Second-Generation Isobutanol Producing Biocatalyst

Isobutanol can be produced biotechnologically from the same biomass sources as ethanol. Compared to ethanol, however, isobutanol is a superior biofuel due to its higher energy content and its compatibility with existing fuel infrastructure. In addition, due to the vapor pressure issues posed by ethanol, requirements to produce gasoline that meet the specifications for reformulated gasoline (RFG) are difficult to mesh with the Renewable Fuel Standards (RFD) program. A renewable fuel molecule that helps meet both the RFG and RFD requirements, provides similar energy density as gasoline, and fits the existing petroleum pipeline infrastructure would be well received by the gasoline refining industry and ultimately by the gasoline market. Isobutanol meets these requirements and clearly outperforms the next best alternative, which is ethanol. The technology developed by this project also has the potential to reduce dependence on imported oil, lower greenhouse gas emissions, and expand markets for agricultural products worldwide. The state-of-the-art technology for biological isobutanol production was developed in an E. coli microorganism at the University of California–Los Angeles, and licensed and optimized by Gevo. Gevo hypothesizes that an increase in isobutanol tolerance in the currently employed host microorganism would allow even higher productivities and titers. Based on tolerance studies with a variety of microorganisms, Gevo has identified several microorganisms that are more tolerant to isobutanol compared to bacteria such as E. coli. An initial experiment in one of these microorganisms expressing an isobutanol production pathway showed limited isobutanol production. Thus, during Phase I of this project, Gevo plans to identify the cause(s) that is (are) preventing the microorganism from producing isobutanol at high yield. During Phase II, isobutanol production in this microorganism will be optimized to generate an advanced biocatalyst that outperforms existing isobutanol producing biocatalysts and can be commercialized.