Engineering a Thermotolerant Bacterium as a Platform Strain for Lignocellulosic Biomass-Based Biorefinery

Abstract

Lignocellulosic biomass is a promising low-cost feedstock for biorefinery after thermoacid hydrolysis, which yields fermentable sugars along with various inhibitory byproducts such as organic acids and aldehydes. Despite of its potential, microbial hosts capable of effectively utilizing such crude hydrolysates under harsh industrial conditions remain scarce. In this study, we engineered a thermotolerant bacterium, which possesses the potential to withstand harsh environments, to enhance metabolic capabilities and robustness. Through a combination of rational and random engineering strategies, we developed a strain exhibiting comparable growth on the most abundant biomass-driven sugar to that of other well-known organisms. Additionally, we introduced three heterologous pathways under sugar-inducible control to enable efficient utilization of the second abundant biomass-driven sugar. Furthermore, this strain demonstrated putative catabolic genes responsible for hydrolysate toxic compounds, suggesting a potential to mitigate toxicity via bioconversion. Lastly, we significantly enhanced its ability to metabolize one of organic acids derived from biomass, which has been regarded as a non sugar-based feedstock, through a random approach. These results suggested that this strain has the potential as the thermotolerant platform host for lignocellulose-based biorefinery.