To observe S. pombe ethanol tolerance under aerobic conditions while promoting adaptation to ethanol inhibition, repetitive cultivations were performed with stepwise increase of ethanol concentration in the growth medium. Ethanol tolerance at each step was analyzed and the cultivation was carried out until the strain was no longer able to grow, producing an ethanol-adapted strain. Subsequently, side-by-side fermentations were carried out using adapted and unadapted S. pombe to test ethanol tolerance under anaerobic conditions.
Our results show that S. pombe is tolerant up to 12.0% w/v ethanol in anaerobic fermentation and 7.0 % w/v ethanol in aerobic cultivation. Evidence of adaptation to ethanol inhibition was observed during repetitive cultivation, although there was negligible difference in ethanol tolerance between unadapted and adapted strains during fermentation. This ethanol-tolerant S. pombe strain combined with Trillium’s SIF technology enables cost-effective conversion of xylose to ethanol.