PJB-2020-446
Impact of Aflatoxins on Growth of Nitrogen Fixing Bacteria
Shazia Shafique
Abstract
Aflatoxins produced by the members of Aspergillus section Flavi are the most potent carcinogenic compounds frequently found in food materials 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; two of Aspergillus flavus (FCBP0616 and FCBP0862) and one A. oryzae (FCBP1202) were assessed for aflatoxins production when grown in coconut cream and malt extract agar/broth media. Preliminary screening carried out on agar media 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 significant decline in growth of all bacteria. Toxins produced by A. flavus (FCBP0616) depicted maximum inhibitory effect on growth of A. agilis and A. lipoferum while A. oryzae (FCBP1202) maximally influenced on 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.
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