S13: Metabolic engineering for production of isoprene

Metabolic Engineering for Production of BioIsoprene^TM Monomer

The annual world market potential for polymer grade isoprene is approximately 1-2 billion dollars.  A majority of polymer grade isoprene is produced as a side-product from oil refinement while the remainder is produced by chemical synthesis.  The result is a market that is heavily dependent on the fluctuating prices of the oil market with an unpredictable supply.  We envision the biological production of isoprene (BioIsoprene^TM monomer) as a sustainable solution that can address the lack of supply and price instability of this valuable commodity.  The biosynthetic production of isoprene presents significant metabolic engineering challenges that include overcoming regulation, channeling carbon to product, balancing redox and energy requirements of the cell, and selection of appropriate enzymes.  We have introduced a mevalonate biosynthetic pathway and an isoprene synthase into Escherichia coli to improve the production of isoprene.  Mevalonate kinase is known to be inhibited by downstream metabolites and, therefore, may serve a regulatory role in the mevalonate pathway.  To determine the relationship between mevalonate kinases from metabolically diverse organisms, we have investigated the catalytic properties and inhibition profiles of the mevalonate kinases from the archaeon Methanosarcina mazei, the eukaryote Saccharomyces cerevisiae, and the bacterium Streptoccocus pneumoniae.  The mevalonate kinases examined can be divided into three classes based on differences in their inhibition profiles.  The M. Mazei mevalonate kinase was not inhibited by any of the mevalonate pathway intermediates or downstream products tested suggesting that it may exemplify a novel class of mevalonate kinase.