Abstract:

Lignocellulosic biomass（LCB）is a promising alternative to fossil material, the biofuels, biochemicals and biomaterials are produced via its biorefinery, which may reduce carbon emissions, contributing to achieve the carbon peaking and carbon neutrality goals. Therefore, LCB is receiving more and more attentions. However, there are multiple steps involved in lignocellulosic biorefinery including pretreatment, microbial fermentation and product purification, in which, various compounds generated from pretreatment of LCB inhibit cell growth and fermentation performance of microbes, which is one of the bottlenecks of bioconversion efficiency. Escherichia coli is a commonly used host for lignocellulosic biorefinery and extensively used for the production of many compounds, thus, it is of great importance to study the stress tolerance of E. coli to inhibitors in lignocellulosic hydrolysates for improving lignocellulosic biorefinery efficiency. This paper first introduced the main components and structures of lignocellulose, and briefly elucidated pretreatment methods to lignocellulose as well as main inhibitors in the hydrolysate after pretreatment. Then the paper summarized the toxic effects of main inhibitor furans, carboxylic acids and phenolics in the hydrolysate of lignocellulose on E. coli, as well as the mechanisms of stress tolerance against these inhibitors and the engineering targets for improving strain tolerance based on the mechanisms. Finally, the paper reviewed the strategies for strain engineering to improve the tolerance of E. coli to above motioned inhibitors, including random mutagenesis, adaptive laboratory evolution and omics-assisted rational design,, aiming to provide references for metabolic engineering of efficient E. coli strains for lignocellulosic biorefinery.

Key words: inhibitors in lignocellulosic hydrolysate, stress tolerance, Escherichia coli, strain engineering, furans, carboxylic acids, phenolics