Bioethanol-Producing Yeast Isolated from Fermented Cocoa

Abstract

Corn and sugarcane-base bioethanol dominantly contributes to the 25 billion gallons of bioethanol worldwide. Recent researches focused on the potential microbes and biomasses for optimum production. This study is, therefore, aimed to screen the bioethanol generating yeast strains of Biotechnology Culture Collection (BTCC), isolated from chocolate fermentation in several medium containing various carbon sources. A total of 72 yeast strains were grown in the media containing sugarcane juice, sorghum juice, and molasses, which served as carbon sources. Based on 26S rDNA gene analysis, these species were included in 9 genera, encompassing Saccharomyces (63.9%), Hanseniaspora (9.7%), Candida (0.7%), Torulaspora (0.4%), Pichia (0.8%), Issatchenkia (0.1%), Wickerhamomyces (0.3%), Metschnikowia (0.1%), and Rhodotorula (0.1%). Therefore, spectrophotometer UV-Vis was used to analyze cell growth, while the fermentation products (sugars and ethanol) were evaluated using the HPLC, and about 70 strains produced bioethanol. The highest yields were obtained during fermentation, using sugarcane juice, molasses, molasses waste, and sorghum juice, at concentrations of 43, 50, and 7 g/L, respectively. Furthermore, the Saccharomyces cerevisiae strain were the most significant producers, as the genus was able to generate various concentrations from several carbon sources. However, the only genus without the ability to yield any related products during fermentation was Pichia (0.8%). Based on these results, it is necessary to further develop the yeast strains from chocolate fermentation, due to the potential for bioethanol production from biomasses.