Takashi Nara

l-Homoserine Fermentation

In the course of studies on “negative feedback control” mechanisms caused by threonine and methionine in l-homoserine fermentation with Micrococcus glutamicus 534-Co147 culture, l-homoserine dehydrogenase was first found to occur in the culture, and effects of various amino acids on the formation and action of the enzyme were then investigated. The result was that l-homoserine dehydrogenase of the culture was repressed by methionine on the one hand, and inhibited by threonine on the other. β-Aspartokinase was found not to be repressed by methionine. From these findings, the sites at which the “negative feedback control” mechanisms work were discussed.

Production of Nucleic Acid-Relatcd substances by Fermentative Processes:Part III. Fermentative Production of 5'-Inosinic Acid by an Adenine Auxotroph of Brevibacterium ammoniagenes

An adenine-requiring mutant (KY7208) of Brevibacterium ammoniagenes ATTC 6872 was found to accumulate an appreciable quantity of IMP and hypoxanthine in the culture liquid.Crystalline IMP was isolated from culture broth of KY7208 by the use of ion-exchange columns. The preparation obtained was definitely identified as 5′-IMP, based on the results on paperchromatography, UV and IR absorption spectra, and analyses of its hydrolysates.Growth responses of this mutant were demonstrated to adenine and adenosine, but not to 5′-AMP, 3′-AMP and 5′-AMP.Over 5 mg of IMP per ml of broth were produced by the organism in natural medium consisting of glucose, yeast extract, urea, high concentrations of phosphate and magnesim salts, and others. The chemical changes showed that hypoxanthine first accumulated in the earlier stage of fermentation, and IMP synthesis then took place with the disappearance of hypoxanthine in the later stage of fermentation.

Production of Nucleic Acid-Related Substances by Fermentative Processes: Part XII. Accumulation of Inosinic Acid by Micrococtus sodonensis and Arthrobacter citreus

Micrococcus sodonensis KY 3765 and Arthrobacter citreus KY 3155 were found to be capable of accumulating an appreciable quantity of IMP on media supplemented with hypoxanthine as a precursor. Inosine was also produced from hypoxanthine by both cultures during a later stage of fermentation. In A. citreus adenine was converted into hypoxanthine and inosine.The requirement of high concentrations of phosphate and magnesium salts was demonstrated for high yields of IMP. Manganese deficiency in media was also essential for IMP accumulation by two organisms. Excessive Mn++ levels stimulated growth and inhibited IMP production markedly.In M. sodonensis α ribose-5-phosphate-like substance, 5-phosphoribose pyrophosphokinase and IMP pyrophosphorylase were leaked out of cells grown in suboptimal Mn++ levels and the excretion was inhibited in high levels of Mn++. Such phenomenon was not noticed in A. citreus.Similar Mn++ effects were also seen in IMP fermentation on defined media with an adenineless mutant of Coryneba...

Production of Nucleic Acid Related Substances by Fermentative Processes: Part VI. Accumulation of 5′-Xanthylic Acid by Guanine-Requiring Mutants of Micrococcus glutamicusI. Isolation and Characterization of 5′-Xanthylic AcidII. Studies on Cultural Conditions

It was found that a guanine and adenine-requiring mutant of Micrococcus glutamicus accumulated the ultraviolet-absorbing substance in the culture fluid. A KY9978 strain, which accumulated the largest amount of the substance, we selected from the guanine auxotrophs derived from the guanineadenine doubleless mutant. The substance was isolated in a crystalline form from the culture fluid by the use of ion exchange resins, Diaion SA 21A and SK No. 1, and identified chemically and enzymatically as 5′-xanthylic acid, an intermediate from 5′-inosinic acid to 5′-guanylic acid on the purine nucleotide biosynthesis.