Interactions between Bacillus amyloliquefaciens AG1 and Aspergillus spp. contaminating food and feedstuffs

Aspergillus is a widespread fungal genus contaminating and degrading food and feeds mostly during storage. Some species can also produce carcinogenic mycotoxins harmful for human and animal health. In this study, Bacillus amyloliquefaciens AG1 (BaAG1), active against fungal pathogens was evaluated by in vitro tests against seven Aspergillus species belonging to six Aspergillus sections. After 7 days of incubation at 25°C, mycelial growth of all fungal species was reduced from 46.53% to 60.92%, compared to the controls. The inhibitory effect of BaAG1 cell-free culture filtrate was tested by turbidimetric measurements by using ScanReady P-800 that allow the automatic and continuous monitoring of the changes in the O.D. of fungal growth over time. Two culture mediums for growth curve optimization were tested, and PDB (Potato Dextrose Broth) was selected. The activity of two concentration of BaAG1 cell-free culture filtrate against three strains (Aspergillus niger SAAF 7, A. flavus SAAF 43 and A. fumigatus SAAF 47) was assessed over 7 d periods with automated measurements every 60 min. Significant differences in AUC (area under growth curve) were recorded between the treatments and the controls. Furthermore, macro and microscopic observation on the fungal colonies showed that both the concentrations of BaAG1 culture filtrates induced morphological changes, such as absence of conidiophores and conidia, presence of cleistothecia and hyphal alterations.