Optimization Of Fermentation Conditions Research Articles

Anti-Inflammatory Ergosteroid Derivatives from the Coral-Associated Fungi Penicillium oxalicum HL-44

To obtain the optimal fermentation condition for more abundant secondary metabolites, Potato Dextrose Agar (PDA) medium was chosen for the scale-up fermentation of the fungus Penicillium oxalicum HL-44 associated with the soft coral Sinularia gaweli. The EtOAc extract of the fungi HL-44 was subjected to repeated column chromatography (CC) on silica gel and Sephadex LH-20 and semipreparative RP-HPLC to afford a new ergostane-type sterol ester (1) together with fifteen derivatives (2–16). Their structures were determined with spectroscopic analyses and comparisons with reported data. The anti-inflammatory activity of the tested isolates was assessed by evaluating the expression of pro-inflammatory factors Tnfα and Ifnb1 in Raw264.7 cells stimulated with LPS or DMXAA. Compounds 2, 9, and 14 exhibited significant inhibition of Ifnb1 expression, while compounds 2, 4, and 5 showed strong inhibition of Tnfα expression in LPS-stimulated cells. In DMXAA-stimulated cells, compounds 1, 5, and 7 effectively suppressed Ifnb1 expression, whereas compounds 7, 8, and 11 demonstrated the most potent inhibition of Tnfα expression. These findings suggest that the tested compounds may exert their anti-inflammatory effects by modulating the cGAS-STING pathway. This study provides valuable insight into the chemical diversity of ergosteroid derivatives and their potential as anti-inflammatory agents.

Production of single cell protein rich in potassium by Nectaromyces rattus using biogas slurry and molasses

Single-cell protein (SCP) is a vital supplement for animal protein feed. This study utilized biogas slurry and sugarcane molasses to ferment Nectaromyces rattus for the production of SCP. The optimal batch fermentation conditions were obtained in a 5L jar with a tank pressure of 0.1 MPa, an initial speed of 300 rpm, and an inoculum volume of 30%. The highest cell dry weight concentrations of the fed-batch fermentation without reflux and the fed-batch fermentation with reflux were 46.33 g/L and 29.71 g/L, respectively. The nitrogen conversion rates (47.05% and 44.12%) and the cell yields of total organic carbon (1 g/g and 1.17 g/g) of both fermentation modes were compared. The SCP contained 42.32% amino acids. Its high concentrations of potassium (19859.96 mg/kg) and phosphorus (7310.44 mg/kg) present a novel approach for the extraction of these essential nutrients from biogas slurry. The enrichment of K was related to the H+ efflux and sugar transport.

Optimation of Green Synthesis Biopolymer Cellulose Using Acetobacter xylinum From Whey as Media of Bacteria

Utilizing waste into a more valuable commodity was one of the objectives of that research. Waste which initially became an environmental pollutant factor could be processed into more useful products. Tofu liquid waste was referred to whey was a by-product of tofu production. Whey was waste that still contains organic materials such as protein, fat, carbohydrates and minerals. That whey was used as a growth medium for Acetobacter xylinum bacteria and produces cellulose biopolymer as a result of carbohydrate fermentation. The process of optimizing carbohydrate fermentation by Acetobacter xylinum bacteria was carried out by varying the ratio of the amount of whey to coconut water, the acidity level of the media, and the fermentation time. The research results showed that the biosynthesis of cellulose biopolymer was obtained from a ratio of whey concentration to coconut water of 1:1, variations in acidity levels showed that the optimum fermentation conditions occurred at pH 4, and the optimal amount of cellulose biopolymer was obtained on day 21, namely with the highest percent yield value. The resulting biocellulose was characterized using FTIR, XRD, and SEM. The characterization results show that biocellulose is well formed with a fiber surface shape and particle size in the range of 50-200 nm

Ethanologenic yeasts from Ethiopian fermented beverages and optimization of fermentation conditions

The rising global demand of renewable energy sources such as bioethanol is pushing stakeholders to search for efficient ethanologenic microbes. This study aimed to isolate yeasts from Ethiopian traditional fermented beverages, evaluate their ethanol yield using banana peel as a substrate, and identify best-performing isolates. Moreover, this study attempted to statistically optimize fermentation conditions through Placket Burman Design and Central Composite Design based Response Surface Methodology (RSM). A progressive screening and selection approach was followed to select best performing isolates. Factors that significantly influence fermentation efficiency were selected using Plackett-Burman Design (PBD) and then optimized via Central Composite Design (CCD). A total of 11 isolates were obtained. Three isolates (DMTD2, GB1D5 and RTj3D3) were selected based on their tolerance to stress conditions, and carbohydrate fermentation and assimilation performances. GB1D5 and RTj3D3 were highly tolerant whereas DMTD2 was moderately tolerant to 10 % ethanol concentration with survival percentages ranging from 40.8 ± 5.6 to 65.7 ± 10.5 %. However, they were slightly tolerant to 15 and 20 %, with an insignificant survival percentage rate. They yield 11.6 ± 0.9 to 12.9 ± 0.3 g/L ethanol from 8 % (w/v) banana peel waste. D1/D2 genotyping identified them as Saccharomyces cerevisiae strains. Glucose concentration and incubation period significantly affect ethanol production. The maximum actual ethanol yield produced by isolates at optimum condition was the same i.e. 31.4 g/L, whereas the ethanol yield predicted by the model ranged between 31.8 and 32.5 g/L. Results demonstrate these strains are promising candidates for bioethanol production. Optimization of fermentation conditions using banana peel waste as substrate is recommended.

Microbial Biotransformation of Agro-waste Into Biovanillin as Flavor: A Process Optimization by Response Surface Methodology

Vanillin is a flavour that is commonly employed in the food industry, but plant sources can yield a small amount of this molecule. Fermentative production of biovanillin by optimizing different process parameters such as specific pH, temperature, incubation time, carbon source, nitrogen source, ferulic acid substrate, and by agro wastes are beneficial in terms of fermentation economics and scale up of the process response surface methodology for an ideal production of biovanillin yield. Hence the present research emphasizes on optimization of fermentation conditions for employing Bacillus licheniformis MSJM5 isolate. As per the experimental results biovanillin production yield was enhanced at neutral pH, mesophilic temperature, in an incubation of 48 hrs, under revolving conditions, in the presence of glucose as carbon source soya bean as nitrogen source ferulic acid 0.3 mg concentration and ground nut oil cake, an agro waste material has stimulated the formation of biovanillin, 326-834 mg/ml. Further stastical analysis by RSM the yield of biovanillin was 1.89 mg/ml. Based on the morphological cultural and biochemical the positive strain MSJM5 is identified as Bacillus licheniformis with 98% homology and accession number ON413745. Strain improvement studies have reveated that UV light and Et Br use reduce the survival capacity of Bacillus licheniformis.

Study on Microbial Degradation Characteristics of Diesel Contaminated Soil

A novel and highly effective Acinetobacter (L15) were obtained from soil by morphological observation, physiological and biochemical tests and 16 SrDNA sequencing. The optimal reaction environment of L15 at different temperatures was determined by shaking test, and the catalytic activity was measured. It was found that the bacteria could withstand n-cetane value above 5000 mg/L when the initial culture pH was 7, the inoculation amount was 5%, the shaking speed was 150 r/min, and the culture temperature was 30℃. Under the optimal 7-day fermentation condition, the degradation rate of n-cetane compounds reached 94.09%, and the decomposition rate of 3000 mg/L diesel oil was basically complete. The results showed that the bacteria had good potential for bioreactor in diesel contaminated soil.

The Characterization of the Inhibitory Substances Produced by Bacillus pumilus LYMC-3 and the Optimization of Fermentation Conditions

Bacillus pumilus plays a very important role in the biological control of plant diseases. In this study, we conducted indoor biocontrol experiments using the LYMC-3 strain of B. pumilus to assess its efficacy against poplar canker and tea gray blight. Simultaneously, we explored the optimal fermentation conditions for the production of inhibitory substances against Phomopsis macrospora and Pestalotiopsis vesicolor. Subsequently, the inhibitory substances were extracted crudely and subjected to a preliminary investigation of their properties. The results of the indoor biocontrol experiments showed that the LYMC-3 strain exhibited disease prevention rates of 44.12% and 48.59% against poplar canker and tea gray blight, respectively. The fermentation optimization experiment showed that a culture medium containing 10 g/L of glucose, 15 g/L of tryptone, and 5 g/L of sodium chloride favored the production of inhibitory substances via the LYMC-3 strain. Among the crude extracts obtained, the non-protein extracts demonstrated the most obvious inhibitory effects. Furthermore, the inhibitory substances exhibited high polarity, excellent thermal stability, and high sensitivity to strong acids and bases. This study establishes a theoretical foundation for the purification and identification of inhibitory substances using the LYMC-3 strain. Additionally, it contributes to elucidating biological control mechanisms and facilitates the application of the LYMC-3 strain in production.

Enhancing the heterologous expression of latex clearing protein from Streptomyces sp. strain K30 in Escherichia coli through fermentation condition optimization and molecular modification

Latex clearing protein from Streptomyces sp. strain K30 (LcpK30) is a natural oxidoreductase that can catalyse the cleavage of rubber through dioxygenation. It has significant potential applications in polymer degradation. However, its limited expression in engineered strains restricts its utility. This study aimed to enhance the soluble expression and enzyme activity of LcpK30 in E. coli BL21 (DE3) by optimizing fermentation conditions and making molecular modifications. The enzyme activity reached 5.05 U·mL−1 by optimizing the induction conditions, adding cofactors, and using chemical chaperones, which was 237.1 % of the initial case. Further enhancements in soluble expression were achieved through site mutations guided by the PROSS server, resulting in 8 out of 13 mutants with increased protein expression, a high positive mutation rate of 61.5 %. Subsequently, combined mutants were created by merging single mutants with enhanced protein expression and enzyme activity. The top three double mutants, G91D/S149A, G91D/A210H, and G91D/H296P, displayed expression levels at 173.3 %, 173.3 %, and 153.3 % of the wild-type LcpK30, respectively. These mutants also exhibited enhanced fermentation enzyme activity, reaching 149.5 %, 250.0 %, and 420.2 % compared to the wild-type, along with improved specific activities. This study provides insights for the efficient production of LcpK30 and a practical foundation for its application.

Analysis of surfactant production by Bacillus cereus GX7 and optimization of fermentation conditions

Although biosurfactants have many advantages compared to chemical surfactants, biosurfactants are still limited by problems such as low yields and high production costs. In the present study, a strain of Bacillus Cereus (GX7) isolated from an oil tank bottom sludge of Shengli Oil Field (China) was selected as a highly effective surfactant producer. The biosurfactant produced by GX7 was extracted, purified, and analyzed by TLC, FT-IR, and LC-MS/MS. The results showed that the biosurfactant was surfactin of lipopeptide surfactant. Single-factor experiments were used to optimize the fermentation process of the strain from two aspects: the composition of the fermentation medium (carbon source, nitrogen source) and the fermentation conditions (temperature, pH, inoculation amount, rotation speed, and fermentation time). The surface tension and emulsification index of the fermentation broth were used to evaluate the optimal fermentation conditions. The results showed that the best carbon and nitrogen sources were glucose and peptone, and the optimum temperature, inoculum amount, pH, rotation speed, and fermentation time were 30 ℃, 1%, 7.5, 150 rpm, and 48 h, respectively. After optimization, the surface tension and emulsification index of fermentation broth were 26.84 mN/m and 57.84%, respectively. Moreover, the results also prove that the biosurfactant produced by this strain has good stability in a wide range of temperature, pH, and salt concentration.

Preparation, purification, and biochemical of fat-degrading bacterial enzymes from pig carcass compost and its application

BackgroundA lot of kitchen waste oil is produced every day worldwide, leading to serious environmental pollution. As one of the environmental protection methods, microorganisms are widely used treating of various wastes. Lipase, as one of the cleaning agents can effectively degrade kitchen waste oil. The composting process of pig carcasses produces many lipase producing microorganisms, rendering compost products an excellent source for isolating lipase producing microorganisms. To our knowledge, there are no reports isolating of lipase producing strains from the high temperature phase of pig carcass compost.MethodologyLipase producing strains were isolated using a triglyceride medium and identified by 16S rRNA gene sequencing. The optimal fermentation conditions for maximum lipase yield were gradually optimized by single-factor tests. The extracellular lipase was purified by ammonium sulfate precipitation and Sephadex G-75 gel isolation chromatography. Amino acid sequence analysis, structure prediction, and molecular docking of the purified protein were performed. The pure lipase's enzymatic properties and application potential were evaluated by characterizing its biochemical properties.ResultsIn this study, a lipase producing strain of Bacillus sp. ZF2 was isolated from pig carcass compost products, the optimal fermentation conditions of lipase: sucrose 3 g/L, ammonium sulfate 7 g/L, Mn2+ 1.0 mmol/L, initial pH 6, inoculum 5%, temperature 25 ℃, and fermentation time 48 h. After purification, the specific activity of the purified lipase reached 317.59 U/mg, a 9.78-fold improvement. Lipase had the highest similarity to the GH family 46 chitosanase and molecular docking showed that lipase binds to fat via two hydrogen bonds at Gln146 (A) and Glu203 (A). Under different conditions (temperature, metal ions, organic solvents, and surfactants), lipase can maintain enzymatic activity. Under different types of kitchen oils, lipase has low activity only for ‘chicken oil’, in treating other substrates, the enzyme activity can exceed 50%.ConclusionsThis study reveals the potential of lipase for waste oil removal, and future research will be devoted to the application of lipase.

Fermentation of brown seaweeds Alaria esculenta and Saccharina latissima for new product development using Lactiplantbacillus plantarum, Saccharomyces cerevisiae and kombucha SCOBY

Two seaweed species were examined (Alaria esculenta and Saccharina latissima) as a fermentation feedstock for the development of a beverage. Three microbial groups were selected for experimentation; a single-species bacterium; Lactiplantibacillus plantarum, a single-species yeast; Saccharomyces cerevisiae and a multi-species culture; kombucha SCOBY (Symbiotic Culture of Bacteria and Yeast). Results showed SCOBY cultures were more successful in fermenting A. esculenta than S. latissima due to the lowered glucose content (4.069 ± 0.174 mg / mL and 12.224 ± 2.249 mg / mL, respectively). Likewise, L. plantarum played a major role in fermenting S. latissima, over A. esculenta, resulting in a lowered pH in the former but not the latter (6.44 ± 0.040 and 4.825 ± 0.045, respectively). S. cerevisiae does not appear to have been suitable as a fermentation medium for these two seaweed species under these conditions due to the lack of pH lowering, glucose reduction and acid production. All treatments showed an increased production of lactic acid, especially the SCOBY treated samples, which is an indicator of fermentation. There is potential for optimization of the seaweed fermentation process through strain selection, fermentation conditions optimization (temperature, time, pH) and seaweed biomass pretreatment. Glutamic acid, the amino acid responsible for umami flavour, was found in greater quantities in the S. cerevisiae treated seaweed, indicating that fermentation using S. cerevisiae cultures may improve the umami flavour profile of a seaweed fermented beverage product. In order to see if the seaweed species used had an impact on the SCOBY microbial makeup, the DNA profiles of the two SCOBYs used were analyzed. There were significant differences between the two SCOBYs. The A. esculenta SCOBY showed slightly rarer species of fungi and the species abundance of fungi was greater than that of S. latissima SCOBY. Furthermore, the number of fungal operational taxonomic units (OTUs) in A. esculenta SCOBY was higher than that in S. latissima SCOBY. This study shows the potential of using brown seaweed species as a fermentation substrate to develop a novel, fermented beverage.

Novel Strain of Paenibacillus phyllosphaerae CS-148 for the Direct Hydrolysis of Raw Starch into Glucose: Isolation and Fermentation Optimization.

The conventional process for converting starch to glucose is energy-intensive. To lower the cost of this process, a novel strain of Paenibacillus phyllosphaerae CS-148 was isolated and identified, which could directly hydrolyze raw starch into glucose and accumulate glucose in the fermentation broth. The effects of different organic and inorganic nitrogen sources, the culture temperature, the initial pH, and the agitation speed on the yield of glucose were optimized through the one-factor-at-a-time method. Nine factors were screened by Plackett-Burman design, and three factors (raw corncob starch, yeast extract and (NH4)2SO4) had significant effects on glucose yield. Three significant factors were further optimized using Box-Behnken design. Under the optimized fermentation conditions (raw corncob starch 40.4 g/L, yeast extract 4.27 g/L, (NH4)2SO4 4.39 g/L, KH2PO4 2 g/L, MgSO4`7H2O 2 g/L, FeSO4`7H2O 0.02 g/L, NaCl 2 g/L, KCl 0.5 g/L, inoculums volume 4%, temperature 35 °C, agitation rate 150 rpm, and initial pH 7.0), the maximum glucose yield reached 17.32 ± 0.46 g/L, which is 1.33-fold compared to that by initial fermentation conditions. The maximum conversion rate and glucose productivity were 0.43 ± 0.01 g glucose/g raw corn starch and 0.22 ± 0.01 g/(L·h), respectively. These results implied that P. phyllosphaerae CS-148 could be used in the food industry or fermentation industry at a low cost.

Valorization of Different Dairy By-Products to Produce a Functional Dairy–Millet Beverage Fermented with Lactobacillus paracasei as an Adjunct Culture

Fermented dairy products not only have a long shelf-life but also have beneficial nutritional values. The products are deficient in dietary fiber and certain bioactive compounds. Adding grains to dairy products is a widespread practice to improve the nutritional and economic aspects. In this work, we studied the effect of fermented millet–milk beverages (FMBs) using pearl millet grains and three different dairy by-products (sweet whey, sweet buttermilk, and skimmed milk). A control treatment prepared with water was also manufactured for comparison. Samples were continuously prepared and fermented using a commercial yogurt starter culture (YC-381) containing L. delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and a pure strain of L. paracasei subsp. Paracasei. Four FMBs (water based: WB-FMB, whey based: WHB-FMB, buttermilk based: BMB-FMB, and skimmed milk based: SMB-FMB) were analyzed during cold storage at 4 °C for up to 15 days for chemical, microbiological properties, minerals content, antioxidant properties, glycemic index, and glycemic load on days 1, 8, and 15. The sensory characteristics of the FMBs were also evaluated during cold storage (4 °C/15 days). In general, the progression of acidity was slower in SMB-FMB and WHB-FMB samples during fermentation compared to in the BMB-FMB sample. The longest fermentation time was for the SMB-FBM sample (3 h), while the shortest was for the BMB-FMB sample (1.5 h). Reflecting the good manufacturing practices, all samples were free of coliform, mold, and yeast. No bacterial growth was detected in the WB-FMB sample at days 8 and 15 of storage, while the growth of Lactobacillus spp. and S. thermophilus was significantly higher (9.97 ± 0.01 and 9.48 ± 0.06, respectively) in the BMB-FMB sample compared to in the other three FMBs. The FMBs produced using dairy by-products had more antioxidant properties. All samples were better perceived during sensory evaluation by panelists than the water-based sample, except for the BMB-FMB sample, in which a bitter taste appeared. In the BMB-FMB sample, the proteolytic degree was significantly higher (4.8 ± 0.09) after 3 h of fermentation by about 460% than in the fresh sample. All samples had a low glycemic index and glycemic load. In addition, acidity progression was slower in SMB-FMB and WHB-FMB samples during fermentation and storage compared to the WB-FMB sample. Therefore, it could be recommended that it is more beneficial to prepare fermented millet–milk beverages using dairy by-products and suitable starter cultures under optimal fermentation conditions instead of using water to maximize the nutritional and economic aspects.

Effects of Zn2+ and Mn2+ on the photo-fermentative performance of HY01 in biohydrogen production from xylose fermentation

ABSTRACT The addition of specific ions has a significant effect on the characteristics and kinetics of hydrogen production by photofermentation (PFHP). In this article, a new basic research investigated by us find that adjusting the addition ratio of Zn2+ and Mn2+ ions in the R. sphaeroides HY01 system can effectively improve their biohydrogen production from xylose. The largest biohydrogen yield can be obtained as high as 219.2 mL/g xylose at concentration levels of 12 mg/L Zn2+ and 8 mg/L Mn2+. The shortest lag time is 5.76 h, along with most of the organic energy in the substrate transferred to H2. To evaluate the effect of Zn2+ and Mn2+, the Gompertz model with appropriately modification is applied on the photosynthetic bacteria R. sphaeroides HY01, and the corresponding constants are obtained by fitting the model, which is of great guiding significance for the optimization of fermentation conditions.

Optimization strategy for inulinase production by Aspergillus niger URM5741 and its biochemical characterization, kinetic/thermodynamic study, and application on inulin and sucrose hydrolysis.

Inulinases are enzymes of great interest in the food industry, especially due to their application in the synthesis of fructose and fructo-oligosaccharides. Moreover, some inulinases (I) also present invertase activity (S), making them useful for sucrose hydrolysis processes. In the present study, the production of inulinase by Aspergillus niger URM5741 was evaluated and optimized using two statistical approaches. First, the composition of the cultivation medium was determined through a simplex centroid mixture design, followed by the selection of optimal fermentation conditions using the Box-Behnken design. Based on these experimental designs, the maximum activities of inulinase (16.68 U mL-1) and invertase (27.80 U mL-1) were achieved using a mixture of wheat, soy, and oat brans (5g), along with 2.5% inulin and 40% moisture. The inulinase exhibited optimum temperature and pH of 60°C and 4.0, respectively, displayed a high affinity for both substrates, as evidenced by very-low Michaelis constant values (1.07-1.54mM). A relative thermostability was observed at 55-60°C as indicated by half-lives values (I: 169.06-137.27min; S: 173.29-141.52min) and D-values (I: 561.61-456.00min; S: 575.65-470.11min) which were further confirmed by the high activation energy (123.01 and 143.29kJmol-1). The enzyme demonstrated favorable results in terms of inulin and sucrose hydrolysis, being a maximum release of reducing sugars of 6.04 and 15.80g L-1, respectively. These results indicate that the sequential statistical approach proved to be beneficial to produce inulinase by A. niger URM5741, with the obtained enzyme considered promising for long-term industrial applications.

Box–Behnken design to determine optimal fermentation conditions for apple-fortified mulberry wine using Saccharomyces bayanus

Wine is a fermented product of fruit juice. Mulberry and apple juice can also be used to produce wine. Several factors influence the alcoholic fermentation of the must; therefore, the optimization of the mulberry wine fermentation conditions with the dry yeast strain Saccharomyces bayanus (concentration varied from 0.15 to 0.25 g/L), fermentation conditions as pH value (from 3.5 to 4.5), and total soluble solid (TSS) content (24–28°Brix) were performed in this study. To evaluate the influence of these factors, a Box–Behnken design was used to minimize the number of factor combinations required, which allows the determination of optimal fermentation conditions (pH, TSS content, and dry yeast concentration) to produce wines with high alcohol and bioactive compounds (total anthocyanin (TAC) and polyphenol content (TPC)). Based on the analysis of experimental data, the second-order response surface models were developed to describe the relationship between initial pH value, TSS, and dry yeast concentration on wine quality acquisition (ethanol content and bioactive compounds). The results of the analysis of variance (ANOVA) showed that the model setup by response surface quadratic regression was suitable for predicting the wine quality. It was observed that the quality of the apple-fortified mulberry wine was significantly affected by all variables. The optimal contents of ethanol, total anthocyanin, and total polyphenol were achieved at 12.97% (v/v), 171.85 mg/L, and 87.17 mgGAE/L, respectively, when fermented in juice medium with optimal values of pH, TSS, and yeast concentration of 3.9, 26°Brix, and 0.22 g/L, respectively.

Purification and characterization of the low molecular weight xylanase from Bacillus cereus L-1.

Xylanase is widely used in various industries such as food processing, paper, textiles, and leather tanning. In this study, Bacillus cereus L-1 strain was isolated and identified as capable of producing low molecular weight xylanase through 16s rRNA sequencing. Maximum xylanase yield of 15.51 ± 2.08 U/mL was achieved under optimal fermentation conditions (5% inoculum, 20g/L xylan, pH 6.0, for 24h). After purification via ammonium sulfate precipitation and High-S ion exchange chromatography, electrophoretic purity xylanase was obtained with a 28-fold purification and specific activity of 244.97 U/mg. Xylanase had an optimal pH of 6.5 and temperature of 60°C and displayed thermostability at 30°C and 40°C with 48.56% and 45.97% remaining activity after 180min, respectively. The xylanase retained more than 82.97% of its activity after incubation for 24h at pH 5.0 and was sensitive to metal ions, especially Mg2+ and Li+. Purified xylanase showed a molecular weight of 23kDa on SDS-PAGE, and partial peptide sequencing revealed homology to the endo-1,4-beta-xylanase with a molecular weight of 23.3kDa through LC/MS-MS (liquid chromatography-tandem mass spectrometry). This study suggests that the purified xylanase is easier to purify and enriches low molecular weight xylanases from bacteria source.

Preparation and Improvement of Physicochemical and Functional Properties of Dietary Fiber from Corn Cob Fermented by Aspergillus niger.

Corn cobs were fermented with Aspergillus niger to produce soluble dietary fiber (SDF) of high quality and excellent food safety. In this work, the fermentation process was optimized by single-factor test and response surface methodology (RSM). The optimal fermentation conditions were determined to be a material-liquid ratio of 1:30, an inoculum concentration of 11%, a temperature of 32°C, a time of 6 days, and a shaking speed of 200 r/min. Under these conditions, the SDF yield of corn cob increased from 2.34% to 11.92%, and the ratio of soluble dietary fiber to total dietary fiber (SDF/TDF) reached 19.08%, meeting the requirements for high-quality dietary fiber (SDF/TDF of more than 10%). Scanning electron microscopy (SEM) and Fourier-transformed infrared spectroscopy (FT-IR) analysis revealed that the fermentation effectively degraded part of cellulose and hemicellulose, resulting in the formation of a loose and porous structure. After fermentation the water swelling capacity, water-holding capacity, and oil-holding capacity of the corn cob SDF were significantly improved and the adsorption capacity of glucose, cholesterol, and nitrite ions all increased by more than 20%. Moreover, the total phenolic content increased by 20.96%, which correlated with the higher antioxidant activity of SDF. Overall, the fermentation of corn cobs by A. niger increased the yield and enhanced the functional properties of dietary fiber (DF) as well.

Engineering Corynebacterium glutamicum for the efficient production of N-acetylglucosamine

N-acetylglucosamine (GlcNAc) is significant functional monosaccharides with diverse applications in medicine, food, and cosmetics. In this study, the GlcNAc synthesis pathway was constructed in Corynebacterium glutamicum and its reverse byproduct pathways were blocked. Simultaneously the driving force of GlcNAc synthesis was enhanced by screening key gene sources and inhibiting the GlcNAc consumption pathway. To maximize carbon flux, some competitive pathways (Pentose phosphate pathway, Glycolysis pathway and Mannose pathway) were weakened and the titer of GlcNAc reached 23.30 g/L in shake flasks. Through transcriptome analysis, it was found that dissolved oxygen was an important limiting factor, which was optimized in a 5 L bioreactor. Employing optimal fermentation conditions and feeding strategy, the titer of GlcNAc reached 138.9 g/L, with the yeild of 0.44 g/g glucose. This study significantly increased the yield and titer of GlcNAc, which lay a solid foundation for the industrial production of GlcNAc in C. glutamicum.

Rewiring Bacillus subtilis and bioprocess optimization for oxidoreductive reaction-mediated biosynthesis of D-tagatose

D-tagatose holds significant importance as a functional monosaccharide with diverse applications in food, medicine, and other fields. This study aimed to explore the oxidoreductive pathway for D-tagatose production, surpassing the contemporary isomerization-mediated biosynthesis approach in order to enhance the thermodynamic equilibrium of the reactions. Initially, a novel galactitol dehydrogenase was discovered through biochemical and bioinformatics analyses. By co-expressing the galactitol dehydrogenase and xylose reductase, the oxidoreductive pathway for D-tagatose synthesis was successfully established in Bacillus subtilis. Subsequently, pathway fine-tuning was achieved via promoter regulation and dehydrogenase-mediated cofactor regeneration, resulting in 6.75-fold higher D-tagatose compared to that produced by the strain containing the unmodified promoter. Finally, optimization of fermentation conditions and medium composition produced 39.57 g/L D-tagatose in a fed-batch experiment, with a productivity of 0.33 g/L/h and a yield of 0.55 mol/mol D-galactose. These findings highlight the potential of the constructed redox pathway as an effective approach for D-tagatose production.