Genetic Engineering to Produce Higher Alcohols in Yeast Saccharomyces cerevisiae

The production of higher alcohols including C3-C5 alcohols in engineered bacteria has received significant attention, because they can be used as fuels, fuel additives, or commodity chemicals. The budding yeast, Saccharomyces cerevisiae, has considerable potential as a producer of higher alcohols because of its capacity to naturally fabricate fusel alcohols, in addition to its robustness and tolerance to low pH. However, because its natural productivity is not significant, we considered a strategy of genetic engineering to increase production of higher alcohols. For example, the branched-chain higher alcohol isobutanol, which is involved in valine biosynthesis, offers higher octane values than their straight-chain counterparts with equivalent carbon numbers and can be used with current infrastructure in addition to possessing almost the same capabilities (energy density, hygroscopicity and octane number) as gasoline. In addition to isobutanol, 2,3-butanediol is also a promising alcohol as a commodity chemical due to its extensive industrial applications. These metabolic pathways for producing isobutanol and 2,3-butanediol are crucially discriminable in terms of cofactor balance such as NADH and NADPH. In this study, we constructed the genetically engineered yeast S. cerevisiae to produce these higher alcohols, and evaluated the difference in the alcohol production levels of the constructed strains. This work was supported by Special Coordination Funds for Promoting Science and Technology, Creation of Innovation Centers for Advanced Interdisciplinary Research Areas (Innovative Bioproduction Kobe; iBioK), MEXT, Japan, and in part by Industrial Technology Research Grant Program in 2011 from New Energy and Industrial Technology Development Organization (NEDO) of Japan.