L-Threonine Production by Auxotrophs of E. coli
1973 年 37 巻 1 号 p. 123-130
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1973 年 37 巻 1 号 p. 123-130
Methionine auxotrophs were derived by the treatment with ultraviolet ray or N-methylN'-nitro-N-nitrosoguanidine from five strains of Escherichia coli. One of the methionine auxotrophs of E. coli C-6, strain No. 15, produced maximum amount of L-threonine (4.3mg/ml) with the medium containing 5% cane-molasses (as sugars). Double auxotrophs were derived with further mutational treatment from strain No. 15. It was found that L-threonine production was greatly enhanced by cultivating methionine-valine auxotrophs in the presence of L-valine and methionine. One of the methionine-valine auxotroph, strain No. 234, produced maximum amount of L-threonine (10.5mg/ml) from cane-molasses.
The requirement of L-valine for the growth of the strain No. 234 was found to be leaky, and it was suggested that some enzymes relating to L-valine metabolism were mutationally altered to temperature-sensitive.
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