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BackgroundThe preparation of broad bean koji is a key process in the production of Pixian broad bean paste (PBP). Protease is essential for the degradation of proteins during PBP fermentation. To obtain broad bean koji with high protease activity using the cocultivated strains of Aspergillus oryzae QM-6 (A. oryzae QM-6) and Aspergillus niger QH-3 (A. niger QH-3), the optimization of acid and neutral protease activities was carried out using Box–Behnken design with response surface methodology (RSM).ResultsThe optimum conditions were found to be as follows: inoculation proportion (X1), 3:1 (A. oryzae QM-6: A. niger QH-3, w/w); culture temperature (X2), 33°C; inoculum size (X3), 0.5% (w/w); incubation time (X4), 5 d. The acid and neutral protease activities were 605.2 ± 12.4 U/g and 1582.9 ± 23.7 U/g, respectively, which were in good agreement with the predicted values. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles revealed that the broad bean koji extracellular proteins in the case of cocultivation were richer compared to those in the case of A. oryzae QM-6 or A. niger QH-3 strain only. In addition, the free amino acids (FAAs) in the fermentation product were 55% higher in the cocultivation process than in that involving only A. oryzae QM-6, further confirming the diversity of proteases in the fermentation products.ConclusionsThe optimal conditions of koji-making in PBP were obtained using RSM. The cocultivation of A. oryzae and A. niger increases the overall enzyme activities in the culture medium and the FAAs content, which would thus have potential application in the PBP industry.How to cite: Tang J, Chen T, Hu Q, et al. Improved protease activity of Pixian broad bean paste with cocultivation of Aspergillus oryzae QM-6 and Aspergillus niger QH-3. Electron J Biotechnol 2020;44. https://doi.org/10.1016/j.ejbt.2020.01.001. 相似文献
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BackgroundXylitol is a five carbons polyol with promising medical applications. It can be obtained from chemical d-xylose reduction or by microbial fermentation of Sugarcane Bagasse Hemicellulosic Hydrolysate. For this last process, some microbial inhibitors, as furfural, constitute severe bottleneck. In this case, the use of strains able to produce xylitol simultaneously to furfural neutralization is an interesting alternative. A wild-type strain of Geotrichum sp. was detected with this ability, and its performance in xylitol production and furfural consumption was evaluated. Furthermore, were analyzed its degradation products.ResultsGeotrichum sp. produced xylitol from d-xylose fermentation with a yield of 0.44 g·g-1. Furfural was fully consumed in fermentation assay and when provided in the medium until concentration of 6 g·L-1. The furfural degradation product is not an identified molecule, presenting a molecular weight of 161 g·mol-1, an uncommon feature for the microbial metabolism of this product.ConclusionThis strain presents most remarkable potential in performing furfural consumption simultaneous to xylitol production. Subsequent efforts must be employed to establish bioprocess to simultaneous detoxification and xylitol production by Geotrichum sp. 相似文献
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The relationship between protease and Desferal production was assayed. Experiments were performed using a cultivation of Streptomyces pilosus ATCC 19797 in soybean broth medium containing 2% soybean flour and 2% mannitol. The metabolism of the trihydroxamic acid sidrophore desferrioxamine B and protease production by a S. pilosus in nine continues days after culture were investigated as well as the effect of protease inhibitors was examined. It is found that the Desferal formation decreased with increased protease production. Also the effect of protease inhibitors and minerals in determined day of protease production in the culture medium by S. pilosus has been investigated. 相似文献
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BackgroundThe development of a potential single culture that can co-produce hydrogen and ethanol is beneficial for industrial application. Strain improvement via molecular approach was proposed on hydrogen and ethanol co-producing bacterium, Escherichia coli SS1. Thus, the effect of additional copy of native hydrogenase gene hybC on hydrogen and ethanol co-production by E. coli SS1 was investigated.ResultsBoth E. coli SS1 and the recombinant hybC were subjected to fermentation using 10 g/L of glycerol at initial pH 7.5. Recombinant hybC had about 2-fold higher cell growth, 5.2-fold higher glycerol consumption rate and 3-fold higher ethanol productivity in comparison to wild-type SS1. Nevertheless, wild-type SS1 reported hydrogen yield of 0.57 mol/mol glycerol and ethanol yield of 0.88 mol/mol glycerol, which were 4- and 1.4-fold higher in comparison to recombinant hybC. Glucose fermentation was also conducted for comparison study. The performance of wild-type SS1 and recombinant hybC showed relatively similar results during glucose fermentation. Additional copy of hybC gene could manipulate the glycerol metabolic pathway of E. coli SS1 under slightly alkaline condition.ConclusionsHybC could improve glycerol consumption rate and ethanol productivity of E. coli despite lower hydrogen and ethanol yields. Higher glycerol consumption rate of recombinant hybC could be an advantage for bioconversion of glycerol into biofuels. This study could serve as a useful guidance for dissecting the role of hydrogenase in glycerol metabolism and future development of effective strain for biofuels production. 相似文献
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BackgroundThe main objective of this study was to isolate fungi associated with Anthopleura xanthogrammica and measure their antimicrobial and enzymatic activities. A total of 93 fungal strains associated with A. xanthogrammica were isolated in this study, of which 32 isolates were identified using both morphological characteristics and internal transcribed spacer (ITS) sequence analysis. The antibacterial activities of 32 fungal isolates were tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Edwardsiella tarda, Vibrio harveyi, Fusarium oxysporum, and Pyricularia oryzae by agar diffusion assay. Extracellular hydrolytic enzyme activities of the fungal isolates were determined by agar diffusion assays. Enzyme activities were detected from clear halo size.ResultsThe isolated fungi belonged to 18 genera within 7 taxonomic orders of 1 phylum. The genera Aspergillaceae were the most diverse and common. The antimicrobial activities of 32 isolates were evaluated, and 19 (59.4%) of fungi isolate displayed unique antimicrobial activities. All fungal strains displayed at least one enzyme activity. The most common enzyme activities in the fungi isolates were amylase and protease, while the least common were pectinase and xylanase.ConclusionsThis is first report on the sea anemone-derived fungi with antimicrobial and enzyme activities. Results indicated that sea anemone is a hot spot of fungal diversity and a rich resource of bioactive natural products.How to cite: Liu S, Ahmed S, Zhang C, et al. Diversity and antimicrobial activity of culturable fungi associated with sea anemone Anthopleura xanthogrammica. Electron J Biotechnol 2020;44. https://doi.org/10.1016/j.ejbt.2020.01.003 相似文献
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《Electronic Journal of Biotechnology》2014,17(1):27-33
BackgroundFor the crossbreeding of Auricularia auricula-judae, selecting the appropriated parents in hybridization is very important. However, the classification and diversity analysis of A. auricula-judae has been equivocal, due to the similarity of the fruiting body morphology and its susceptibility to environmental influences. For this purpose, the molecular diversity of 32 A. auricula-judae commercial cultivars in China was analyzed by using the nuclear ribosomal DNA intergenic spacer.ResultsThe complete nuclear rDNA gene complex of A. auricula-judae isolate is 11,210 bp long, and contains the 18S, 5.8S, and 28S rRNA gene as well as the ITS and IGS regions. Based on the sequence data, four more effective primer combinations for the IGS region of A. auricula-judae were designed. Nucleotide sequence variation in the IGS among 32 A. auricula-judae commercial cultivars in China sorted into three strongly supported clades, which is correlated with geographical regions. Most strains originated from the same area were with a narrow genetic basis and could possibly be domesticated from the local wild-type strains.ConclusionThe grouping information obtained in the present work provides significant information for further genetic improvement in A. auricula-judae, and suggested that the IGS region can be used as an excellent tool for identification of genetic variation. 相似文献
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BackgroundHong Qu glutinous rice wine (HQGRW) is brewed under non-aseptic fermentation conditions, so it usually has a relatively high total acid content. The aim of this study was to investigate the dynamics of the bacterial communities and total acid during the fermentation of HQGRW and elucidate the correlation between total acid and bacterial communities.ResultsThe results showed that the period of rapid acid increase during fermentation occurred at the early stage of fermentation. There was a negative response between total acid increase and the rate of increase in alcohol during the early fermentation stage. Bacterial community analysis using high-throughput sequencing technology was found that the dominant bacterial communities changed during the traditional fermentation of HQGRW. Both principal component analysis (PCA) and hierarchical clustering analysis revealed that there was a great difference between the bacterial communities of Hong Qu starter and those identified during the fermentation process. Furthermore, the key bacteria likely to be associated with total acid were identified by Spearman's correlation analysis. Lactobacillus, unclassified Lactobacillaceae, and Pediococcus were found, which can make significant contributions to the total acid development (| r | > 0.6 with FDR adjusted P < 0.05), establishing that these bacteria can associate closely with the total acid of rice wine.ConclusionsThis was the first study to investigate the correlation between bacterial communities and total acid during the fermentation of HQGRW. These findings may be helpful in the development of a set of fermentation techniques for controlling total acid.How to cite: Liang Z, Lin X, He Z, et al. Dynamic changes of total acid and bacterial communities during the traditional fermentation of Hong Qu glutinous rice wine. Electron J Biotechnol 2020;43. https://doi.org/10.1016/j.ejbt.2019.12.002 相似文献
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BackgroundIn industrial yeasts, selection and breeding for resistance to multiple stresses is a focus of current research. The objective of this study was to investigate the tolerance to multiple stresses of Saccharomyces cerevisiae obtained through an adaptive laboratory evolution strategy involving a repeated liquid nitrogen freeze–thaw process coupled with multi-stress shock selection. We also assessed the related resistance mechanisms and very high-gravity (VHG) bioethanol production of this strain.ResultsElite S. cerevisiae strain YF10-5, exhibiting improved VHG fermentation capacity and stress resistance to osmotic pressure and ethanol, was isolated following ten consecutive rounds of liquid nitrogen freeze–thaw treatment followed by plate screening under osmotic and ethanol stress. The ethanol yield of YF10-5 was 16% higher than that of the parent strain during 35% (w/v) glucose fermentation. Furthermore, there was upregulation of three genes (HSP26, HSP30, and HSP104) encoding heat-shock proteins involved in the stress response, one gene (TPS1) involved in the synthesis of trehalose, and three genes (ADH1, HXK1, and PFK1) involved in ethanol metabolism and intracellular trehalose accumulation in YF10-5 yeast cells, indicating increased stress tolerance and fermentative capacity. YF10-5 also showed excellent fermentation performance during the simultaneous saccharification and fermentation of VHG sweet potato mash, producing 13.40% (w/v) ethanol, which corresponded to 93.95% of the theoretical ethanol yield.ConclusionsA multiple-stress-tolerant yeast clone was obtained using adaptive evolution by a freeze–thaw method coupled with stress shock selection. The selected robust yeast strain exhibits potential for bioethanol production through VHG fermentation.How to cite: Zhang Q, Jin Y, Fang Y, et al. Adaptive evolution and selection of stress-resistant Saccharomyces cerevisiae for very high gravity bioethanol fermentation. Electron J Biotechnol 2019;41. https://doi.org/10.1016/j.ejbt.2019.06.003 相似文献
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BackgroundZymomonas mobilis is a Gram-negative microaerophilic bacterium with excellent ethanol-producing capabilities. The RecET recombination system provides an efficient tool for direct targeting of genes in the bacterial chromosome by PCR fragments.ResultsThe plasmids pSUZM2a-RecET and pSUZM2a-RecE588T were first developed to co-express RecE or RecE588 and RecT for homologous recombination. Thereafter, the PCR fragments of the tetracycline resistance marker gene flanked by 60 bp of adhA (alcohol dehydrogenase I) or adhB (alcohol dehydrogenase II) homologous sequences were electroporated directly into ZM4 cells harboring pSUZM2a-RecET or pSUZM2a-RecE588T. Both adhA and adhB were replaced by the tetracycline resistance gene in ZM4, yielding two mutant strains, Z. mobilis ZM4 ΔadhA and Z. mobilis ZM4 ΔadhB. These two mutants showed varying extent of reduction in ethanol production, biomass generation, and glucose metabolism. Furthermore, enzyme activity of alcohol dehydrogenase II in Z. mobilis ZM4 ΔadhB exhibited a significant reduction compared to that of wild-type ZM4.ConclusionThis approach provided a simple and useful method for introducing mutations and heterologous genes in the Z. mobilis genome. 相似文献
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BackgroundSalep is obtained by grinding dried orchid tubers and used as a valuable ingredient in the food industry. Because of the glucomannan content of salep, it is thought to have prebiotic potential. However, there is little information in studies concerning the fermentation characteristics and potential prebiotic properties of salep. The objective of this study was to investigate the effect of salep on bifidobacterial growth by measuring the highest optical density (OD), calculating the specific growth rates, and determining the production of lactic acid and short-chain fatty acids (acetic, propionic, and butyric acid) as a result of bacterial fermentation.ResultThe OD and pH values obtained in this study showed that salep was utilized as a source of assimilable carbon and energy by the Bifidobacterium species (BS). All Bifidobacterium strains produced lactic, acetic, propionic, and butyric acid, indicating that salep is readily fermented by these bacteria. Salep at 1% (w/v) showed a similar effect on bifidobacterial growth as that promoted by 1% (w/v) glucose used as a traditional carbon source.ConclusionsBifidobacterium species can develop in media containing salep as well as in glucose and exhibit the potential to be used as new sources of prebiotics.How to cite: Usta-Gorgun B, Yilmaz-Ersan L. Short-chain fatty acid production by the Bifidobacterium species in the presence of salep. Electron J Biotechnol 2020;47. https://doi.org/10.1016/j.ejbt.2020.06.004. 相似文献
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BackgroundPoly(dl-lactic acid), or PDLLA, is a biodegradable polymer that can be hydrolyzed by various types of enzymes. The protease produced by Actinomadura keratinilytica strain T16-1 was previously reported to have PDLLA depolymerase activity. However, few studies have reported on PDLLA-degrading enzyme production by bacteria. Therefore, the aims of this study were to determine a suitable immobilization material for PDLLA-degrading enzyme production and optimize PDLLA-degrading enzyme production by using immobilized A. keratinilytica strain T16-1 under various fermentation process conditions in a stirrer fermenter.ResultsAmong the tested immobilization materials, a scrub pad was the best immobilizer, giving an enzyme activity of 30.03 U/mL in a shake-flask scale. The maximum enzyme activity was obtained at aeration 0.25 vvm, agitation 170 rpm, 45°C, and 48 h of cultivation time. Under these conditions, a PDLLA-degrading enzyme production of 766.33 U/mL with 15.97 U/mL·h productivity was observed using batch fermentation in a 5-L stirrer fermenter. Increased enzyme activity and productivity were observed in repeated-batch (942.67 U/mL and 19.64 U/mL·h) and continuous fermentation (796.43 U/mL and 16.58 U/mL·h) at a dilution rate of 0.013/h. Scaled-up production of the enzyme in a 10-L stirrer bioreactor using the optimized conditions showed a maximum enzyme activity of 578.67 U/mL and a productivity of 12.06 U/mL·h.ConclusionsThis research successfully scaled-up the enzyme production to 5 and 10 L in a stirrer fermenter and is helpful for many applications of poly(lactic acid). 相似文献
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BackgroundDegP is a serine protease that specifically cleaves and refolds unfolding proteins in the periplasmic space of the cells. To date, there is no information regarding DegP from halophilic bacteria. Chromohalobacter salexigens BKL5 is a moderately halophilic bacterium that has the ability to grow in a media containing more than 15% salt. Therefore, the objectives of this work were to clone and overexpress DegP-encoding gene from C. salexigens BKL5 and characterize its biochemical properties.ResultsDegP-encoding gene was overexpressed in Escherichia coli BL21(DE3) CodonPlus in an active form. SDS-PAGE analysis showed that the molecular weight of the recombinant DegP was 45 kDa. Size-exclusion chromatography analysis suggested that recombinant DegP was present in two multimeric states, hexameric and dodecameric, with molecular weights of 297.9 and 579.12 kDa, respectively. Both conformations were enzymatically active when casein was used as substrate for enzymatic assay. Circular dichroism analysis showed that recombinant DegP was composed of 0.21–0.29 helical content, which was comparable to the helical content in the crystal structure of E. coli DegP. The basic/acidic residue ratio of recombinant DegP was 0.56, which was slightly higher than that of DegP from extreme halophiles (average, 0.45) but significantly lower than that of DegP from nonhalophiles (average, 0.94).ConclusionsRecombinant DegP from C. salexigens BKL5 showed proteolytic activity when β-casein was used as a substrate. In silico analysis indicated that recombinant DegP had characteristics similar to those of halophilic proteins depending on its amino acid composition. 相似文献
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BackgroundThe alga Laminaria japonica is the most economically important brown seaweed cultured in China, which is used as food and aquatic animal feedstuff. However, the use of L. japonica as a feedstuff in Apostichopus japonicas farming is not ideal because A. japonicas does not produce enough enzyme activity for degrading the large amount of algin present in L. japonica. In this study, semi solid fermentation of the L. japonica feedstuff employing a Bacillus strain as the microbe was used to as a mean to degrade the algin content in L. japonica feedstuff.ResultsThe Bacillus strain, Bacillus amyloliquefaciens WB1, was isolated by virtue of its ability to utilize sodium alginate as the sole carbon source. Eight factors affecting growth and algin-degrading capacity of WB1 were investigated. The results of Plackett–Burman design indicated that fermentation time, beef extract, and solvent to solid ratio were the significant parameters. Furthermore, the mutual interaction between the solvent to solid ratio and beef extract concentration was more significant than the other pairs of parameters on algin degradation. Optimal values obtained from Central-Composite Design were 113.94 h for fermentation time, 0.3% (w/v) beef extract and 44.87 (v/w) ratio of solvent to feedstuff. Under optimal conditions, 56.88% of the algin was degraded when a 50-fold scale-up fermentation was carried out, using a 5-L fermenter.ConclusionsThis study provides an alternative and economical way to reduce the algin content in L. japonica through degradation by WB1, making it a promising potential source of feed for cultured L. japonica. 相似文献
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BackgroundBiologically active peptides produced from fish wastes are gaining attention because their health benefits. Proteases produced by halophilic microorganisms are considered as a source of active enzymes in high salt systems like fish residues. Hence, the aim of this study was the bioprospection of halophilic microorganisms for the production of proteases to prove their application for peptide production.ResultsHalophilic microorganisms were isolated from saline soils of Mexico and Bolivia. An enzymatic screening was carried out for the detection of lipases, esterases, pHB depolymerases, chitinases, and proteases. Most of the strains were able to produce lipases, esterases, and proteases, and larger hydrolysis halos were detected for protease activity. Halobacillus andaensis was selected to be studied for proteolytic activity production; the microorganism was able to grow on gelatin, yeast extract, skim milk, casein, peptone, fish muscle (Cyprinus carpio), and soy flour as protein sources, and among these sources, fish muscle protein was the best inducer of proteolytic activity, achieving a protease production of 571 U/mL. The extracellular protease was active at 50°C, pH 8, and 1.4 M NaCl and was inhibited by phenylmethylsulfonyl fluoride. The proteolytic activity of H. andaensis was used to hydrolyze fish muscle protein for peptide production. The peptides obtained showed a MW of 5.3 kDa and a radical scavenging ability of 10 to 30% on 2,2-diphenyl-1-picrylhydrazyl and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and a ferric reducing ability of plasma.ConclusionThe use of noncommercial extracellular protease produced by H. andaensis for biologically active peptide production using fish muscle as the protein source presents a great opportunity for high-value peptide production.How to cite: Delgado-García M, Flores-Gallegos AC, Kirchmayr M, et al. Bioprospection of proteases from Halobacillus andaensis for bioactive peptide production from fish muscle protein. Electron J Biotechnol 2019;39. https://doi.org/10.1016/j.ejbt.2019.03.001. 相似文献
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BackgroundThe hydrolysis of keratin wastes by microorganisms is considered a biotechnological alternative for recycling and valorization through keratinolytic microorganisms. Despite their resistant structure, keratin wastes can be efficiently degraded by various microorganisms through the secretion of keratinases, which are promising enzymes for several applications, including detergents, fertilizers, and leather and textile industry. In an attempt to isolate keratinolytic microorganisms that can reach commercial exploitation as keratinase producers, the current work assesses the dynamics of keratin biodegradation by several keratinolytic fungal strains isolated from soil. The activity of fungal strains to degrade keratin substrates was evaluated by SEM, FTRIR-ATR spectra and TGA analysis.ResultsSEM observations offered relevant information on interactions between microorganism and structural elements of hair strands. FTIR spectra of the bands at 1035–1075 cm-1 assigned to sulfoxide bond appeared because of S–S bond breaking, which demonstrated the initiation of keratin biodegradation. According to TGA, in the second zone of thermal denaturation, where keratin degradation occurs, the highest weight loss of 71.10% was obtained for sample incubated with Fusarium sp. 1A.ConclusionsAmong the tested strains, Fusarium sp. 1A was the most active organism in the degradation process with the strongest denaturation of polypeptide chains. Because keratinolytic microorganisms and their enzymes keratinases represent a subject of scientific and economic interest because of their capability to hydrolyze keratin, Fusarium sp. 1A was selected for further studies. 相似文献