Technology Review has an article on "renewable rubber" - Rubber from Microbes.
Working with Goodyear, biotechnology company Genencor has been engineering bacteria that make isoprene--the chemical used to make tire rubber--from sugars derived from biomass. But ramping up microbial production of isoprene to such a scale that it can compete with petroleum-derived rubber has proven to be a major challenge.
Yesterday at the American Chemical Society meeting in San Francisco, researchers from a Palo Alto, CA-based research division of Genencor described further modifications to the metabolic pathways of the microbes that improve the yield of bioisoprene. The company will decide on plans for building a bioisoprene pilot plant next year.
Microbes including E. coli naturally make small amounts of isoprene as part of their metabolism, but not nearly enough to be used on an industrial scale. To improve the yield, bioengineers at Genencor, which began working on bacterial systems for producing isoprene in 2007, initially made changes to two metabolic pathways that converge to create an isoprene precursor. But yields were still low because the bacteria's existing genetic machinery takes a meandering path to create isoprene from this precursor. In the most recent results, the company added to the E. coli a plant gene coding for isoprene synthase, an enzyme that converts the precursor directly into isoprene.
Isoprene, which is a gas at room temperature, bubbles out of the cells without damaging them, then out of the fermentation broth. Genencor senior director of business development Rich Laduca says that with no refinement, this system can produce 99 percent pure isoprene gas. Purity is critical because trace contaminants can foul the catalysts used to polymerize isoprene to make synthetic rubber. Goodyear has used Genencor's bioisoprene to make synthetic rubber, which it then used to make several prototype tires.
"We're looking for renewable resources to reduce our dependence on foreign oil," says Jesse Roeck, director of global materials science at Goodyear. Roeck says the isoprene work is still a research project, but that the chemical may be in tires on the market in three to five years.