The effect of fungal competition on colonization of soybeans by moulds of the genus Aspergillus, Trichothecium and Fusarium and the ochratoxin A accumulation as related to temperature and moisture content

Abstract

The relationship between mould biomass and accumulation of ochratoxin A (OTA) on solid substrate (slightly cracked soybeans) at temperatures from 15 to 35°C and a water content in the substrate of 20 to 38% was been investigated. The experiments were carried out with the mould Aspergillus ochraceus NRRL 3174 in pure culture and in mixed culture, respectively; the latter with the moulds Trichothecium roseum ZMPBF 1226 and Fusarium graminearum ZMPBF 1244. The biomass growth during cultivation was monitored by measuring the analysis of chitin as glucosamine, and the concentration of OTA was measured by high performance liquid chromatography (HPLC) method using Hewlett-Packard instrument with fluorescence detector. It was established that the accumulation of the examined OTA primarily depend on the temperature of cultivation rather than on the growth of the biomass. The
biomass of the mixed culture of A. ochraceus, T. roseum and F. graminearum after 35 days of cultivation reduced the amount of OTA by 48, 72 and 85%, respectively. The decrease of concentration of OTA is more pronounced in the substrate with a higher initial water content and at higher temperature of cultivation.

Keywords: Moulds, mycotoxins, ochratoxin A, chitin, HPLC