In order to investigate the effect of pyruvate dehydrogenase on citric acid production in Aspergillus niger,overexpression plasmids of pyruvate dehydrogenase p14(pGAS)and p16(pGAP)with different pro-moters were constructed,and overexpression strains p14-45 and p16-5 with good acid-producing performance and genetic stability were obtained.The fermentation results in the 30 L fermenter showed that the acid produc-tion of mutant strains p14-45 and p16-5 increased by 5.17%and 4.01%,respectively,compared with that of the original strain CGMCC 10142 at the end of fermentation.
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