Key Laboratory of Systems Bioengineering (Tianjin University), Ministry of Education, Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University Tianjin, P. R. China.
Front Microbiol. 2012 Oct 5;3:355. doi: 10.3389/fmicb.2012.00355. eCollection 2012.
Reducing xylitol formation is necessary in engineering xylose utilization in recombinant Saccharomyces cerevisiae for ethanol production through xylose reductase/xylitol dehydrogenase pathway. To balance the expression of XYL1 and mutant XYL2 encoding xylose reductase (XR) and NADP(+)-dependent xylitol dehydrogenase (XDH), respectively, we utilized a strategy combining chassis selection and direct fine-tuning of XYL1 and XYL2 expression in this study. A XYL1 gene under the control of various promoters of ADH1, truncated ADH1 and PGK1, and a mutated XYL2 with different copy numbers were constructed into different xylose-utilizing modules, which were then expressed in two yeast chassises W303a and L2612. The strategy enabled an improved L2612-derived recombinant strain with XYL1 controlled by promoter PGK1 and with two copies of XYL2. The strain exhibited a 21.3% lower xylitol yield and a 40.0% higher ethanol yield. The results demonstrate the feasibility of the combinatorial strategy for construction of an efficient xylose-fermenting S. cerevisiae.
在通过木糖还原酶/木糖醇脱氢酶途径利用重组酿酒酵母中的木糖生产乙醇的工程中，有必要减少木糖醇的形成。为了平衡木糖还原酶（XR）编码基因 XYL1 和突变型 XYL2 的表达，以及 NADP(+) 依赖的木糖醇脱氢酶（XDH），我们在本研究中利用了一种结合底盘选择和 XYL1 和 XYL2 表达直接微调的策略。将受 ADH1、截断的 ADH1 和 PGK1 各种启动子控制的 XYL1 基因，以及具有不同拷贝数的突变型 XYL2 构建到不同的木糖利用模块中，然后在两个酵母底盘 W303a 和 L2612 中表达。该策略使 L2612 衍生的重组菌株得到了改善，其 XYL1 由 PGK1 启动子控制，并且含有两个拷贝的 XYL2。该菌株的木糖醇得率降低了 21.3%，乙醇得率提高了 40.0%。结果表明，该组合策略构建高效木糖发酵酿酒酵母是可行的。
