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Appl. Environ. Microbiol., Dec 1997, 4765-4769, Vol 63, No. 12
F Wang and SY Lee
Recombinant Escherichia coli XL1-Blue harboring a high-copy-number plasmid
containing the Alcaligenes eutrophus polyhydroxyalkanoate synthesis genes
could efficiently synthesize poly(3-hydroxybutyrate) (PHB) in a complex
medium containing yeast extract and tryptone but not in a defined medium.
One of the reasons for the reduced PHB production in a defined medium was
thought to be severe filamentation of cells in this medium. By
overexpressing an essential cell division protein, FtsZ, in recombinant E.
coli producing PHB, filamentation could be suppressed and PHB could be
efficiently produced in a defined medium. A high PHB concentration of 149
g/liter, with high productivity of 3.4 g of PHB/liter/h, could be obtained
by the pH-stat fed-batch culture of the filamentation-suppressed
recombinant E. coli in a defined medium. It was also found that
insufficient oxygen supply at a dissolved oxygen concentration (DOC) of 1
to 3% of air saturation during active PHB synthesis phase did not
negatively affect PHB production. By growing cells to the concentration of
110 g/liter and then controlling the DOC in the range of 1 to 3% of air
saturation, a PHB concentration of 157 g/liter and PHB productivity of 3.2
g of PHB/liter/h were obtained. For the scale-up studies, fed-batch culture
was carried out in a 50-liter stirred tank fermentor, in which the DOC
decreased to zero when cell concentration reached 50 g/liter. However, a
relatively high PHB concentration of 101 g/liter and PHB productivity of
2.8 g of PHB/liter/h could still be obtained, which demonstrated the
possibility of industrial production of PHB in a defined medium by
employing the filamentation-suppressed recombinant E. coli.
Copyright © 1997, American Society for Microbiology
Production of poly(3-hydroxybutyrate) by fed-batch culture of filamentation-suppressed recombinant Escherichia coli
Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, Taejon, Korea.
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