Genetic modification of Escherichia coli to improve 1,2,4-butanetriol production from cellulose hydrolysate

Abstract

The presence of various furan aldehydes in cellulose hydrolysate affects the fermentation of 1,2,4-butanetriol (BT) in a similar way. In this study, furfural was used as a representative for the modification of BT-producing E. coli for tolerance. The engineered Escherichia coli harboring the recombinant BT pathway had decreased the biomass by 58% and the BT titer by 52% in the presence of 0.4 g/L furfural. To improve the tolerance of the strain and the efficiency of BT synthesis in the hydrolysate, seven furfural tolerance genes, ucpA, fucO, groESL, lpcA, pncB, nadD, and nadE were introduced into the BT-producing E. coli. All these genes differentially improved the furfural tolerance performance of the cells. Overexpression of these tolerance genes reduces the accumulation of reactive oxygen species and promotes glycolysis. Oxidoreductase UcpA was the best candidate for improving cell growth. UcpA also increased the activities of Xdh and YqhD and the RNA levels of YjhG and KivD, leading to a 32% increase in BT yield per biomass and the best BT titer of 14.4 g/L in the presence of 0.4 g/L furfural. In the shaker and 5 L fermenter, the BT titer reached 5.2 g/L and 11.2 g/L, respectively, by using corn cob cellulose as substrate.