Abstract The co-production of xylitol and ethanol from agricultural straw has more economic advantages than the production of ethanol only. Saccharomyces cerevisiae, the most widely used ethanol-producing yeast, can be genetically engineered to ferment xylose to xylitol. In the present study, the effects of xylose-specificity, cofactor preference, and the gene copy number of xylose reductase (XR; encoding by XYL1 gene) on xylitol production of S. cerevisiae were investigated. The results showed that overexpression of XYL1 gene with a lower xylose-specificity and a higher NADPH preference favored the xylitol production. The copy number of XYL1 had a positive correlation with the XR activity but did not show a good correlation with the xylitol productivity. The overexpression of XYL1 from Candida tropicalis (CtXYL1) achieved a xylitol productivity of 0.83 g/L/h and a yield of 0.99 g/g-consumed xylose during batch fermentation with 43.5 g/L xylose and 17.0 g/L glucose. During simultaneous saccharification and fermentation (SSF) of pretreated corn stover, the strain overexpressing CtXYL1 produced 45.41 g/L xylitol and 50.19 g/L ethanol, suggesting its application potential for xylitol and ethanol co-production from straw feedstocks.

中文翻译：

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木糖还原酶基因对工业酿酒酵母葡萄糖和木糖发酵生产木糖醇的影响

摘要 农用秸秆联产木糖醇和乙醇比单纯生产乙醇更具经济优势。Saccharomyces cerevisiae 是最广泛使用的产乙醇酵母，可以通过基因工程将木糖发酵成木糖醇。在本研究中，研究了木糖特异性、辅因子偏好和木糖还原酶（XR；由 XYL1 基因编码）的基因拷贝数对酿酒酵母木糖醇生产的影响。结果表明，具有较低木糖特异性和较高 NADPH 偏好的 XYL1 基因的过表达有利于木糖醇的产生。XYL1 的拷贝数与 XR 活性呈正相关，但与木糖醇生产率没有很好的相关性。来自热带念珠菌 (CtXYL1) 的 XYL1 的过度表达在使用 43.5 g/L 木糖和 17.0 g/L 葡萄糖的分批发酵过程中实现了 0.83 g/L/h 的木糖醇生产率和 0.99 g/g 消耗的木糖产量。在预处理玉米秸秆的同步糖化发酵 (SSF) 过程中，过表达 CtXYL1 的菌株产生 45.41 g/L 木糖醇和 50.19 g/L 乙醇，表明其在秸秆原料中联合生产木糖醇和乙醇的应用潜力。