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Engineered Bacterium with Resistance to Ionic Liquid




Researchers at the Joint BioEnergy Institute (JBEI) have determined the genes responsible for the molecular mechanism of ionic liquid tolerance in microorganisms. The resulting technology enables the engineering of host microorganisms suitable for biofuel processing using ionic liquid pretreatment, therefore significantly increasing biofuel yield. It may also enable fermentation under otherwise septic conditions since invasive organisms are unlikely to tolerate ionic liquid residuals at the concentrations tolerated by the JBEI host.

The researchers performed a functional screen of genomic DNA isolated from Enterobacter lignolyticus, a microbe tolerant to high osmotic pressures similar to those generated by exposure to ionic liquids. The microbe is found in some tropical rainforests noted for high rates of biomass decomposition. When the resulting DNA sequence was inserted into a common laboratory strain of E. coli, it conferred tolerance to certain imidazolium-based ionic liquids, including 1-ethyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate at the same or higher levels as the source bacteria.

Since ionic liquid can be toxic to microbes, such as E. coli, used in downstream biofuel processing steps, current methods using ionic liquid pretreatment require the ionic liquids to be thoroughly washed out of the hydrolysate before microbes are added. Relaxing the requirement to remove ionic liquids between the pretreatment and biofuel production stages improves the cost effectiveness of ionic liquid pretreatment, which is noted for its improved sugar recovery.

DEVELOPMENT STAGE: Proven principle. Laboratory tests indicated that an engineered strain of E. coli carrying the IL-tolerance genes was able to grow and produce the fuel precursor, bisabolene, in the presence of 4% 1-ethyl-3-methylimidazolium chloride, a concentration that completely inhibited the standard E. coli biofuel host.


Khudyakov, J.I., D’haeseleer, P.D., Borglin, S.E., DeAngelis, K.M., Woo, H., Lindquist, E.A., Hazen, T.C., Simmons, B.A., Thelan, M.P., “Global transcriptome response to ionic liquid by a tropical rain forest soil bacterium, Enterobacter lignolytius,” Proceedings of the National Academy of Sciences (PNAS), August 7, 2012, Vol. 109, No. 32, E2173-E2182.

Yarris, Lynn. “Microbe that Can Handle Ionic Liquids,” Berkeley Lab News Center, May 14, 2012.

STATUS: Patent pending. Available for licensing or collaborative research.


Halophilic and Thermostable Cellulases Tolerant to Ionic Liquids, EJIB-3028




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