Temperature and incubation time effects on growth and ochratoxin A production by Aspergillus sclerotioniger and Aspergillus lacticoffeatus on culture media

Aims: As there is no knowledge of the influence of abiotic factors on the two new ochratoxin A (OTA)-producing species Aspergillus sclerotioniger and Aspergillus lacticoffeatus, the aim of this study was to evaluate the effect of temperature and incubation time on growth and OTA production by these species on culture media. Methods and Results: The study was carried out on yeast extract sucrose agar (YES) and Czapek yeast extract agar (CYA) incubated at ten different temperatures from 5 to 50 degrees C (at 5 degrees C intervals). Growth assessment and OTA production were determined after 5, 10, 15, 20 and 30 days of incubation at each temperature. Aspergillus sclerotioniger grew from 10 to 35 degrees C; OTA was detected from 10 to 35 degrees C and the highest concentration was achieved at 15 degrees C in CYA. Aspergillus lacticoffeatus grew from 10 to 45 degrees C; OTA was detected from 15 to 45 degrees C, and the maximum concentration was produced after 5 days at 25 degrees C in YES. Conclusions: The studied species can produce OTA over a wide range of temperatures and significant amounts can be produced in only 5 days. Significance and Impact of the Study: This is the first report on the influence of ecophysiological factors on these two ochratoxigenic species. The pattern of effects of temperature on growth and OTA production by A. sclerotioniger and A. lacticoffeatus was similar to those reported for the closely related species Aspergillus carbonarius and Aspergillus niger, respectively. The two new OTA-producing species have both been isolated from coffee beans, and the closely related ochratoxigenic species of section Nigri, A. carbonarius and A. niger are important sources of OTA in this substrate.