SL) fraction. Cellulase hydrolysis of WIS produced 97.7% of glucose yield, while the LNPs of an average particle size of 98.0 nm with 76.3 % yield (based on the untreated EHR) were obtained from the diluted SL. LNPs demonstrated higher detoxification ability than EHR at the same dosage. Moreover, the fermentability of the detoxified xylose-rich prehydrolyzate was significantly improved. The sugar utilization ratio was 94.8%, and the ethanol yield reached its peak value of 85.4% after 36 h of fermenting the detoxified xylose-rich prehydrolyzate.
 
Response surface (a) and contour curve (b) of the effects of gelatin and CaCl2 concentrations on the immobilization of Erwinia sp. D12 cells, and conversion of sucrose into isomaltulose in the CCRD-2² design trials
Conversion of sucrose into isomaltulose by Erwinia sp. D12 cells immobilized in the optimized matrix using a packed bed reactor
Stability (%) of sucrose (black square), palatinose (dark grey square), and isomaltulose (light grey square) added to cola drink (a), lemon drink (b), orange energy drink (c), and grape energy drink (d) during 30 days of storage at 5 °C
Kinetic growth of Bifidobacterium animalis Bb12 (a) and Lactobacillus lactis (b) in MRS broth (black square) and MRS broth supplemented with 1% lactulose (dark grey square), 1% palatinose (light grey square), and 1% isomaltulose (shaded square)
Article
Isomaltulose is a potential substitute for sucrose, with a high stability and prebiotic potential, for wide use in candies and soft drinks. This sugar is obtained from sucrose through enzymatic conversion using microbial glucosyltransferases. This work aimed to optimize a matrix to immobilize glucosyltransferase producing Erwinia sp. D12 cells using a sequential experimental strategy. The cell mass of Erwinia sp. D12 obtained in a bioreactor was immobilized in beads formed by ionic gelation. The conversion of sucrose into isomaltulose using the beads was performed in batch and continuous processes, and the isomaltulose was recovered through crystallization. The stability of isomaltulose was assessed in beverages of different pH values, and its prebiotic potential was verified with the growth of probiotic microorganisms. The optimized matrix composed of alginate (2.0% w/v), CaCl2 (2.0% w/v), gelatin (2.0% w/v), and transglutaminase (0.2% w/v) showed the highest mean of produced isomaltulose (199.82 g/L) after four batches. In addition, high stability during the continuous process resulted in an isomaltulose production above of 230 g/L for up to 72 h. The produced isomaltulose was more stable than sucrose in lemon soft drink and orange and grape energy drinks after 30 days of storage; and promoted the growth of Bifidobacterium animalis and Lactobacillus lactis. In conclusion, the production of isomaltulose by Erwinia sp. D12 cells immobilized using optimized conditions is recommended, due to its high conversion capacity, high stability, and prebiotic potential of crystals obtained.
 
Article
Rapid transmission of infectious microorganisms such as viruses and bacteria through person-to-person contact has contributed significantly to global health issues. The high survivability of these microorganisms on the material surface enumerates their transmissibility to the susceptible patient. The antimicrobial coating has emerged as one of the most interesting technologies to prevent growth and subsequently kill disease-causing microorganisms. It offers an effective solution a non-invasive, low-cost, easy-in-use, side-effect-free, and environmentally friendly method to prevent nosocomial infection. Among antimicrobial coating, zinc oxide (ZnO) stands as one of the excellent materials owing to zero toxicity, high biocompatibility to human organs, good stability, high abundancy, affordability, and high photocatalytic performance to kill various infectious pathogens. Therefore, this review provides the latest research progress on advanced applications of ZnO nanostructure-based antibacterial coatings for medical devices, biomedical applications, and health care facilities. Finally, future challenges and clinical practices of ZnO-based antibacterial coating are addressed.
 
Article
To reach an efficient and economical gas-phase bioreactor is still one of the most critical challenges in biotechnology engineering. The numerous advantages of gas-phase bioreactors (GPBs) as well as disadvantages of these bioreactors should be exactly recognized, and efforts should be made to eliminate these defects. The first step in upgrading these bioreactors is to identify their types and the results of previous research. In the present work, a summary of the studies carried out in the field of cultivation in these bioreactors, their classification, their components, their principles and relations governing elements, modeling them, and some of their inherent engineering aspects are presented. Literature review showed that inoculation of shoots, roots, adventurous roots, callus, nodal explants, anther, nodal segment, somatic embryo, hairy roots, and fungus is reported in 15, 2, 2, 2, 3, 2, 1, 1, 37, and 5 cases, respectively.
 
The reaction equation of NPMI treated wool fabric and Schematic diagram of composite wool fabric preparation
Schematic illustrations: a–c Scanning Electron Microscope (SEM) images of original wool, reduced wool and composite wool fabric; d FTIR of original wool, reduced wool and composite wool fabric; e Raman spectra of original wool and reduced wool. f water contact angle of original wool, reduced wool and composite wool. i composite wool fabric with the antibacterial feature
Schematic illustrations: a–d high-resolution scanning electron micrographs of raw wool fibers and reduced wool fibers; e–n high-resolution scanning electron micrographs of the composite wool at different concentrations of N-phenylmaleimide at 1%, 3%, 5%, 7%, and 9%
Evaluation of the antibacterial activity of virgin and treated PET fabrics. e, f Antimicrobial activity of virgin wool fabrics against E. coli and S. aureus after 24 h incubation; d, g Persistent antimicrobial activity of treated wool fabrics after 1 standard wash and e, h Persistent antimicrobial activity of treated wool fabrics after 10 standard washes a, b Inhibition circle test for virgin and composite wool fabrics. Bacterial plates exposed to E. coli and S. aureus for 24 h
Comprehensive performance evaluation of original wool, reduced wool and composite wool: a density of felting ball; b air permeability; c Water evaporation rate d breaking strength; e electrostatic voltage; f half-life. The same test was performed on the three samples to calculate the average value as the measured value of the sample. The error bar is determined by the difference between the maximum and minimum values of three parallel patterns
Article
In this study, we successfully synthesized N-phenylmaleimide (NPMI) and applied it to wool fabrics to obtain robust antimicrobial properties. First, tris(2-carboxyethyl) phosphine (TCEP) was utilized as a reducing agent to produce thiol-active groups on wool fibers. These thiol groups were then reacted with the C=C group of NPMI via thiol-ene click chemistry. The morphology and structure of the finished NPMI composite wool fabric were characterized using FT-IR spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The composite wool fabrics exhibited durable antibacterial properties against both S. aureus and E. coli and the antimicrobial rates of both E. coli and S. aureus were around 99% after one standard washing cycle, with only a slight decrease of 95% after ten standard washing cycles, respectively. In addition, the composite wool fabric exhibited good anti-felting performance and maintained its original excellent breathability and moisture permeability. The present work provides a facile and sustainable strategy for constructing durable antimicrobial wool fabrics without losing their original properties.
 
Top-cited authors
Beom Soo Kim
  • Chungbuk National University
Sung-Koo Kim
  • Pukyong National University
He Huang
  • Sun Yat-Sen University Cancer Center
Débora de Oliveira
  • Federal University of Santa Catarina
Helen Treichel
  • Universidade Federal da Fronteira Sul