Engineering an efficient H2 utilizing Escherichia coli platform by modulation of endogenous hydrogenases

Abstract

Abstract H2 is extensively available from geological reservoirs, industrial byproducts or natural processes, which makes H2 an ideal supplemental substrate providing additional reductive equivalents for increasing anaerobic fermentation efficiency. While it has been applied broadly in industrial and pharmaceutical fileds, Escherichia coli was not shown to efficiently utilize hydrogen. To construct a versatile biological platform for efficient utilization of H2, the endogenous hydrogenase genes of E. coli were investigated. Consequently, overexpression of the endogenous hydrogenases Hyd-1 and Hyd-2 induced respective 26.5 % and 36.7 % increases of succinate yield, indicating that both Hyd-1 and Hyd-2 contributed to the increased pool of reductive equivalents. Additionally, simultaneously modulating the expression of hya and hyb genes by introducing the strong promoter P10 resulted in the higher yield of succinate. To further improve the utilization of H2, pathway of rTCA cycle and CO2 supplementation were engineered in the strain ZL014(pBTCA), which produced the highest succinate yield of 1.50 mol per mol glucose. Our work successfully engineered a novel E. coli platform that could efficiently utilize H2, which could be employed to construct a variety of microbial cell factories requiring substantial amounts of reductive equivalents.