Ishida Yoko, Nguyen Trinh Thi My, Izawa Shingo
Laboratory of Microbial Technology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
Laboratory of Microbial Technology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
J Biotechnol. 2017 Jun 20;252:65-72. doi: 10.1016/j.jbiotec.2017.04.024. Epub 2017 Apr 27.
Lignocellulosic biomass conversion inhibitors such as vanillin, furfural, and 5-hydroxymethylfurfural (HMF) inhibit the growth of and fermentation by Saccharomyces cerevisiae. A high concentration of each fermentation inhibitor represses translation and increases non-translated mRNAs. We previously reported that the mRNAs of ADH7 and BDH2, which encode putative NADPH- and NADH-dependent alcohol dehydrogenases, respectively, were efficiently translated even with translation repression in response to severe vanillin stress. However, the combined effects of these fermentation inhibitors on the expression of ADH7 and BDH2 remain unclear. We herein demonstrated that exposure to a combined stress of vanillin, furfural, and HMF repressed translation. The protein synthesis of Adh7, but not Bdh2 was significantly induced under combined stress conditions, even though the mRNA levels of ADH7 and BDH2 were up-regulated. Additionally, adh7Δ cells were more sensitive to the combined stress than wild-type and bdh2Δ cells. These results suggest that induction of the ADH7 expression plays a role in the tolerance to the combined stress of vanillin, furfural, and HMF. Furthermore, we succeeded in improving yeast tolerance to the combined stress by controlling the expression of ALD6 with the ADH7 promoter. Our results demonstrate that the ADH7 promoter can overcome the pronounced translation repression caused by the combined stress of vanillin, furfural, and HMF, and also suggest a new gene engineering strategy to breed robust and optimized yeasts for bioethanol production from a lignocellulosic biomass.
木质纤维素生物质转化抑制剂，如香草醛、糠醛和5-羟甲基糠醛（HMF），会抑制酿酒酵母的生长和发酵。每种发酵抑制剂的高浓度都会抑制翻译并增加未翻译的mRNA。我们之前报道过，分别编码假定的NADPH和NADH依赖性乙醇脱氢酶的ADH7和BDH2的mRNA，即使在响应严重香草醛胁迫导致翻译受到抑制的情况下，仍能有效翻译。然而，这些发酵抑制剂对ADH7和BDH2表达的联合作用仍不清楚。我们在此证明，暴露于香草醛、糠醛和HMF的联合胁迫下会抑制翻译。在联合胁迫条件下，Adh7的蛋白质合成显著诱导，但Bdh2的蛋白质合成未诱导，尽管ADH7和BDH2的mRNA水平上调。此外，adh7Δ细胞对联合胁迫比野生型和bdh2Δ细胞更敏感。这些结果表明，ADH7表达的诱导在对香草醛、糠醛和HMF联合胁迫的耐受性中起作用。此外，我们通过用ADH7启动子控制ALD6的表达，成功提高了酵母对联合胁迫的耐受性。我们的结果表明，ADH7启动子可以克服由香草醛、糠醛和HMF联合胁迫引起的明显翻译抑制，并且还提出了一种新的基因工程策略，用于培育用于从木质纤维素生物质生产生物乙醇的强壮且优化的酵母。
