TECHNOLOGY UPDATE: Development of a gas-phase bioprocess for isoprene-monomer production using metabolic pathway engineering

A sustainable production system for isoprene is being developed based on microbial fermentation of renewable sugars (BioIsoprene™). Isoprene is an important commodity chemical used in a wide range of industrial applications, ranging from the production of synthetic rubber for tires and coatings, to use in adhesives and development of specialty elastomers. Current production of isoprene is derived entirely from petrochemical sources. There is an increasing global need for more isoprene and a simultaneous environmental imperative to reduce greenhouse gases, both of which can be achieved by a highefficiency fermentation-based process for polymer-grade isoprene production. The key to such a process is engineering a microbial cell factory that is streamlined in physiology to drive sugar conversion through engineered biosynthetic pathways, to produce isoprene at near theoretical yields. Two biosynthetic isoprenoid pathways being optimized towards this end, and processes delivering >60g/L of isoprene are described. The product produced in the gas-phase is recovered from the fermentation off-gas in a continuous process. Current state-of-the-art technology has resulted in production, recovery, polymerization, and manufacture of tires with the isoprene component produced via fermentation. Continued improvements in both the cell factory and the production process are being actively pursued.