Engineering Robust Hosts to Improve Microbial Biofuel Production

A major challenge when using microorganisms to produce biofuels is that next-generation fuels are often toxic to cells. Microbes that thrive in oil rich environments (around natural oil seeps or near oil spills) have mechanisms for tolerating the toxic effects of hydrocarbons. Our goal is to identify tolerance mechanisms from these hydrocarbon-tolerant microbes and express them in biofuel production hosts to improve yields. For example, we have demonstrated that efflux pumps are effective at increasing biofuel tolerance. By isolating pump genes and expressing them heterologously in a biofuel-producing strain of E. coli, we have been able to increase biofuel yields. We next asked whether tolerance mechanisms could be used in combination, expressing multiple efflux pumps in the same strain. We found that combinations of pumps can increase tolerance, but the benefits are limited by toxic effects associated with pump overexpression. In addition, we are searching for novel tolerance strategies using a genomic library approach to select for mechanisms that further improve biofuel tolerance. The overall goal of this research is to enhance microbial synthesis of next-generation biofuels by developing tools for improving microbial tolerance of biofuel production conditions.