engleski

The growth of Aspergillus ochraceus mould cultivated in pure and mixed cultures on corn grains and the influence of certain parameters on the ochratoxin A biosynthesis

The growth of ochratoxigenic mould Aspergillus ochraceus NRRL 3174 on corn grains and in vitro contiditions for ochratoxin A (OTA) biosynthesis in pure culture as well as in the mixed culture with the nonochratoxigenic mould Trichotecium roseum ZMPBF 1226 have been investigated. The biomass growth was followed by a chitin method, while OTA concentration was measured by TLC and fluorodensitometrically. The moulds were cultivated during 35 days in a stationary culture at temperatures 15 C, 20 C, 25 C and 30 C and 38 % water content in corn grains. It was found that OTA production the temperatures between 15 C and 20 C and the water content higher than 20 % were necessary, both in the pure and the mixed culture. The highest amount of OTA produced in the pure culture was 1225 micrograms x g mycelium dry weight, and ws reached two weeks of cultivation at 20 C with 38 % water content in the corn. Under the same conditions, the maximal value obtained in the mixed culture was 790 micrograms x g mycelium dry weight reached after three weeks of incubation. The elevation of the incubation temeprature to 20 C caused 50 % increase in the biomass sytnhesis, while at the same time the OTA amount decreased 15-45 %, the most probably becaouse of the less ability of the mycelium to synthesize OTA. Athe the incubation temperature of 30 C biosynthesis was inhibited.

biosynthesis; chitin; biomass; A. ochraceus; T. roseum; ochratoxin A

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