Study on yeast response to vanillin, a fermentation inhibitor derived from lignocellulosic biomass

リグノセルロース系バイオマス由来発酵阻害物質バニリンに対する酵母のストレス応答の解析

2016-09-26

2016-09-26

Vanillin is a phenolic aldehyde compound generated during the saccharification pretreatment of the lignocellulosic biomass in bioethanol production. It has been reported that vanillin inhibits yeast growth, represses translation and induces the formation of ribonucleoprotein granules such as P-bodies and stress granules in Saccharomyces cerevisisae. I herein demonstrated that vanillin causes oxidative stress and induces mitochondrial fragmentation in yeast cells, providing some new information regarding the effects of vanillin on yeast. Additionally, I found that the null mutant of glucose-6-phosphate dehydrogenase (G6PDH), which catalyzes the rate-limiting NADPH-producing step in the pentose phosphate pathway (PPP), was more susceptible to vanillin than the wild-type, suggesting the importance of G6PDH and PPP in vanillin tolerance. It has been known that vanillin can be reduced to its less toxic form, vanillyl alcohol, by the yeast NADPH-dependent medium chain alcohol dehydrogenases, Adh6 and Adh7 in vitro. In this study, I verified the roles of these proteins in vanillin tolerance in vivo. I also showed that although both the ADH6 and ADH7 genes were transcriptionally upregulated, the protein levels of Adh7 but not Adh6 were significantly increased in the presence of high concentration of vanillin, indicating that the ADH7 mRNA was preferentially translated under severe vanillin stress. In addition to the ADH7 gene, we found that the expression of VIE1 gene, coding an unknown protein, was also significantly induced upon vanillin treatment. Both the ADH7 and VIE1 promoter can drive the expression of non-native genes under severe vanillin stress despite the overall translation repression, suggesting that these promoters are useful to overexpress genes in bioethanol production. Importantly, the VIE1 promoter also enabled the increased expression of genes in the presence of furfural and 2-hydroxymethylfurfural, other fermentation inhibitors derived from lignocellulosic biomass. Therefore, the VIE1 promoter would be more practical in modification of gene expression in order to improve the efficiency of ethanol production from lignocellulosic biomass.

博士（学術）

京都工芸繊維大学

14303甲第807号

http://hdl.handle.net/10212/2343

eng

none

Thesis or Dissertation

Thesis