Biodegradation of aflatoxin B1 in contaminated rice straw by Pleurotus ostreatus MTCC 142 and Pleurotus ostreatus GHBBF10 in the presence of metal salts and surfactants.

Aflatoxin B1 (AFB1) is a highly toxic fungal metabolite having carcinogenic, mutagenic and teratogenic effects on human and animal health. Accidental feeding of aflatoxin-contaminated rice straw may be detrimental for ruminant livestock and can lead to transmission of this toxin or its metabolites into the milk of dairy cattle. White-rot basidiomycetous fungus Pleurotus ostreatus produces ligninolytic enzymes like laccase and manganese peroxidase (MnP). These extracellular enzymes have been reported to degrade many environmentally hazardous compounds. The present study examines the ability of P. ostreatus strains to degrade AFB1 in rice straw in the presence of metal salts and surfactants. Laccase and MnP activities were determined spectrophotometrically. The efficiency of AFB1 degradation was evaluated by high performance liquid chromatography. Highest degradation was recorded for both P. ostreatus MTCC 142 (89.14 %) and P. ostreatus GHBBF10 (91.76 %) at 0.5 µg mL(-1) initial concentration of AFB1. Enhanced degradation was noted for P. ostreatus MTCC 142 in the presence of Cu(2+) and Triton X-100, at toxin concentration of 5 µg mL(-1). P. ostreatus GHBBF10 showed highest degradation in the presence of Zn(2+) and Tween 80. Liquid chromatography-mass spectrometric analysis revealed the formation of hydrated, decarbonylated and O-dealkylated products. The present findings suggested that supplementation of AFB1-contaminated rice straw by certain metal salts and surfactants can improve the enzymatic degradation of this mycotoxin by P. ostreatus strains.