Sunday, July 26, 2009
P111
The proteome of Zymomonas mobilis strains grown under ethanol fermentation conditions
Chia-Wen Hsieh, Department of Microbiology and Immunology, National ChiaYi University Taiwan, No. 300, University Rd., ChiaYi, Taiwan, Long-Wei Shih, Graduate Institute of Biomedical Sciences, National ChiaYi University, Taiwan, No. 300, University Road,, ChiaYi, Taiwan, and Feisheng Ou, Suzhou Gaofeng Sweetener Co., Ltd, Suzhou, China.
Zymomonas mobilis is the most efficient ethanol producer among the candidates with the production of 1.5-1.9 mol ethanol from each mol glucose, and the production rate is 3-5 folds higher than that of Saccharomyces cerevisiae. However, accumulated metabolites like as acetic acid is inhibitory to growth and fermentation, and this limits industrial application of Z. mobilis. To cope with medium acidity, Z. mobilis should evolve a number of inducible mechanisms commonly referred as acetate tolerant response (ATR). To better understand the molecular basis of this response, several mutants constitutively tolerant to acidity were previously obtained by random mutagenesis of Z. mobilis ATCC 31821. Mutants in which Z. mobilis ATCC 31823 is further characterized in this study. In ethanol fermentation medium (10% glucose contained), Z. mobilis ATCC 31823 produced less acetate than wild-type did. Two dimensional electrophoresis was performed to analysis intracellular protein expression between these two strains grown with ethanol fermentation medium. Wild-type and acid-tolerant Z. mobilis displayed similar spot diversity from purified cytoplasma fractions were observed. Compare with acid-tolerant to wild-type Z. mobilis, 6 and 5 differentially expressed proteins were up-regulated and down-regulated, respectively. We identified these protein spots by MALDI-Q-TOF MS/MS. The synthesis of 2 proteins significantly increased (MF > 5) in Z. mobilis ATCC 31823. These 2 proteins belonged to glucose metabolic pathway, could involve in lowering cytoplasmic acetate levels.
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