セルレニン耐性による酢酸低生産性清酒酵母の分離

Abstract

Low acetic acid-producing strains were isolated from cerulenin-resistant mutants of the sake yeast K 7 (Saccharomyces cerevisiae). Acetic acid is considered to be an intermediate metabolite of the cytosolic acetyl CoA synthetic pathway from acetaldehyde.Cytosolic acetyl CoA is used for the biosynthesis of sterols, fatty acids, etc. Cerulenin is an inhibitor of fatty acid synthase.Thus, a mutant producing lower levels of acetic acid and higher levels of acetyl CoA is supposed to show cerulenin resistance. Out of 80 cerulenin-resistant mutants, four were selected as low acetic acid-producing mutants using a fermentation test with a liquid synthetic medium and a small scale sake fermentation test. K 7 and one mutant, K 7-163, produced 136.6mg/l and 16.4mg/l of acetic acid, respectively, in pilot scale sake making. Three of the four mutants showed higher acetyl CoA synthetase (ACS) activity than K 7 during the late period of growth, which appeared to be the reason for their low acetic acid productivity. However, all four mutants showed multi-drug resistance, and/or high ethyl caproate productivity, which was probably caused by FAS 2 mutation. Thus, further studies are needed to confirm the relationship between low acetic acid productivity and cerulenin resistance.