Isolation and Screening of Ethanol-tolerant Yeast from Palm Wine for Potential Use as a Starter Culture in Ethanol Production

This study conducted to the isolate and screen ethanol-tolerant yeast from traditional palm wine for potential starter culture in ethanol production. Palm wine, also known as emu, is a widely consumed and popular beverage in rural communities in Nigeria and other parts of the world. In this study, two different samples of palm wine were collected from Ilora, Afijio Local government, Oyo State. Eighteen (18) yeast were isolated from palm wine using Yeast Extract Peptone Dextrose Agar (YEPDA) medium comprising of peptone (2%, w/v), yeast extract (1%, w/v), dextrose (2%, w/v) and agar (2%, w/v). Cryptococcus luteolu had the highest percentage of occurrence of 33.3 % followed by Candida guillieromondi (27.8%), Torulopsis glabrata (22.2%). Saccharomyce cerevisiae had the least percentage (16.7%). The isolated yeast was screened for ethanol tolerance. All the isolates were able to tolerates 10% ethanol medium, some of the isolates tolerates and also grow at 15% ethanol, while some struggled. The results confirmed that yeast isolated from palm wine has high degree of ethanol tolerance. Three (3) of the isolates (Candida glabrata08, Candida guillieromondii11 and Candida glabrata15) showed unique characteristics as were able to tolerate and grow well in 20% ethanol medium. The ethanol tolerance of the three isolates was further assessed using an ethanol assay and they were found to have ethanol tolerance up to 30% (v/v). The results of this study suggest that yeast from traditional palm wine could be used as a potential starter culture for ethanol production.