High-solids saccharification and fermentation of ball-milled corn stover enabling high titer bioethanol production

Abstract

High-solids saccharification and fermentation is central to the cost-competitive production of cellulosic ethanol, but it often comes with unsatisfactory conversion efficiency because of mixing and heat/mass transfer limitations. The use of ball milling can considerably enhance enzymatic hydrolysis with desirable rheological properties at high solids, and we obtained a high sugar concentration of 162 g/L with a glucose yield of 74% after enzymatic hydrolysis. However, little is known about the impact of ball milling on subsequent fermentation of sugars to ethanol as well as the feasibility of producing high titer bioethanol from ball-milled materials at high solids loading. Here, we systematically evaluated various fermentation strategies to maximize the efficiency and economic benefits of bioethanol production using ball-milled corn stover at high solids loading. A high ethanol titer and productivity can be achieved up to 71.8 g/L and 2 g/L/h, respectively, with an ethanol yield of 58.8%. These results suggest the tremendous potential of ball milling for bioethanol production.