Atividade ocratoxigênica de Aspergillus carbonarius e Asergillus niger na presença de dois isolados bacterianos

Abstract

Aspergillus carbonarius and Aspergillus niger stand out as a major source of contamination of ochratoxin A (OTA) in foods such as dried fruits, wine and coffe. For this reason it is very important to evaluate about their presence in food, the physicochemical conditions optimal for their growth and OTA production. Currently, several researches have been conducted in order to find microorganisms capable of exerting an antagonistic effect on the growth of A. carobonarius and A. niger and production of the OTA, as alternatives to chemical fungicides. This study aimed to find the physical and chemical condition most favorable to the action of antagonistic bacteria UFLABIO 05.1 and 35.1.1 UFLABIO forward to the growth of A. carbonarius and A. niger and OTA production by these fungi. For this we performed the co-cultivation of A. carbonarius and A. niger with each of the bacteria under different conditions of temperature, pH and water activity, using the Design Central Composite Rotational (DCCR) as a tool to optimize growing conditions. Both bacterial isolates, UFLABIO 05.1 and 35.1.1 UFLABIO were able, under certain physicochemical conditions, to inhibit the growth of A. carbonarius and growth of A. niger, besides reducing its production of ochratoxin A in vitro. The isolate UFLABIO 05.1, under a temperature of 27.5°C, pH of 5.35 and 0.99 water activity, although not interfering with the final growth of A. carbonarius, reduced by 77.6% the production of ochratoxin A. Under the same physicochemical conditions, the isolated UFLABIO 35.1.1, in addition to 86.6% reduction in the growth end of A. carbonarius, led to the production of ochratoxin A at levels not quantifiable. According the central composite rotational design (DCCR), the pH was the most significant factor on the antagonistic activity of UFLABIO 35.1.1 forward to the growth of A. carbonarius, with the highest values of pH favored their action against the growth of the bacterial isolate fungi. The UFLABIO 05.1 bacteria, under the temperature of 27.5 ° C, pH 5.35 and water activity of 0.99, despite not to interfere in the final growth of A. niger, decreased 78.7% in the production of ochratoxin A. Under the same physicochemical conditions, the isolated UFLABIO 35.1.1, in addition to 89.7% reduction in the growth end of A. niger reduced OTA production by 95.5%. According to the central composite rotational design (DCCR), the pH was the most significant factor on the antagonistic activity of UFLABIO 35.1.1 forward to the growth of A. niger, and the highest values of pH favored its action against fungal growth. Regarding the production of ochratoxin A, the same experimental design showed that temperature and pH were the most significant factors on the antagonistic activity of the same bacteria, with the highest values of temperature and pH favor its action against ochratoxin A production by Aspergillus niger.