Influence of environmental conditions of atoxigenic Aspergillus flavusHFB1 on biocontrol of patulin produced by a novel apple contaminant isolate, A. terreusHAP1, in vivo and in vitro

Patulin (PAT) is a mycotoxin produced in food and feed stuff by several filamentous fungi causing sever hazard for the human being. A novel fruit contaminant strain, A. terreusHAP1, was isolated from Egyptian apples. Screening study showed that A. terreusHAP1 produced a significant amount of PAT in its culture broth. Three atoxigenic strains of A. flavus, isolated from Egyptian fruits, were tested as biocontrol agents against A. terreusHAP1. The results showed that A. flavusHFB1 was the most potential agent for controlling of pathogen growth. The biocontrol activity of this strain was tested for reduction of patulin produced by A. terreusHAP1 in culture medium and in apple fruits under different environmental conditions. The maximum percentage of mycotoxin reduction was recorded when 1 x 10(6) spores of pathogen was co-cultured with 1 x 10(8) spores of antagonist in Potato Dexstrose Broth (PDB) medium adjusted at pH 5 and incubated at 30 degrees C for 15 days. In vivo study, A. flavusHFB1 reduced 62.43 +/- 4.34% and 58.53 +/- 4.6 of PAT in Egyptian and golden apples, respectively, whereas the rotting lesion increased in Egyptian apples faster than the other cultivars. The maximum reduction of patulin accumulation without apples decaying was detected when the Egyptian apples were pre-treated with 1 x 10(8) spores of A. flavusHFB1 at 36 h earlier their infection with A. terreusHAP1 and stored at 15 degrees C for 20 days. The fruits totally decayed after 15 days of storage at 30 degrees C whereas they decayed totally after 55 days of storage at 15 degrees C.