Multi-modular Engineering for Renewable Production of Isoprene Via Mevalonate Pathway in Escherichia Coli

Aims: To establish the biotechnology platforms for production of bio-based chemicals in various micro-organisms is considered as a promising target to improve renewable production of isoprene.

Methods And Results: In this study, we heterologously expressed the mevalonate (MVA) isoprene biosynthesis pathway, and explored three strategies of increasing isoprene production in Escherichia coli. We first manipulated the expression levels of the MVA pathway genes through changing the gene cassettes and promoters. To introduce cofactor engineering, we then overexpressed NADP-dependent glyceraldehyde-3-phosphate dehydrogenase gene from Clostridium acetobutylicum to supply available NADPH. To reduce the inhibitory by-product accumulation, we finally knocked out acetate-producing genes, phosphate acetyl transferase and pyruvate oxidase B in E. coliJM109 (DE3), decreasing acetate accumulation 89% and increasing isoprene production 39%. The strategies described here finally increased the isoprene titre to 92 mg l in two-gene deletion strain JMAB-4T7P1Trc, increasing 2·6-fold comparing to strain JM7T7.

Conclusion: The multimodularly engineering approaches including promoter engineering, cofactor engineering and by-product reducing could be used to improve isoprene production in E. coli.

Significance And Impact Of The Study: The metabolic strategies in this study show us directions for further studies to promote transformation of renewable sources to isoprene.