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Appl. Environ. Microbiol., 02 1995, 413-420, Vol 61, No. 2
M Shinjoh, N Tomiyama, A Asakura and T Hoshino
Cloning and expression of the gene encoding Acetobacter liquefaciens IFO
12258 membrane-bound L-sorbosone dehydrogenase (SNDH) were studied. A
genomic library of A. liquefaciens IFO 12258 was constructed with the
mobilizable cosmid vector pVK102 (mob+) in Escherichia coli S17-1 (Tra+).
The library was transferred by conjugal mating into Gluconobacter oxydans
OX4, a mutant of G. oxydans IFO 3293 that accumulates L-sorbosone in the
presence of L-sorbose. The transconjugants were screened for SNDH activity
by performing a direct expression assay. One clone harboring plasmid p7A6
converted L- sorbosone to 2-keto-L-gulonic acid (2KGA) more rapidly than
its host did and also converted L-sorbose to 2KGA with no accumulation of
L- sorbosone. The insert (25 kb) of p7A6 was shortened to a 3.1-kb
fragment, in which one open reading frame (1,347 bp) was found and was
shown to encode a polypeptide with a molecular weight of 48,222. The SNDH
gene was introduced into the 2KGA-producing strain G. oxydans IFO 3293 and
its derivatives, which contained membrane-bound L-sorbose dehydrogenase.
The cloned SNDH was correctly located in the membrane of the host. The
membrane fraction of the clone exhibited almost stoichiometric formation of
2KGA from L-sorbosone and L-sorbose. Resting cells of the clones produced
2KGA very efficiently from L- sorbosone and L-sorbose, but not from
D-sorbitol; the conversion yield from L-sorbosone was improved from
approximately 25 to 83%, whereas the yield from L-sorbose was increased
from 68 to 81%. Under fermentation conditions, cloning did not obviously
improve the yield of 2KGA from L- sorbose.
Copyright © 1995, American Society for Microbiology
Cloning and nucleotide sequencing of the membrane-bound L-sorbosone dehydrogenase gene of Acetobacter liquefaciens IFO 12258 and its expression in Gluconobacter oxydans [published erratum appears in Appl Environ Microbiol 1995 May;61(5):2069]
Department of Applied Microbiology, Nippon Roche Research Center, Kanagawa, Japan.
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