Improvement of environmental tolerance of E. coli through biological membrane engineering to boost succinic acid conversion

Abstract

Escherichia coli has been applied as an important platform for carboxylic acids production, such as succinic acid (SA). However, carboxylic acids will cause membrane damage, inhibiting E. coli growth and metabolism, which has been considered as one of the main obstacles to large-scale SA production. In this study, the approach of biological membrane engineering was attempted to improve the environmental tolerance of E. coli, which resulted from the change of membrane lipid composition. After introduction of whiB with function of stress responses and cell division, and cti with capability of trans unsaturated fatty acids biosynthesis, the SA production in the 5-L fermenter reached 80.0 g/L, which was 37.0% higher than that of the control group. Further incorporating fabA and fabB to promote unsaturated fatty acid biosynthesis of membrane, the engineered E. coli showed higher survival rate and better metabolic performance under the harsh environments, including exogenous octanoic acid (C8) addition, high osmotic pressure and low pH. The change of membrane composition contributed to the stronger resistance of E. coli, in particular the SA production still reached 29.9 g/L with 0.79 g/g of yield under low pH (pH 5.6) in the 5-L fermenter. The membrane engineering strategy is proved to be effective in improving strain robustness, paving the way to boost the large-scale production of carboxylic acids.