底物选择性大肠杆菌共发酵葡萄糖和木糖产生乙醇

Ethanol production from mixed glucose and xylose by substrate-selective Escherichia coli strains

为了实现混合糖发酵产乙醇过程中葡萄糖和木糖的同步利用,采用基因删除技术,经代谢工程改造,构建了葡萄糖/木糖选择性代谢产乙醇大肠杆菌,并通过摇瓶发酵试验研究双菌株共发酵产乙醇的发酵性能。在删除了甲酸、乙酸、乳酸和琥珀酸合成途径的出发菌株Escherichia coli B0013-1031 (pta-ackA,ldh A,pfl B,frd A)基础上,删除木糖异构酶基因xyl A,得到木糖不利用菌株B0013-2010;通过回复突变修复B0013-1031 xyl H功能,并删除其中葡萄糖运输和代谢途径关键酶基因pts G、glk和man Z,得到葡萄糖不利用菌株B0013-2011H。将携带Zymomonas mobilis乙醇合成途径关键酶基因pdc和adh B的质粒p Etac-PA分别转入上述菌株,获得产乙醇重组菌B0013-2010PA和B0013-2011HPA;以此双菌株共发酵葡萄糖和木糖合成乙醇,乙醇合成速率为1. 01 g/(L·h),葡萄糖和木糖消耗速率分别为2. 02 g/(L·h)和1. 05 g/(L·h)。双菌株共发酵显著改善了乙醇发酵过程葡萄糖和木糖的同步利用。

For simultaneous conversion of glucose and xylose to ethanol from mixed sugars,ethanologenic glucose/xylose selective E. coli strains were developed by genes deletion and metabolic engineering and their cooperative ethanol fermentation performance was evaluated by shaking flasks fermentation. Strain B0013-2010,a glucose-selective strain,was developed by deleting xylA with blocking of formation of acetate,lactate,formate and succinate by deleting pta-ackA,ldhA,pflB and frd A in E. coli B0013-1031( pta-ackA,ldhA,pflB,frdA). Strain B0013-2011 H,a xylose-selective strain,was obtained by deleting pts G,glk and man Z and by restoring xyl H with a reverse mutation.Two ethanologenic strains,B0013-2010 PA and B0013-2011 HPA,were developed by transforming pEtac-PA( bearing pdc and adhB from Zymomonas mobilis) into B0013-2010 and B0013-2011 H. Ethanol fermentation on glucose and xylose mixture with B0013-2010 PA and B0013-2011 HPA in cooperative manner was conducted and ethanol production rate was 1. 01 g/( L·h),with glucose consumption rate of 2. 02 g/( L·h) and xylose of 1. 05 g/( L·h). In conclusion,the co-fermentation with sugar-selective strains significantly improved simultaneous utilization of glucose and xylose for ethanol fermentation.