Biodegradation of aflatoxins by bacteria

Abstract

Aflatoxins (AFs) have great side effects on human, animals and crops. It causes severe illness to both human and animals, and play a major role in economic loss. Biological decontamination seems to be attractive. The present investigation aimed to found new and safe microorganisms able to degrade AFs and inhibit its producing fungi. Forty three bacterial isolates were isolated from different cultivated soils and animal feces. All isolates were screened for their ability to degrade AFs using Thin Layer Chromatography (TLC). Nine bacterial isolates were able to degrade AFs using TLC and HPLC. HPLC results showed that AFs degradation ratio higher than 90% occurred by 3 bacterial cultures. The identification of the highly degrading isolate CaG6 (with 98.1% degradation ratio) was established by using 16S rRNA gene sequencing as Bacillus cereus. Then sequence was acquiesced to GenBank in accession number MG 751322 with 99% similarity to Bacillus cereus. Bacterial isolates CaG7 and IsW1 (with 94.6, 90.7% degradation ratio, respectively) has been identified by MALDI-TOF MS using the VITEK MS system (bioMérieux) as Brevibacillus sp1 and Brevibacillus sp2. Results showed that cell cultures (viable cells) were more effective in the degradation of AFs than cell free supernatant (CFS), while ppt exhibited no degradation. The three bacteria not only reduced AFs but it could also inhibit Aspergillus flavus NRRL 3145 with inhibition zone ≥20mm after incubation for 96h at 28°C. The AFs degradation by B. cereus, Brevibacillus sp1 and Brevibacillus sp2 enhanced by addition Mn+2 ions to the liquid media.