Enhanced direct ethanol production by cofactor optimization of cell surface-displayed xylose isomerase in yeast
Enhanced direct ethanol production by cofactor optimization of cell surface-displayed xylose isomerase in yeast
复制标题
通过酵母细胞表面展示的木糖异构酶的辅因子优化增强直接乙醇生产
DOI：
10.1002/btpr.2478
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发表时间：
2017
影响因子：
2.9
通讯作者：
Mitsuyoshi Ueda
中科院分区：
文献类型：
--
作者：
Yusuke Sasaki;Toshiyuki Takagi;Keisuke Motone;Kouichi Kuroda;Mitsuyoshi Ueda
纤维素梭菌产生的木糖异构酶(XylC)能同时对木质纤维生物质的主要成分D-木糖进行异构化和发酵，是一种有吸引力的候选酶。在这项研究中，我们优化了一种特定的金属阳离子，在以前建立的酿酒酵母菌株中展示了木质C。我们考察了每种金属离子对显示木质C的酿酒酵母催化功能的影响。结果表明，二价钴离子(Co2+)尤其能使酶活性提高46倍。Co2+对木糖发酵也有促进作用，乙醇产量和木糖消耗率分别提高了6.0倍和2.7倍。在混合糖存在下，胞外木糖异构化系统的实用性被展示出来。显示木糖C的酵母比胞内产生XI的酵母对木糖的吸收更快。此外，还利用独特的酵母共培养体系进行了木聚糖的直接糖化和发酵。通过显示两种木聚糖酶--内切-1，4-β-木聚糖酶(Xyn11B)和黑曲霉β-木糖苷酶(XlnD)，建立了一株降解木聚糖酶的酵母菌。酵母共培养系统可以通过调整显示木聚糖酶(Xyn11B和XlnD)的接种比例和显示木聚糖酶的酵母和显示木聚糖酶的酵母的接种比例来微调显示酶(Xyn11B：XinD：XylC)的初始比例。当接种量为1：1：2(分子比为1.39×1013：1.39×1013：2.78×1013)时，木聚糖得率为6.0g/L。因此，本研究开发的辅因子优化和酵母共培养体系为木质纤维生物质生产生物燃料提供了广阔的前景。©2017美国化学工程师学会生物技术。程序，33：1068-1076,2017
Xylose isomerase (XylC) from Clostridium cellulovorans can simultaneously perform isomerization and fermentation ofd‐xylose, the main component of lignocellulosic biomass, and is an attractive candidate enzyme. In this study, we optimized a specified metal cation in a previously established Saccharomyces cerevisiae strain displaying XylC. We investigated the effect of each metal cation on the catalytic function of the XylC‐displaying S. cerevisiae. Results showed that the divalent cobalt cations (Co2+) especially enhanced the activity by 46‐fold. Co2+also contributed tod‐xylose fermentation, which resulted in improving ethanol yields and xylose consumption rates by 6.0‐ and 2.7‐fold, respectively. Utility of the extracellular xylose isomerization system was exhibited in the presence of mixed sugar. XylC‐displaying yeast showed the fasterd‐xylose uptake than the yeast producing XI intracellularly. Furthermore, direct xylan saccharification and fermentation was performed by unique yeast co‐culture system. A xylan‐degrading yeast strain was established by displaying two kinds of xylanases; endo‐1,4‐β‐xylanase (Xyn11B) from Saccharophagus degradans, and β‐xylosidase (XlnD) from Aspergillus niger. The yeast co‐culture system enabled fine‐tuning of the initial ratios of the displayed enzymes (Xyn11B:XlnD:XylC) by adjusting the inoculation ratios of Xylanases (Xyn11B and XlnD)‐displaying yeast and XylC‐displaying yeast. When the enzymes were inoculated at the ratio of 1:1:2 (1.39 × 1013: 1.39 × 1013: 2.78 × 1013molecules), 6.0 g/L ethanol was produced from xylan. Thus, the cofactor optimization and the yeast co‐culture system developed in this study could expand the prospect of biofuels production from lignocellulosic biomass. © 2017 American Institute of Chemical EngineersBiotechnol. Prog., 33:1068–1076, 2017