engleski

Relationship between biomass synthesis and the specific growth rate for mould Aspergillus ochraceus NRRL 3174, Trichothecium roseum ZMBPF 1226 and Fusarium sp. ZMBPF 1215 during the growth on a solid substrate

The objective of this study was to reveal the relationship between biomass production and the specific growth rate for the ochratoxicogenic mould Aspergillus ochraceus NRRL 3174 and nonochratoxicogenic moulds Trichothecium roseum ZMBPF 1226 and Fusarium sp. ZMPBF 1215, grown on corn. The moulds were incubated as a stationary culture oat 20, 25, and 30 0C for 35 days. Inoculation was performed by 1 x 10-6 spores g -1 substrate, which initially contained 38 % of water. Biomass synthesis was followed indirectly by a chitin method, while the amount of ochratoxin A was determined fluorodensitometrically. Values for biomass synthesis and the specific growth rate obtained after 7 days of cultivation at 20 0C in pure cultures were: 2.4 mg g-1 and 1.25x10-1 day-1 for Aspergillus ochraceus NRRL 3174 ; 5.9 mg g-1 and 2.55x10-1 day-1 for Trichothecium roseum ZMPBF 1226 ; and 5.2 mg g-1 and 2.4x10-1 day-1 for Fusarium sp. ZMPBF 1215, revealing the fact that under these conditions moulds T. roseum and Fusarium sp. are predominant ones. At higher temperature, 25 0C, Aspergillus ochraceus NRRL 3174 reaches the maximum of biomass synthesis of 6.5 mg g -1 , with the specific growth rate 2.68x10 -1 day -1. At the same time growth of Trichothecium roseum ZMPBF 1226 and Fusarium sp. ZMPBF 1215 was reduced 15-20 %. Cultivation at 30 0C caused the decrease of growth rate of all three researched moulds. By monitoring these three moulds, cultivated as a mixed culture, the peak of the specific growth rate was found after 7 days (particularly at 25 0C, 2.9x 10 -1 day -1), and the minimum after 35 days (1.17x10-1 day-1), at all three used temperatures (20, 25 and 30 0C). Comparing the results obtained during the cultivation of moulds as pure cultures as well as the mixed culture, it was concluded that Aspergillus ochraceus NRRL 3174 achieves lower specific growth rate and shows reduced ochratoxin A biosynthesis when grown as a mixed culture. It was also concluded that the best relationship between the biomass synthesis and the specific growth rate for A. ochraceus is reached after 7 days at 25 0 C.

Aspergillus ochraceus; Trichothecium roseum; Fusarium sp.; biomass synthesis; growth rate

nije evidentirano