Danielle Tullman-ErcekView all speakers
Danielle Tullman-Ercek is an assistant professor in the Department of Chemical and Biomolecular Engineering at the University of California Berkeley. Danielle received her B.S. in Chemical Engineering at Illinois Institute of Technology in Chicago, and her Ph.D. in Chemical Engineering from the University of Texas at Austin. She carried out her postdoctoral research at UCSF and the Joint Bioenergy Institute prior to joining Cal in 2009.
Her research focuses on building protein-based devices for applications in bioenergy and drug delivery. She is particularly interested in engineering multi-protein complexes, such as the machines that transport proteins and small molecules across cellular membranes. She is a member of the Berkeley Synthetic Biology Institute, the Synthetic Biology Engineering Research Center, and the Energy Biosciences Institute, and was recently awarded an NSF CAREER award for her work on the construction of bacterial organelles using protein membranes.
The use of microbes to convert biomass to fuel is a promising technology, but the fuels are often toxic to genetically tractable microbial hosts, such as Escherichia coli, at industrially relevant levels. One promising solution to this challenge is to evolve multidrug resistance efflux pumps to secrete fuels from the cell, enabling increased fuel titers in addition to microbial tolerance. To that end, we have used directed evolution to engineer bacterial efflux pumps for enhanced tolerance to butanol. Using multiple rounds of directed evolution involving a selective growth competition method, we have isolated variants of the Escherichia coli AcrB efflux pump that enhance the growth of E. coli in the presence of n-butanol by approximately 25%. The growth enhancement is maintained even as the concentration of inhibitor is increased. Each variant is comprised of several mutations, and we have identified the single amino acid changes in AcrB that are responsible for the enhanced growth phenotype. Furthermore, expression of the variant pumps confers enhanced tolerance to isobutanol and straight-chain alcohols up to n-heptanol, but not chloramphenicol or geraniol. Significantly, we have also found that overexpressing these pumps in butanol production strains leads to increased titers of butanol.