Robust Saccharomyces cerevisiae by rational metabolic engineering for effective ethanol production from undetoxified steam-exploded corn stover hydrolysate

Abstract

Lignocellulosic bioethanol production by S.cerevisiae is severely hampered by xylose assimilation and inhibitors. Aiming to solve these barriers, the xylose isomerase pathway was heterologously introduced into parental strain, followed by conducting the adaptive laboratory evolution. Meanwhile, the reduced glutathione and NADPH synthesis systems to reduce excess intracellular reactive oxygen species (ROS) were further enhanced. Results indicated the bioethanol production from undetoxified steam-exploded corn stover hydrolysate (SECSH) without any nutrients supplementation was improved using the customized strain. Up to 70.52 ± 0.38 g/L of bioethanol with yield of 0.450 g/g total sugars were obtained. This study provided an effective strategy combining genetic modification and adaptive laboratory evolution to simultaneously improve xylose assimilation and inhibitors’ tolerance of S. cerevisiae, providing a basis for large-scale lignocellulosic bioethanol production.