Xylose: absorption, fermentation, and post-absorptive metabolism in the pig

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.

Improved Ethanol Production from Xylose by Candida shehatae Induced by Dielectric Barrier Discharge Air Plasma

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.

Predisposing factors for positive D-Xylose breath test for evaluation of small intestinal bacterial overgrowth:A retrospective study of 932 patients

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.

Dehydration of xylose to furfural over niobium phosphate catalyst in biphasic solvent system

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.

Optimization of L(+)-Lactic Acid Production from Xylose with Rhizopus Oryzae Mutant RLC41-6 Breeding by Low-Energy Ion Implantation

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.

Enhancement of Simultaneous Xylose and Glucose Utilization by Regulating ZWF1 and PGI1 in Saccharomyces Cerevisiae

Xylose utilization is one of the key issues in lignocellulose bioconversion.Because of glucose repression,in most engineered yeast with heterogeneous xylose metabolic pathway,xylose is not consumed until glucose is completely utilized.Although simultaneous glucose and xylose utilization have been achieved in yeast by RPE1 deletion,we regulated ZWF1 and PGI1 transcription to improve simultaneous xylose and glucose utilization by controlling the metabolic flux from glucose into the PP pathway.Xylose and glucose consumption increased by approximately 80 and 72%,respectively,whereas ZWF1 was overexpressed by multi-copy plasmids with a strong transcriptional promoter.PGI1 expression was knocked down by promoter replacement; the glucose and xylose metabolism increased when PGI1p was replaced by weak promoters,SSA1p and PDA1p.ZWF1 overexpression decreased while PGI1 down-regulation increased the ethanol yield to some extent in the recombinant strains.

Preliminary Characterization of Xylose Reductase Partially Purified by Reversed Micelles from <i>Candida tropicalis</i>IEC5-ITV, an Indigenous Xylitol-Producing Strain

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.

ETHANOL FERMENTATION OF MIXED GLUCOSE AND XYLOSE BY PICHIA STIPITIS

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.

Effect of Dissolved Oxygen and Inoculum Concentration on Xylose Reductase Production from <i>Candida guilliermondii</i>Using Sugarcane Bagasse Hemicellulosic Hydrolysate

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.

Synthesis of New Thiazine and Thiosemicarbazone Derivatives from D-Xylose

1,2-O-Isopropylidene-5-O-p-toluenesulfonyl-α-D-erythro-pentofuranos-3-ulose 1 was treated with thiourea and aminothiourea to give a D-ribose derivative 2 bearing a 2-amino 1,3-thiazine ring and a thiosemicarbazone derivative 5, respectively. 2 was acylated with Ac20 and propandioic acid to afford two acylation derivatives 3 and 4, respectively. Reduction of 5 with NaBH4 in methanol produced a hydrothiosemicarbazone derivative 6. The absolute configuration of 2 was confirmed by X-ray crystallographic analysis. The structures of all products were elucidated by IR, NMR and HRMS spectra.

Development on ethanol production from xylose by recombinant Saccharomyces cerevisiae

Xylose is the second major fermentable sugar present in lignocellulosic hydrolysates, so its fermentation is essential for the economic con- version of lignocellulose to ethanol. However, the traditional ethanol production strain Sacch- aromyces cerevisiae does not naturally use xy-lose as a substrate. A number of different ap-proaches have been used to engineer yeasts to reconstruct the gene background of S. cerevi- siae in recent years. The recombinant strains showed better xylose fermentation quality by comparison with the natural strains. This review examines the research on S. cerevisiae strains that have been genetically modified or adapted to ferment xylose to ethanol from three aspects including construction of xylose transportation, xylose-metabolic pathway and inhibitor toler-ance improvement of S. cerevisiae.

XYLOS——被用来收藏的家具

XYLOS是由三个志同道合的建筑师、手工艺者、工匠组成的一个非常特别的设计工作室,他们在艺术的道路上追求、探索完美的设计;他们的作品让人惊喜、遐想、并焕发起人们对美好生活的热爱。他们至今仍是完全用手工完成所有的作品,令人叹为观止。

Kinetics of Non-catalyzed Decomposition of D-xylose in High Temperature Liquid Water

高温度液体水(HTLW ) 里的木糖和它的分解产品糠醛的非催化的分解的动力学从 180 ～ 220 ° C 并且在 10MPa 的压力下面为温度被学习。木糖分解的主要产品是糠醛和蚁的酸，并且糠醛进一步在 HTLW 状况下面降级了到蚁的酸。与第一个顺序动力学方程的假设，木糖和糠醛分解的评估激活精力是 123.27kJ ·摩尔 ? 1 并且 58.84kJ ·摩尔 ? 1 分别地。

Degradation Kinetics of Xylose and Glucose in Hydrolysate Containing Dilute Sulfuric Acid

In preparation of fuel alcohol from biomass as feedstock, hydrolysis with dilute acid as catalyst is one way to produce fermentable saccharide, xylose and glucose. However, the acid is also the catalyst in degradation of xylose and glucose and the yield of sacchride is dependent on the kinetic behaviors of saccharide. The degradation kinetics of xylose and glucose in the hydrolysate was investigated under the conventional process conditions of hydrogen ion concentration from 0.05 to 0.2 mol/L and temperature from 150 to 200 ℃ . With a numerical calculation method, the kinetic parameters were estimated, and the activation energy of xylose and glucose in the degradation reaction was obtained. The kinetic equations correlating the effect of hydrogen ion concentration on the rate constants of degradation reaction were established. Comparison between the calculated results from the equations and experimental ones proved that the established kinetic model could satisfactorily predict the degradation behavior of xylose and glucose in the acidic hydrolysate.

Experimental measurement and thermodynamic modeling of binary and ternary solid–liquid phase equilibrium for the systems formed by L-arabinose,D-xylose and water

Solid–liquid phase equilibrium data for binary(L-arabinose–water) and(D-xylose–water) systems at temperatures from(269.85–298.05) K and ternary(L-arabinose–D-xylose–water) system at temperatures of 273.85 K,278.85 K and 284.45 K were measured at atmospheric pressure.The ternary phase diagrams of the systems were constructed on the base of the measured solubility.Two pure solid phases were formed at given temperatures,including pure L-arabinose and pure D-xylose,which were con firmed and determined by the method of Schreinemakers' wet residue.At the same temperature,the crystallization region of L-arabinose was larger than D-xylose's.The acquired solubility data were then correlated using the NRTL model,Wilson model and Xu model.The calculated solubility with the three models agreed well with the experimental values.

Molecular Dynamics Simulation of Temperature-dependent Flexibility of Thermophilic Xylose Isomerase

有 D 木糖的 Thermus thermophilus 木糖 isomerase (TtXI ) 的复杂模型被构造，并且分子的动力学(MD ) 模拟被 NAMD2.5 为 10 ns 在 300 和 360 K 执行。旋转(Rg ) 的半径，子单元相互作用，和残余灵活性被分析。结果表演残余 6069， 142148， 169172，和 332340 在 300 和 360 K 有高灵活性。有在 360 K 的更高的灵活性的残余能主要在 300 K 比那被划分成二个组：一个人在由残余组成的 helix-loop-helix 区域定位 5580 在里面催化领域；其它在子单元连接。在 360 K 的催化领域的 Rg 显示出 0.16 吗？高，比那，在小 C 终端的 300 K，而是 Rg，领域没有明显的差别。结果显示催化领域的那提高的 Rg 可以导致 TtXI 的活跃地点的强烈运动并且支持 D 木糖 isomization 反应。八张氢契约和五离子对与 300 K 相比在 360 K 在子单元接口被减少，那可以是为在在在 TtXI 的高温度的活动的刚硬和增加的减少的主要原因。也，解释 TtXI E372G 异种的冷改编的现象的帮助以前报导了的这结果。我们的结果揭示在温度和 TtXI 的结构灵活性之间的关系，并且在与多重子单元理解 thermophile 蛋白质的 thermostability 起一个重要作用。

Engineering of Saccharomyces cerevisiae for co-fermentation of glucose and xylose:Current state and perspectives

The use of non-food lignocellulosic biomass to produce ethanol fits into the strategy of a global circular economy with low dependence on fossil energy resources.Xylose is the second most abundant sugar in lignocellulosic hydrolysate,and its utilization in fermentation is a key issue in making the full use of raw plant materials for ethanol production and reduce production costs.Saccharomyces cerevisiae is the best ethanol producer but the organism is not a native xylose user.In recent years,great efforts have been made in the construction of xy-lose utilizing S.cerevisiae strains by metabolic and evolutionary engineering approaches.In addition,managing global transcriptional regulation works provides an effective means to increase the xylose utilization capacity of recombinant strains.Here we review the common strategies and research advances in the research field in order to facilitate the researches in xylose metabolism and xylose-based fermentation.

Low-temperature caproate production,microbial diversity,and metabolic pathway in xylose anaerobic fermentation

Mixed culture fermentation(MCF)is challenged by the unqualified activity of enriched bacteria and unwanted methane dissolution under low temperatures.In this work,caproate production from xylose was investigated by MCF at a low temperature(20°C).The results showed that a 9 d long hydraulic retention time(HRT)in a continuously stirred tank reactor was necessary for caproate production(~0.3 g/L,equal to 0.6 g COD/L)from xylose(10 g/L).The caproate concentration in the batch mode was further increased to 1.6 g/L.However,changing the substrate to ethanol did not promote caproate production,resulting in~1.0 g/L after 45 d of operation.Four genera,Bifidobacterium,Caproiciproducens,Actinomyces,and Clostridium_sensu_stricto_12,were identified as the enriched caproate-producing bacteria.The enzymes in the fatty acid biosynthesis(FAB)pathway for caproate production were identified via metagenomic analysis.The enzymes for the conversion of(C_(n+2))-2,3-Dehydroxyacyl-CoA to(C_(n+2))-Acyl-CoA(i.e.,EC 1.3.1.8 and EC 1.3.1.38)in the reverseβ-oxidation(RBO)pathway were not identified.These results could extend the understanding of low-temperature caproate production.

木糖合成纳米木聚糖在抗菌材料中的应用研究

以木糖为原料,加入适量的山梨醇与柠檬酸,以高温聚合法制备低聚木糖;随后将其与氢氧化钠溶液混合反应制备纳米木聚糖。结果表明:当木糖、山梨醇、柠檬酸的物料比为18∶6∶1,处理温度为170℃,处理时间为1 h时,低聚木糖的产率最高;当碱液浓度3.5%,处理温度为60℃,处理时间为2 h时,制得的纳米木聚糖粒径较小。抗菌试验表明:纳米木聚糖在金黄色葡萄球菌和大肠杆菌中的抑菌圈直径分别为11 mm和12 mm,显示出良好的抗菌效果。

高光纯D-乳酸生产菌株假肠膜明串珠菌HL64-1的分离鉴定及其发酵特性

从自然界中筛选分离产酸菌是获得高光学纯度乳酸生产菌株有效的途径之一。从腐烂果实中分离获得一株产高光学纯度D-乳酸菌株HL64-1,经形态学、16S rDNA序列分析、序列相似性Blast比对分析鉴定为假肠膜明串珠菌(Leuconostoc pseudomesenteroides)。在基础发酵培养基中摇瓶发酵24 h,产D-乳酸的量达到62.18 g/L,产酸速率达2.59 g/(L·h),光学纯度达99.90%(ee);在5 L发酵罐中放大培养,通过补加碳源,发酵72 h,D-乳酸产量达到78.74 g/L,平均产酸速率达1.09 g/(L·h)。该菌株可以有效利用农业副产物花生饼粉和棉籽粉作为替代氮源以降低发酵原料成本。该菌还可利用木糖产生D-乳酸,且葡萄糖能显著提高木糖的利用效率,极具工业应用前景。