Screening of Acetate-Tolerant Yeast and Its Effect on Controlling Bacterial Contamination During Ethanol Production from Sugarcane Molasses

Growth and ethanol fermentation ability of the acetate-tolerant yeast Saccharomyces cerevisiae KU 002-3 strain were investigated in acetate-addition medium. Under simulated industrial conditions, acetate did not affect on sugar consumption and ethanol production of KU 002-3. Moreover, KU 002-3 strain demonstrated a higher capability for ethanol production than other commercial strains. Co-fermentation was conducted with Lactobacillus fermentum IFRPD 2021, the major contaminating bacteria, during the ethanol production at 0.8% (v/v) acetate (130 mM of the undissociated form of acetate). Under these conditions, growth of L. fermentum IFRPD 2021 was inhibited but the growth and ethanol production ability of S. cerevisiae KU 002-3 strain were not significantly affected. Data indicated the possibility of producing ethanol under high acetate accumulation and reducing Lactobacillus sp. in molasses medium or acetate-containing condition. Producing ethanol under high acetate accumulation and lower the contamination of Lactobacillus sp. in a molasses medium can be useful at industrial scale to produce ethanol with S. cerevisiae KU 002-3 under non-sterilized conditions.