l-Threonine Production by Auxotrophs of E. coli |
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Authors: | Tamotsu Hirakawa Tsutomu Tanaka Kiyoshi Watanabe |
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Institution: | Biochemical Research Laboratory, Kanegafuchi Chemical Ind. Co., Ltd., Takasago-shi, Hyogo |
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Abstract: | 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 (4.3 mg/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. o.ne of the methionine-valine auxotroph, strain No. 234, produced maximum amount of l-threonine (10.5 mg/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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Keywords: | oligotroph Rhodococcus erythropolis carbon dioxide formaldehyde dehydrogenase methanol dehydrogenase |
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