Herein,one-pot chemocatalytic conversion of xylose to value-added C_(5)/C_(4) cyclic ethers over a novel ZrO_(2)-doped Ni-Pd catalyst supported on H-βzeolite was demonstrated.Optimized catalyst,namely,Ni_(2) Pd_(0.5)...Herein,one-pot chemocatalytic conversion of xylose to value-added C_(5)/C_(4) cyclic ethers over a novel ZrO_(2)-doped Ni-Pd catalyst supported on H-βzeolite was demonstrated.Optimized catalyst,namely,Ni_(2) Pd_(0.5)Zr_(1)/H-β(25),achieved a high xylose transformation(>99%)with high selectivities toward 2-methyltetrahydrofuran(48.6%)and tetrahydropyran(20.2%)under mild reaction conditions(200℃,1.0 MPa H_(2),and 2 h).Systematic investigation of the physicochemical properties of the catalyst revealed that ZrO_(2) doping induced O vacancies,enhanced H_(2) activation,and improved metal dispersion,thereby promoting hydrogenation and hydrodeoxygenation.In situ diffuse reflectance infrared Fourier transform spectroscopy using furfural and furfuryl alcohol probes confirmed preferential adsorption geometries and electronic interactions at metal-ZrO_(2) interfaces.Time-resolved and feedstock variation studies further elucidated the reaction mechanism and highlighted the roles of key intermediates.The proposed catalyst exhibited excellent recyclability with only a minor decline in performance after multiple xylose conversion cycles.This study provides mechanistic insights and design principles for the development of efficient multifunctional catalysts for biomass valorization.展开更多
Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products.CoSe_(2)is a promising nonprecious,efficient cocatalyst for photooxidation,which can facilitate the separati...Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products.CoSe_(2)is a promising nonprecious,efficient cocatalyst for photooxidation,which can facilitate the separation of photogenerated electron–holes,increase the reaction rates,and enhance photocatalytic efficiency.In this work,we synthesized a stable and efficient photocatalysis system of CoSe_(2)/g-C_(3)N_(4)through attaching CoSe_(2)on g-C_(3)N_(4)sheets,with a yield of 50.12%for the selective photooxidation of xylose to xylonic acid.Under light illumination,the photogenerated electrons were prone to migrating from g-C_(3)N_(4)to CoSe_(2)due to the higher work function of CoSe_(2),resulting in the accelerated separation of photogenerated electron–holes and the promoted photooxidation.Herein,this study reveals the unique function of CoSe_(2),which can significantly promote oxygen adsorption,work as an electron sink and accelerate the generation of ·O_(2)^(-),thereby improving the selectivity toward xylonic acid over other by-products.This work provides useful insights into the design of selective photocatalysts by engineering g-C_(3)N_(4)for biomass high-value utilization.展开更多
Saccharomyces cerevisiae is not naturally capable of efficiently utilizing xylose as a carbon source.When cultured with lignocellulosic hydrolysates containing pretreatment-derived inhibitors,S.cerevisiae suffers from...Saccharomyces cerevisiae is not naturally capable of efficiently utilizing xylose as a carbon source.When cultured with lignocellulosic hydrolysates containing pretreatment-derived inhibitors,S.cerevisiae suffers from much lower sugar uptake,ethanol yield and fermentation efficiency.Thus,considering efficient xylose conversion into ethanol during non-detoxified hydrolysate culture,genetic engineering and adaptive evolution of S.cerevisiae might be a promising joint strategy for improving xylose uptake and ethanol production.In this study,an inhibitor-tolerant strain S.cerevisiae SPSC01-TAF94 was genetically engineered by overexpressing both xylose transport-and metabolism-related genes(N360F,Ru-xyl A,TAL1,TKL1,RKI1 and RPE1),yielding the xylose-utilizing strain TAF94-X,followed by three-stage adaptation in non-detoxified corn stover hydrolysate containing 5 g·L^(-1)acetic acid,0.32 g·L^(-1)furfural,0.17 g·L(-1)HMF and 0.19 g·L^(-1)vanillin as the major inhibitors as well as 20,40 and 60 g·L^(-1)xylose adjusted as the major carbon source,respectively.Finally,an active xylose-utilizing and ethanolproducing strain TAF94-X60 was obtained,which achieved 44.9 g·L^(-1)ethanol with yield of0.41 g·g^(-1),productivity of 0.62 g·L^(-1)·h^(-1)and xylose consumption rate of 0.42 g·L^(-1)·h^(-1)during hydrolysate culture,compared to those of 36.5 g·L^(-1),0.38 g·g^(-1),0.50 g·L^(-1)·h^(-1)and 0.20 g·L^(-1)·h^(-1)obtained with the control strain TAF94-X.The proposed joint strategy effectively utilizes hydrolyzed sugars while eliminating the need for conventional detoxification or water washing processes,thus enhancing the economic feasibility of large-scale lignocellulosic ethanol production.展开更多
It is highly attractive for the catalysts prepared from renewable materials and/or industrial by-products.Herein,lignosulfonate(LS)as the by-product in the papermaking industry was utilized to fabricate Sn-containing ...It is highly attractive for the catalysts prepared from renewable materials and/or industrial by-products.Herein,lignosulfonate(LS)as the by-product in the papermaking industry was utilized to fabricate Sn-containing organic-inorganic complexing catalysts(Sn(x)@LS)by a simple hydrothermal self-assembly process.The fabricated Sn(x)@LS played an excellent performance in the dehydration of xylose into furfural in the carbon tetrachloride(CTC)-water biphasic system,yielding 78.5%furfural at 180℃for 60 min.It was revealed that strong coordination between Sn4+and the phenolic hydroxyl groups of LS created a robust organic-inorganic skeleton(-Ar-O-Sn-O-Ar-),simultaneously generating potent Lewis acidic sites,and sulfonic acid groups of LS acted as Bronsted acidic sites.Gromacs simulations verified that CTC did not form hydrogen bonds with xylose,which may reduce xylose consumption.The CTC phase effectively extracted furfural,thereby preventing its side reactions throughout the entire process.In addition,Sn(x)@LS exhibited excellent cyclic stability in at least five reaction cycles with only a 5.0% decrease in furfural yield.Thus,this work will give a new window for the catalysts prepared from LS as the industrial by-products in the production of platform chemicals,which is a sustainable chemical conversion process.展开更多
Xylose, as β-1,4-linked xylan, makes up much of the hemicel ulose in cel wal s of cereal carbohydrates fed to pigs. As inclusion of fibrous ingredients in swine diets continues to increase, supplementation of carbohy...Xylose, as β-1,4-linked xylan, makes up much of the hemicel ulose in cel wal s of cereal carbohydrates fed to pigs. As inclusion of fibrous ingredients in swine diets continues to increase, supplementation of carbohydrases, such as xylanase,is of interest. However, much progress is warranted to achieve consistent enzyme efficacy, including an improved understanding of the utilization and energetic contribution of xylanase hydrolysis product（i.e. xylooligosaccharides or monomeric xylose）. This review examines reports on xylose absorption and metabolism in the pig and identifies gaps in this knowledge that are essential to understanding the value of carbohydrase hydrolysis products in the nutrition of the pig. Xylose research in pigs was first reported in 1954, with only sporadic contributions since. Therefore, this review also discusses relevant xylose research in other monogastric species, including humans. In both pigs and poultry, increasing purified D-xylose inclusion general y results in linear decreases in performance, efficiency, and diet digestibility. However,supplementation levels studied thus far have ranged from 5% to 40%, while theoretical xylose release due to xylanase supplementation would be less than 4%. More than 95% of ingested D-xylose disappears before the terminal ileum but mechanisms of absorption have yet to be ful y elucidated. Some data support the hypothesis that mechanisms exist to handle low xylose concentrations but become overwhelmed as luminal concentrations increase. Very little is known about xylose metabolic utilization in vertebrates but it is wel recognized that a large proportion of dietary xylose appears in the urine and significantly decreases the metabolizable energy available from the diet. Nevertheless, evidence of labeled D-xylose-1-^（14）C appearing as expired^（14）CO_2 in both humans and guinea pigs suggests that there is potential,although small, for xylose oxidation. It is yet to be determined if pigs develop increased xylose metabolic capacity with increased adaptation time to diets supplemented with xylose or xylanase. Overall, xylose appears to be poorly utilized by the pig, but it is important to consider that only one study has been reported which supplemented D-xylose dietary concentrations lower than 5%. Thus, more comprehensive studies testing xylose metabolic effects at dietary concentrations more relevant to swine nutrition are warranted.展开更多
ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve an...ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve and fermentation curve of P. stipi-tis, the optimal incubation duration and fermentation duration of P. stipitis mutant strain were 18 and 48 h, respectively. The cel concentration of original yeast liquid was 107 cel s/ml. After mutagenesis by UV irradiation and 60Co-γ irradiation, yeast liquid was incubated in 20 g/L xylose media for 48 h. According to the results, after UV irradiation for 45-75 s, transformation efficiency reached 0.3794 g/g, which was 74.39% of the theoretical value; after irradiation with 800-1 000 Gy 60Co-γ, transforma-tion efficiency reached 0.3165 g/g, which was 62.06% of the theoretical value. Therefore, both UV irradiation and 60Co-γ irradiation could improve the efficiency of xylose fermentation to ethanol by P. stipitis under appropriate conditions.展开更多
Xylose fermentation is essential for ethanol production from lignocellulosic biomass. Exposure of the xylose-fermenting yeast Candida shehatae （C. shehatae） CICC1766 to atmospheric pressure dielectric barrier discha...Xylose fermentation is essential for ethanol production from lignocellulosic biomass. Exposure of the xylose-fermenting yeast Candida shehatae （C. shehatae） CICC1766 to atmospheric pressure dielectric barrier discharge （DBD） air plasma yields a clone （designated as C81015） with stability, which exhibits a higher ethanol fermentation rate from xylose, giving a maximal enhancement in ethanol production of 36.2% compared to the control （untreated）. However, the biomass production of C81015 is lower than that of the control. Analysis of the NADH （nicotinamide adenine dinucleotide）- and NADPH （nicotinamide adenine dinucleotide phosphate）- linked xylose reductases and NAD＋-linked xylitol dehydrogenase indicates that their activities are enhanced by 34.1%, 61.5% and 66.3%, respectively, suggesting that the activities of these three enzymes are responsible for improving ethanol fermentation in C81015 with xylose as a substrate. The results of this study show that DBD air plasma could serve as a novel and effective means of generating microbial strains that can better use xylose for ethanol fermentation.展开更多
The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water （HTLW） was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The ma...The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water （HTLW） was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The main products of xylose decomposition were furfural and formic acid, and furfural further degraded to formic acid under HTLW condition. With the assumption of first order kinetics e.quation, the evaluated activation energy of xylose and furfural decomposition was 123.27kJ·mol^-1 and 58.84kJ·mol^-1, respectively.展开更多
AIM: To investigate, in the largest cohort to date, patient characteristics and associated risk factors for developing small intestinal bacterial overgrowth(SIBO) using the D-Xylose breath test(XBT).METHODS: We perfor...AIM: To investigate, in the largest cohort to date, patient characteristics and associated risk factors for developing small intestinal bacterial overgrowth(SIBO) using the D-Xylose breath test(XBT).METHODS: We performed a retrospective crosssectional study to analyze patient characteristics who underwent the XBT for evaluation of SIBO. Diagnostic testing with the XBT was performed based on a clinical suspicion for SIBO in patients with symptoms of bloating, abdominal pain, abdominal distension, weight loss, diarrhea, and/or constipation. Consecutive electronicmedical records of 932 patients who completed the XBT at the University of Florida between 2005 and 2009 were reviewed. A two-way Analysis of Variance(ANOVA) was used to test for several associations including age, gender, and body mass index(BMI) with a +XBT. A two-way ANOVA was also performed to control for the differences and interaction with age and between genders. A similar analysis was repeated for BMI. Associations between medical conditions and prior surgical histories were conducted using the Mantel-Haenszel method for 2 by 2 contingency tables, stratified for gender. Reported odds ratio estimates reflect the odds of the prevalence of a condition within the +XBT group to that of the-XBT group. P values of less than 0.05(two-sided) were considered statistically significant.RESULTS: In the 932 consecutive eligible subjects studied, 513 had a positive XBT. A positive association was found between female gender and a positive XBT(P = 0.0025), and females with a positive test were, on average, greater than 5 years older than those with a negative test(P = 0.024). The mean BMI of positive XBT subjects was normal(24.5) and significantly lower than the subjects with a negative XBT(29.5)(P = 0.0050). A positive XBT was associated with gastroesophageal reflux disease(GERD)(OR = 1.35; 95%CI: 1.02-1.80, P = 0.04), peptic ulcer disease(PUD)(OR = 2.61; 95%CI: 1.48-4.59, P < 0.01), gastroparesis(GP)(OR = 2.04; 95%CI: 1.21-3.41, P < 0.01) and steroid use(OR = 1.35; 95%CI: 1.02-1.80, P = 0.01). Irritable bowel syndrome, independent protonpump inhibitor(PPI) usage, or previous abdominal surgery was not significantly associated with a positive XBT. No single subdivision by gender or PPI use was associated with a significant difference in the odds ratios between any of the subsets. CONCLUSION: Female gender, lower BMI, steroid use, PUD, GERD(independent of PPI use), and GP were more prevalent in patients with SIBO, determined by a positive XBT. Increasing age was associated with SIBO in females, but not in males.展开更多
An environmentally benign processing approach for furfural production from xylose and xylan under very mild conditions（353–373 K） was developed with the addition of metal chlorides in ChCl–oxalic acid（a deep eute...An environmentally benign processing approach for furfural production from xylose and xylan under very mild conditions（353–373 K） was developed with the addition of metal chlorides in ChCl–oxalic acid（a deep eutectic solvent（DES）） synthesized from cheap and renewable starting materials）. ChCl–oxalic acid acted as both a Br？nsted acid catalyst and a reaction medium in this catalytic route. In addition, a biphasic system with methyl isobutyl ketone as an extracting reagent（DES/MIBK） to further increase furfural yield was also proposed. This processing approach for producing furfural eliminated the large energy consumption for high pressure saturated steam and the generation of acidic effluent, which was very difficult to handle. The whole catalytic system was more environmentally friendly compared with the commercial process for furfural production.展开更多
Phosphoric acid treated niobic acid(NbP)was used for the dehydration of xylose to furfural in biphasic solvent system,which was found to exhibit the best performance among the tested catalysts.The excellent performanc...Phosphoric acid treated niobic acid(NbP)was used for the dehydration of xylose to furfural in biphasic solvent system,which was found to exhibit the best performance among the tested catalysts.The excellent performance of NbP could be explained by the better synergistic cooperation between Bro¨nsted and Lewis acid sites.Moreover,NbP showed good stability and no obvious deactivation or leaching of Nb could be observed after six continuous recycles.展开更多
The conversion of hemicellulose-derived xylose to furfuryl alcohol is a practical procedure for producing value-added chemicals from biomass.In this study,a bifunctional Cu/SBA-15-SO3 H catalyst was employed for the o...The conversion of hemicellulose-derived xylose to furfuryl alcohol is a practical procedure for producing value-added chemicals from biomass.In this study,a bifunctional Cu/SBA-15-SO3 H catalyst was employed for the one-pot catalytic conversion of xylose to furfuryl alcohol with a yield of up to 62.6% at the optimized conditions of 140℃,4 MPa,and for 6 h in a biphasic water/n-butanol solvent.A high reaction temperature resulted in further hydrogenation to 2-methyl furan,while a high hydrogen pressure led to a side hydrogenation reaction to xylitol.The biphasic solvent allowed xylose solvation as well as furfuryl product extraction.The acidic-SO3 H sites and Cu sites co-existed,maintained a balance,and cooperatively catalyzed the cascade conversion.Excessive acidic sites and large pores could promote the xylose conversion,although a low furfuryl alcohol yield was obtained.This catalytic system could be potentially applied to the one-pot synthesis of furfuryl alcohol from hemicellulose-derived xylose.展开更多
In order to obtain an industrial strain with a higher L（＋）-lactic acid yield, the strain Rhizopus oryzae PW352 was mutated by means of nitrogen ion beam implantation and the mutant strain Rhizopus oryzae RLC41-6 wa...In order to obtain an industrial strain with a higher L（＋）-lactic acid yield, the strain Rhizopus oryzae PW352 was mutated by means of nitrogen ion beam implantation and the mutant strain Rhizopus oryzae RLC41-6 was obtained. An experimental finding was made in surprise that Rhizopus oryzae mutant RLC41-6 is not only an L（＋）-lactic acid producer from corn starch but also an efficient producer of L（＋）-lactic acid from xylose. Under optimal conditions, the production of L（＋）-lactic acid from 100 g/L xylose reached 77.39 g/L after 144 h fed-batch fermentation, A high mutation rate and a wide mutation spectrum of low-energy ion implantation were observed in the experiment.展开更多
D-Glucose, L-arabinose, D-mannose, D-xylose, and cellobiose are saccharification products of lignocellulose and important carbon sources for industrial fermentation. The fermentation efficiency with each of the five s...D-Glucose, L-arabinose, D-mannose, D-xylose, and cellobiose are saccharification products of lignocellulose and important carbon sources for industrial fermentation. The fermentation efficiency with each of the five sugars and the mixture of the two most dominant sugars, D-glucose and D-xylose, was evaluated for acetone- butanol-ethanol （ABE） fermentation by Clostridium acetobutylicum ATCC 824. The utilization efficacy of the five reducing sugars was in the order of D-glucose, L-arabinose, D-mannose, o-xylose and cellobiose, o-Xylose, the second most abundant component in lignocellulosic hydrolysate, was used in the fermentation either as sole carbon source or mixed with glucose. The results indicated that maintaining pH at 4.8, the optimal pH value for solventogenesis, could increase D-xylose consumption when it was the sole carbon source. Different media con- taining D-glucose and D-xylose at different ratios （1：2, 1：5, 1.5：1, 2：1 ） were then attempted for the ABE fermenta- tion. When pH was at 4.8 and xylose concentration was five times that of glucose, a 256.9% increase in xylose utilization and 263.7% increase in solvent production were obtained compared to those without pH control. These results demonstrate a possible approach combining optimized pH control and D-glucose and D-xylose ratio to increase the fermentation efficiency of lignocellulosic hydrolysate.展开更多
The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyrati...The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyration （Rg）, subunit interactions, and residue flexibility were analyzed. The results show that residues 60-69, 142-148, 169-172, and 332-340 have high flexibility at 300 and 360 K. Residues with higher flexibility at 360 K than that at 300 K can mainly be divided into two groups： one locates in the helix-loophelix region consisting of residues 55-80 in catalytic domain; the other at subunit interfaces. The Rg of catalytic domain at 360 K shows 0.16 A higher than that at 300 K, but Rg of small C-terminal domain has no obvious difference. The results indicate that enhanced Rg of catalytic domain may lead to the intense motion of the active site of TtXI and promote the D-xylose isomization reaction. Eight hydrogen bonds and five ion pairs are reduced at subunit interfaces at 360 K compared with 300 K, that may be the main reason for the decrease in rigidity and increase in activity at high temperature of TtXI. This result also help to explain the cold-adaption phenomenon of TtXI E372G mutant reported previously. Our results reveal the relationship between temperature and structure flexibility of TtXI, and play an important role in understanding the thermostability of thermophile protein with multiple subunits.展开更多
In this paper kinetics of xylose dehydration into furfural using acetic acid as catalyst was studied comprehensively and systematically. The reaction order of both furfural and xylose dehydration was determined and th...In this paper kinetics of xylose dehydration into furfural using acetic acid as catalyst was studied comprehensively and systematically. The reaction order of both furfural and xylose dehydration was determined and the reaction activation energy was obtained by nonlinear regression. The effect of acetic acid concentration was also investi- gated. Reaction rate constants were gained. Reaction rate constant of xylose dehydration is kl = 4.189 × 10^10[A]^0.1676 axp （-108.5×1000/RT）, reaction rate constant of furfural degradation is k2=1.271×10^10[A]0.1375 exp （-63.413×1000/RT）and reaction rate constant of condensation reaction is k3-3.4051×10^10[A]0.1676 exp （-104.99×1000/RT）, Based on this, the kinetics equation of xylose dehydration into furfural in acetic acid was set up according to theory of Dunlop and Furfural generating rate equation is d[F]/dt=K1[x]0e-k1t-k2[F]-k3[X]0E-k1 1[F]展开更多
Xylose reductase (EC 1.1.1.21) of Candida tropicalis IEC5-ITV, an indigenous xylitol-producing strain, was partially purified by reversed micelles and characterized, an 8.1 fold purification factor being obtained. The...Xylose reductase (EC 1.1.1.21) of Candida tropicalis IEC5-ITV, an indigenous xylitol-producing strain, was partially purified by reversed micelles and characterized, an 8.1 fold purification factor being obtained. The XR present in the crude extract exhibited its highest specific activity at pH 6.0 and 40℃, while in that obtained by reverse micelles, this occurs at pH 6.0 and 30℃. XR before and after extraction is stable within a range of 30 to 40℃, pH 7 after one hour of incubation under these conditions. After two months’storage at –18℃, the enzyme obtained by reverse micelles lost 76.60% specific activity. The estimated molecular weight by PAGE-SDS was 32.42 kD. KM for xylose was higher for the XR extracted by reverse micelles (0.026 M) than that obtained for the enzyme before extraction (0.0059 M), while KM for cofactor NADPH was lower after than before extraction (1.85 mM to 12.0 mM respectively). There was no activity with NADH as a cofactor. Variations in pH and temperature optima, as well as kinetic parameters before and after partial XR purification by reverse micelles are probably due to an alteration in enzyme molecule structure caused by the solvents used during extraction.展开更多
Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilizat...Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilization and ethanol yield were evaluated.During batch fermentation,the oscillation phenomena in cell growthwere observed at low aeration rate,whereas the diauxic growth at high aeration rate.The substrate utilizationratio and ethanol yield reached 95％ and 0.46g/g respectively under appropriate operation conditions.Amodified unstructural model was proposed to simulate the diauxic cell growth,substrate consumption andproduct formation.展开更多
This work evaluated the effect of dissolved oxygen and the initial inoculum concentration on xylose reductase (XR) production by Candida guilliermondii from sugarcane bagasse hemicellulosic hydrolysate. Both the param...This work evaluated the effect of dissolved oxygen and the initial inoculum concentration on xylose reductase (XR) production by Candida guilliermondii from sugarcane bagasse hemicellulosic hydrolysate. Both the parameters were studied under an experimental design 22 with triplicate at central point. The statistical analysis of the results indicated a significant negative effect on XR production from the variable inoculum. The variable dissolved oxygen also showed a negative effect on XR production. We found the maximum enzyme activity (2.5 U?mg?1) when both the factors were applied at their lowest levels. The yeast showed to be potentially capable for xylose reductase production when sugarcane bagasse hemicellulosic hydrolysate was used as carbon source. Also, the results presented important information for further optimization of xylose reductase attainment.展开更多
基金supported by the Bio&Medical Technology Development Program(no.RS-2022-NR067354)established by the National Research Foundation(NRF)funded by the Korean Ministry of Science and ICT(MSIT)+2 种基金an NRF grant funded by the Korean MSIT(no.RS-2023-00261322)Additional support from the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea(RS-2024-00469587)was also appreciated。
文摘Herein,one-pot chemocatalytic conversion of xylose to value-added C_(5)/C_(4) cyclic ethers over a novel ZrO_(2)-doped Ni-Pd catalyst supported on H-βzeolite was demonstrated.Optimized catalyst,namely,Ni_(2) Pd_(0.5)Zr_(1)/H-β(25),achieved a high xylose transformation(>99%)with high selectivities toward 2-methyltetrahydrofuran(48.6%)and tetrahydropyran(20.2%)under mild reaction conditions(200℃,1.0 MPa H_(2),and 2 h).Systematic investigation of the physicochemical properties of the catalyst revealed that ZrO_(2) doping induced O vacancies,enhanced H_(2) activation,and improved metal dispersion,thereby promoting hydrogenation and hydrodeoxygenation.In situ diffuse reflectance infrared Fourier transform spectroscopy using furfural and furfuryl alcohol probes confirmed preferential adsorption geometries and electronic interactions at metal-ZrO_(2) interfaces.Time-resolved and feedstock variation studies further elucidated the reaction mechanism and highlighted the roles of key intermediates.The proposed catalyst exhibited excellent recyclability with only a minor decline in performance after multiple xylose conversion cycles.This study provides mechanistic insights and design principles for the development of efficient multifunctional catalysts for biomass valorization.
基金financial support by National Key Research and Development Project(Grant No.2023YFE0109600)Guangzhou Key Research and Development Program(Grant No.2023B03J1330)+5 种基金National Program for Support of Topnotch Young Professionals(Grant No.x2qsA4210090)Guangzhou Basic and Applied Basic Research Foundation(Grant No.2024A04J3413)National Natural Science Foundation of China(Grant No.32201499)State Key Laboratory of Pulp and Paper Engineering(Grant Nos.2023PY01 and 202215)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2023A1515012519 and 2023B1515040013)China Postdoctoral Science Foundation(Grant No.2023M732021).
文摘Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products.CoSe_(2)is a promising nonprecious,efficient cocatalyst for photooxidation,which can facilitate the separation of photogenerated electron–holes,increase the reaction rates,and enhance photocatalytic efficiency.In this work,we synthesized a stable and efficient photocatalysis system of CoSe_(2)/g-C_(3)N_(4)through attaching CoSe_(2)on g-C_(3)N_(4)sheets,with a yield of 50.12%for the selective photooxidation of xylose to xylonic acid.Under light illumination,the photogenerated electrons were prone to migrating from g-C_(3)N_(4)to CoSe_(2)due to the higher work function of CoSe_(2),resulting in the accelerated separation of photogenerated electron–holes and the promoted photooxidation.Herein,this study reveals the unique function of CoSe_(2),which can significantly promote oxygen adsorption,work as an electron sink and accelerate the generation of ·O_(2)^(-),thereby improving the selectivity toward xylonic acid over other by-products.This work provides useful insights into the design of selective photocatalysts by engineering g-C_(3)N_(4)for biomass high-value utilization.
基金supported by the National Key Research and Development Program of China(2021YFC2101303)the National Natural Science Foundation of China(U22A20424 and 22378048)+5 种基金the Major scientific and technological projects of Sinopecthe Dalian Technology Talents Project for Distinguished Young Scholars(2021RJ03)the Fundamental Research Funds for the Central Universities(DUT25LAB104)the Liaoning Revitalization Talents Program(XLYC2202049)the Ningbo Natural Science Foundation(2022J013)the Ningbo Municipal Public Welfare Science and Technology Foundation(2024S004)。
文摘Saccharomyces cerevisiae is not naturally capable of efficiently utilizing xylose as a carbon source.When cultured with lignocellulosic hydrolysates containing pretreatment-derived inhibitors,S.cerevisiae suffers from much lower sugar uptake,ethanol yield and fermentation efficiency.Thus,considering efficient xylose conversion into ethanol during non-detoxified hydrolysate culture,genetic engineering and adaptive evolution of S.cerevisiae might be a promising joint strategy for improving xylose uptake and ethanol production.In this study,an inhibitor-tolerant strain S.cerevisiae SPSC01-TAF94 was genetically engineered by overexpressing both xylose transport-and metabolism-related genes(N360F,Ru-xyl A,TAL1,TKL1,RKI1 and RPE1),yielding the xylose-utilizing strain TAF94-X,followed by three-stage adaptation in non-detoxified corn stover hydrolysate containing 5 g·L^(-1)acetic acid,0.32 g·L^(-1)furfural,0.17 g·L(-1)HMF and 0.19 g·L^(-1)vanillin as the major inhibitors as well as 20,40 and 60 g·L^(-1)xylose adjusted as the major carbon source,respectively.Finally,an active xylose-utilizing and ethanolproducing strain TAF94-X60 was obtained,which achieved 44.9 g·L^(-1)ethanol with yield of0.41 g·g^(-1),productivity of 0.62 g·L^(-1)·h^(-1)and xylose consumption rate of 0.42 g·L^(-1)·h^(-1)during hydrolysate culture,compared to those of 36.5 g·L^(-1),0.38 g·g^(-1),0.50 g·L^(-1)·h^(-1)and 0.20 g·L^(-1)·h^(-1)obtained with the control strain TAF94-X.The proposed joint strategy effectively utilizes hydrolyzed sugars while eliminating the need for conventional detoxification or water washing processes,thus enhancing the economic feasibility of large-scale lignocellulosic ethanol production.
基金supported by theNationalNatural Science Foundation of China(No.22361132543)China Postdoctoral Science Foundation(Pre-Station)(No.2023TQ0121)State Key Laboratory of Pulp and Paper Engineering(No.2024ZD05).
文摘It is highly attractive for the catalysts prepared from renewable materials and/or industrial by-products.Herein,lignosulfonate(LS)as the by-product in the papermaking industry was utilized to fabricate Sn-containing organic-inorganic complexing catalysts(Sn(x)@LS)by a simple hydrothermal self-assembly process.The fabricated Sn(x)@LS played an excellent performance in the dehydration of xylose into furfural in the carbon tetrachloride(CTC)-water biphasic system,yielding 78.5%furfural at 180℃for 60 min.It was revealed that strong coordination between Sn4+and the phenolic hydroxyl groups of LS created a robust organic-inorganic skeleton(-Ar-O-Sn-O-Ar-),simultaneously generating potent Lewis acidic sites,and sulfonic acid groups of LS acted as Bronsted acidic sites.Gromacs simulations verified that CTC did not form hydrogen bonds with xylose,which may reduce xylose consumption.The CTC phase effectively extracted furfural,thereby preventing its side reactions throughout the entire process.In addition,Sn(x)@LS exhibited excellent cyclic stability in at least five reaction cycles with only a 5.0% decrease in furfural yield.Thus,this work will give a new window for the catalysts prepared from LS as the industrial by-products in the production of platform chemicals,which is a sustainable chemical conversion process.
基金supported in part by grants from Iowa Pork Producers Association and Elanco Animal Health
文摘Xylose, as β-1,4-linked xylan, makes up much of the hemicel ulose in cel wal s of cereal carbohydrates fed to pigs. As inclusion of fibrous ingredients in swine diets continues to increase, supplementation of carbohydrases, such as xylanase,is of interest. However, much progress is warranted to achieve consistent enzyme efficacy, including an improved understanding of the utilization and energetic contribution of xylanase hydrolysis product（i.e. xylooligosaccharides or monomeric xylose）. This review examines reports on xylose absorption and metabolism in the pig and identifies gaps in this knowledge that are essential to understanding the value of carbohydrase hydrolysis products in the nutrition of the pig. Xylose research in pigs was first reported in 1954, with only sporadic contributions since. Therefore, this review also discusses relevant xylose research in other monogastric species, including humans. In both pigs and poultry, increasing purified D-xylose inclusion general y results in linear decreases in performance, efficiency, and diet digestibility. However,supplementation levels studied thus far have ranged from 5% to 40%, while theoretical xylose release due to xylanase supplementation would be less than 4%. More than 95% of ingested D-xylose disappears before the terminal ileum but mechanisms of absorption have yet to be ful y elucidated. Some data support the hypothesis that mechanisms exist to handle low xylose concentrations but become overwhelmed as luminal concentrations increase. Very little is known about xylose metabolic utilization in vertebrates but it is wel recognized that a large proportion of dietary xylose appears in the urine and significantly decreases the metabolizable energy available from the diet. Nevertheless, evidence of labeled D-xylose-1-^（14）C appearing as expired^（14）CO_2 in both humans and guinea pigs suggests that there is potential,although small, for xylose oxidation. It is yet to be determined if pigs develop increased xylose metabolic capacity with increased adaptation time to diets supplemented with xylose or xylanase. Overall, xylose appears to be poorly utilized by the pig, but it is important to consider that only one study has been reported which supplemented D-xylose dietary concentrations lower than 5%. Thus, more comprehensive studies testing xylose metabolic effects at dietary concentrations more relevant to swine nutrition are warranted.
文摘ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve and fermentation curve of P. stipi-tis, the optimal incubation duration and fermentation duration of P. stipitis mutant strain were 18 and 48 h, respectively. The cel concentration of original yeast liquid was 107 cel s/ml. After mutagenesis by UV irradiation and 60Co-γ irradiation, yeast liquid was incubated in 20 g/L xylose media for 48 h. According to the results, after UV irradiation for 45-75 s, transformation efficiency reached 0.3794 g/g, which was 74.39% of the theoretical value; after irradiation with 800-1 000 Gy 60Co-γ, transforma-tion efficiency reached 0.3165 g/g, which was 62.06% of the theoretical value. Therefore, both UV irradiation and 60Co-γ irradiation could improve the efficiency of xylose fermentation to ethanol by P. stipitis under appropriate conditions.
基金supported by National Natural Science Foundation of China(No.20576018)
文摘Xylose fermentation is essential for ethanol production from lignocellulosic biomass. Exposure of the xylose-fermenting yeast Candida shehatae （C. shehatae） CICC1766 to atmospheric pressure dielectric barrier discharge （DBD） air plasma yields a clone （designated as C81015） with stability, which exhibits a higher ethanol fermentation rate from xylose, giving a maximal enhancement in ethanol production of 36.2% compared to the control （untreated）. However, the biomass production of C81015 is lower than that of the control. Analysis of the NADH （nicotinamide adenine dinucleotide）- and NADPH （nicotinamide adenine dinucleotide phosphate）- linked xylose reductases and NAD＋-linked xylitol dehydrogenase indicates that their activities are enhanced by 34.1%, 61.5% and 66.3%, respectively, suggesting that the activities of these three enzymes are responsible for improving ethanol fermentation in C81015 with xylose as a substrate. The results of this study show that DBD air plasma could serve as a novel and effective means of generating microbial strains that can better use xylose for ethanol fermentation.
基金Supported by the National Natural Science Foundation of China （No.20476089） and the Project of the Ministry of Science and Technology of China （No.2004CCA05500）.
文摘The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water （HTLW） was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The main products of xylose decomposition were furfural and formic acid, and furfural further degraded to formic acid under HTLW condition. With the assumption of first order kinetics e.quation, the evaluated activation energy of xylose and furfural decomposition was 123.27kJ·mol^-1 and 58.84kJ·mol^-1, respectively.
基金Supported by KL2 Scholar Award to Baharak Moshiree KL2 RR029888-01 from the National Institute of Health(NIH)NIH grant No.1UL1TR000064,from the National Center for Advancing Translational Sciences
文摘AIM: To investigate, in the largest cohort to date, patient characteristics and associated risk factors for developing small intestinal bacterial overgrowth(SIBO) using the D-Xylose breath test(XBT).METHODS: We performed a retrospective crosssectional study to analyze patient characteristics who underwent the XBT for evaluation of SIBO. Diagnostic testing with the XBT was performed based on a clinical suspicion for SIBO in patients with symptoms of bloating, abdominal pain, abdominal distension, weight loss, diarrhea, and/or constipation. Consecutive electronicmedical records of 932 patients who completed the XBT at the University of Florida between 2005 and 2009 were reviewed. A two-way Analysis of Variance(ANOVA) was used to test for several associations including age, gender, and body mass index(BMI) with a +XBT. A two-way ANOVA was also performed to control for the differences and interaction with age and between genders. A similar analysis was repeated for BMI. Associations between medical conditions and prior surgical histories were conducted using the Mantel-Haenszel method for 2 by 2 contingency tables, stratified for gender. Reported odds ratio estimates reflect the odds of the prevalence of a condition within the +XBT group to that of the-XBT group. P values of less than 0.05(two-sided) were considered statistically significant.RESULTS: In the 932 consecutive eligible subjects studied, 513 had a positive XBT. A positive association was found between female gender and a positive XBT(P = 0.0025), and females with a positive test were, on average, greater than 5 years older than those with a negative test(P = 0.024). The mean BMI of positive XBT subjects was normal(24.5) and significantly lower than the subjects with a negative XBT(29.5)(P = 0.0050). A positive XBT was associated with gastroesophageal reflux disease(GERD)(OR = 1.35; 95%CI: 1.02-1.80, P = 0.04), peptic ulcer disease(PUD)(OR = 2.61; 95%CI: 1.48-4.59, P < 0.01), gastroparesis(GP)(OR = 2.04; 95%CI: 1.21-3.41, P < 0.01) and steroid use(OR = 1.35; 95%CI: 1.02-1.80, P = 0.01). Irritable bowel syndrome, independent protonpump inhibitor(PPI) usage, or previous abdominal surgery was not significantly associated with a positive XBT. No single subdivision by gender or PPI use was associated with a significant difference in the odds ratios between any of the subsets. CONCLUSION: Female gender, lower BMI, steroid use, PUD, GERD(independent of PPI use), and GP were more prevalent in patients with SIBO, determined by a positive XBT. Increasing age was associated with SIBO in females, but not in males.
基金the Major National Science & Technology Projects of China on Water Pollution Control and Treatment (No. 2012ZX07501002-001)for the financial support
文摘An environmentally benign processing approach for furfural production from xylose and xylan under very mild conditions（353–373 K） was developed with the addition of metal chlorides in ChCl–oxalic acid（a deep eutectic solvent（DES）） synthesized from cheap and renewable starting materials）. ChCl–oxalic acid acted as both a Br？nsted acid catalyst and a reaction medium in this catalytic route. In addition, a biphasic system with methyl isobutyl ketone as an extracting reagent（DES/MIBK） to further increase furfural yield was also proposed. This processing approach for producing furfural eliminated the large energy consumption for high pressure saturated steam and the generation of acidic effluent, which was very difficult to handle. The whole catalytic system was more environmentally friendly compared with the commercial process for furfural production.
基金supported by the Natural Science Foundation of China (No.21106143)100-talent project of Dalian Institute of Chemical Physics (DICP)the Independent Innovation Foundation of State Key Laboratory of Catalysis (No.R201113)
文摘Phosphoric acid treated niobic acid(NbP)was used for the dehydration of xylose to furfural in biphasic solvent system,which was found to exhibit the best performance among the tested catalysts.The excellent performance of NbP could be explained by the better synergistic cooperation between Bro¨nsted and Lewis acid sites.Moreover,NbP showed good stability and no obvious deactivation or leaching of Nb could be observed after six continuous recycles.
基金supported by the National Key R&D Program of China(2018YFB1501600)the National Natural Science Foundation of China(21572212,51821006,51961135104)+2 种基金the Major Science and Technology Projects of Anhui Province(18030701157)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA21060101)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01N092)~~
文摘The conversion of hemicellulose-derived xylose to furfuryl alcohol is a practical procedure for producing value-added chemicals from biomass.In this study,a bifunctional Cu/SBA-15-SO3 H catalyst was employed for the one-pot catalytic conversion of xylose to furfuryl alcohol with a yield of up to 62.6% at the optimized conditions of 140℃,4 MPa,and for 6 h in a biphasic water/n-butanol solvent.A high reaction temperature resulted in further hydrogenation to 2-methyl furan,while a high hydrogen pressure led to a side hydrogenation reaction to xylitol.The biphasic solvent allowed xylose solvation as well as furfuryl product extraction.The acidic-SO3 H sites and Cu sites co-existed,maintained a balance,and cooperatively catalyzed the cascade conversion.Excessive acidic sites and large pores could promote the xylose conversion,although a low furfuryl alcohol yield was obtained.This catalytic system could be potentially applied to the one-pot synthesis of furfuryl alcohol from hemicellulose-derived xylose.
基金supported by the Key‘863’Fund of China (No.2006AA020102)Key Technology Research and Development Program of Anhui Province in 2007 (No.07010202076)
文摘In order to obtain an industrial strain with a higher L（＋）-lactic acid yield, the strain Rhizopus oryzae PW352 was mutated by means of nitrogen ion beam implantation and the mutant strain Rhizopus oryzae RLC41-6 was obtained. An experimental finding was made in surprise that Rhizopus oryzae mutant RLC41-6 is not only an L（＋）-lactic acid producer from corn starch but also an efficient producer of L（＋）-lactic acid from xylose. Under optimal conditions, the production of L（＋）-lactic acid from 100 g/L xylose reached 77.39 g/L after 144 h fed-batch fermentation, A high mutation rate and a wide mutation spectrum of low-energy ion implantation were observed in the experiment.
基金Supported by the National Natural Science Foundation of China(20306026 and 21376215)the National High Technology Research and Development Program of China(2012AA022302)
文摘D-Glucose, L-arabinose, D-mannose, D-xylose, and cellobiose are saccharification products of lignocellulose and important carbon sources for industrial fermentation. The fermentation efficiency with each of the five sugars and the mixture of the two most dominant sugars, D-glucose and D-xylose, was evaluated for acetone- butanol-ethanol （ABE） fermentation by Clostridium acetobutylicum ATCC 824. The utilization efficacy of the five reducing sugars was in the order of D-glucose, L-arabinose, D-mannose, o-xylose and cellobiose, o-Xylose, the second most abundant component in lignocellulosic hydrolysate, was used in the fermentation either as sole carbon source or mixed with glucose. The results indicated that maintaining pH at 4.8, the optimal pH value for solventogenesis, could increase D-xylose consumption when it was the sole carbon source. Different media con- taining D-glucose and D-xylose at different ratios （1：2, 1：5, 1.5：1, 2：1 ） were then attempted for the ABE fermenta- tion. When pH was at 4.8 and xylose concentration was five times that of glucose, a 256.9% increase in xylose utilization and 263.7% increase in solvent production were obtained compared to those without pH control. These results demonstrate a possible approach combining optimized pH control and D-glucose and D-xylose ratio to increase the fermentation efficiency of lignocellulosic hydrolysate.
基金This work was supported by the National Natural Science Foundation of China （No.20336010） and the State Key Basic Research and Development Plan of China （No.2003CB716000）.
文摘The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyration （Rg）, subunit interactions, and residue flexibility were analyzed. The results show that residues 60-69, 142-148, 169-172, and 332-340 have high flexibility at 300 and 360 K. Residues with higher flexibility at 360 K than that at 300 K can mainly be divided into two groups： one locates in the helix-loophelix region consisting of residues 55-80 in catalytic domain; the other at subunit interfaces. The Rg of catalytic domain at 360 K shows 0.16 A higher than that at 300 K, but Rg of small C-terminal domain has no obvious difference. The results indicate that enhanced Rg of catalytic domain may lead to the intense motion of the active site of TtXI and promote the D-xylose isomization reaction. Eight hydrogen bonds and five ion pairs are reduced at subunit interfaces at 360 K compared with 300 K, that may be the main reason for the decrease in rigidity and increase in activity at high temperature of TtXI. This result also help to explain the cold-adaption phenomenon of TtXI E372G mutant reported previously. Our results reveal the relationship between temperature and structure flexibility of TtXI, and play an important role in understanding the thermostability of thermophile protein with multiple subunits.
基金supported by the National Basic Research Program of China(‘‘973’’Program,No.2013CB733601)the National High Technology Research and Development Program of China(‘‘863’’Program,No.2012AA02A701)+1 种基金the National Natural Science Foundation of China(No.21390203)the Tianjin Municipal Science and Technology Committee(No.13RCGFSY19800)
文摘In this paper kinetics of xylose dehydration into furfural using acetic acid as catalyst was studied comprehensively and systematically. The reaction order of both furfural and xylose dehydration was determined and the reaction activation energy was obtained by nonlinear regression. The effect of acetic acid concentration was also investi- gated. Reaction rate constants were gained. Reaction rate constant of xylose dehydration is kl = 4.189 × 10^10[A]^0.1676 axp （-108.5×1000/RT）, reaction rate constant of furfural degradation is k2=1.271×10^10[A]0.1375 exp （-63.413×1000/RT）and reaction rate constant of condensation reaction is k3-3.4051×10^10[A]0.1676 exp （-104.99×1000/RT）, Based on this, the kinetics equation of xylose dehydration into furfural in acetic acid was set up according to theory of Dunlop and Furfural generating rate equation is d[F]/dt=K1[x]0e-k1t-k2[F]-k3[X]0E-k1 1[F]
文摘Xylose reductase (EC 1.1.1.21) of Candida tropicalis IEC5-ITV, an indigenous xylitol-producing strain, was partially purified by reversed micelles and characterized, an 8.1 fold purification factor being obtained. The XR present in the crude extract exhibited its highest specific activity at pH 6.0 and 40℃, while in that obtained by reverse micelles, this occurs at pH 6.0 and 30℃. XR before and after extraction is stable within a range of 30 to 40℃, pH 7 after one hour of incubation under these conditions. After two months’storage at –18℃, the enzyme obtained by reverse micelles lost 76.60% specific activity. The estimated molecular weight by PAGE-SDS was 32.42 kD. KM for xylose was higher for the XR extracted by reverse micelles (0.026 M) than that obtained for the enzyme before extraction (0.0059 M), while KM for cofactor NADPH was lower after than before extraction (1.85 mM to 12.0 mM respectively). There was no activity with NADH as a cofactor. Variations in pH and temperature optima, as well as kinetic parameters before and after partial XR purification by reverse micelles are probably due to an alteration in enzyme molecule structure caused by the solvents used during extraction.
文摘Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilization and ethanol yield were evaluated.During batch fermentation,the oscillation phenomena in cell growthwere observed at low aeration rate,whereas the diauxic growth at high aeration rate.The substrate utilizationratio and ethanol yield reached 95％ and 0.46g/g respectively under appropriate operation conditions.Amodified unstructural model was proposed to simulate the diauxic cell growth,substrate consumption andproduct formation.
文摘This work evaluated the effect of dissolved oxygen and the initial inoculum concentration on xylose reductase (XR) production by Candida guilliermondii from sugarcane bagasse hemicellulosic hydrolysate. Both the parameters were studied under an experimental design 22 with triplicate at central point. The statistical analysis of the results indicated a significant negative effect on XR production from the variable inoculum. The variable dissolved oxygen also showed a negative effect on XR production. We found the maximum enzyme activity (2.5 U?mg?1) when both the factors were applied at their lowest levels. The yeast showed to be potentially capable for xylose reductase production when sugarcane bagasse hemicellulosic hydrolysate was used as carbon source. Also, the results presented important information for further optimization of xylose reductase attainment.
