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J. Microbiol. Biotechnol. 1999; 9(5): 593-603

Published online October 28, 1999

Copyright © The Korean Society for Microbiology and Biotechnology.

Metabolic Analysis of Poly(3-Hydroxybutyrate) Production by Recombinant Escherichia coli

Sang-Yup Lee , Anton P . J . Middelberg 1, Richard J . Van Wegen 2, Heng-Ho Wong 2 and Jong-Il Choi 2

Department of Chemical Engineering and Bioprocess Engineering Research Center Korea Advanced Institute of Science and Technology 373-1 Kusong-Dong Yusong-Gu Taejon 305-701 Korea, 1Department of Chemical Engineering University of Cambridge Pembroke Street Cambridge CB2 3RA U.K., 2Department of Chemical Engineering University of Adelaide SA 5005 Australia

Abstract

Poly(3-hydroxybutyrate) (PHB) production by fermentation was examined under both restricted- and ample-oxygen supply conditions in a single fed-batch fermentation. Recombinant Escherichia coli transformed with the PHB production plasmid pSYLl07 was grown to reach high cell density (227 g/l dry cell weight) with a high PHB content (78% of dry cell weight), using a glucose-based minimal medium. A simple flux model containing 12 fluxes was developed and applied to the fermentation data. A superior closure (95%) of the carbon mass balance was achieved. When the data were put into use, the results demonstrated a surprisingly large excretion of formate and lactate. Even though periods of severe oxygen limitation coincided with rapid acetate and lactate excretion, PHB productivity and carbon utilization efficiency were not significantly impaired. These results are very positive in reducing oxygen demand in an industrial PHA fermentation without sacrificing its PHA productivity, thereby reducing overall production costs.

Keywords: Escherichiacoli, metabolicfluxanalysis, poly-(3-hydroxybutyrate), oxygenlimitation, fermentation, highcelldensityculture