Overexpression of key enzymes of the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway for improving squalene production in Escherichia coli

2-C-Methyl-D-erythritol-4-phosphate (MEP) pathway has been extensively employed for terpenoids biosynthesis in Escherichia coli. In this study, to obtain key-enzymes of MEP pathway for squalene production, overexpression of different combination of MEP pathway genes were compared. Squalene production in strain YSS12 with overexpressed dxs, idi and ispA of MEP pathway from E. coli was improved by 71-fold when compared with strain YSS3 which only contained double copy SQS. Analysis of transcriptional levels of MEP pathway genes in engineering strains showed that different squalene production can be attributed to changed transcriptional levels of co-overexpressed genes dxs, idi, ispG and ispA in engineering strains. Furthermore, different E. coli expression hosts were compared for squalene production, among which BL21(DE3) was the best squalene producer. These results illustrate that dxs, idi and ispA of the MEP pathway from E. coli were key-enzymes for squalene production in E. coli. These key-enzymes of MEP pathway could also be applied to other terpenoids production in E. coli.