Isolation and Characterization of Yeast Strains for the Production of Bioethanol

Bioethanol is a promising renewable biofuel that addresses challenges associated with rising oil prices, greenhouse gas emissions and limited fossil fuel reserves. Yeast is considered the most efficient microorganism for ethanol production. The study aims to investigate the isolation and utilisation of yeast in bioethanol production. In this study, twenty-five yeast isolates were obtained from banana peel varieties Ellakki bale, G-9, Rajapuri, and Rasabale, collected from the local market of Dharwad city. The isolates were characterized based on morphological traits, carbohydrate assimilation, and further evaluated for bioethanol production efficiency. Most isolates formed white, smooth, circular colonies with entire margins and exhibited budding. Isolates YBS6, YBS12, and YBS13 demonstrated broad carbohydrate utilization, fermenting glucose, maltose, galactose, sucrose, and xylose, with additional utilization of raffinose (YBS6) and trehalose (YBS12, YBS13). None utilized lactose. These isolates produced 22.88, 20.36, and 19.15 g/L of ethanol, respectively, compared to 30.27 g/L by Saccharomyces cerevisiae MTCC 170. Thus, YBS12, YBS6, and YBS13 show strong potential for bioethanol production. The study concludes that all 25 isolates were positive for glucose utilization and negative for lactose utilization.