系列过表达非氧化磷酸戊糖途径基因对重组酿酒酵母菌株木糖代谢的影响

Effects of systematic overexpression of genes involved in the non-oxidative pentose phosphate pathway on xylose metabolism of recombinant Saccharomyces cerevisiae strains

摘要:

【目的】通过系统研究一个、两个及多个非氧化磷酸戊糖(PP)途径基因组合过表达对酿酒酵母木糖代谢的影响，以优化重组菌株的构建过程，构建高效的木糖代谢酿酒酵母菌株。【方法】在酿酒酵母中双拷贝过表达上游代谢途径的关键酶(木糖还原酶XR，木糖醇脱氢酶XDH，木酮糖激酶XKS)，在此基础上构建了一系列PP途径基因过表达菌株，并对其木糖发酵性能进行比较研究。【结果】木糖发酵结果显示，不同组合过表达PP途径基因能不同程度改善重组菌株的木糖发酵性能。其中，过表达PP途径全部基因(RKI1，RPE1，TAL1和TKL1)使菌株的发酵性能最优，其乙醇产率和产量较对照菌株分别提高了39.25%和12.57%，同时较其他基因组合过表达菌株也有不同程度的改善。【结论】通过构建PP途径基因不同组合过表达酿酒酵母菌株，首次对PP途径基因对酿酒酵母木糖代谢的影响进行了系统研究，结果表明，不同组合强化PP途径基因对重组菌株木糖代谢的影响存在差异，相对于其他基因过表达组合，同步过表达PP途径全部基因最有利于碳通量流向乙醇。

Abstract:

[Objective] Construction of highly efficient xylose-utilizing Saccharomyces cerevisiae strains by single, double or multiple overexpression of genes involved in the non-oxidative pentose phosphate (PP) pathway. [Methods] TAL1, TKL1, RPE1 and RKI1 under the control of different strong promoters were integrated either alone or in combination into the xyloses-fermenting recombinant yeast strain AYHNEW2. The fermentation performances of the resulting strains were studied on 5% xylose. [Results] The recombinant strains generated with our approach showed improved xylose fermentation performance with varying degrees. The best results were obtained by simultaneous overexpression of all the non-oxidative PP pathway genes, and compared to the reference strain AYHNEW2, the strain resulted from this genetic modification showed a 39.25% and 12.57% increase in ethanol productivity and yield, respectively. [Conclusion] Previous studies for enhancing xylose fermentation rate by genetic modification of the non-oxidative PP pathway had been more focused on overexpression of the individual genes in the pathway. In this work, we demonstrated that, compared to single or partial over-expression of the non-oxidative PP pathway, simultaneous overexpression of all the genes in the pathway was more effective in increasing the rate of carbon flow from xylose to ethanol.