Vitalized yeast with high ethanol productivity

Abstract

Fuel ethanol is an attractive alternative to fossil-based fuels or fuel additives. Very-high-gravity (VHG) ethanol fermentation is a promising technology to reduce energy consumption in distillation. However, yeast cells subjected to a high concentration of ethanol and osmotic stress readily lose cell viability, resulting in reduced ethanol productivity. Here we report the beneficial effect of fully water-soluble polyethylene glycol (PEG) in chemically exo-protecting yeast cells during fermentation, resulting in largely boosted cell vitality and tolerance to high ethanol concentration. The final ethanol concentration and the yeast cell viability were substantially increased as compared to PEG-free fermentation. The recovered exo-protected yeast was further demonstrated to continue to deliver superior bio-catalytic performance in subsequent fermentations over that recovered from PEG-free broth. Furthermore, the water-soluble PEG was readily recycled for reuse after distillation of ethanol.