Influence of Saccharomyces cerevisiae and Rhotodorula mucilaginosa on the growth and ochratoxin A production of Aspergillus carbonarius

Abstract

The aim of the present study was to investigate the influence of two yeast species, namely Saccharomyces cerevisiae Y33 and Rhotodorula mucilaginosa Y38 on the growth and ochratoxin A (OTA) production of four Aspergillus carbonarius isolates, grown either individually or in mixed culture. Fungal growth was assayed at five temperatures (15, 20, 25, 30, and 35 °C) and in two growth media, Czapek Yeast Extract Agar (CYA) and grape juice medium (JA). Fungal/yeast interactions were studied at different inoculum levels. Specifically, yeast species were inoculated at 103, 104, and 105 CFU/mL whereas fungal inoculum was maintained at 105 conidia/mL. Results showed that in the case of single cultures, higher values of growth rates were observed for A. carbonarius ITEM 5010 (12.79 cm2/day) on CYA at 30 °C followed by the other fungal strains with growth rates ranging from 9.74 to 10.96 cm2/day. Significantly higher values were estimated when the aspergilli were grown on JA, with A. carbonarius F80 and ITEM 5010 presenting the highest (40.11 cm2/day) and lowest (17.68 cm2/day) values, respectively. Toxin data showed that the maximum OTA production depended on the isolate and culture conditions. Specifically, A. carbonarius F71 and F80 were the highest OTA producing fungi on CYA with 91,659.6 and 74,364.2 ng/g at 20 and 15 °C, respectively. Both yeasts, but primarily S. cerevisiae Y33, were able to suppress fungal growth and reduce OTA production. A. carbonarius mixed culture produced the highest OTA amount (14,182.2 ng/g) on CYA at 20 °C. However, when co-cultured at the same conditions with S. cerevisiae Y33 and R. mucilaginosa Y38, OTA production amounted to 5.3, 11.6, 10.2 and 26.8, 3027.4, 3103.8 ng/g for 103, 104, 105 CFU/mL yeast inoculum, respectively.