Overcoming factors limiting high-solids fermentation of lignocellulosic biomass to ethanol

Significance Future production of renewable transportation fuels such as ethanol must rely on abundant nonfood plant sources also known as lignocellulosic biomass. However, a major historical barrier to low-cost production of ethanol from biomass is the low ethanol yields and titers that result from fermentation of biomass solids at high solids when compared with simple sugar fermentations. Here, we show that combining a cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment process with subsequent simultaneous saccharification and fermentation (SSF) can achieve similar high ethanol yields and titers that match that of separate pure glucose fermentations. We demonstrate a strategy whereby direct fermentation of biomass to ethanol is now limited by the microbe rather than by the process.