Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, Lund, SE-22100, Sweden.
University of Milano Bicocca, Piazza della Scienza 2, Milan, 20126, Italy.
AMB Express. 2014 Jul 22;4:56. doi: 10.1186/s13568-014-0056-5. eCollection 2014.
Development of robust yeast strains that can efficiently ferment lignocellulose-based feedstocks is one of the requirements for achieving economically feasible bioethanol production processes. With this goal, several genes have been identified as promising candidates to confer improved tolerance to S. cerevisiae. In most of the cases, however, the evaluation of the genetic modification was performed only in laboratory strains, that is, in strains that are known to be quite sensitive to various types of stresses. In the present study, we evaluated the effects of overexpressing genes encoding the transcription factor (YAP1) and the mitochondrial NADH-cytochrome b5 reductase (MCR1), either alone or in combination, in an already robust and xylose-consuming industrial strain of S. cerevisiae and evaluated the effect during the fermentation of undiluted and undetoxified spruce hydrolysate. Overexpression of either gene resulted in faster hexose catabolism, but no cumulative effect was observed with the simultaneous overexpression. The improved phenotype of MCR1 overexpression appeared to be related, at least in part, to a faster furaldehyde reduction capacity, indicating that this reductase may have a wider substrate range than previously reported. Unexpectedly a decreased xylose fermentation rate was also observed in YAP1 overexpressing strains and possible reasons behind this phenotype are discussed.
开发能够高效发酵木质纤维素原料的健壮酵母菌株是实现经济可行的生物乙醇生产工艺的要求之一。为此，已经确定了几个基因作为有前途的候选基因，以提高酵母对各种胁迫的耐受性。然而，在大多数情况下，遗传修饰的评估仅在实验室菌株中进行，即已知对各种类型的胁迫非常敏感的菌株中进行。在本研究中，我们评估了在已经健壮且能够消耗木糖的工业酵母菌株中单独或组合过表达编码转录因子（YAP1）和线粒体 NADH-细胞色素 b5 还原酶（MCR1）的基因的效果，并在未稀释和未解毒的云杉水解物的发酵过程中评估了效果。过表达任一基因都导致六碳糖代谢更快，但同时过表达没有观察到累积效应。MCR1 过表达的改善表型至少部分与更快的糠醛还原能力有关，表明该还原酶的底物范围可能比之前报道的更广泛。出人意料的是，在 YAP1 过表达菌株中也观察到木糖发酵速率降低，并且讨论了这种表型背后的可能原因。
