Stress-driven dynamic regulation of multiple tolerance genes improves robustness and productive capacity of Saccharomyces cerevisiae in industrial lignocellulose fermentation

Abstract

Yeast productivity in lignocellulosic ethanol fermentation is clearly impeded by stress. Enhancing the robustness of xylose-fermenting yeast is important for improving lignocellulosic ethanol production. In this study, the glutathione biosynthesis pathway and acetic acid degradation pathway were strengthened to enhance yeast tolerance to stress due to elevated reactive oxygen species (ROS) and acetic acid. Dynamic feedback regulation of the anti-stress genetic circuits was achieved using stress-driven promoters discovered from the transcriptome to maintain low intracellular ROS, relieve the metabolic burden, and ultimately improve the robustness and ethanol production of yeast. The cell growth, xylose utilization and ethanol production of the engineered strain were enhanced under both stress and nonstress conditions. The engineered strain showed 49.5% and 17.5% higher ethanol productivity in laboratory media and industrial lignocellulosic media, respectively, at 36 °C compared with the parent strain. This study provides novel insights on the rational design and construction of feedback genetic circuits for dynamically improving yeast robustness.

Keywords: Lignocellulosic ethanol; Robustness; Saccharomyces cerevisiae; Stress-driven promoter; Xylose fermentation.