S204: Synthetic biology approaches to produce C3-C5 alcohols from microorganisms

Biofuels synthesized from renewable resources are of increasing interest because of global energy and environmental problems. Compared to the traditional biofuel, ethanol, higher alcohols such as isobutanol and 1-butanol offer advantages such as higher energy density, lower hygroscopicity, lower vapor pressure, and compatibility with existing transportation infrastructure. Some Clostridia species are known to naturally produce isopropanol and 1-butanol. However, these fuels are not synthesized economically using native organisms.  Additionally, other C3-C5 alcohols are not produced in large quantities by natural microorganisms. Synthetic biology offers an alternative approach in which synthetic pathways are engineered into user-friendly hosts for the production of these fuel molecules. We built up unnatural synthetic pathways to produce higher-order alcohols.  Moreover, we improved the productivity by combining gene deletion and overexpression techniques.  Our demonstration shows that the strategy enables the exploration of biofuels beyond those naturally accumulated to high quantities in microbial fermentation.