Comparative stability of ethanol production by Escherichia coliKO11 in batch and chemostat culture |
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Authors: | G J Dumsday B Zhou W Yaqin G A Stanley N B Pamment |
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Institution: | (1) Department of Chemical Engineering, University of Melbourne, Parkville, Victoria, Australia 3052, AT;(2) School of Life Sciences and Technology, Victoria University of Technology, Werribee Campus (W008), PO Box 14428, Melbourne City MC, Victoria, Australia 8001, AT |
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Abstract: | Differing claims regarding the stability of the recombinant ethanologen E. coli KO11 are addressed here in batch and chemostat culture. In repeat batch culture, the organism was stable on glucose, mannose,
xylose and galactose for at least three serial transfers, even in the absence of a selective antibiotic. Chemostat cultures
on glucose were remarkably stable, but on mannose, xylose and a xylose/glucose mixture, they progressively lost their hyperethanologenicity.
On xylose, the loss was irreversible, indicating genetic instability. The loss of hyperethanologenicity was accompanied by
the production of high concentrations of acetic acid and by increasing biomass yields, suggesting that the higher ATP yield
associated with acetate production may foster the growth of acetate-producing revertant strains. Plate counts on high chloramphenicol-containing
medium, whether directly, or following preliminary growth on non-selective medium, were not a reliable indicator of high ethanologenicity
during chemostat culture. In batch culture, the organism appeared to retain its promise for ethanol production from lignocellulosics
and concerns that antibiotics may need to be included in all media appear unfounded.
Received 13 January 1999/ Accepted in revised form 23 April 1999 |
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Keywords: | : ethanol recombinant E coli KO11 lignocellulosic chemostat stability |
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