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

Bio-ethanol can be obtained from simple sugars, starch-based biomass, or lignocellulosic biomass through fermentation. Conventional yeast acts as a bioethanol producer but has limited tolerance to temperatures above 40°C and high concentrations of ethanol. Therefore, thermo-tolerant and ethanol-tolerant yeast are required because it has many benefits on high-temperature fermentation in the industry. This research is a descriptive study conducted in three stages. The first stage is to isolate yeast from eggplant, cabbage, potatoes, mustard greens, bitter melon, squash, green beans, kale, and celery. The second stage is to test the temperature and ethanol tolerance from yeast that has been obtained. The third stage is to test the ethanol productivity of the isolated yeasts. The results showed isolates S17c, S17d, S17a, S17b, S09, S12, S13a, S13b, S17e, S18a, and S18b grew at 45°C. While in the ethanol tolerance test found that isolates S17c, S17d, S17b, S17a, S09, S12, S13a, S13b, S18a, and S18b grew on YPG agar supplemented with 15% ethanol content. Isolate S17d has the highest ethanol production with 3.13% ethanol in 24th-hour fermentation.