不同非氧化磷酸戊糖途径基因的过表达对酿酒酵母木糖发酵性能的影响

以双拷贝过表达木糖代谢上游途径关键酶(木糖还原酶XR、木糖醇脱氢酶XDH和木酮糖激酶XKS)的酿酒酵母菌株为背景,在过表达非氧化磷酸戊糖(PP)途径中转醛酶基因TAL1的基础上,对途径中其他基因TKL1(转酮酶)、RPE1(核酮糖-5-磷酸差向异构酶)和RKI1(核酮糖-5-磷酸异构酶)进行了不同程度的过表达,以研究PP途径基因过表达对酿酒酵母木糖代谢的影响。在不同培养基条件下对重组菌株木糖代谢进行研究,结果显示,在过表达TAL1的基础上不同组合过表达PP途径其他基因不同程度改善了酿酒酵母木糖发酵性能,重组菌株能在36~48 h耗完质量分数(下同)为5%的木糖。其中,过表达PP途径全部基因比其他过表达基因组合表现出明显的优势,在8%木糖发酵条件下其乙醇产量达到了每1 g木糖0.337 g,较对照菌株提高了7.86%。这说明同步过表达PP途径基因更有利于酿酒酵母木糖发酵。

Xylose Fermentation Performance of Saccharomyces cerevisiae with Different Combination of the Overexpressed Non-Oxidative Pentose Phosphate Pathway Genes

To study the influence of non-oxidative pentose phosphate pathway (PPP) on xylose utilization in Saccharomyces cerevisiae, different combinations of PPP genes TKL1, RPE1 and RKI1 were overexpressed in the TAL1-enhanced yeast strain, which also had the double-copy integration of upstream pathway genes XYL1, XYL2 and XKS1. Performance of recombinant yeasts was investigated at both 5% and 8% xylose as well as glucose and xylose mixture, results showed that overproduction of PPP genes stimulated cell growth and xylose conversion at both xylose concentrations, concomitant with higher ethanol yield at the expense of xylitol and glycerol formation, and all recombinant strains can use up 5% xylose within 36 to 48 h. Yeast strains of S. cerevisiae with four PPP genes co-overexpressed showed more advantages, and under the 8% xylose concentration, ethanol yield was about 0.337 g/g xylose, 7.86% higher than parent strain. It indicated that co-overproduction of all PPP genes may be the top priority for enhancing xylose metabolism in S. cerevisiae strains.