(462e) Comparative Genomic Analysis of a High n-Butanol Tolerant and Producing Mutant Strain of Clostridium Acetobutylicum

Butanol is an important organic solvent and has been considered as potential fuel or fuel additive. Biological production of butanol through bacterial fermentation has many advantages over petrochemical process; however, so far, it cannot compete with the petrochemical process economically because of the relatively low titer of butanol. To improve the butanol tolerance and final titer, a mutant strain of Clostridium acetobutylicum ATCC 55025 has been obtained through efficient strain evolution in the fibrous bed bioreactor. Compared with the parental strain, the mutant showed better butanol tolerance, much higher butanol titer, improved autolysis resistance and more complete substrate utilization. Further research showed that there are remarkable changes of membrane fatty acid composition and proteomic expression profiling. To better understand the differences between the parental and the mutant strain at the molecular level, complete genomic analysis was conducted. The result revealed 7 mutations in the mutant genome, which might have contributed to its improved butanol tolerance and fermentation performance. Among the 7 mutations, the C-terminal truncated histidine kinase and the C-terminal extended membrane protein were identified as targets for further inverse metabolic engineering to investigate their functions in affecting butanol biosynthesis and tolerance. The results from this study will provide better understanding of butanol tolerance, which can lead to the development of high butanol producing strains for industrial applications, and will be presented in this paper.