Degradation of aflatoxin B by a recombinant laccase from Trametes sp. C30 expressed in Saccharomyces cerevisiae: A mechanism assessment study in vitro and in vivo.

Aflatoxin B (AFB) is the most harmful mycotoxin and presents risks to human health. Utilization of enzyme to degrade AFB1 is a promising strategy to overcome this problem. In this study, we evaluated the effect of recombinant laccase expressed in Saccharomyces cerevisiae on the degradation of AFB. It was found that AFB could be degraded effectively by laccase up to 91%.The results of ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) showed that there were four main degradation products of AFB including CHO, CHNO, CHNO and CHO. Two possible degradation pathways were proposed: 1) AFB lost -CO continuously, and then double bonds of furan ring were broken after reactions with HO, H, and -NH; 2) AFB occurred decarbonylation reaction after losing -CO and double bonds were broken by additional reaction with H. Two toxicological activity sites in AFB, including a double bond of furo-furan ring and lactone ring in the coumarin in moiety, were destroyed. The toxicity of AFB degradation products was evaluated on HepG2 cells and in vivo tests, and the results indicated a decrease in hepatocytes apoptosis, liver and kidney histopathological lesions, oxidative stress, and inflammation as compared to non-laccase degraded AFB Moreover, the AFB degradation products significantly decreased the cytotoxicity and hepatotoxicity. This investigation provides innovative evidence on the effectiveness of laccase expressed in Saccharomyces cerevisiae in detoxifying AFB.