Construction of mixed-sugar fermenting recombinant Saccharomyces cerevisiae and ethanol production from Jerusalem artichoke stalk by simultaneous saccharification and fermentation

Abstract:

[Objective] This study aimed to construct highly efficient recombinant Saccharomyces cerevisiae strain for cellulosic bioethanol production from Jerusalem artichoke stalk (JAS). [Methods] S. cerevisiae strain YB-2625 was selected as a host strain to construct xylose co-fermenting strain YB-2625 CCX, after which multicopies of xylitol dehydrogenase (XDH) encoding gene were integrated into the rDNA locus of YB-2625 CCX, and the most efficient strain named YB-73 was obtained. Finally, ethanol production from JAS was investigated by simultaneous saccharification and fermentation (SSF) using YB-73. [Results] YB-73 showed improved ethanol production by 13.9% compared with that of YB-2625 CCX and the xylitol yield of YB-73 was reduced to 0.31 g/g xylose from 0.89 g/g xylose by YB-2625 CCX when fermenting with 90 g/L glucose and 30 g/L xylose. Meanwhile, flocculation of YB-73 was observed in the presence of xylose, and the strain also showed high tolerance towards 5 g/L acetic acid and high temperature. The highest ethanol titer of 6.10% (v/v) was achieved from JAS in the process of SSF using YB-73. [Conclusion] Combination of host selection, introduction of xylose-consuming pathway and multi-copy overexpression of XDH in rDNA locus is a rational strategy to improve cellulosic bioethanol production performance of S. cerevisiae using JAS. This is the first report using recombinant S. cerevisiae to produce cellulosic ethanol from JAS.