Bio-ethanol penetration into the marketplace is limited by its cost, making it non-competitive with petroleum-based fuels. Energy consumed during fermentation and distillation steps accounts for 17% of the total cost. Because fermentation is exothermic, the reactor must be cooled to preserve mesophilic microbial viability. Then, the product must then be heated to vaporize the ethanol for purification by distillation. A simplified, energy-efficient process operating at higher temperatures (e.g. 80°C, which is above the boiling point of neat ethanol) would reduce energy use and cost. The primary barrier to higher-temperature fermentation is finding the right microbe, which must both survive and produce ethanol efficiently in the 80°C reactor. However, the discovery and study of such micorbes is challenging because 99% or more of microorganisms in the environment cannot be cultivated in the laboratory. This project will develop a high-temperature version of a previously-developed technology that provides a dramatically enhanced ability to culture novel environmental microbes. In Phase I, the previously-developed process will be used to screen a large collection of novel hyper-thermophiles, in order to identify one that produces ethanol above 75°C. In Phase II, a better hyper-thermophilic ethanolagen having several desirable traits (e.g. cellulase production, ethanol yield, and tolerance) will be isolated, characterized, and developed in bench-top and pilot-scale processes operating above 80°C.
Commercial Applications and Other Benefits as described by the awardee: The enhanced process should improve the fermentative production of biofuels such as ethanol, resulting in increased energy security, reduced greenhouse gas and other chemical emissions, sustainable use of natural resources, and rural job development. Based on data from NREL, fermentation at 80°C will cut energy use by 50%, equipment cost by 5%, and per-gallon ethanol cost by 10%. The technology also should find use in other important fermentations (such as production of industrial enzymes), monomers for plastics, small-molecule drugs, and protein-based therapeutics.
