Ishida Yoko, Nguyen Trinh T M, Kitajima Sakihito, Izawa Shingo
Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology Kyoto, Japan.
Front Microbiol. 2016 Jul 6;7:1059. doi: 10.3389/fmicb.2016.01059. eCollection 2016.
Vanillin is a potent fermentation inhibitor derived from the lignocellulosic biomass in biofuel production, and high concentrations of vanillin result in the pronounced repression of bulk translation in Saccharomyces cerevisiae. Studies on genes that are efficiently translated even in the presence of high concentrations of vanillin will be useful for improving yeast vanillin tolerance and fermentation efficiency. The BDH1 and BDH2 genes encode putative medium-chain alcohol dehydrogenase/reductases and their amino acid sequences are very similar to each other. Although BDH2 was previously suggested to be involved in vanillin tolerance, it has yet to be clarified whether Bdh1/Bdh2 actually contribute to vanillin tolerance and reductions in vanillin. Therefore, we herein investigated the effects of Bdh1 and Bdh2 on vanillin tolerance. bdh2Δ cells exhibited hypersensitivity to vanillin and slower reductions in vanillin than wild-type cells and bdh1Δ cells. Additionally, the overexpression of the BDH2 gene improved yeast tolerance to vanillin more efficiently than that of BDH1. Only BDH2 mRNA was efficiently translated under severe vanillin stress, however, both BDH genes were transcriptionally up-regulated. These results reveal the importance of Bdh2 in vanillin detoxification and confirm the preferential translation of the BDH2 gene in the presence of high concentrations of vanillin. The BDH2 promoter also enabled the expression of non-native genes under severe vanillin stress and furfural stress, suggesting its availability to improve of the efficiency of bioethanol production through modifications in gene expression in the presence of fermentation inhibitors.
香草醛是生物燃料生产中源自木质纤维素生物质的一种强效发酵抑制剂，高浓度的香草醛会导致酿酒酵母中整体翻译受到明显抑制。研究即使在高浓度香草醛存在的情况下仍能有效翻译的基因，将有助于提高酵母对香草醛的耐受性和发酵效率。BDH1和BDH2基因编码假定的中链醇脱氢酶/还原酶，它们的氨基酸序列彼此非常相似。尽管之前有人认为BDH2与香草醛耐受性有关，但Bdh1/Bdh2是否真的有助于香草醛耐受性和香草醛的减少仍有待阐明。因此，我们在此研究了Bdh1和Bdh2对香草醛耐受性的影响。与野生型细胞和bdh1Δ细胞相比，bdh2Δ细胞对香草醛表现出超敏性，且香草醛的减少速度较慢。此外，BDH2基因的过表达比BDH1更有效地提高了酵母对香草醛的耐受性。在严重的香草醛胁迫下，只有BDH2 mRNA能有效翻译，然而，两个BDH基因在转录水平上均上调。这些结果揭示了Bdh2在香草醛解毒中的重要性，并证实了在高浓度香草醛存在的情况下BDH2基因的优先翻译。BDH2启动子还能在严重的香草醛胁迫和糠醛胁迫下使非天然基因表达，这表明它可用于通过在发酵抑制剂存在的情况下修饰基因表达来提高生物乙醇生产的效率。
