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首页> 外文期刊>BMC Biotechnology >Highly thermostable GH39 β-xylosidase from a Geobacillus sp. strain WSUCF1
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Highly thermostable GH39 β-xylosidase from a Geobacillus sp. strain WSUCF1

机译：来自地芽孢杆菌属的高度耐热的GH39β-木糖苷酶。菌株WSUCF1

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Background Complete enzymatic hydrolysis of xylan to xylose requires the action of endoxylanase and β-xylosidase. β-xylosidases play an important part in hydrolyzing xylo-oligosaccharides to xylose. Thermostable β-xylosidases have been a focus of attention as industrially important enzymes due to their long shelf life and role in the relief of end-product inhibition of xylanases caused by xylo-oligosaccharides. Therefore, a highly thermostable β-xylosidase with high specific activity has significant potential in lignocellulose bioconversion. Results A gene encoding a highly thermostable GH39 β-xylosidase was cloned from Geobacillus sp. strain WSUCF1 and expressed in Escherichia coli . Recombinant β-xylosidase was active over a wide range of temperatures and pH with optimum temperature of 70°C and pH?6.5. It exhibited very high thermostability, retaining 50% activity at 70°C after 9?days. WSUCF1 β-xylosidase is more thermostable than β-xylosidases reported from other thermophiles (growth temperature?≤?70°C). Specific activity was 133 U/mg when incubated with p-nitrophenyl xylopyranoside, with Km and Vmax values of 2.38?mM and 147 U/mg, respectively. SDS-PAGE analysis indicated that the recombinant enzyme had a mass of 58?kDa, but omitting heating prior to electrophoresis increased the apparent mass to 230?kDa, suggesting the enzyme exists as a tetramer. Enzyme exhibited high tolerance to xylose, retained approximately 70% of relative activity at 210?mM xylose concentration. Thin layer chromatography showed that the enzyme had potential to convert xylo-oligomers (xylobiose, triose, tetraose, and pentaose) into fermentable xylose. WSUCF1 β-xylosidase along with WSUCF1 endo-xylanase synergistically converted the xylan into fermentable xylose with more than 90% conversion. Conclusions Properties of the WSUCF1 β-xylosidase i.e. high tolerance to elevated temperatures, high specific activity, conversion of xylo-oligomers to xylose, and resistance to inhibition from xylose, make this enzyme potentially suitable for various biotechnological applications.
机译：背景技术木聚糖完全酶促水解为木糖需要木聚糖内切酶和β-木糖苷酶的作用。 β-木糖苷酶在将木糖寡糖水解为木糖中起重要作用。由于热稳定的β-木糖苷酶具有较长的货架期，并且在减轻由木糖寡糖引起的木聚糖酶对终产物的抑制作用中起着重要的作用，因此作为工业上重要的酶已成为关注的焦点。因此，具有高比活性的高度热稳定的β-木糖苷酶在木质纤维素生物转化中具有显着的潜力。结果从地芽孢杆菌（Geobacillus sp）中克隆了编码高度耐热的GH39β-木糖苷酶的基因。菌株WSUCF1并在大肠杆菌中表达。重组β-木糖苷酶在很宽的温度和pH范围内均具有活性，最适温度为70°C，pH≥6.5。它表现出非常高的热稳定性，在9天后于70°C保持50％的活性。 WSUCF1β-木糖苷酶比其他嗜热菌报道的β-木糖苷酶更热稳定（​​生长温度≤70°C）。与对硝基苯基吡喃吡喃糖苷孵育时的比活度为133 U / mg，K m 和V max 值分别为2.38？mM和147 U / mg。 SDS-PAGE分析表明重组酶的质量为58kkDa，但在电泳前省略加热使表观质量增加至230kkDa，表明该酶以四聚体形式存在。酶表现出对木糖的高耐受性，在210？mM木糖浓度下保留了约70％的相对活性。薄层色谱法表明该酶具有将木糖寡聚体（木糖，三糖，四糖和五糖）转化为可发酵木糖的潜力。 WSUCF1β-木糖苷酶与WSUCF1内木聚糖酶协同将木聚糖转化为可发酵的木糖，转化率超过90％。结论WSUCF1β-木糖苷酶的性质，即对高温的高耐受性，高比活性，木糖寡聚物转化为木糖以及对木糖抑制的抵抗力，使得该酶潜在地适合于各种生物技术应用。

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