Degradation of aflatoxin B1 by fungal laccase enzymes

The enzymatic degradation of aflatoxin B1 (AFB1) by white rot fungi through laccase production was investigated in different liquid media. A significant (P < 0.0001) correlation was observed between laccase activity and AFB1 degradation exhibited by representatives of Peniophora and Pleurotus ostreatus cultivated in minimal salts (MSM) (r = 0.93) and mineral salts — malt extract (MSB–MEB) (r = 0.77) liquid media. Peniophora sp. SCC0152 cultured in MSB–MEB liquid medium supplemented with veratryl alcohol and sugarcane bagasse showed high laccase activity (496 U/L), as well as 40.45% AFB1 degradation as monitored using high performance liquid chromatography. P. ostreatus St2-3 cultivated in MSM liquid medium supplemented with veratryl alcohol resulted in laccase activity of 416.39 U/L and 35.90% degradation of AFB1. Aflatoxin B1 was significantly (P < 0.0001) degraded when treated with pure laccase enzyme from Trametes versicolor (1 U/ml, 87.34%) and recombinant laccase produced by Aspergillus niger D15-Lcc2#3 (118 U/L, 55%). Aflatoxin B1 degradation by laccase enzyme from T. versicolor and recombinant laccase enzyme produced by A. niger D15-Lcc2#3 coincided with significant (P < 0.001) loss of mutagenicity of AFB1, as evaluated in the Salmonella typhimurium mutagenicity assay. The degradation of AFB1 by white rot fungi could be an important bio-control measure to reduce the level of this mycotoxin in food commodities.