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Applied and Environmental Microbiology, December 2007, p. 7837-7843, Vol. 73, No. 24
0099-2240/07/$08.00+0     doi:10.1128/AEM.01546-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Improved Succinic Acid Production in the Anaerobic Culture of an Escherichia coli pflB ldhA Double Mutant as a Result of Enhanced Anaplerotic Activities in the Preceding Aerobic Culture{triangledown}

Hui Wu, Zhi-min Li, Li Zhou, and Qin Ye*

State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China

Received 9 July 2007/ Accepted 11 October 2007

Escherichia coli NZN111 is a pflB ldhA double mutant which loses its ability to ferment glucose anaerobically due to redox imbalance. In this study, two-stage culture of NZN111 was carried out for succinic acid production. It was found that when NZN111 was aerobically cultured on acetate, it regained the ability to ferment glucose with succinic acid as the major product in subsequent anaerobic culture. In two-stage culture carried out in flasks, succinic acid was produced at a level of 11.26 g/liter from 13.4 g/liter of glucose with a succinic acid yield of 1.28 mol/mol glucose and a productivity of 1.13 g/liter·h in the anaerobic stage. Analyses of key enzyme activities revealed that the activities of isocitrate lyase, malate dehydrogenase, malic enzyme, and phosphoenolpyruvate (PEP) carboxykinase were greatly enhanced while those of pyruvate kinase and PEP carboxylase were reduced in the acetate-grown cells. The two-stage culture was also performed in a 5-liter fermentor without separating the acetate-grown NZN111 cells from spent medium. The overall yield and concentration of succinic acid reached 1.13 mol/mol glucose and 28.2 g/liter, respectively, but the productivity of succinic acid in the anaerobic stage dropped to 0.7 g/liter·h due to cell autolysis and reduced anaplerotic activities. The results indicate the great potential to take advantage of cellular regulation mechanisms for improvement of succinic acid production by a metabolically engineered E. coli strain.

* Corresponding author. Mailing address: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China. Phone: 86-21-64252095. Fax: 86-21-64252250. E-mail: qye{at}ecust.edu.cn

{triangledown} Published ahead of print on 19 October 2007.

Applied and Environmental Microbiology, December 2007, p. 7837-7843, Vol. 73, No. 24
0099-2240/07/$08.00+0     doi:10.1128/AEM.01546-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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