A technical challenge to the production of isoprene from renewable sources such as biomass has been the development of an efficient process for converting carbohydrates into isoprene. In a presentation at the 239^th National Meeting of the American Chemical Society (ACS), Dr. Joseph McAuliffe of Genencor described how Genencor engineered bacteria to efficiently convert sugars derived from sugar cane, corn, corn cobs, switchgrass or other biomass to isoprene and how the smooth integration of fermentation and recovery processes can deliver a new route to this strategically important ingredient used to make synthetic rubber.

An intensive search has been underway for years for alternative sources of isoprene, in particular those from renewable resources such as biomass. One technical challenge has been the development of an efficient process for converting sugars into isoprene. One means by which we’re addressing this challenge is by using a fermentation process based on a modified bacterial strain that is designed to convert carbohydrate feedstocks into BioIsoprene product.

—Joseph McAuliffe

Genencor developed a fermentation route to BioIsoprene using an engineered organism in an integrated bioprocess whereby the volatile product is continuously recovered from the gas-phase. An important aspect of this work is the optimization of the metabolic pathways that deoxygenate carbohydrate substrates, leading to the 5-carbon isoprenoid precursor 3,3-dimethylallyl pyrophosphate (DMAPP), which is then subsequently converted to the BioIsoprene product in a reaction catalyzed by the enzyme isoprene synthase.

As reported at the ACE meeting, the work has enabled the production of the equivalent of more than 60 g/L of BioIsoprene monomer in the fermentation volume. Overall, Genencor notes, the process highlights the potential for the conversion of carbohydrates to valuable chemicals using a combination of biological and process engineering.

Goodyear and other large tire manufacturers use isoprene to produce synthetic rubber for use in tires to supplement use of natural rubber. Additionally, isoprene is used in a wide range of other industrial applications including, for example: use in other elastomers; block copolymers such as styrene-isoprene-styrene (SIS) used in hot melt adhesives in products such as diapers and feminine hygiene products; surgical gloves and other rubber-based products.

Worldwide production of high purity isoprene derived today from petroleum-based feedstocks totals about 1.7 billion pounds. Goodyear, which manufactures 200 million tires annually, is one of the world’s largest users of isoprene. The firm plans to supplement its use of petroleum-based isoprene with BioIsoprene product.

This is an enormous market. BioIsoprene product will serve as a renewable and cost-competitive alternative to isoprene. It’s a material that can drive new markets, so I believe those numbers highlighting global consumption would grow if new material became available. We want to make biochemicals from renewable materials partially as a hedge against rising crude oil prices and much more so because this approach moves us to a more sustainable future.

—Joseph McAuliffe

Resources

• Ilana S Aldor, Anthony R Calabria, Joseph C McAuliffe (2010) BioIsoprene: Development of a bio-based process for production of isoprene from renewable resources (ACS239 Paper 349)

• Joseph McAuliffe, Gregg Whited\, Maggie Cervin, Karl Sanford, Frank Feher, Dave Benko (2010) Bioprocess for the conversion of carbohydrates into bioisoprene (ACS 239 Paper 104)