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| Effect of overexpression of NAD+-Dependent Malic Enzyme on Anaerobic Mixed Acid Fermentation of E.coli FMJ39 |
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Abstract In order to investigate the effect of malic enzyme on anaerobic mixed acid fermentation, the gene encoding NAD+-dependent malic enzyme was amplified from E.coli DH5α genome by using PCR and cloned into vector pTrc99a to give an expression vector pTrc99a-sfcA. Malic enzyme was over-produced by E.coli FMJ39（ldh，pfl）harboring pTrc99a-sfcA under the condition of IPTG inducement, so a weak metabolic pathway was constructed and strengthened in anaerobic mixed acid fermentation. The results of anaerobic fermentation indicate overexpression of malic enzyme would have influence on the pathway of formate, acetate and succinate in FMJ39. The concentration of formate and acetate were 17.58% and 15.27% higher than FMJ39, the succinate concentration was reduced by 26.87%. No obvious change on citrate concentration. The fact that high L-Thr and L-Ser concentration would induce the Tdc operon to convert pyruvate into formate and acetate even when pfl gene encoding the pyruvate formate lyase had been inactivated. The experimental results lay the foundation for further modifying and utilizing FMJ39.
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Received: 31 October 2006
Published: 10 May 2010
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