Metabolically Engineered Escherichia coli for Isoprene Biosynthesis

Abstract: As an important feedstock in petrochemistry, isoprene is used in a wide range of industrial applications. It is produced almost entirely from petrochemical source, however depleting progressively. A reliable biological process for isoprene production utilizing renewable feedstocks will be an industry-redefining development. There are two biosynthetic pathways producing isoprene: the mevalonate (MVA) pathway and the methyl erythritol 1-phosphate (MEP) pathway. In this study, the MEP pathway was modified in Escherichia coli BL21 (DE3) to produce isoprene. The gene isoprene synthase (IspS) chemically synthesized after codon optimization from Populus alba was heterologously expressed. The endogenous genes of 1-deoxy-D-xylulose-5-phosphate synthase (DXS) and 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) were over-expressed. The gene isopentenyl pyrophosphate isomerase (Idi) from streptococcus pneumoniae was exogenously over-expressed, and farnesyl diphosphate synthase (ispA) was weakened to enhance the yield in E. coli BL21 (DE3). It was shown that the control strain harboring empty plasmids did not emit any isoprene at all. The overexpression of single DXR gene had little impact on the yield of isoprene. Idi from streptococcus pneumoniae played a significant role in the improvement of isoprene production. The highest yield was achieved by ispA weakened DXS-IDI-IspS recombinant with 19.9 mg /L, i.e., 33-fold enhancement of isoprene yield of the IspS recombinant.