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The enzymatic synthesis of xylose fatty acid esters was carried out in two steps: hydrolysis of degummed soybean oil (DSO) and esterification of the produced and purified free fatty acids (FFA) with xylose. Different lipases immobilized on a hydrophobic support were evaluated in the hydrolysis of DSO and an experimental design was used to optimize the reaction. Eversa® Transform 2.0 (EV-Purolite) yielded 93% conversion after 6 h using biocatalyst load of 6.53 wt%, water/oil mass ratio of 5.5 and temperature of 48.4 °C. High operational stability for EV-Purolite was found using a sequential batch strategy and the possibility of concentrating glycerol. In the esterification stage, lipase from Thermomyces lanuginosus (TLL-Purolite) and lipase B from Candida antarctica showed better performance than lipase from porcine pancreas and EV-Purolite. About 17% of FFAs (0.85 molecules of FAA per xylose molecule) was consumed using an enzyme load of 5 wt% of TLL-Purolite and FFA/xylose molar ratio of 5. Sequential esterification batches showed low operational stability of TTL-Purolite due to the desorption of TLL from the support. The final mixture of the reaction medium containing xylose fatty acid esters showed emulsifying properties similar to those of commercial surfactant. [Display omitted] • Xylose fatty acid esters production by degummed soybean oil hydroesterification. • Hydrolysis catalyzed by immobilized Eversa produced 92% of FFAs after 6 h. • Reuse of immobilized Eversa for five consecutive 3 h-batches of hydrolysis. • Modification of 85% xylose as monoester using immobilized TLL. • Xylose esters showed emulsifying properties similar to commercial surfactants. [ABSTRACT FROM AUTHOR]

Microbial production of polyhydroxyalkanoate (PHA) is greatly restricted by high production cost arising from high‐temperature sterilization and expensive carbon sources. In this study, a low‐cost PHA production platform was established from Halomonas cupida J9. First, a marker‐less genome‐editing system was developed in H. cupida J9. Subsequently, H. cupida J9 was engineered to efficiently utilize xylose for PHA biosynthesis by introducing a new xylose metabolism module and blocking xylonate production. The engineered strain J9UΔxylD‐P8xylA has the highest PHA yield (2.81 g/L) obtained by Halomonas with xylose as the sole carbon source so far. This is the first report on the production of short‐ and medium‐chain‐length (SCL‐co‐MCL) PHA from xylose by Halomonas. Interestingly, J9UΔxylD‐P8xylA was capable of efficiently utilizing glucose and xylose as co‐carbon sources for PHA production. Furthermore, fed‐batch fermentation of J9UΔxylD‐P8xylA coupled to a glucose/xylose co‐feeding strategy reached up to 12.57 g/L PHA in a 5‐L bioreactor under open and unsterile condition. Utilization of corn straw hydrolysate as the carbon source by J9UΔxylD‐P8xylA reached 7.0 g/L cell dry weight (CDW) and 2.45 g/L PHA in an open fermentation. In summary, unsterile production in combination with inexpensive feedstock highlights the potential of the engineered strain for the low‐cost production of PHA from lignocellulose‐rich agriculture waste. [ABSTRACT FROM AUTHOR]

Objective: New characterized carbohydrate-active enzymes are needed for use as tools to discriminate complex carbohydrate structural features. Fungal glycoside hydrolase family 3 (GH3) β-xylosidases have been shown to be useful for the structural elucidation of glucuronic acid (GlcA) and arabinofuranose (Araf) substituted oligoxylosides. A homolog of these GH3 fungal enzymes from the bacterium Segatella baroniae (basonym Prevotella bryantii), Xyl3C, has been previously characterized, but those studies did not address important functional specificity features. In an interest to utilize this enzyme for laboratory methods intended to discriminate the structure of the non-reducing terminus of substituted xylooligosaccharides, we have further characterized this GH3 xylosidase. Results: In addition to verification of basic functional characteristics of this xylosidase we have determined its mode of action as it relates to non-reducing end xylose release from GlcA and Araf substituted oligoxylosides. Xyl3C cleaves xylose from the non-reducing terminus of β-1,4-xylan until occurrence of a penultimate substituted xylose. If this substitution is O2 linked, then Xyl3C removes the non-reducing xylose to leave the substituted xylose as the new non-reducing terminus. However, if the substitution is O3 linked, Xyl3C does not hydrolyze, thus leaving the substitution one-xylose (penultimate) from the non-reducing terminus. Hence, Xyl3C enables discrimination between O2 and O3 linked substitutions on the xylose penultimate to the non-reducing end. These findings are contrasted using a homologous enzyme also from S. baroniae, Xyl3B, which is found to yield a penultimate substituted nonreducing terminus regardless of which GlcA or Araf substitution exists. [ABSTRACT FROM AUTHOR]

In order to obtain high yields of chemicals and fuels from biomass, feedstocks need to be selected that contain high amounts of glucose, xylose, or lignin, depending on the end product. The first objective of this study was to evaluate the biomass composition of 20 samples from 11 broadleaf and grass crop species grown at two distinct sites in Montana. Another objective was to investigate the influence of growing location and seed type to determine which cultivars may be best for renewable chemical production in the northern Great Plains. There was a significant effect due to the growing location as the biomass samples from the site that had higher precipitation exhibited a significantly higher acid-insoluble lignin (23.8%) content compared to the biomass samples from the lower precipitation site (20.0%). Additionally, the 357 napus had a significantly higher amount of glucose (1.8% more) and acid-soluble lignin (0.2% more) than compared to the 940 napus both grown at the Froid site that may be attributed to genetic modifications. In terms of sugar content for potential upgrading, the grasses had significantly more glucose (36.1% total), xylose (24.3%), and arabinose (2.3%) than the Brassicaceae biomasses, but the lignin content was not significantly different. Switchgrass, in particular, had the highest total sugar content of close to 70 wt%. Understanding the impact of growing location on biomass composition is an important consideration for optimizing biomass utilization strategies and developing sustainable bioenergy production systems. [ABSTRACT FROM AUTHOR]

Serratia marcescens is utilized as a significant enterobacteria in the production of various high‐value secondary metabolites. Acetoin serves as a crucial foundational compound of development and finds application in a broad range of fields. Furthermore, S. marcescens HBQA‐7 is capable of utilizing xylose as its exclusive carbon source for acetoin production. The objective of this study was to utilize a constitutive promoter screening strategy to enhance both xylose utilization and acetoin production in S. marcescens HBQA‐7. By utilizing RNA‐seq, we identified the endogenous constitutive promoter P6 that is the most robust, which facilitated the overexpression of the sugar transporter protein GlfL445I, α‐acetyl lactate synthase, and α‐acetyl lactate decarboxylase, respectively. The resultant recombinant strains exhibited enhanced xylose utilization rates and acetoin yields. Subsequently, a recombinant plasmid, denoted as pBBR1MCS‐P6‐glfL445IalsSalsD, was constructed, simultaneously expressing the aforementioned three genes. The resulting recombinant strain, designated as S3, demonstrated a 1.89‐fold boost in xylose consumption rate compared with the original strain during shake flask fermentation. resulting in the accumulation of 7.14 g/L acetoin in the final fermentation medium. Subsequently, in a 5 L fermenter setup, the acetoin yield reached 48.75 g/L, corresponding to a xylose‐to‐acetoin conversion yield of 0.375 g/g. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: Pectobacterium betavasculorum is a member of the Pectobacerium genus that inhabits a variety of niches and is found in all climates. Bacteria from the Pectobacterium genus can cause soft rot disease on various plants due to the secretion of plant cell wall degrading enzymes (PCWDEs). The species P. betavasculorum is responsible for the vascular necrosis of sugar beet and soft rot of many vegetables. It also infects sunflowers and artichokes. The main sugar present in sugar beet is sucrose while xylose is one of the main sugars in artichoke and sunflower. Methods: In our work, we applied metabolomic studies coupled with genomics to investigate the metabolism of P. betavasculorum in the presence of xylose and sucrose as the only carbon source. The ability of the strains to use various sugars as the only carbon source were confirmed by the polypyridyl complex of Ru(II) method in 96-well plates. Results: Our studies provided information on the metabolic pathways active during the degradation of those substrates. It was observed that different metabolic pathways are upregulated in the presence of xylose in comparison to sucrose. Discussion: The presence of xylose enhances extracellular metabolism of sugars and glycerol as well as stimulates EPS and IPS synthesis. In contrast, in the presence of sucrose the intensive extracellular metabolism of amines and amino acids is promoted. [ABSTRACT FROM AUTHOR]

BACKGROUND: Glycation is a green processing technology. Based on our previous studies, glycation with l‐arabinose and xylose was beneficial to enhance the texture properties of silver carp mince (SCM) gels. However, the possible enhancement mechanism remained unclear. Therefore, in this study, SCM gels with different types of reducing sugar (glucose, l‐arabinose, and xylose) were prepared based on our previous study. The possible mechanism of texture enhancement of SCM gels was analyzed by investigating the changes in water distribution, protein structures, and microstructure in the gel system. RESULTS: The glycation of l‐arabinose and xylose enhanced the hardness, cohesiveness, chewiness, and resilience of SCM gels. Hardness increased from 1883.04 (control group) to 3624.54 (l‐arabinose group) and 4348.18 (xylose group). Low‐field nuclear magnetic resonance (LF‐NMR) showed that glycation promoted the tight binding of immobilized water to proteins. Raman spectroscopic analysis showed that glycation increased the surface hydrophobicity and promoted the formation of disulfide bonds. Scanning electron microscopy (SEM) showed that glycation promoted the formation of uniform and dense three‐dimensional network structure in SCM gels. CONCLUSION: In summary, glycation enhanced the binding ability of immobilized water to proteins, improved the surface hydrophobicity, promoted the formation of disulfide bonds, and led to a more uniform and dense gel network structure of proteins, thus enhancing the texture properties of SCM gels. This research provided a theoretical basis for a better understanding of the mechanism of the effect of glycation on the quality of gel products and also provided technical support for the application of l‐arabinose and xylose in new functional gel foods. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Hansenula polymorpha is a non-conventional and thermo-tolerant yeast that is well-known for its use in the industrial production of recombinant proteins. However, research to evaluate this yeast's potential for the high-temperature fermentation of sugar to produce alcohols for biofuel applications is limited. The present work investigated a wild-type H. polymorpha strain (DSM 70277) for the production of ethanol at a temperature of 40 °C under limited oxygen presence by using a batch fermentation reactor. Fermentation experiments were performed using three types of sugar (glucose, fructose, xylose) as substrates with two initial inoculum concentrations (1.1 g·L−1 and 5.0 g·L−1). The maximum specific growth rates of H. polymorpha yeast were 0.121–0.159 h−1 for fructose, 0.140–0.175 h−1 for glucose, and 0.003–0.009 h−1 for xylose. The biomass volumetric productivity was 0.270–0.473 g·L−1h−1 (fructose), 0.185–0.483 g·L−1h−1 (glucose), and 0.001–0.069 g·L−1h−1 (xylose). The overall yield of ethanol from glucose (0.470 g·g−1) was higher than that from fructose (0.434 g·g−1) and xylose (0.071 g·g−1). The H. polymorpha yeast exhibited different behavior and efficacy regarding the use of glucose, fructose, and xylose as substrates for producing ethanol. The present knowledge could be applied to improve the fermentation process for valorization of waste biomass to produce bioethanol. [ABSTRACT FROM AUTHOR]

Xylose isomerase (XI, also known as glucose isomerase) is an oxidoreductase that interconverts aldoses and ketoses. XI catalyzes the reversible isomerization of D-glucose and D-xylose into D-fructose and D-xylulose, respectively. The molecular function of XI is widely applied in producing high-fructose corn syrup (HFCS) in the food industry and bioethanol from hemicellulose in the biofuel industry. The structural information of XI from diverse strains is important for understanding molecular properties that can provide insights into protein engineering to improve enzyme efficiency. To extend the knowledge of the structural information on XI, the crystal structure of XI from Streptomyces avermitilis (SavXI) was determined at a 2.81 Å resolution. SavXI containing TIM barrel and extended α-helix domains formed the tetrameric assembly. The two metal-binding sites and their coordinating residues showed diverse conformations, providing the structural flexibility of the active site of SavXI. The structural comparison of SavXI and XI homologs exhibited unique metal-binding sites and conformations of the C-terminal α-helix domain. These structural results extend our knowledge of the molecular flexibility and mechanism of the XI family. [ABSTRACT FROM AUTHOR]

The endo-β-1,4-xylanase glycosyl hydrolase (GH11) decomposes the backbone of xylan into xylooligosaccharides or xylose. These enzymes are important for industrial applications in the production of biofuel, feed, food, and value-added materials. β-D-xylopyranose (XYP, also known as β-D-xylose) is the fundamental unit of the substrate xylan, and understanding its recognition is fundamental for the initial steps of GH11's molecular mechanism. However, little is known about the recognition of a single XYP molecule by GH11. In this study, the crystal structures of GH11 from Thermoanaerobacterium saccharolyticum (TsaGH11) complexed with an XYP molecule were determined at a resolution of 1.7–1.9 Å. The XYP molecule binds to subsite −2 of the substrate-binding cleft. The XYP molecule is mainly stabilized by a π–π interaction with the conserved Trp36 residue. The O2 and O3 atoms of XYP are stabilized by hydrogen bond interactions with the hydroxyl groups of Tyr96 and Tyr192. The conformation of the thumb domain of TsaGH11 does not play a critical role in XYP binding, and XYP binding induces a shift in the thumb domain of TsaGH11 toward the XYP molecule. A structural comparison of TsaGH11 with other GH11 xylanases revealed that the XYP molecule forms π–π stacking with the center between the phenyl and indoline ring of Trp36, whereas the XYP molecule unit from xylobiose or xylotetraose forms π–π stacking with the indoline of Trp36, which indicates that the binding modes of the substrate and XYP differ. These structural results provide a greater understanding of the recognition of XYP by the GH11 family. [ABSTRACT FROM AUTHOR]

Both grape pomace and whey are waste products from the food industry that are rich in valuable ingredients. The utilization of these two by-products is becoming increasingly possible as consumer awareness of upcycling increases. The biological activities of grape pomace extract (GPE) are diverse and depend on its bioavailability, which is influenced by processes in the digestive system. In this work, goat whey protein (GW) was used as the primary coating to protect the phenolic compounds of GPE during the spray drying process. In addition, trehalose (T), sucrose (S), xylose (X), and maltodextrin (MD) were added to the goat whey proteins as co-coatings and protein stabilizers. All spray drying experiments resulted in microcapsules (MC) with a high encapsulation efficiency (77.6–95.5%) and yield (91.5–99.0%) and almost 100% recovery of phenolic compounds during the release test. For o-coumaric acid, the GW-coated microcapsules (MC) showed a bioavailability index of up to 731.23%. A semi-crystalline structure and hydrophilicity were characteristics of the MC coated with 10% T, S, X, or 5% MD. GW alone or in combination with T, S, MD, or X proved to be a promising carrier for polyphenols from grape pomace extract and ensured good bioavailability of these natural antioxidants. [ABSTRACT FROM AUTHOR]

Indan and tetralin are widely used as fuel additives and the intermediates in the manufacture of thermal-stable jet fuel, many chemicals, medicines, and shockproof agents for rubber industry. Herein, we disclose a two-step route to selectively produce 5-methyl-2,3-dihydro-1H-indene (abbreviated as methylindan) and tetralin with xylose or the hemicelluloses from agricultural or forestry waste. Firstly, cyclopentanone (CPO) was selectively formed with ~60% carbon yield by the direct hydrogenolysis of xylose or hemicelluloses on a non-noble bimetallic Cu-La/SBA-15 catalyst. Subsequently, methylindan and tetralin were selectively produced with CPO via a cascade self-aldol condensation/rearrangement/aromatization reaction catalyzed by a commercial H-ZSM-5 zeolite. When we used cyclohexanone (another lignocellulosic cycloketone) in the second step, the main product switched to dimethyltetralin. This work gives insights into the selective production of bicyclic aromatics with lignocellulose. Indan and tetralin are used as fuel additives and intermediates in the manufacture of many products, including thermal-stable jet fuel. Here the authors report a route for the synthesis of methylindan and tetralin by the hydrogenolysis of xylose or hemicellulose over a non-noble metal catalyst, followed by further reaction over zeolite H-ZSM-5. Reviewer recognition: [ABSTRACT FROM AUTHOR]

Full conversion of glucose and xylose from lignocellulosic hydrolysates is required for obtaining a high ethanol yield. However, glucose and xylose share flux in the pentose phosphate pathway (PPP) and glycolysis pathway (EMP), with glucose having a competitive advantage in the shared metabolic pathways. In this work, we knocked down ZWF1 to preclude glucose from entering the PPP. This reduced the [NADPH] level and disturbed growth on both glucose or xylose, confirming that the oxidative PPP, which begins with Zwf1p and ultimately leads to CO2 production, is the primary source of NADPH in both glucose and xylose. Upon glucose depletion, gluconeogenesis is necessary to generate glucose-6-phosphate, the substrate of Zwf1p. We re-established the NADPH regeneration pathway by replacing the endogenous NAD+-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene TDH3 with heterogenous NADP + -GAPDH genes GDH, gapB, and GDP1. Among the resulting strains, the strain BZP1 (zwf1Δ, tdh3::GDP1) exhibited a similar xylose consumption rate before glucose depletion, but a 1.6-fold increased xylose consumption rate following glucose depletion compared to the original strain BSGX001, and the ethanol yield for total consumed sugars of BZP1 was 13.5% higher than BSGX001. This suggested that using the EMP instead of PPP to generate NADPH reduces the wasteful metabolic cycle and excess CO2 release from oxidative PPP. Furthermore, we used a copper-repressing promoter to modulate the expression of ZWF1 and optimize the timing of turning off the ZWF1, therefore, to determine the competitive equilibrium between glucose-xylose co-metabolism. This strategy allowed fast growth in the early stage of fermentation and low waste in the following stages of fermentation.

Abstract Corn cob is a major waste mass-produced in corn agriculture. Corn cob hydrolysate containing xylose, arabinose, and glucose is the hydrolysis product of corn cob. Herein, a recombinant Escherichia coli strain BT-10 was constructed to transform corn cob hydrolysate into 1,2,4-butanetriol, a platform substance with diversified applications. To eliminate catabolite repression and enhance NADPH supply for alcohol dehydrogenase YqhD catalyzed 1,2,4-butanetriol generation, ptsG encoding glucose transporter EIICBGlc and pgi encoding phosphoglucose isomerase were deleted. With four heterologous enzymes including xylose dehydrogenase, xylonolactonase, xylonate dehydratase, α-ketoacid decarboxylase and endogenous YqhD, E. coli BT-10 can produce 36.63 g/L 1,2,4-butanetriol with a productivity of 1.14 g/[L·h] using xylose as substrate. When corn cob hydrolysate was used as the substrate, 43.4 g/L 1,2,4-butanetriol was generated with a productivity of 1.09 g/[L·h] and a yield of 0.9 mol/mol. With its desirable characteristics, E. coli BT-10 is a promising strain for commercial 1,2,4-butanetriol production.

Glucose oxidase (GOx) catalyzes the oxidation of D -glucose to D -glucono-1,5-lactone and has a wide range of applications in various industries. However, the strict substrate specificity of GOx hampers its application in the conversion of other abundant sugars such as D -xylose. In this study, the substrate preference of GOx from Aspergillus niger (AnGOx) was engineered using a semi-rational design approach. The mutant T110V/F414L exhibited a 5.7-fold increase in D -xylose oxidation activity compared to that of the wild-type enzyme, which was attributed to its enhanced affinity for the substrate. Molecular dynamics simulations indicated that the T110V and F414L mutations may mitigate the non-productive binding of D -xylose at the entrance of the substrate-binding pocket, and therefore, are beneficial for providing access of its C1 hydroxyl group to the catalytic residues. Moreover, the mutant simultaneously oxidized D -xylose and D -glucose in the corncob hydrolysate to the corresponding aldonic acids when coupled with catalase. These findings provide new insights into substrate recognition by GOx and offer a new method for the utilization of D -xylose from lignocellulosic feedstocks. [ABSTRACT FROM AUTHOR]

This study aims to utilize the microbial resources found within Laphet-so, a traditional fermented tea in Myanmar. A total of 18 isolates of thermotolerant yeasts were obtained from eight samples of Laphet-so collected from southern Shan state, Myanmar. All isolates demonstrated the tannin tolerance, and six isolates were resistant to 5% (w/v) tannin concentration. All 18 isolates were capable of carboxy-methyl cellulose (CMC) degrading, but only the isolate DK showed ethanol production at 45 °C noticed by gas formation. This ethanol producing yeast was identified to be Cyberlindnera rhodanensis based on the sequence analysis of the D1/D2 domain on rRNA gene. C. rhodanensis DK produced 1.70 ± 0.01 U of thermostable extracellular β-glucosidase when cultured at 37 °C for 24 h using 0.5% (w/v) CMC as a carbon source. The best two carbon sources for extracellular β-glucosidase production were found to be either xylose or xylan, with β-glucosidase activity of 3.07–3.08 U/mL when the yeast was cultivated in the yeast malt extract (YM) broth containing either 1% (w/v) xylose or xylan as a sole carbon source at 37 °C for 48 h. The optimal medium compositions for enzyme production predicted by Plackett–Burman design and central composite design (CCD) was composed of yeast extract 5.83 g/L, peptone 10.81 g/L and xylose 20.20 g/L, resulting in a production of 7.96 U/mL, while the medium composed (g/L) of yeast extract 5.79, peptone 13.68 and xylan 20.16 gave 9.45 ± 0.03 U/mL for 48 h cultivation at 37 °C. Crude β-glucosidase exhibited a remarkable stability of 100%, 88% and 75% stable for 3 h at 35, 45 and 55 °C, respectively. [ABSTRACT FROM AUTHOR]

Microbial conversion of agri-food waste to valuable compounds offers a sustainable route to develop the bioeconomy and contribute to sustainable biorefinery. Clostridium tyrobutyricum displays a series of native traits suitable for high productivity conversion of agri-food waste, which make it a promising host for the production of various compounds, such as the short-chain fatty acids and their derivative esters products. In this study, a butanol synthetic pathway was constructed in C. tyrobutyricum, and then efficient butyl butyrate production through in situ esterification was achieved by the supplementation of lipase into the fermentation. The butyryl-CoA/acyl-CoA transferase (cat1) was overexpressed to balance the ratio between precursors butyrate and butanol. Then, a suitable fermentation medium for butyl butyrate production was obtained with xylose as the sole carbon source and shrimp shell waste as the sole nitrogen source. Ultimately, 5.9 g/L of butyl butyrate with a selectivity of 100%, and a productivity of 0.03 g/L·h was achieved under xylose and shrimp shell waste with batch fermentation in a 5 L bioreactor. Transcriptome analyses exhibited an increase in the expression of genes related to the xylose metabolism, nitrogen metabolism, and amino acid metabolism and transport, which reveal the mechanism for the synergistic utilization of xylose and shrimp shell waste. This study presents a novel approach for utilizing xylose and shrimp shell waste to produce butyl butyrate by using an anaerobic fermentative platform based on C. tyrobutyricum. This innovative fermentation medium could save the cost of nitrogen sources (~97%) and open up possibilities for converting agri-food waste into other high-value products. [ABSTRACT FROM AUTHOR]

To broaden the substrate scope of microbial cell factories towards renewable substrates, rational genetic interventions are often combined with adaptive laboratory evolution (ALE). However, comprehensive studies enabling a holistic understanding of adaptation processes primed by rational metabolic engineering remain scarce. The industrial workhorse Pseudomonas putida was engineered to utilize the non-native sugar D-xylose, but its assimilation into the bacterial biochemical network via the exogenous xylose isomerase pathway remained unresolved. Here, we elucidate the xylose metabolism and establish a foundation for further engineering followed by ALE. First, native glycolysis is derepressed by deleting the local transcriptional regulator gene hexR. We then enhance the pentose phosphate pathway by implanting exogenous transketolase and transaldolase into two lag-shortened strains and allow ALE to finetune the rewired metabolism. Subsequent multilevel analysis and reverse engineering provide detailed insights into the parallel paths of bacterial adaptation to the non-native carbon source, highlighting the enhanced expression of transaldolase and xylose isomerase along with derepressed glycolysis as key events during the process. Pseudomonas putida is becoming a host of choice for the valorization of lignocellulosic substrates. Here, the authors provide insight into the adaptation of this bacterium to the non-native substrate D-xylose, enabled by metabolic engineering and adaptive laboratory evolution. [ABSTRACT FROM AUTHOR]

Catalytic conversion of xylose and waste biomass to furfural is important in augmenting the existing supply of fossil-fuel-derived fuels and chemicals. Here, thermal treatment was used to successfully generate a sulfonated carbonaceous zirconia catalyst comprising bio renewable glucose, p-toluene sulfonic acid, and zirconium isopropoxide. This solid acid catalyst was used for heterogeneous catalytic hydrolysis of biomass and xylose dehydration to furfural. Using N2-physisorption, NH3-temperature-programmed desorption (NH3-TPD), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and elemental analysis, the acidity, porosity, presence, and influence of the sulfonic acid group and zirconium were studied. The performance of the catalyst for xylose dehydration and lignocellulosic biomass transformation to furfural was examined. This heterogeneous catalyst demonstrated good catalytic activity in the manufacture of furfural, resulting in a 40% increase in furfural yield from flax straw biomass at 190 °C after 120 min. This heterogeneous catalyst also allowed for xylose dehydration to furfural without the formation of degradation products, and a recyclability investigation revealed that the catalyst was relatively stable, with only a 5% loss in furfural yield. [ABSTRACT FROM AUTHOR]

Heterojunction photocatalysts receive significant interest due to their high performance and easy fabrication. An S-scheme heterojunction is developed on the basis of conventional type II heterojunctions, which can further promote charge separation and migration. In this work, a photocatalyst with a dual S-scheme heterojunction (denoted as C-s-ZIS/CN) is developed by the hybridization of CuInS2 quantum dot-sensitized ZnIn2S4 nanosheets and g-C3N4 nanosheets. CuInS2 quantum dot sensitization efficiently enhanced light absorption. Meanwhile, the unique charge migration pathway in the dual S-scheme heterojunction accelerated the separation and transfer of photogenerated carriers. The photocatalyst was innovatively employed in the simultaneous photocatalytic production of xylonic acid and CO. Under 10 W LED light irradiation (790 mW cm−2), the CO evolution rate reached a high of 228.94 μmol g−1 h−1. When a xenon lamp was employed, the CO evolution rate increased to 964.27 μmol g−1 h−1. Moreover, the optimal xylonic acid yield achieved was up to 58.56%. [ABSTRACT FROM AUTHOR]

Heterojunction photocatalysts receive significant interest due to their high performance and easy fabrication. An S-scheme heterojunction is developed on the basis of conventional type II heterojunctions, which can further promote charge separation and migration. In this work, a photocatalyst with a dual S-scheme heterojunction (denoted as C-s-ZIS/CN) is developed by the hybridization of CuInS2 quantum dot-sensitized ZnIn2S4 nanosheets and g-C3N4 nanosheets. CuInS2 quantum dot sensitization efficiently enhanced light absorption. Meanwhile, the unique charge migration pathway in the dual S-scheme heterojunction accelerated the separation and transfer of photogenerated carriers. The photocatalyst was innovatively employed in the simultaneous photocatalytic production of xylonic acid and CO. Under 10 W LED light irradiation (790 mW cm−2), the CO evolution rate reached a high of 228.94 μmol g−1 h−1. When a xenon lamp was employed, the CO evolution rate increased to 964.27 μmol g−1 h−1. Moreover, the optimal xylonic acid yield achieved was up to 58.56%. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenolysis of xylose to ethylene glycol (EG) and 1,2-propanediol (1,2-PG) is an important way for the high-value valorization of biomass. Herein, Ni-W/CeO2 catalysts prepared by incipient-wetness impregnation method were used for the hydrogenolysis of xylose to EG and 1,2-PG. Several characterizations such as X-ray diffraction (XRD), Transmission electron microscopy (TEM) and X-ray photoelectronic spectroscopy (XPS) were used to analyze the physicochemical properties of the catalysts. The effects of different Ni/W ratios and reaction conditions on the hydrogenolysis performance of the catalyst were investigated. The doping of W promoted the selective cleavage of C–C and C-O bonds of xylose, thus improved the yield of EG 1,2-PG. The doping of W can form interactions with Ni and increase the oxygen vacancy concentration of CeO2, which have a significant impact on the catalyst activity. When the Ni: W ratio is around 1:1, the catalyst has the best activity, and the total yield of diols can reach about 43.2%.. When xylan was used as the substrate, the total yield of diols can reach to 58.7%. The possible reaction mechanism of xylose hydrogenolysis was also discussed. This work developed a new catalyst system for the directional conversion of xylose to EG and 1,2-PG, which provided a new idea for the design of catalyst to converting lignocellulose, especially carbohydrate into high-value chemicals. Ni-W/CeO2 with different Ni/W ratio are efficient catalysts for hydrogenolysis of xylose to EG and 1,2-PG. [ABSTRACT FROM AUTHOR]

In this study, bacterial cellulose (BC) was obtained from Komagataeibacter xylinus S4 and characterized in detail. The effects of a various of carbon sources and media, different pH conditions, incubation temperatures, Surface area/Volume ratios, and incubation durations were determined for BC production. Considering the carbon types, the amount of BC production from high to low was realized as sucrose, fructose, mannitol, xylose, arabinose, and lactose. The highest BC amount (1.303 g/L) was achieved by combining M1A05P5 broth, 30 °C, 1.06 cm-1 Surface area/Volume ratio, pH 3.5 and 21 days. According to scanning electron microscope (SEM) analysis, the cellulose fibril diameters were 34.87-45.97 nm at pH 3.5 and 29.71-102.3 nm at pH 6.5 in M1A05P5. Also, TGA analysis exhibited that the weight loss of BC in the removal of water step initialized between 50 °C and 150 °C and the degradation step initialized between 215 °C and 228 °C. Finally, the electrical conductivity values of the BC samples were determined on the 27-137 °C temperature scale. It was observed that the conductivity was temperature dependent, and the conductivity increased exponentially as the temperature increased. In conclusion, the cellulose from K. xylinus S4 typically showed a semiconducting behavior. [ABSTRACT FROM AUTHOR]

The extraction of xylose, glucose, fructose, and other sugars in different brown juice (BJ) biomasses in a green biorefinery may be used on a large scale for fermentation and biobased production. A comparative study of different BJ obtained in a biorefinery demonstration platform was conducted employing white clover, red clover, grass-clover mixture, alfalfa, festulolium, and ryegrass as feedstock. In the green biorefinery, the biomass was submitted to mechanica wetl fractionation in which a green juice (GJ) and a fiber cake fraction were separated. The protein was extracted from the GJ by using heat precipitation at 85 ˚C and, sent to a decanter centrifugation, where a leaf protein concentrate was separated from the BJ. Total sugar content varied between 29.10 g/L to 10.82 g/L, in BJ from the different feedstocks. Glucose constitutes the carbohydrate with the highest concentration in BJ of festulolium, ryegrass, red clover, and grass-clover feedstock. Among all the remaining carbohydrates in the BJ, xylose is the major sugar in BJ from alfalfa and white clover. However, the highest xylose concentration was in red clover with 7.04 g/L. Ryegrass showed a higher concentration of fructose with 9.17 g/L. In general, fructose was extracted in all the BJ biomasses with quantities up to 4.73 g/L, except alfalfa with 1.81 g/L. Ryegrass and festulolium exhibited a majority concentration with 5.19 and 8.43 g/L of sucrose. Maltose and galactose presented low sugar concentrations and arabinose had the lower concentrations in BJ biomasses. [ABSTRACT FROM AUTHOR]

The results of studies of the carbohydrate components of birch and pine wood samples torrefied in the temperature range of 200–300°C are presented. An analysis of the monosaccharide composition of carbohydrates hydrolyzed by trifluoroacetic acid has been performed. Resulting from torrefaction, the level of all the monosaccharides except for glucose exhibits a decrease. Already at 200°C, the amount of xylose extracted with the use of trifluoroacetic acid decreases by approximately two times as to compare to the reference sample. Increasing the torrefaction temperature to 250°C results in a decrease in the level of extractable xylose to 1% of the dry weight of initial material. The difference between changes in the monosaccharide composition of pine and birch cell walls is represented by the dynamics of the level of extracted glucose. Owing to torrefaction, a decrease in the amount of carbohydrate components occurs and, consequently, a decrease in the biodegradability of wood is observed, which should be taken into account in the course of composite materials development. [ABSTRACT FROM AUTHOR]

Succinic acid is a key platform chemical in modern biochemical manufacturing. Optimization of the production of succinic acid production in terms of product titers and economy of resources is of vital importance. In this work, we have studied the succinic acid production by using both produced using growing and resting cells of Actinobacillus succinogenes. First, the process catalyzed by resting cells was enabled by the development of a two-step inoculum strategy which was crucial for the bacterial adaptation to the carbon source. The process was performed in the absence of nitrogen source, disabling cell duplication, and restricting endogenous respiration. While the product yields were almost identical when using growing cells (0.44 g‧g−1) and cells in resting state (0.43 g‧g−1); very interestingly, the by-product formation was dramatically reduced when operating with resting cells. Next, the format of resting cells was studied; biofilms were found to be more active than cells in suspension, in terms of specific activity, but the lower cellular concentration in biofilms affected negatively the acid final titers. Finally, a complete and simplified kinetic model was proposed and successfully fitted to the relevant retrieved data of biomass, substrate, products, and by-products both in production with growing and resting cells. These results pave the way for the optimization of succinic acid production processes with reduced nitrogen source consumption, promoting a higher selectivity to the target acid, which facilitates the subsequent downstream separation operations. [ABSTRACT FROM AUTHOR]

In Saccharomyces cerevisiae, pH homeostasis is reliant on ATP due to the use of proton-translocating ATPase (H+-ATPase) which constitutes a major drain within cellular ATP supply. Here, an exogenous proton-translocating pyrophosphatase (H+-PPase) from Arabidopsis thaliana, which uses inorganic pyrophosphate (PPi) rather than ATP, was evaluated for its effect on reducing the ATP burden. The H+-Ppase was localized to the vacuolar membrane or to the cell membrane, and their impact was studied under acetate stress at a low pH. Biosensors (pHluorin and mQueen-2m) were used to observe changes in intracellular pH (pHi) and ATP levels during growth on either glucose or xylose. A significant improvement of 35% in the growth rate at a pH of 3.7 and 6 g·L−1 acetic acid stress was observed in the vacuolar membrane H+-PPase strain compared to the parent strain. ATP levels were elevated in the same strain during anaerobic glucose and xylose fermentations. During anaerobic xylose fermentations, co-expression of pHluorin and a vacuolar membrane H+-PPase improved the growth characteristics by means of an improved growth rate (11.4%) and elongated logarithmic growth duration. Our study identified a potential method for improving productivity in the use of S. cerevisiae as a cell factory under the harsh conditions present in industry. [ABSTRACT FROM AUTHOR]

Almond hulls can be used as an inexpensive source of nutrients for producing fungi that can be used as nontraditional foods such as alternative protein, probiotics, and food ingredients. Nutrients were extracted from almond hulls using hot water and their utility in cultivating filamentous fungus Aspergillus awamori (A. awamori) in submerged cultivation was investigated using batch fermentation in flasks with passive aeration. The almond hulls extract supplied all the nutrients required for A. awamori growth. The uptake preference of various sugars was investigated and the growth kinetic parameters of A. awamori were determined. Utilization of sugars by A. awamori grown in almond hull extract proceeded sequentially with preference for glucose followed by sucrose, fructose, and then xylose. Compared to potato dextrose broth medium, the fungal biomass produced using almond hull extract as growth medium had higher protein (19.59%) and lower fat (1.50%) contents. The modified Gompertz model described the kinetics of A. awamori well with a lag phase of 0.18 days and a specific growth rate of 1.77 d−1. [ABSTRACT FROM AUTHOR]

The present work models the fermentation process parameters of the newly isolated, Meyerozyma caribbica CP02 for enhanced xylitol production and its fermentability study on rice straw hydrolysate. The study examined the impact of each of the process variables by one variable at a time optimization followed by statistical validation. Temperature of 32 °C, pH of 3.5, agitation of 200 rpm, 1.5% (v/v) inoculum, 80 gL−1 initial xylose was optimized. Subsequently, a sequential two-stage agitation approach was adopted for fermentation. At these optimized conditions, xylitol yield of 0.77 gg−1 and 0.64 gg−1 was achieved using media containing commercial and rice straw derived xylose, respectively. For scale up, in 3L batch bioreactor, the highest xylitol yield (0.63 gg−1) was attained at 72 h with rice straw hydrolysate media containing initial xylose (59.48 ± 0.82 gL−1) along with inhibitors (1.55 ± 0.10 gL−1 aliphatic acids, 0.0.048 ± 0.11 gL−1 furans, 0.64 ± 0.23 gL−1 total phenols). The results imply that even under circumstances characterized by an acidic pH and elevated initial xylose level, M. caribbica CP02, as an isolate, displays robustness and shows favorable fermentability of rice straw hydrolysate. Therefore, isolate CP02 has potential to be used in bio-refineries for high yield xylitol production with minimal hydrolysate processing requirements. [ABSTRACT FROM AUTHOR]

Corn cob is a major waste mass-produced in corn agriculture. Corn cob hydrolysate containing xylose, arabinose, and glucose is the hydrolysis product of corn cob. Herein, a recombinant Escherichia coli strain BT-10 was constructed to transform corn cob hydrolysate into 1,2,4-butanetriol, a platform substance with diversified applications. To eliminate catabolite repression and enhance NADPH supply for alcohol dehydrogenase YqhD catalyzed 1,2,4-butanetriol generation, ptsG encoding glucose transporter EIICBGlc and pgi encoding phosphoglucose isomerase were deleted. With four heterologous enzymes including xylose dehydrogenase, xylonolactonase, xylonate dehydratase, α-ketoacid decarboxylase and endogenous YqhD, E. coli BT-10 can produce 36.63 g/L 1,2,4-butanetriol with a productivity of 1.14 g/[L·h] using xylose as substrate. When corn cob hydrolysate was used as the substrate, 43.4 g/L 1,2,4-butanetriol was generated with a productivity of 1.09 g/[L·h] and a yield of 0.9 mol/mol. With its desirable characteristics, E. coli BT-10 is a promising strain for commercial 1,2,4-butanetriol production. [ABSTRACT FROM AUTHOR]

One of the challenges in biofuel production from lignocellulosic wastes is to improve its conversion to solvents; therefore, new strategies to enhance xylose uptake are required due to be the secondary abundant sugar. In this context, a novel fermentation strategy integrating a co-culture of Clostridium acetobutylicum and Saccharomyces cerevisiae with pH control was developed. Initially, two different buffers, ammonium acetate and calcium carbonate, were tested under pHmin > 4.8 by fermenting 60 g L−1 of glucose with the C. acetobutylicum monoculture. Ammonium acetate was selected for fermenting media as butanol production was increased from 9.8 to 10.9 g L−1 over the calcium carbonate test. Comparing with the spontaneous acetone-butanol-ethanol (ABE) fermentation with C. acetobutylicum when no xylose consumption was observed, xylose consumption was efficiently increased by controlling pHmin > 4.8. The xylose consumption was > 47% either by using a 45:15 g L−1 glucose:xylose mixture or with rice straw (RS) hydrolysate. Clostridium monoculture using RS hydrolysate and pHmin > 4.8 produced a butanol (ABE) concentration of 6.5 (9.5) g L−1. While it increased to 7.0 (13.1) g L−1 when the co-culture with S. cerevisiae was used using same pH regulation strategy mainly due to ethanol increase up to 2.7 g L−1. Moreover, the xylose uptake doubled to 94% due to amino-acid secretion by yeast. Overall, this combined strategy was a very effective method for promoting sugar consumption and ABE solvent production from lignocellulosic waste. [ABSTRACT FROM AUTHOR]

Background: Cost-effective production of biofuels from lignocellulose requires the fermentation of d-xylose. Many yeast species within and closely related to the genera Spathaspora and Scheffersomyces (both of the order Serinales) natively assimilate and ferment xylose. Other species consume xylose inefficiently, leading to extracellular accumulation of xylitol. Xylitol excretion is thought to be due to the different cofactor requirements of the first two steps of xylose metabolism. Xylose reductase (XR) generally uses NADPH to reduce xylose to xylitol, while xylitol dehydrogenase (XDH) generally uses NAD+ to oxidize xylitol to xylulose, creating an imbalanced redox pathway. This imbalance is thought to be particularly consequential in hypoxic or anoxic environments. Results: We screened the growth of xylose-fermenting yeast species in high and moderate aeration and identified both ethanol producers and xylitol producers. Selected species were further characterized for their XR and XDH cofactor preferences by enzyme assays and gene expression patterns by RNA-Seq. Our data revealed that xylose metabolism is more redox balanced in some species, but it is strongly affected by oxygen levels. Under high aeration, most species switched from ethanol production to xylitol accumulation, despite the availability of ample oxygen to accept electrons from NADH. This switch was followed by decreases in enzyme activity and the expression of genes related to xylose metabolism, suggesting that bottlenecks in xylose fermentation are not always due to cofactor preferences. Finally, we expressed XYL genes from multiple Scheffersomyces species in a strain of Saccharomyces cerevisiae. Recombinant S. cerevisiae expressing XYL1 from Scheffersomyces xylosifermentans, which encodes an XR without a cofactor preference, showed improved anaerobic growth on xylose as the primary carbon source compared to S. cerevisiae strain expressing XYL genes from Scheffersomyces stipitis. Conclusion: Collectively, our data do not support the hypothesis that xylitol accumulation occurs primarily due to differences in cofactor preferences between xylose reductase and xylitol dehydrogenase; instead, gene expression plays a major role in response to oxygen levels. We have also identified the yeast Sc. xylosifermentans as a potential source for genes that can be engineered into S. cerevisiae to improve xylose fermentation and biofuel production. [ABSTRACT FROM AUTHOR]

1,2,4-butanetriol (BT) is a polyol with unique chemical properties, which has a stereocenter and can be divided into D-BT (the S-enantiomer) and L-BT (the R-enantiomer). BT can be used for the synthesis of 1,2,4-butanetriol trinitrate, 3-hydroxytetrahydrofuran, polyurethane, and other chemicals. It is widely used in the military industry, medicine, tobacco, polymer. At present, the BT is mainly synthesized by chemical methods, which are accompanied by harsh reaction conditions, poor selectivity, many by-products, and environmental pollution. Therefore, BT biosynthesis methods with the advantages of mild reaction conditions and green sustainability have become a current research hotspot. In this paper, the research status of microbial synthesis of BT was summarized from the following three aspects: (1) the biosynthetic pathway establishment for BT from xylose; (2) metabolic engineering strategies employed for improving BT production from xylose; (3) other substrates for BT production. Finally, the challenges and prospects of biosynthetic BT were discussed for future methods to improve competitiveness for industrial production. [ABSTRACT FROM AUTHOR]

Corn straw is an abundant and renewable alternative for microbial biopolymer production. In this paper, an engineered Sphingomonas sanxanigenens NXG‐P916 capable of co‐utilising glucose and xylose from corn straw total hydrolysate to produce xanthan gum was constructed. This strain was obtained by introducing the xanthan gum synthetic operon gum as a module into the genome of the constructed chassis strain NXdPE that could mass produce activated precursors of polysaccharide, and in which the transcriptional levels of gum genes were optimised by screening for a more appropriate promoter, P916. As a result, strain NXG‐P916 produced 9.48 ± 0.34 g of xanthan gum per kg of fermentation broth (g/kg) when glucose was used as a carbon source, which was 2.1 times improved over the original engineering strain NXdPE::gum. Furthermore, in batch fermentation, 12.72 ± 0.75 g/kg xanthan gum was produced from the corn straw total hydrolysate containing both glucose and xylose, and the producing xanthan gum showed an ultrahigh molecular weight (UHMW) of 6.04 × 107 Da, which was increased by 15.8 times. Therefore, the great potential of producing UHMW xanthan gum by Sphingomonas sanxanigenens was proved, and the chassis NXdPE has the prospect of becoming an attractive platform organism producing polysaccharides derived from biomass hydrolysates. [ABSTRACT FROM AUTHOR]

As advances are made toward the industrial feasibility of mass-producing biofuels and commodity chemicals with sugar-fermenting microbes, high feedstock costs continue to inhibit commercial application. Hydrolyzed lignocellulosic biomass represents an ideal feedstock for these purposes as it is cheap and prevalent. However, many microbes, including Escherichia coli, struggle to efficiently utilize this mixture of hexose and pentose sugars due to the regulation of the carbon catabolite repression (CCR) system. CCR causes a sequential utilization of sugars, rather than simultaneous utilization, resulting in reduced carbon yield and complex process implications in fed-batch fermentation. A mutant of the gene encoding the cyclic AMP receptor protein, crp*, has been shown to disable CCR and improve the co-utilization of mixed sugar substrates. Here, we present the strain construction and characterization of a site-specific crp* chromosomal mutant in E. coli BL21 star (DE3). The crp* mutant strain demonstrates simultaneous consumption of glucose and xylose, suggesting a deregulated CCR system. The proteomics further showed that glucose was routed to the C5 carbon utilization pathways to support both de novo nucleotide synthesis and energy production in the crp* mutant strain. Metabolite analyses further show that overflow metabolism contributes to the slower growth in the crp* mutant. This highly characterized strain can be particularly beneficial for chemical production by simultaneously utilizing both C5 and C6 substrates from lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Effective separation of various components in biomass is critical for biorefinery. Autohydrolysis is a commercialized unit operation to remove hemicelluloses, such as xylan, in producing high‐quality cellulose (the so‐called dissolving pulp) in the pre‐hydrolysis kraft process. In the present study, the autohydrolysis of eucalyptus woodchips was investigated for the purpose of producing dissolving pulps, with a focus on the production of cellulose acetate grade dissolving pulp. First, the effects of liquid‐to‐solid ratio, maximum temperature, and time on hemicelluloses removal were comprehensively studied, and the total xylose saccharides concentration and total xylose saccharides yield were determined as a function of the P factor and log(Ro). The three‐variable Box–Behnken design of the response surface methodology was followed to optimize the autohydrolysis conditions, aiming to achieving the maximum removal of xylan. The as‐obtained optimal conditions were: liquid‐to‐solid ratio of 5.5 mL · g−1, maximum temperature of 165°C, and time of 120 min, with its P factor of 867 h and log(Ro) of 4.03. Under these conditions, the total xylose saccharides concentration was 16.43 g · L−1. Furthermore, the autohydrolysis yield was investigated. The results showed that the purity of as‐prepared cellulose substrate as a result of autohydrolysis at a P factor of 867 h (log(Ro) of 4.03) can meet the stringent requirement of cellulose acetate grade dissolving pulp. Furthermore, the pre‐hydrolysis liquor compositions were compared between the typical autohydrolysis conditions for rayon grade dissolving pulp (a P factor of 690 h and log(Ro) of 3.91) and the optimal conditions (a P factor of 867 h and log(Ro) of 4.03). [ABSTRACT FROM AUTHOR]

IntroductionPectobacterium betavasculorum is a member of the Pectobacerium genus that inhabits a variety of niches and is found in all climates. Bacteria from the Pectobacterium genus can cause soft rot disease on various plants due to the secretion of plant cell wall degrading enzymes (PCWDEs). The species P. betavasculorum is responsible for the vascular necrosis of sugar beet and soft rot of many vegetables. It also infects sunflowers and artichokes. The main sugar present in sugar beet is sucrose while xylose is one of the main sugars in artichoke and sunflower.MethodsIn our work, we applied metabolomic studies coupled with genomics to investigate the metabolism of P. betavasculorum in the presence of xylose and sucrose as the only carbon source. The ability of the strains to use various sugars as the only carbon source were confirmed by the polypyridyl complex of Ru(II) method in 96-well plates.ResultsOur studies provided information on the metabolic pathways active during the degradation of those substrates. It was observed that different metabolic pathways are upregulated in the presence of xylose in comparison to sucrose.DiscussionThe presence of xylose enhances extracellular metabolism of sugars and glycerol as well as stimulates EPS and IPS synthesis. In contrast, in the presence of sucrose the intensive extracellular metabolism of amines and amino acids is promoted.

Abstract Background Significant genetic diversity exists across Saccharomyces strains. Natural isolates and domesticated brewery and industrial strains are typically more robust than laboratory strains when challenged with inhibitory lignocellulosic hydrolysates. These strains also contain genes that are not present in lab strains and likely contribute to their superior inhibitor tolerance. However, many of these strains have poor sporulation efficiencies and low spore viability making subsequent gene analysis, further metabolic engineering, and genomic analyses of the strains challenging. This work aimed to develop an inhibitor tolerant haploid with stable mating type from S. cerevisiae YB-2625, which was originally isolated from bagasse. Results Haploid spores isolated from four tetrads from strain YB-2625 were tested for tolerance to furfural and HMF. Due to natural mutations present in the HO-endonuclease, all haploid strains maintained a stable mating type. One of the haploids, YRH1946, did not flocculate and showed enhanced tolerance to furfural and HMF. The tolerant haploid strain was further engineered for xylose fermentation by integration of the genes for xylose metabolism at two separate genomic locations (ho∆ and pho13∆). In fermentations supplemented with inhibitors from acid hydrolyzed corn stover, the engineered haploid strain derived from YB-2625 was able to ferment all of the glucose and 19% of the xylose, whereas the engineered lab strains performed poorly in fermentations. Conclusions Understanding the molecular mechanisms of inhibitor tolerance will aid in developing strains with improved growth and fermentation performance using biomass-derived sugars. The inhibitor tolerant, xylose fermenting, haploid strain described in this work has potential to serve as a platform strain for identifying pathways required for inhibitor tolerance, and for metabolic engineering to produce fuels and chemicals from undiluted lignocellulosic hydrolysates.

Abstract Background Yarrowia lipolytica, one of the most charming chassis cells in synthetic biology, is unable to use xylose and cellodextrins. Results Herein, we present work to tackle for the first time the engineering of Y. lipolytica to produce lipids from cellodextrins and xylose by employing rational and combinatorial strategies. This includes constructing a cellodextrin-phosphorolytic Y. lipolytica by overexpressing Neurospora crassa cellodextrin transporter, Clostridium thermocellum cellobiose/cellodextrin phosphorylase and Saccharomyces cerevisiae phosphoglucomutase. The effect of glucose repression on xylose consumption was relieved by installing a xylose uptake facilitator combined with enhanced PPP pathway and increased cytoplasmic NADPH supply. Further enhancing lipid production and interrupting its consumption conferred the obese phenotype to the engineered yeast. The strain is able to co-ferment glucose, xylose and cellodextrins efficiently, achieving a similar μmax of 0.19 h−1, a qs of 0.34 g-s/g-DCW/h and a YX/S of 0.54 DCW-g/g-s on these substrates, and an accumulation of up to 40% of lipids on the sugar mixture and on wheat straw hydrolysate. Conclusions Therefore, engineering Y. lipolytica capable of assimilating xylose and cellodextrins is a vital step towards a simultaneous saccharification and fermentation (SSF) process of LC biomass, allowing improved substrate conversion rate and reduced production cost due to low demand of external glucosidase.

Stimbiotics are a new category of feed additives that can increase fibre fermentability by stimulating fibre-degrading microbiota in the gut. The aim of this study was to test, ex vivo, if the microbiota of broilers fed a stimbiotic are better able to ferment different xylose-rich substrates in an ileal and a caecal environment. The ileal and caecal contents from broiler chickens fed a stimbiotic or from a control group were used as an inoculum in the ex vivo fermentation experiment. Different xylose-rich substrates including monomeric xylose (XYL), XOS with DP 2 to 6 (XOS), short DP XOS of 2 to 3 (sDP-XOS), long DP XOS of 4 to 6 (lDP-XOS) and de-starched wheat bran (WB), were added to each ileal and caecal inoculum in fermentation vessels. Total gas, short-chain fatty acids (SCFA) production, bacterial quantification, and carbohydrate utilisation were monitored for 9 h post-inoculation. No significant interactions were observed in any of the parameters measured in either the ileal or caecal contents (p > 0.05). Stimbiotic ileal inocula resulted in higher total gas (p < 0.001) and volatile fatty acid (VFA) (p < 0.001) production, increased numbers of Lactobacillus spp. (p < 0.001), and decreased numbers of Enterococcus spp. (p < 0.01) after 9 h regardless of the xylose-rich substrate added. Stimbiotic caecal inocula resulted in a higher ratio of VFA to branched-chain fatty acids (BCFAs) by up to +9% (p < 0.05). Ileal microbiota were found to preferentially metabolise WB, while caecal microbiota favoured XOS substrates, particularly lDP-XOS. These results indicate that stimbiotics can promote the abundance of lactic acid bacteria involved in the establishment of fibre-degrading bacteria and VFA content in the gut, which could have beneficial effects on broiler performance. Further, ileal and caecal microbiota differ in their utilisation of different substrates which may impact the effectiveness of different stimbiotic products. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pistachio shell is a valuable lignocellulosic biomass because almost 90% of its hemicellulose fraction is xylan, which can be converted into high value‐added compounds such as xylooligosaccarides, xylose, xylitol and furfural. The present study represents a green and novel approach to produce xylose from lignocellulosic biomass. Microwave‐assisted high‐pressure CO2/H2O hydrolysis (MW‐HPCO2) comprising a combination never previously used was performed to produce xylose from pistachio shell. RESULTS: Response surface methodology with a Box–Behnken design was implemented to optimize microwave‐assisted high‐pressure CO2/H2O hydrolysis (MW‐HPCO2). The effect of temperature, time and liquid‐to‐solid ratio was studied in the ranges of 180–210 °C, 10–30 min and 5–30 mL g−1, respectively. A maximum xylose yield of 61.39% and minimum degradation compounds (5‐hydroxymethyl furfural and furfural) of 11.07% were attained under reaction conditions of 190 °C, 30 min and 18 mL g−1. CONCLUSION: The results showed that hydrolysis temperature, time and liquid‐to‐solid ratio had a strong influence on the xylose yield, as well as on the formation of degradation compounds. MW‐HPCO2 significantly increased accessibility to cellulose‐derived products in the subsequent enzymatic hydrolysis. The results of the present study reveal that MW‐HPCO2 can be a promising green technique for the hydrolysis of lignocellulosic biomass. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

For the first time, the process of extraction fractionation of "hemicelluloses-free" birch wood in an ethanol medium into cellulose product and ethanol lignin is studied and optimized. The composition and structure of cellulose product and ethanol lignin obtained by extraction fractionation of "hemicellulose-free" birch wood and other products of their subsequent transformations are characterized by methods of infra-red spectroscopy, nuclear magnetic resonance, X-ray diffractometry, scanning electron microscopy, BET surface area analysis, high-performance liquid chromatography, gel permeation chromatography, gas chromatography, and chemical and elemental analysis. The possibility of producing enterosorbents from birch ethanol lignin that are more effective than the commercial enterosorbents "Polyphepan" based on hydrolyzed lignin is established. A new approach to the biorefinery of birch wood into xylose, levulinic acid and enterosorbents is proposed based on the integration of an optimized process of extraction fractionation of "hemicellulose-free" birch wood in ethanol medium, alkaline isolation of xylan and its hydrolysis to xylose, cellulose product conversion into levulinic acid and ethanol lignin processing to enterosorbents. [ABSTRACT FROM AUTHOR]

During the normal production of ethanol from pretreated lignocellulosic biomass, only the solid fraction containing C6 sugars is generally used by unmodified yeasts in the fermentation process – the remaining liquid fraction, rich in xylose, is used almost exclusively by genetically modified organisms (GMOs) or for other purposes. As the liquor can be used in the manufacture of a series of chemical inputs, microorganisms that metabolize C5 sugars from different sources were initially isolated with the aim of converting these sugars into acetic acid (AA) and lactic acid (LA). Experiments were carried out with pretreated elephant grass liquor, evaluating the effect of adding commonly referenced nutrients through experimental design. Thus, the present work involves the isolation, screening, and molecular characterization of bacteria, easily found in nature, with the potential to metabolize xylose and produce AA and LA, with yields similar or superior to those shown in studies employing GMOs. Using wild‐type strains, high yields were obtained with Acetobacter cerevisiae (0.96 g LA and 0.71 g AA per g total sugars) and Levilactobacillus brevis (0.77 g LA and 0.61 g AA per g total sugars) in relation to the organic acids of interest, highlighting the total conversion of the sugar blend (xylose, glucose, and arabinose) in 24 h. Ammonium citrate also significantly influenced the final yields, being responsible for the increase in production. The results are useful for biorefinery platforms and may contribute to the full use of sugars released in the lignocellulosic pretreatment of raw materials. [ABSTRACT FROM AUTHOR]

Anthranilate and its derivatives are important basic chemicals for the synthesis of polyurethanes as well as various dyes and food additives. Today, anthranilate is mainly chemically produced from petroleum‐derived xylene, but this shikimate pathway intermediate could be also obtained biotechnologically. In this study, Corynebacterium glutamicum was engineered for the microbial production of anthranilate from a carbon source mixture of glucose and xylose. First, a feedback‐resistant 3‐deoxy‐arabinoheptulosonate‐7‐phosphate synthase from Escherichia coli, catalysing the first step of the shikimate pathway, was functionally introduced into C. glutamicum to enable anthranilate production. Modulation of the translation efficiency of the genes for the shikimate kinase (aroK) and the anthranilate phosphoribosyltransferase (trpD) improved product formation. Deletion of two genes, one for a putative phosphatase (nagD) and one for a quinate/shikimate dehydrogenase (qsuD), abolished by‐product formation of glycerol and quinate. However, the introduction of an engineered anthranilate synthase (TrpEG) unresponsive to feedback inhibition by tryptophan had the most pronounced effect on anthranilate production. Component I of this enzyme (TrpE) was engineered using a biosensor‐based in vivo screening strategy for identifying variants with increased feedback resistance in a semi‐rational library of TrpE muteins. The final strain accumulated up to 5.9 g/L (43 mM) anthranilate in a defined CGXII medium from a mixture of glucose and xylose in bioreactor cultivations. We believe that the constructed C. glutamicum variants are not only limited to anthranilate production but could also be suitable for the synthesis of other biotechnologically interesting shikimate pathway intermediates or any other aromatic compound derived thereof. [ABSTRACT FROM AUTHOR]

Areca nut husk is the most promising alternative source of low-cost raw materials because it contains a considerable amount of five-carbon monosaccharide sugar in the form of xylose. This polymeric sugar can be isolated and transformed into a value-added chemical using fermentation. To extract sugars from areca nut husk fibers, preliminary pretreatment, such as dilute acid hydrolysis (H2SO4), was performed. The hemicellulosic hydrolysate of areca nut husk can produce xylitol through fermentation, but toxic components inhibit the growth of microorganisms. To overcome this, a series of detoxification treatments, including pH adjustment, activated charcoal, and ion exchange resin, were carried out to reduce the concentration of inhibitors in the hydrolysate. This study reports a remarkable 99% removal of inhibitors in the hemicellulosic hydrolysate. Subsequently, a fermentation process using Candida tropicalis (MTCC6192) was executed with the detoxified hemicellulosic hydrolysate of areca nut husk, yielding an optimum xylitol yield of 0.66 g/g. This study concludes that detoxification techniques like pH adjustment, activated charcoal, and ion exchange resins are the most economical and effective methods for eliminating toxic compounds in hemicellulosic hydrolysates. Therefore, the medium derived after detoxification from areca nut hydrolysate may be considered to have significant potential for xylitol production. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse is an agro-industrial waste produced from the sugar industry, which is composed of cellulose, hemicellulose, and lignin. It can be used as a raw material to get xylose, which is used to obtain various products of industrial interest, such as bioethanol and xylitol, among others. The objective of this work was to optimize the acid hydrolysis stage of sugarcane bagasse to obtain the maximum of xylose and the minimum of acetic acid concentration. The response surface methodology and the desirability criterion were used, evaluating the concentration of sulfuric acid (H2SO4: 1, 2, 3% v/v), the solid-liquid ratio (LSR: 6, 9, 12 ml/g), and reaction time (t: 10, 20, 30 min), as dependent variables and as response variables the maximum of xylose and the minimum of acetic acid concentration. The optimal conditions found by acid hydrolysis were 0.86% v/v of H2SO4, 22.7 min of reaction time, and 6.2 of LSR showing values of 20.0 g/L of xylose and 3.05 g/L of acetic acid. These conditions were experimentally validated, obtaining 20.37 ± 0.12 g/L, while the acetic acid concentration was 2.82 ± 0.05 g/L. These results showed that the optimization method used is good, since it was possible to accurately validate the conditions obtained, achieving similar results to those found by the optimization model, and also 75% of removal of hemicellulose was revealed. [ABSTRACT FROM AUTHOR]

Biomass conversion is challenged by the heterogeneity and lignin, a component that acts as a barrier to the enzymatic hydrolysis of polysaccharides. This study evaluated the effect of pretreatments on different fractions of sugarcane biomass lignin and cellulose exposure. Two different methods were used: dilute sulfuric acid (5%, 10%, and 20% w/w at 121 °C/30 min) and partial delignification with sodium chlorite (30% m/m at 70 °C/1 h) to reduce the exposed surface of lignin. The surface area of ​​lignin was obtained through the cationic dye Azure B, and cellulose access by enzymatic hydrolysis (15 FPU/g for 24 h—Cellic Cetec 2—Novozymes) was employed. Acid pretreatment was efficient in hemicellulose removal, and delignification removed lignin from all the biomasses fractions. Azure B dyes determined the surface area filled with lignin after dilute sulfuric acid pretreatment and partial delignification. The sample with the largest total surface area of lignin (52 m2/g of material) was the leaf pretreated with 5% sulfuric acid. The external fraction presented the largest specific surface area (240 m2/g) after partial delignification. These results indicate that reducing the lignin surface area enhances the glucose yield of enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Production of potential value-added products from different lignocellulosic biomass is becoming more common due to the availability of the feedstocks in abundance and the environment- friendly nature of the microbial production process. Due to the large array of its applications in the pharmaceutical and food sectors, xylitol is considered as potential value-added compound for production. In this study, organic waste samples were collected from various habitats and screened for potential yeast isolates for xylitol production. Among 124 tested isolates, Candida tropicalis K2 showed the highest potential for xylitol production as well as inhibitors tolerance (Furfural, 5-hydroxymethyl furfural and acetic acid) phenotypes. C. tropicalis K2 produced 90 g/L of xylitol in batch fermentation (100 g/L xylose supplemented with 20 g/L of glycerol as co-substrate) with the yield and productivity of 0.90 g/g and 1.5 g/L.h, respectively, at pH 5.5 and 30°C temperature. Together, >10% higher xylitol yield was achieved when glycerol was used as a co-substrate with pure xylose. Moreover, with non-detoxified corncob and Albizia pod hydrolysates, C. tropicalis K2 isolate produced 0.62 and 0.69 g/g of xylitol yields and 1.04 and 0.75 g/L.h xylitol productivities, respectively. Thus, C. tropicalis K2 isolate could be considered as promising candidate for xylitol production from different lignocellulosic biomass. HIGHLIGHTS Candia tropicalis K2 isolate was screened from natural sites of biomass degradation and characterized for xylitol production. Non-detoxified Albizia pod and corncob hydrolysates were explored for xylitol production using selected C. tropicalis K2 isolate. A maximum of 0.90 g/g yield and 1.07 g/L.h xylitol productivity was achieved with pure xylose. A >10% increase in xylitol yield was achieved using glycerol as a co-substrate. [ABSTRACT FROM AUTHOR]

Xylose is nowadays converted into xylitol, a popular special chemical sweetener. Xylitol can be used not only in the pharmaceutical and food industries, but also in cosmetics and synthetic resins because of its countless properties. Conventionally, xylitol is produced by slurry reactors operating in batch with dispersed or supported catalysts. Hydrogen is continuously fed to maintain a constant pressure. In this work, the kinetics of the reaction were investigated to find the optimal operating conditions to minimize the by-products obtained. Given the great performances shown by the new Ru/SiO2 sol–gel derived catalyst in glucose hydrogenation, in this work the mentioned catalyst was tested in the hydrogenation of xylose to xylitol both in batch and in continuous production to prove its stability and activity. [ABSTRACT FROM AUTHOR]