Improving Cellular Robustness and Butanol Titers of Clostridium Acetobutylicum ATCC824 By Introducing the Heat Shock Proteins from Extremophilic Bacteria

In recent years, increasing concerns over environment, energy and climate have renewed interest in biotechnological production of butanol. However, growth inhibition by fermentation products and inhibitory components of raw biomass hindered the development of ABE fermentation. Improving cellular robustness of Clostridium acetobutylicum is of great importance for efficient ABE production. In this study, we attempt to improve the robustness and butanol titers of C. acetobutylicum ATCC824 by overexpressing the groESL and dnaK from the extremely radioresistant bacteria Deinococcus wulumuqiensis R12 and C. acetobutylicum ATCC824. Three recombinants were obtained and designated as ATCC824(groESLR12), ATCC824(dnaK R12) and ATCC824(groESL824). These three recombinants were found to significantly improve diverse types of stress-tolerances including furfural, butanol, oxidative, acid and osmotic-tolerance. Meanwhile, the butanol titers increased to 11.22g/L, 13.04g/L and 10.68g/L, which were 29.7%, 51% and 23.5% higher compared with the wild type, respectively. Especially for ATCC824(dnaK R12), the production of acetic and butyric acid decreased about 50% and 100% compared with the wild strain. These results indicated that overexpression of groESL and dnaK enhanced the metabolic rate of EMP pathway and improved acids re-uptake efficiency. In addition, ATCC824(groESLR12) was superior to ATCC824(groESL824) in diverse types of stress-tolerances and butanol titers because GroESL from an extreme bacterium could more efficiently perform their function in the heterologous host. Our study provided a new clue and a theoretical basis for improve the robustness and butanol titers of C. acetobutylicum ATCC824.