Aflatoxins produced by Aspergillus are the potent carcinogenic compounds frequently found in foods contaminated with Aspergillus species of section Flavi. The purpose of this study was to determine the type(s) of aflatoxins in strains isolated from different food sources grown on different growth media; and to assess the impact of aflatoxins in reducing growth of soil nitrogen fixing bacteria. Three fungal strains; Aspergillus flavus (FCBP0616 and FCBP0862) and A. oryzae (FCBP1202) were assessed for aflatoxins production when grown in coconut cream and malt extract agar/broth. Preliminary screening indicated stronger signal of aflatoxins by A. flavus strains than A. oryzae under UV light. Mycotoxigenic assays through Thin Layer Chromatography (TLC) revealed presence of aflatoxins B1, G1 and G2 in all three stains grown on coconut cream agar with aflatoxin B1 as the most pronounced. Coconut broth medium showed maximum toxin production ability as compared to other media. Afterwards, extracted aflatoxins were screened for their efficacy against three bacteria; Azospirillum lipoferum, Azomonas agilis and Azotobacter insignis. Results revealed that toxins produced by A. flavus (FCBP0616) depicted maximum inhibitory effect on the growth of A. agilis and A. lipoferum while A. oryzae (FCBP1202) maximally influenced A. insignis. Results suggested that under different growth conditions ability of strains to produce aflatoxin(s) varies and presence of aflatoxigenic strains in soil reduces its fertility.
