Isolation of thermo-tolerant and ethanol-tolerant yeast from local fermented foods and their potential as bioethanol producers

Abstract

Abstract Bioethanol is a liquid chemical produced from sugar-, starch-or lignocellulosic-based biomass through fermentation by ethanol-producing microbes. Ethanol-producing yeast generally has limited tolerance to ethanol and has limitation to high temperatures above 40°C. High-temperature tolerant yeast is required because it potentially reduces the risk of contamination and it also reduces the cost of the cooling process. This study aims to determine ethanol-producing yeasts that have tolerance to ethanol and high temperatures from local fermented food products. This study uses a descriptive method conducted in three stages. Isolation and selection of yeast were performed from 18 local fermented foods in Indonesia. Temperature and ethanol tolerance of selected yeast were performed by using a spot test method. The ethanol content was tested using Gas Chromatography (GC). The results exhibited that isolate F08b had the highest tolerance to ethanol and temperature. The isolate was able to grow up to a temperature of 50°C and a concentration of 18% ethanol. Meanwhile, isolate F10 was able to produce the highest ethanol concentration at 3.37% (v/v) in 48th-hour fermentation.