Biochemical basis for carbon monoxide tolerance and butanol production by Butyribacterium methylotrophicum |
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Authors: | G-J Shen J-S Shieh A J Grethlein M K Jain J G Zeikus |
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Institution: | (1) MBI International, 3900 Collins Road, Lansing, MI 48910, USA e-mail: zeikus@mbi.org Tel.: +1-517-337-3181 Fax: +1-517-332-7810, US;(2) Departments of Biochemistry and Microbiology, Michigan State University, 410 Biochemistry Building, East Lansing, MI 48824, USA, US |
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Abstract: | The biochemical mechanisms for growth tolerance to a 100% CO headspace in cultures, and butanol plus ethanol production from
CO by Butyribacterium methylotrophicum were assessed in the wild-type and CO-adapted strains. The CO-adapted strain grew on glucose or CO under a 100% CO headspace,
whereas, the growth of the wild-type strain was severely inhibited by 100% CO. The CO-adapted strain, unlike the wild-type,
also produced butyrate, from either pyruvate or CO. The CO-adapted strain was a metabolic mutant having higher levels of ferredoxin–NAD
oxidoreductase activity, which was not inhibited by NADH. Consequently, only the CO-adapted strain can grow on CO because
CO oxidation generates reduced ferredoxin which, via the mutated ferredoxin–NAD reductase activity, forms reduced NADH required
for catabolism. When the CO-adapted strain was grown at pH 6.0 it produced butanol (0.33 g/l) and ethanol (0.5 g/l) from CO
and the cells contained the following NAD-linked enzyme activities (μmol min−1 mg protein−1): butyraldehyde dehydrogenase (227), butanol dehydrogenase (686), acetaldehyde dehydrogenase (82) and ethanol dehydrogenase
(129).
Received: 15 September 1998 / Received revision: 12 February 1999 / Accepted: 19 February 1999 |
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