Fermentable Carbon Sources Research Articles

Enhanced Tolerance to Antifungals as a General Feature of Rho− Mutants in Yeast Species: Implications to Positive Selection of Respiratory Deficiency

Although the mitochondrial genome is an attribute of all eukaryotes, some yeast species (called petite-positive) can replicate without mitochondrial DNA (mtDNA). Strains without mtDNA (known as rho− mutants or petite mutants) are respiration-deficient and require fermentable carbon sources (such as glucose) for their metabolism. However, they are compromised in many aspects of fitness and competitiveness. Nevertheless, a few research groups have reported that some petite mutants of Candida glabrata and Saccharomyces cerevisiae manifested higher levels of tolerance to the antifungal fluconazole than their wild-type (WT) counterparts. In this study, we show that elevated tolerance to two or three out of four tested antifungals is a generic feature of at least five petite-positive species of yeasts including C. glabrata (higher tolerance of petites to clotrimazole and miconazole), S. bayanus (tolerance to clotrimazole, fluconazole, and miconazole), S. cerevisiae (tolerance to clotrimazole and fluconazole), S. paradoxus (tolerance to clotrimazole, fluconazole, and miconazole), and S. pastorianus (tolerance to clotrimazole and fluconazole). Comparing the levels of tolerance to the antifungals in WT and petite mutants was based on measuring the diameters of the zones of inhibition (ZOIs) using disc diffusion assays. The mode of inhibition in the majority of WT strains by all antifungals was fungicidal; most of the rho− mutants manifested fungistatic inhibition. We observed partial (not complete) inhibition in WT, with four different types of ZOI patterns that were species- and antifungal-specific. The partial inhibition was characterised by the presence of antifungal-tolerant colonies within ZOI areas. The inability of these colonies selected from ZOIs to grow on glycerol, as a single source of carbon, proved that they were rho− mutants spontaneously generated in the WT populations. The results on the elevated tolerance of petite strains to antifungals are discussed in terms of the prospective positive selection of respiratory-deficient mutants and the various implications of such selection.

Exploring the potential of soapstock over a glycerol in vitamin K2 production by Bacillus subtilis natto: a comparative analysis

BackgroundVitamin K2 is an essential nutrient for blood coagulation and cardiovascular health and mainly produced by bacteria strain like B. subtilis. researchers have explored producing strain improvement, cultivation mode, environmental optimization, increased secretion, and using cheaper carbon and nitrogen sources in order to increase vitamin K2 productivity. This study examines the impact of varioius concentration of soapstock, which is a by-product of vegetable oil refining, as an alternative carbon source with lower pirce, in the fermentation medium instead of glycerol on the microbial synthesis of vitamin K2 using B. subtilis natto ATCC 23857.ResultsThe results demonstrate that when the glycerol in fermentation medium was substituted with soapstock, by 75% concentartion, the fermentation process produced a yield of 158.16 mg/L of vitamin K2 after 72 h; This was 3.8 times more than the control medium containing glycerol. When the entire culture medium was replaced with wastewater, the vitamin K2 concentration reached 21.18 mg/L, 52% of the control medium’s concentration. If the carbon sources in the fermentation medium consisted of 20% soapstock and 47.4 g/L glycerol (maintaining the same final glycerol concentration as the control medium), the vitamin K2 concentration reached 35.7 mg/L or 85.8% of the control medium. The analysis of soapstock fermentation medium characteristics reveals that after fermentation with B. subtilis, the COD of soapstock fermentation medium was dramatically reduced from 259,500 mg/L to 57,830 mg/L.ConclusionsUsing soapstock as an alternative carbon source for fermentation did not negatively impact the bioprocess and increased vitamin K2 production. Therefore, this research introduces an alternative carbon resource for vitamin K2 production and paves the way for the biorefinement of soapstock.

Complete genome sequencing of Enterobacter ludwigii strain T977 revealed its great ability for starch degradation of Nicotiana tabacum L. Yunyan 97

Enterobacter ludwigii has been proven by numerous studies to be an effective plant growth promoter. Enterobacter ludwigii T977 was isolated from leaves of Nicotiana tabacum L. Yunyan 97 which showing high starch degrading ability. The optimal fermentation carbon source of strain T977 was starch, with optimal starch concentration as 2.5 g/L, and the most suitable fermentation nitrogen source for the strain T977 was ammonium acetate, with optimal concentration as 0.25 g/L. The spaying treatment of strain T977 could reduce the starch content of upper leaves from 3.77% to 1.43%, the total sugar and reducing sugar decreased slightly, the starch content of middle leaves decreased from 5.63% to 3.18%, the content of total sugar and reducing sugar increased in middle leaves, and the other chemical components were in the appropriate range. Here, we reported 4.77 MB whole genome of a starch-degrading E. ludwigii T977 that encodes 4501 proteins, 11 α-amylases in GH13 family were identified, and the amylase (GM000159) with signal peptide may play important role in degradation of starch in tobacco leaves. Our study may provide an effective microbiological mean for reducing starch content in tobacco leaves.

Two-step biocatalytic conversion of post-consumer polyethylene terephthalate into value-added products facilitated by genetic and bioprocess engineering

Solving the plastic crisis requires high recycling quotas and technologies that allow open loop recycling. Here a biological plastic valorization approach consisting of tandem enzymatic hydrolysis and monomer conversion of post-consumer polyethylene terephthalate into value-added products is presented. Hydrolysates obtained from enzymatic degradation of pre-treated post-consumer polyethylene terephthalate bottles in a stirred-tank reactor served as the carbon source for a batch fermentation with an engineered Pseudomonas putida strain to produce 90mg/L of the biopolymer cyanophycin. Through fed-batch operation, the fermentation could be intensified to 1.4 g/L cyanophycin. Additionally, the upcycling of polyethylene terephthalate monomers to the biosurfactants (hydroxyalkanoyloxy)alkanoates and rhamnolipids is presented. These biodegradable products hold significant potential for applications in areas such as detergents, building blocks for novel polymers, and tissue engineering. In summary, the presented bio-valorization process underscores that addressing challenges like the plastic crisis requires an interdisciplinary approach.

Potential and characteristics of bio-H2 production from the garden waste of ornamental plant Malus prunifolia fruit: Comparison between ethanol-type and butyrate-type fermentations

Edible fruit waste has been studied and considered to be the ideal substrates for low-cost bio-H2 production. However, the garden waste of ornamental plant fruits, which has similar components to edible fruit, is rarely studied. In this study, the potential and characteristics of fermentative bio-H2 production from the campus ornamental plant fruit of Malus prunifolia (MP) in both ethanol- and butyrate-types were investigated. Ethanoligenens harbinense B49 and Clostridium neuense G1 were employed as the inoculums for the ethanol- and butyrate-type fermentations, respectively. The results indicated that the fruit of MP is rich in fructose and sucrose, both of strains B49 and G1 could grow well with MP powder as the carbon source for fermentation. However, a higher H2 yield of 1.77 mol-H2/mol-hexose was obtained in the butyrate-type fermentation with strain G1, which was 1.4 times of that with strain B49. C. neuense G1 was more suitable for the H2 fermentation with MP as substrate, and a H2 yield of 0.55 mol-H2/mol-hexose by strain B49 was observed in the test of buffer system exchanging from ethanol-type to the butyrate-type. In summary, garden wastes such as fruits of ornamental plants should be given more attention as low-cost fermentation substrate candidates for bio-H2 production.

Conserved mechanism of Xrn1 regulation by glycolytic flux and protein aggregation

The regulation of gene expression in eukaryotes relies largely on the action of exoribonucleases, evolutionarily conserved enzymes that digest decapped messenger RNAs in the 5’-3’ direction. The activity of Xrn1, the major yeast exoribonuclease, is regulated by targeted changes in its cellular localisation in direct response to the cell’s metabolic state. When fermentable carbon sources are available, active Xrn1 is diffusely localised in the cytosol. Upon depletion of these sources, Xrn1 is sequestered at the plasma membrane-associated protein complex, the eisosome, and becomes inactive. Although this phenomenon has been described previously, the molecular mechanisms underlying these changes remain unknown. We report that the binding of Xrn1 to the plasma membrane is subject to glycolytic flux, rather than the availability of a fermentable carbon source, is independent of TORC1 activity and requires the core eisosomal proteins Pil1 and Lsp1. We identify the SH3-like domain of the Xrn1 protein as a putative interaction domain. In addition, we show that when expressed in Saccharomyces cerevisiae, the human orthologue of Xrn1 mirrors its yeast counterpart, i.e., it segregates to the eisosome under conditions of halted glycolysis. Our results not only advance our understanding of Xrn1 regulation but also indicate that this regulatory principle is conserved from yeast to humans.

Synthetic redesign of Escherichia coli W for faster metabolism of sugarcane molasses

BackgroundSugarcane molasses, rich in sucrose, glucose, and fructose, offers a promising carbon source for industrial fermentation due to its abundance and low cost. However, challenges arise from the simultaneous utilization of multiple sugars and carbon catabolite repression (CCR). Despite its nutritional content, sucrose metabolism in Escherichia coli, except for W strain, remains poorly understood, hindering its use in microbial fermentation. In this study, E. coli W was engineered to enhance sugar consumption rates and overcome CCR. This was achieved through the integration of a synthetically designed csc operon and the optimization of glucose and fructose co-utilization pathways. These advancements facilitate efficient utilization of sugarcane molasses for the production of 3-hydroxypropionic acid (3-HP), contributing to sustainable biochemical production processes.ResultsIn this study, we addressed challenges associated with sugar metabolism in E. coli W, focusing on enhancing sucrose consumption and improving glucose-fructose co-utilization. Through targeted engineering of the sucrose utilization system, we achieved accelerated sucrose consumption rates by modulating the expression of the csc operon components, cscB, cscK, cscA, and cscR. Our findings revealed that monocistronic expression of the csc genes with the deletion of cscR, led to optimal sucrose utilization without significant growth burden. Furthermore, we successfully alleviated fructose catabolite repression by modulating the binding dynamics of FruR with the fructose PTS regulon, enabling near-equivalent co-utilization of glucose and fructose. To validate the industrial applicability of our engineered strain, we pursued 3-HP production from sugarcane molasses. By integrating heterologous genes and optimizing metabolic pathways, we achieved improvements in 3-HP titers compared to previous studies. Additionally, glyceraldehyde-3-phosphate dehydrogenase (gapA) repression aids in carbon flux redistribution, enhancing molasses conversion to 3-HP.ConclusionsDespite limitations in sucrose metabolism, the redesigned E. coli W strain, adept at utilizing sugarcane molasses, is a valuable asset for industrial fermentation. Its synthetic csc operon enhances sucrose consumption, while mitigating CCR improves glucose-fructose co-utilization. These enhancements, coupled with repression of gapA, aim to efficiently convert sugarcane molasses into 3-HP, addressing limitations in sucrose and fructose metabolism for industrial applications.

Bioprocess Optimization by Taguchi Design and Response Surface Analysis for Obtaining Active Yeast Used in Vinification

This study presents the behavior of the identified yeast strain S. cerevisiae, isolated from Busuioacă de Bohotin grapes from the Pietroasa winery, during the process of fermentation to obtain dry active yeast biomass for the winemaking process. In this respect, we promoted an optimization strategy for obtaining active dry yeast biomass. The cultivation conditions for micropilot fermentation (temperature, pH, carbon source, and nitrogen source) were selected and designed according to a Taguchi design with four factors and three levels. Reproducibility testing was conducted under specific fermentation parameters: temperature (32 °C), pH (4.5), carbon source (12%), and nitrogen source (0.7%). Following the optimization process, two combinations of cultivation parameters were selected, and one of them, based on the results, was selected for further analysis. Quantitative data were obtained, showing dry yeast biomass (DCW) at 1.39 g/100 mL and protein content at 45.57%. The active yeast was then used in the winemaking process for Tămâioasă Românească and Busuioacă de Bohotin varieties at Pietroasa winery for validation. This optimization aims to facilitate easy and rapid production of fresh wine yeast tailored to the local winemaking practices of Pietroasa winery, with real application potential in other viticultural areas, aligning with the terroir concept.

Amino acids trigger MDC-dependent mitochondrial remodeling by altering mitochondrial function.

Cells utilize numerous pathways to maintain mitochondrial homeostasis, including a recently identified mechanism that adjusts the content of the outer mitochondrial membrane (OMM) through formation of OMM-derived multilamellar domains called mitochondrial-derived compartments, or MDCs. MDCs are triggered by perturbations in mitochondrial lipid and protein content, as well as increases in intracellular amino acids. Here, we sought to understand how amino acids trigger MDCs. We show that amino acid-activation of MDCs is dependent on the functional state of mitochondria. While amino acid excess triggers MDC formation when cells are grown on fermentable carbon sources, stimulating mitochondrial biogenesis blocks MDC formation. Moreover, amino acid elevation depletes TCA cycle metabolites in yeast, and preventing consumption of TCA cycle intermediates for amino acid catabolism suppresses MDC formation. Finally, we show that directly impairing the TCA cycle is sufficient to trigger MDC formation in the absence of amino acid stress. These results demonstrate that amino acids stimulate MDC formation by perturbing mitochondrial metabolism.

Development of oil-producing microbiota and its application in fermenting distiller's grains to obtain microbial oil and ruminant feed

With the depletion of global fossil energy, it is a good choice to produce biodiesel (renewable energy) from waste biomass resources. We tried to domesticate microbiota with distiller's grains as medium, and obtained genetically stable and acid-resistant microbiota JQY1, which could convert lignocellulose into microbial oil. Amplicon sequencing results showed that Proteobacteria (94.05 %) and ascomycetes (100 %) were the main phyla, and Rhizobiaceae_unclassified (41.19 %) and Pseudomonas (24.47 %) were the dominant genera, The fungi are Wickerhamomyces and Meyerozyma, and their abundance accounts for 70.8 % and 26.32 % respectively. Using external carbon sources in the microbial body one-step fermentation of distiller's grains by microbiota JQY1 can yield a microbial oil content of 2.52 g/L. The fatty acid composition, including palmitic acid, stearic acid, oleic acid, and linoleic acid, conforms to the specifications for biodiesel raw materials set by the American ASTM. The contents of distiller's grains after fermentation were detected, in which the crude protein increased by 6.19 % and the crude fiber decreased by 10.18 %. Microbial cooperation can effectively degrade lignocellulose and transform it into microbial oil. In addition, the distiller's grains after fermentation have higher value as ruminant feed. Through one-step fermentation, we can achieve a win-win strategy of efficiently harvesting biodiesel and improving the nutritional components of distiller's grains to feed animals, which not only reduces the production cost of microbial oil, but also solves the final destination problem of distiller's grains and makes important contributions to promoting the circular economy of distiller's grains.

Study on Enhancement of Acid Production by Combination Fermentation of Caproic Acid-producing Bacteria and Lactic Acid-producing Bacteria

A new caproic acid bacteria 20-5 (Caproicibacterium sp.) was newly screened in the laboratory, and several high-quality lactic acid bacteria A2-3 ( Sporolactobacillus fermentans ), GCB-3 ( Pediococcus acidilactici ), KR-4 ( Lactiplantibacillus plantarum ), LY-5 ( Levilactobacillus brevis ), B2-1 ( Lactiplantibacillus plantarum ) were used for exploratory compound fermentation experiments. The compound fermentation was a caproic acid bacteria (20-5) alone plus four lactic acid bacteria ( A2-3, GCB-3, KR-4, LY-5, B2-1 ), the experimental ratio was set up four groups of compound ratio of 1 : 2,1 : 1,5 : 1,10 : 1. The optimum ratio of 20-5 to B2-1 was 10 : 1, and the total acid yield reached 26.75 g / L. The best caproic acid production capacity after compounding was the 10: 1 group of 20-5 and B2-1, and the caproic acid yield was 7.22 g / L. The average lactic acid content in the fermentation broth was 4.52 g / L after compounding. After compounding, the acid production of the 1 : 1 and 5 : 1 groups of 20-5 : A2-3 and the 10 : 1 group of 20-5 : B2-1 increased compared with that of single bacteria. In the other compound groups, the acid production capacity decreased after the compound operation, and the lactic acid production generally decreased, but the caproic acid production increased, indicating that caproic acid bacteria can use lactic acid as a carbon source for fermentation and acid production activities, so that caproic acid bacteria can produce caproic acid.

Bioproduction of yeast single cell oil with acute oral toxicity study intended for edible oil application.

Human nutrition and health rely on edible oils. Global demand for edible oils is expanding, necessitating the discovery of new natural oil sources subjected to adequate quality and safety evaluation. However, in contrast to other agricultural products, India's edible oil supply is surprisingly dependent on imports. The microbial oil is generated by fermentation of oleaginous yeast Rhodotorula mucilaginosa IIPL32 MTCC 25056 using biodiesel plant byproduct crude glycerol as a fermentable carbon source. Enriched with monounsaturated fatty acid, nutritional indices mapping based on the fatty acid composition of the yeast SCO, suggested its plausible use as an edible oil blend. In the present study, acute toxicity evaluation of the yeast SCO in C57BL/6 mice has been performed by randomly dividing the animals into 5 groups with 50, 300, 2000, and 5000mg/Kg yeast SCO dosage, respectively, and predicted the median lethal dose (LD50). Detailed blood biochemistry and kidney and liver histopathology analyses were also reported. The functions of the liver enzymes were also evaluated to check and confirm the anticipated toxicity. To determine cell viability and in vitro biocompatibility, the 3T3-L1 cell line and haemolysis tests were performed. The results suggested the plausible use of yeast SCO as an edible oil blend due to its non-toxic nature in mice models.

Effect of storage condition on the viability of sago effluents as carbon source in fermentation medium for bioethanol production

In Sarawak, Malaysia, approximately 237 tons/day of sago effluent is commonly discharged into nearby river due to the sago starch extraction process. Due to the high concentration of polymeric compounds, particularly starch, in sago wastewater, which petrifies easily, this condition severely pollutes the environment in the affected area. This study was conducted to determine the viability of using sago effluent as a carbon source and fermentation medium for bioethanol production which indirectly help to minimize the environmental impact as well as the economics of the sago industry. The sago effluent obtained from the local sago mill was analysed for starch content and pH profile while stored at room and cold (4°C) temperature facility. Enzymatic hydrolysis was conducted to convert the residual starch into glucose as carbon source for bioethanol fermentation. Fresh sago effluent can be stored for up to 5 days in cold temperature where the starch content remains constant. The highest starch concentration in sago effluent was 61.33 g/L, in which 50.57 g/L glucose was obtained through the enzymatic hydrolysis process. Hence 82.5% of the starch to glucose conversion yield is revealed. Then, the sago effluent hydrolysate which acts as a carbon source as well as a fermentation medium able to generate 23.14 g/L of bioethanol, displays a 91% theoretical yield of glucose to ethanol. In conclusion, the utilization of sago wastewater as feasible alternative to cheap and locally available and sustainable source of raw materials to produce bioethanol.

Optimizing Curdlan Synthesis: Engineering Agrobacterium tumefaciens ATCC31749 for Enhanced Production Using Dextrin as a Carbon Source

A key goal in current research on industrial curdlan production is the expansion of carbon sources for fermentation. In this study, a recombinant bacterial strain, sp-AmyAXCC, capable of fermenting and synthesizing curdlan using dextrin as a carbon source, was produced via heterologous expression of IPTG-inducible α-amylase from Xanthomonas campestris NRRL B-1459 in Agrobacterium tumefaciens ATCC31749. External expression of the enzyme was confirmed by western blotting, and the expression levels of exogenous proteins during the fermentation process were monitored. Additionally, the properties of the curdlan product were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray diffraction. The recombinant strain produced curdlan at a titer of 30.40 ± 0.14 g/L, gel strength of 703.5 ± 34.2 g/cm2, and a molecular weight of 3.58 × 106 Da, which is 33% greater than the molecular weight of native curdlan (2.69 × 106 Da). In the batch fermentation of sp-AmyAXCC with 12% dextrin as a carbon source, the titer of curdlan was 66.7 g/L with a yield of 0.56 g/g, and a productivity rate of 0.62 g/L/h at 108 h. The results of this study expand the substrate spectrum for Agrobacterium fermentation in curdlan production and provides guidance for further industrialization of curdlan production.

Virtually identical does not mean exactly identical: Discrepancy in energy metabolism between glucose and fructose fermentation influences the reproductive potential of yeast cells

The physiological efficiency of cells largely depends on the possibility of metabolic adaptations to changing conditions, especially on the availability of nutrients. Central carbon metabolism has an essential role in cellular function. In most cells is based on glucose, which is the primary energy source, provides the carbon skeleton for the biosynthesis of important cell macromolecules, and acts as a signaling molecule. The metabolic flux between pathways of carbon metabolism such as glycolysis, pentose phosphate pathway, and mitochondrial oxidative phosphorylation is dynamically adjusted by specific cellular economics responding to extracellular conditions and intracellular demands. Using Saccharomyces cerevisiae yeast cells and potentially similar fermentable carbon sources i.e. glucose and fructose we analyzed the parameters concerning the metabolic status of the cells and connected with them alteration in cell reproductive potential. Those parameters were related to the specific metabolic network: the hexose uptake - glycolysis and activity of the cAMP/PKA pathway - pentose phosphate pathway and biosynthetic capacities - the oxidative respiration and energy generation. The results showed that yeast cells growing in a fructose medium slightly increased metabolism redirection toward respiratory activity, which decreased pentose phosphate pathway activity and cellular biosynthetic capabilities. These differences between the fermentative metabolism of glucose and fructose, lead to long-term effects, manifested by changes in the maximum reproductive potential of cells.

A Multi-Streamline Approach for Upcycling PET into a Biodiesel and Asphalt Modifier.

The non-degradable nature of petroleum-based plastics and the dependence on petroleum-based products in daily life and production are dilemmas of human development today. We hereby developed a plastic waste upcycling process to address these challenges. A multi-stream fraction strategy was developed to process poly (ethylene terephthalate) (PET) plastics into soluble and insoluble fractions. The soluble fraction was used as a sole carbon source for microbial fermentation to produce biodiesel precursor lipids with an appreciable bioconversion yield. The insoluble fraction containing fractionated polymers was used as the asphalt binder modifiers. The downsized PET additive improved the high-temperature performance of the asphalt binder by 1 performance grade (PG) without decreasing the low-temperature PG. Subsequent SEM imaging unveiled alterations in the micromorphology induced by PET incorporation. Further FTIR and 1H NMR analysis highlighted the aromatic groups of PET polymers as a crucial factor influencing performance enhancement. The results demonstrated the multi-stream fraction as a promising approach for repurposing plastic waste to produce biodiesel and modify asphalt. This approach holds the potential to tackle challenges in fuel supply and enhance infrastructure resilience to global warming.

A novel and efficient strategy for the biodegradation of di(2-ethylhexyl) phthalate by Fusarium culmorum.

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer that is used worldwide and raises concerns because of its prevalence in the environment and potential toxicity. Herein, the capability of Fusarium culmorum to degrade a high concentration (3 g/L) of DEHP as the sole carbon and energy source in solid-state fermentation (SSF) was studied. Cultures grown on glucose were used as controls. The biodegradation of DEHP by F. culmorum reached 96.9% within 312 h. This fungus produced a 3-fold higher esterase activity in DEHP-supplemented cultures than in control cultures (1288.9 and 443.2 U/L, respectively). In DEHP-supplemented cultures, nine bands with esterase activity (24.6, 31.2, 34.2, 39.5, 42.8, 62.1, 74.5, 134.5, and 214.5 kDa) were observed by zymography, which were different from those in control cultures and from those previously reported for cultures grown in submerged fermentation. This is the first study to report the DEHP biodegradation pathway by a microorganism grown in SSF. The study findings uncovered a novel biodegradation strategy by which high concentrations of DEHP could be biodegraded using two alternative pathways simultaneously. F. culmorum has an outstanding capability to efficiently degrade DEHP by inducing esterase production, representing an ecologically promising alternative for the development of environmental biotechnologies, which might help mitigate the negative impacts of environmental contamination by this phthalate. KEY POINTS: •F. culmorum has potential to tolerate and remove di(2-ethylhexyl) phthalate (DEHP) •Solid-state fermentation is an efficient system for DEHP degradation by F. culmorum •High concentrations of DEHP induce high levels of esterase production by F. culmorum.

Efficient secretion of an enzyme cocktail in Escherichia coli for hemicellulose degradation

The use of host to secrete several hemicellulase is a cost-effective way for hemicellulose degradation. In this study, the xylose utilization gene xylAB of Escherichia coli BL21 was knocked out, and the xylanase (N20Xyl), β-xylosidase (Xys), and feruloyl esterase (FaeLam) were co-expressed in this strain. By measuring the content of reducing sugars generated by enzymatic hydrolysis of wheat bran in the fermentation supernatant, the order of the three enzymes was screened to obtain the optimal recombinant strain of E. coli BL21/∆xylAB/pDIII-2. Subsequently, fermentation conditions including culture medium, inducer concentration, induction timing, metal ions, and glycine concentration were optimized. Then, different concentrations of wheat bran and xylan were added to the fermentation medium for degradation. The results showed that the extracellular reducing sugars content reached the highest value of 33.70 ± 0.46 g/L when 50 g/L xylan was added. Besides, the scavenging rates of hydroxyl radical by the fermentation supernatant was 81.0 ± 1.41 %, and the total antioxidant capacity reached 2.289 ± 0.55. Furthermore, it showed the growth promotion effect on different lactic acid bacteria. These results provided a basis for constructing E. coli strain to efficiently degrade hemicellulose, and the strain obtained has great potential application to transform hemicellulose into fermentable carbon source.

Effect of Microbial Fermentation on The Yield of Vfas for Kitchen Waste Decomposition

Fruit and vegetable waste is an important kind of kitchen waste, its production can not be underestimated. The volatile fatty acids (VFAs) produced can be used as an added carbon source for microbial fermentation. This paper studied the effect of volatile fatty acids in the process of spring anaerobic hydrolysis, and investigated the concentration and composition of VFAs and the conversion rate of VS (volatile solid) over time. The results showed that in the intermittent mode of pH 6 and temperature of 35℃, the acid production of fruit and vegetable waste in spring was good, and the conversion rate of VFAs was 0.36g ·(gVfed ) -1.

Waste valorization through acetone-butanol-ethanol (ABE) fermentation

BackgroundBiobutanol, produced through acetone-butanol-ethanol (ABE) fermentation, has been proposed for use as a transportation fuel and for the development of butanol-based materials. However, the economic viability of ABE fermentation is heavily dependent on the cost of raw materials. MethodsThis study assesses various carbon and nitrogen sources for ABE fermentation. Carbon sources examined include local molasses (M1), Thai molasses (M2), Taiwan sugar agricultural molasses (M3), and Taiwan sugar edible molasses (M4). Nitrogen sources considered are corn steep liquor (CSL), acid-hydrolyzed black soldier fly larval meal (IA), and enzyme-hydrolyzed black soldier fly larval meal (IE). Significant findingsOur findings reveal that M2CSL, a combination of Thai molasses and corn steep liquor, serves as a cost-effective and efficient medium for ABE fermentation, resulting in a butanol concentration of 7.4 ± 3.5 g/L. Furthermore, our research identifies variations in molasses and their impact on sucrose consumption inhibition. Notably, this study underscores the potential of insect peptone derived from enzyme-hydrolyzed black soldier fly larval meal (IE) as an alternative nitrogen source, while cautioning against the use of insect peptone obtained from acid-hydrolyzed black soldier fly larval meal (IA) due to its inhibitory properties.