Takeshi Tabuchi

Intracellular accumulation of mannosylerythritol lipids as storage materials by Candida antarctica

SummaryCandida antarctica strain T-34, which was isolated as a biosurfactant producer, was found to produce organic acids and polyols extracellularly but not to produce biosurfactants, when grown on glucose or other carbohydrates as the sole carbon source. It was also observed microscopically that the strain contained oil globules within the cells. The intracellular lipids of the strain mainly consisted of triglycerides and mannosylerythritol lipids (MEL). The MEL content of the cells during the culture exceeded 10% of the dry cell weight, and the pattern of variation of the MEL content was very similar to that of triglycerides. All three stock strains of C. antarctica tested also accumulated a relatively large amount of MEL from glucose. These results suggested that these strains accumulated the MEL intracellularly as one of the storage materials together with triglycerides.

Production of Isocitric Acid from Glucose by Candida ravautii

A strain of yeast, No. 325, having been isolated as a threo-Ds-isocitric acid producer and identified as Candida brumptii, was reidentified as Candida ravautii after taxonomical reexam-ination. All the tested strains of C. ravautii produced mainly isocitric acid. The tested strains were found to be unable to assimilate isocitric acid, although the assimilability of citric acid is one of the taxonomical characteristics of C. ravautii. A mutant was selected as the best producer of isocitric acid in media supplemented with yeast extract: the yield of isocitric acid amounted to about 50% on the basis of glucose supplied under suitable conditions in shaken culture.

UPTAKE AND OXIDATION OF HYDROCARBONS BY A MUTANT DERIVED FROM ITACONATE-PRODUCING YEAST

ABSTRACT A mutant capable of growing on n -alkanes supplied in liquid state was derived from a yeast deficient in the ability. The mutant produced a surface-active metabolite which stimulated markedly the growth of both the mutant and the parent. The metabolite was found to contain various fatty acids as moieties. The composition of fatty acids of the metabolite corresponded to n -alkanes used as carbon source, indicating that α-oxidation as well as β-oxidation took part in the degradation of n -alkanes by the mutant.

2-METHYLCITRATE DEHYDRATASE, A NEW ENZYME OF PROPIONATE METABOLISM IN SACCHAROMYCOPSIS LIPOLYTICA

ABSTRACT The presence of a new enzyme functioning at the methylcitric acid cycle concerning propionate metabolism was demonstrated. The enzyme was separated from the usual aconitate hydratase (EC 4.2.1.3) of Saccharomycopsis lipolytica by DEAE-Sephadex column chromatography. The partially purified enzyme preparation could dehydrate synthetic 2-methylcitrate to form 2-methyl- cis -aconitate. The enzyme preparation had no activity on citrate, threo - DL -isocitrate, threo - D s -2-methylisocitrate, DL -homocitrate and DL -citramalate. The optimum pH for enzyme activity was observed between 6.5 to 7.0. The molecular weight was estimated to be about 78,000. The trivial name of 2-methylcitrate dehydratase was hereafter given to the new enzyme. On the other hand, the enzyme fraction separated as aconitate hydratase with the chromatography could strongly catalyze the reversible reaction between 2-methyl- cis -aconitate and threo- D s -2-methylisocitrate but had no activity on synthetic 2-methylcitrate. KEYWORDS Methylcitric acid cycle;, propionate metabolism;, 2-methylcitrate dehydratase;, aconitate hydratase;, Saccharomycopsis lipolytica.