Crescimento de Aspergillus carbonarius e Aspergillus ochraceus e produção de ocratoxina A em meio de cultura sintético e a base de produtos agrícolas

Abstract

Mycotoxins are secondary metabolites produced by different filamentous fungiand can be found in different agricultural products. Among the currently known mycotoxins, the ochratoxin A stands out, produced mainly by species of Aspergillus and Penicillium, which has nephrotoxic, teratogenic and immunotoxic properties representing a serious risk to human and animal health. Their presence in any food or beverage is undesirable from an economic and health point of view. The objective of this study was to evaluate the growth rate and production of ochratoxin A by Aspergillus carbonarius and Aspergillus ochraceus in different synthetic and food-based culture media. Culture media based on green coffee beans and, wheat and corn meal were used, which were prepared in the following proportions : 30 g of feed, 20 g of agar and 1000 ml of water, and the synthetic culture medium: Yeast Extract Sucrose Agar(YES) prepared according to package directions. A. ochraceus and A. carbonarius were inoculated in the four culture media and incubated in a chamber at 15 °C and 25 °C for 25 days. The colony diameter measurements were taken every 48 hours for growth rate description. The initial screening of OTA production was done through Layer Chromatography (TLC). Quantification of OTA was performed by High Performance Liquid Chromatography (HPLC) for three different periods (5th to 15th and 25th day). The pH measurements were performed by Quantitative test strips. A. carbonarius dramatically lowered the pH of the media tested, reaching the acid value of 2. All isolates showed a higher growth rate in YES medium at 25 °C, however, there was growth in all culture media at both temperatures. The culture medium leading to the lowest growth rate was the corn based medium. The medium that most induced the production of OTA was YES. In culture media based on the food isolates, A. ochraceus produced low amounts of OTA, reaching a maximum of 0.39 mg / g . However, isolates of A. carbonarius produced a much higher amount, highlighting the CDCA0126 isolates that produced 29.83 mg/g at 15° in YES, 13.06 in the wheat based at 15 °C and isolate CDCA0169 that produced 8.3μg/g in the coffee medium at 15 °C. Isolate CDCA0126 produced 5.07 mg/g in the coffee medium at 25 ° C. Therefore, we conclude that different conditions of temperature, incubation time and substrate type can influence fungal growth, as the production of ochratoxin A, and that knowing the favorable and unfavorable conditions for the synthesis of OTA, it is possible to minimize the chances of food contamination.