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

Abstract

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 AFB_1. 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.

Keywords: AFB(1); Cytotoxicity; Degradation products; Evaluation; Hepatotoxicity; Laccase.