Potential Yeast from Lau as an Ethanol Fermentation Starter from the Arrack Industryin Bali, Indonesia

Arak Bali is a well-known spirit in Indonesia, which is made from coconut sap using a traditional fermentation method.However, the microbe responsible for converting coconut sap sugar into ethanol in arak has yet to be clearly identified.This research aimed to elucidate the potential of the highest-performing microbe found in the traditional starter called lau in the arak (arrack) industry in Tri Eka Buana-Karangasem, Bali, named IS258.The IS258 isolate, previously assumed to be yeast, was found capable of producing 8.9% (v/v) ethanol in unoptimized rich PYG (peptone, yeast extract, and glucose) fermentation media.In this study, Response Surface Methodology (RSM) was utilized to test and optimize the ethanol yield using various fermentation media compositions.This work aimed to maximize the yield of the yeast IS258, which resulted in 11.2% (v/v) ethanol/liter of media with 20% glucose, and 84% stoichiometric glucose conversion rate.The genetic analysis conducted in this work revealed that IS258 belongs to the Nakaseomyces glabrata, known as Candida glabrata, which is widely recognized as an opportunistic pathogen, despite being found on many fermented foods in Southeast Asia.The discoveries found in this work suggest IS258's potential use as a bioethanol fermentation starter for the biofuel industry.