Degradation of aflatoxin B1 by a recombinant laccase from Trametes sp. C30 expressed in Saccharomyces cerevisiae: A mechanism assessment study in vitro and in vivo

Aflatoxin B1 (AFB1) 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 AFB1. It was found that AFB1 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 AFB1 including C16H22O4, C14H16N2O2, C7H12N6O and C24H30O6. Two possible degradation pathways were proposed: 1) AFB1 lost –CO continuously, and then double bonds of furan ring were broken after reactions with H2O, H+, and –NH2; 2) AFB1 occurred decarbonylation reaction after losing –CO and double bonds were broken by additional reaction with H+. Two toxicological activity sites in AFB1, including a double bond of furo-furan ring and lactone ring in the coumarin in moiety, were destroyed. The toxicity of AFB1 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 AFB1. Moreover, the AFB1 degradation products significantly decreased the cytotoxicity and hepatotoxicity. This investigation provides innovative evidence on the effectiveness of laccase expressed in Saccharomyces cerevisiae in detoxifying AFB1.