Isolation and Identification of a Novel Yeast Fermenting Ethanol under Acidic Conditions

Abstract

An acid-tolerant yeast strain MF-121 showing an excellent ability of ethanol fermentation in acidic media containing salt of pH 2.0-2.5 was isolated. Some brewing yeast, Saccharomyces cerevisiae, could scarcely ferment in the acidic media. The yeast strain MF-121 could ferment around 9% ethanol in acidic media of pH 2.5 containing 20% glucose and 1-5% sodium sulfate. Physiological properties and PCR-based 18S rRNA gene sequence showed that the yeast was closely related to Issatchenkia orientalis. The yeast could ferment ethanol in the acidic media prepared from complete hydrolysates of starch and bread.