Metabolic Engineering of Microorganisms to Produce Isoprene

Isoprene is an industrially important five carbon compound primarily used for production of high quality synthetic rubber. Two major pathways are involved in isoprene synthesis. The mevalonate pathway is present in eukaryotes, archaebacteria and cytosol of higher plants whereas the non-mevalonate pathway exists in many eubacteria and plastids in algae/plants. There have been continuous efforts to study and understand the phenomenon of biological production of isoprene for more than half a century. Although, the current feasibility and cost advantage of chemical processes leading to production of isoprene seems to be far from being dominated by a suitable biological substitute, the fear of extinction of non-renewable resources (raw material for chemical processes) in the near future prompts for a colossal expectation from the synthetic biology community. Technological advances in the field of metabolic engineering have made it possible to vigorously modify and swap genes among different organisms and push the limits for microorganisms to over-produce isoprene to an enormous extent. This review touches upon the limitations faced while improving isoprene titres and the meticulous strategies used to overcome them. It analyzes recent approaches that have resulted in significant improvement of biologically produced isoprene, summarizes the lessons learned from them, and compiles an exhaustive list of potential gene targets that could facilitate prospective research in this widespread arena.