Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Increasing the tolerance of a biofuel-producing organism to the biofuels themselves is an important step in the commercialization of lignocellulosic biofuels. Biofuels cause leakage of important cofactors, affect intracellular pH control, decreases the cell’s ability to replicate and divide, and create protein aggregates that ultimately lead to cell death. One general mechanism cells induce in response to environmental stresses, including exposure to biofuels like ethanol or butanol, is the heat shock response. This response includes the increased expression of several heat shock proteins, such as GroEL, that are able to sequester and refold denatured proteins. One group of HSPs expressed during stress is small heat shock proteins (sHsp), which are ATP-independent and have been shown to be essential for the survival of an organism during thermal or chemical stress. The goal of this study is to improve the growth tolerance of E. coli with the expression of sHsps and to understand the function of sHsps in E. coli. The growth of E. coli expressing sHsps was measured in the presence of ethanol and butanol, and specific growth rates were calculated. The expression of the sHsps improved the tolerance of E. coli in high concentrations of ethanol (50 g L-1) compared to control strains. Protein aggregation assays were performed with the sHsps to demonstrate that these proteins remained functional during alcohol exposure. This work shows an important step towards the generation of a more tolerant biofuel-producing organism.