酵母によるアントラニル酸よりトリプトフアンの醗酵生産 : (第3報) 収率向上に関する二, 三の知見

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In an effort to improve the yield of L-tryptophan, the conditions for replacing cultures employing mainly a strain (H095) of Hansenula were first investigated. Secondly, the isolatino of improved mutants through ultraviolet irradiation and screening was attempted.For the first problem it was considered to be important to find out some means for enhancing the tendency of preferential synthesis of tryptophan. Such a tendency had been observed, though slight, in the later phase of a culture conducted at an adequate rate of aeration. At optimum pH (ca. 6) determined by the replacement culture method, the following substances, more or less inhibitory to growth, were examined for their effects on growth and tryptophan formation from anthranilic acid : sorbic acid. kabicidin, salicylic acid, thiouracil, butyl p-hydroxybenzoate, antimycin and indole Among these substances applied at various levels of concentration, sorbic acid and indole were shown to be somewhat stimulative for tryptophan formation within certain ranges of the growth-inhibiting concentraiton. In an experiment with indole added as inhibitor, conversion of the substance into tryptophan was observed only in the ansence of anthranilic acid added as precursor.For the second problem, the following series of mutations and selections was conducted starting with strain H096. The first mutant strain (63) was selected from the survivors by their resistance to indole and using the test of tryptophan-producing activity. This was again subjected to ultraviolet irradiation and, out of the survivors. the second mutant strain (631) for further study was selected by tests of growth rate in an cidic medium (pH, 4) and tryptophan-producing activity.As observed previously, the toxicity of anthranilic acid to the yeast strain was increased as the pH of medium was lowered. Reflecting upon the above, a third mutant strain (6319) was isolated, through ultraviolet irradiation, using an acidic medium (pH. 4) containing 5g/l of anthranilic acid.The third strain was shown to have the capability of accumulating tryptophan to a level ca. 1.5-fold higher than was attained by the original strain, H096.With the improved strain, a fermentation test in a 200 l fermentor was performed in which dissolved oxygen and pH were adjusted reffering to the results obtained previously (cf. preceding paper). Concentrated solutions of anthranilic acid and glucose together wiht nitrogen source were fed at intervals. As shown in Fig. 1,growth continued throughout the culture period of 144 hours at 27℃, and the tryptophan concentration attained a level of ca. 3.2g/l. As to the combined application of the results. i.e. improved conditions with improved strains, studies are in progress.
社団法人日本生物工学会の論文
1962-09-15

酵母によるアントラニル酸よりトリプトフアンの醗酵生産 : (第3報) 収率向上に関する二, 三の知見

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