Ochratoxigenic potential of Aspergillus westerdijkiae NRRL 3174 under laboratory conditions

Abstract

Ochratoxin A (OTA) production by Aspergillus westerdijkiae NRRL 3174 in liquid medium (yeast extract and sucrose) and solid substrates (maize and rice) was studied under laboratory conditions. Liquid medium containing 2% yeast extract and various concentrations of sucrose (0–16%) was inoculated with fresh spores of Aspergillus westerdijkiae NRRL 3174 and incubated for 14 days at 25±0.5°C as stationary cultures. The OTA production increased with the increase in sucrose concentration up to 8%, however, above 8%, a decrease in OTA production was recorded. The highest production of OTA (21 mg/100ml) was recorded at 8% sucrose concentration containing 2% yeast extract medium. In case of solid substrates, the OTA yield increased with the increase in moisture content of the substrates from 15 to 35 percent. Considerably lower yield of OTA was recorded at 20 and 35°C as compared to 25 and 30°C temperatures. The highest production of OTA (0.99 g/kg maize and 0.98 g/kg rice) was harvested at 35% moisture and 30°C temperature in 14 days of incubation period. It is thus concluded that fungal growth is not related to ochratoxin production and the maximum yield of OTA can be harvested at 8% sucrose and 2% yeast extract medium. Further, the maximum yield of OTA on solid substrate can be harvested at 35% moisture level and between 25 and 30°C temperature.