构建大肠杆菌C4途径强化血红素合成OA

Heme is an iron porphyrin derivative composed of a ferrous ion and protoporphyrin.The demand of heme is increasing in fields such as food and medicine.Microbial fermentation is one of the methods for obtaining heme,but the titer is low.In this study,Esch-erichia coli BL21(DE3)was used as chassis strain and genetically modified to obtain a high-yield heme producing strain through metabolic engineering strategies.Firstly,the native C5 heme biosynthetic pathway in E.coli was blocked and a heterologous C4 pathway was intro-duced.The resulting engineered strain demonstrated superior heme production compared to strains with enhanced native C5 pathway or co-existing C4/C5 pathways.Subsequently,a further increase of heme production was achieved by over expressing the key genes of hemB or hemH involved in the heme synthetic pathway in E.coli.Finally,by optimizing the supplement of the precursors of glycine and ferrous chloride,the heme content in the engineered strain reached 82.39 μmol/L after 24 h of shaking flask fermentation,which was 4.2-fold compared to that of the starting strain.It is a new strategy to construct an engineered E.coli which uses sole heterologous C4 pathway to produce heme with high titer.