Mode of action of a minor xylanase from Thermoascus aurantiacus on polysaccharides and model substrates

The mode of action of a minor xylanase on a variety of polysaccharides and model substrates was investigated. The enzyme was excreted by Thermoascus aurantiacus grown in solid state fermentation (SSF). The purified enzyme had a molecular mass of 33,000. Thin layer chromatography analysis showed that the endoxylanase liberated short fragments from polysaccharides. The enzyme hydrolysed aryl-β- -cellobioside and the chromogenic (fluorogenic) 4-methylumbelliferyl-β-glycosides of xylobiose (MeUmbXyl₂) and xylotriose (MeUmbXyl₃) at the agluconic linkage. The results suggested that the endoxylanase belonged to family 10.     

凝胶过滤色谱法研究酶解过程中木聚糖分子结构的变化

采用凝胶过滤色谱法研究了木聚糖在酶解过程中分子量分布的变化。结果表明,木聚糖酶对高分子量组分的木聚糖的降解能力较差,而主要降解分子量介于15000～3000之间组分的木聚糖,使得这部分木聚糖变为分子量更低的木聚糖组分。随着酶解时间的延长,酶解得率上升,酶解产物中低聚木糖含量增多,未被酶解的木聚糖的平均聚合度上升,当酶解时间超过4h时,这种变化趋势缓慢。随着酶解轮次的增加,酶解产物中可溶性木聚糖的含量越来越少,木聚糖被降解的难度越来越大。在实际生产中,用来作为低聚木糖生产的木聚糖其聚合度应在20～100之间,酶解时间以4h为宜,重复利用未水解木聚糖的轮次以2轮为宜。     

3种酶制剂对生产面包的体积影响

研究真菌木聚糖酶、β-葡聚糖酶对面粉粉质及拉伸性能的影响,并考察真菌α-淀粉酶、真菌木聚糖酶和β-葡聚糖酶3种单酶对面包的作用效果。通过正交试验确立20 mg/kg真菌α-淀粉酶、50mg/kg真菌木聚糖酶和50 mg/kgβ-葡聚糖为加工面包的最优化工艺条件。在上述条件下,面包平均体积为885 mL,该体积比不使用酶制剂的平均体积提高了17%。     

食用菌产胞外纤维素半纤维素降解酶类的研究进展

我国是食用菌生产大国。食用菌可以分泌降解纤维素、半纤维素和木质素相关的酶,能够利用秸秆、木屑、棉籽壳等多种农业废弃物,具有广泛的应用前景。本文以食用菌所产的主要胞外水解酶类纤维素酶和木聚糖酶为研究对象,从其种类、发酵条件、理化性质和基因克隆等方面综述了食用菌产胞外水解酶的研究现状。     

Benefits of β-xylanase for wheat biomass conversion to bioethanol

BACKGROUND: The efficiency of bioethanol production from wheat biomass is related to the quality of end products as well as to safety criteria of co‐products such as distiller's dried grains with solubles (DDGS). The inclusion of a new biocatalyst for non‐starch polysaccharide degradation in fermentation processes could be one of the solutions. The objective of this study was to evaluate the influence of β‐xylanases in combination with traditional amylolytic enzymes on the efficiency of bioethanol production and DON detoxification during fermentation of Fusarium‐contaminated wheat biomass with high concentration of deoxynivalenol (DON; 3.95 mg kg^?1). RESULTS: The results showed that the negative effect of Fusarium spp. on yield and quality of bioethanol could be eliminated by the application of Trichoderma reesei xylanase in combination with amylolytic enzymes. This technological solution allowed to increase the concentration of ethanol in the fermented wort by 35.3% and to improve the quality of bioethanol by decreasing the concentrations of methanol, methyl acetate, isoamyl and isobutyl alcohols. Mass balance calculations showed that DDGS was the main source of DON contamination, comprising 74% of toxin found in wheat biomass. By using new enzyme combination for wheat biomass saccharification, a higher level of detoxification (41%) of DON was achieved during the fermentation process. CONCLUSION: The addition of Trichoderma reesei xylanase played a positive role in bioethanol production from Fusarium‐contaminated wheat biomass, indicating that the yeast‐growing medium was enriched during the enzymatic treatment. Copyright © 2011 Society of Chemical Industry     

Properties of an Alkaline‐Tolerant,Thermostable Xylanase from Streptomyces chartreusis L1105, Suitable for Xylooligosaccharide Production

Abstract: An extracellular xylanase was purified to homogeneity from a culture of Streptomyces chartreusis L1105 by a 2‐step method of ammonium sulfate precipitation and carboxymethyl sepharose fast‐flow chromatography (CMSFF). The xylanase was purified by 6.86‐fold, with a recovery yield of 31.96%. The purified xylanase appeared as a single protein band on SDS‐PAGE with a molecular mass of about 34.2 kDa. The optimum temperature and pH of the purified xylanase activity were 70 °C and 7.2 respectively. The xylanase was more stable under alkaline conditions and retained more than 80% activity after 30 min incubation at pH 6 to 10. It also showed specific activity towards different xylans. Hydrolysis of oat‐spelt and corn‐cob xylans by the xylanase yielded xylobiose and xylotriose as principle products without the formation of xylose. These properties indicate that the purified xylanase may potentially be useful in biotechnological applications, such as xylooligosaccharide preparation. This is the first report about the purification and characterization of a xylanase from S. chartreusis.