Inactivation of aldehyde dehydrogenase: A key factor for engineering 1,3-propanediol production by Klebsiella pneumoniae.
Production of 1,3-propanediol (1,3-PD) from glycerol by Klebsiella pneumoniae is restrained by ethanol formation. The first step in the formation of ethanol from acetyl-CoA is catalyzed by aldehyde dehydrogenase (ALDH), an enzyme that competes with 1,3-PD oxidoreductase for the cofactor NADH. This study aimed to improve the production of 1,3-PD by engineering the ethanol formation pathway. An inactivation mutation of the aldA gene encoding ALDH in K. pneumoniae YMU2 was generated by insertion of a tetracycline resistance marker. Inactivation of ALDH resulted in a nearly abolished ethanol formation but a significantly improved 1,3-PD production. Metabolic flux analysis revealed that a pronounced redistribution of intracellular metabolic flux occurred. The final titer, the productivity of 1,3-PD and the yield of 1,3-PD relative to glycerol of the mutant strain reached 927.6mmolL(-1), 14.05mmolL(-1)h(-1) and 0.699molmol(-1), respectively, which were much higher than those of the parent strain. In addition, the specific 1,3-PD-producing capability (1,3-PD produced per gram of cells) of the mutant strain was 2-fold that of the parent strain due to a lower growth yield of the mutant. By increasing NADH availability, this study demonstrates an important metabolic engineering approach to improve the efficiency of oxidoreduction-coupled bioprocesses.[1]References
- Inactivation of aldehyde dehydrogenase: A key factor for engineering 1,3-propanediol production by Klebsiella pneumoniae. Zhang, Y., Li, Y., Du, C., Liu, M., Cao, Z. Metab. Eng. (2006) [Pubmed]
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