Abstract: Aflatoxin B1 (AFB1), a mycotoxin widespread in foods and feed, exerts carcinogenic, teratogenic, and mutagenic effects on humans and livestock, and has been classified as a Group 1 carcinogen by the World Health Organization. The exploration of efficient and thermostable AFB1-degrading enzymes is crucial for advancing the practical application of bioenzymatic approaches in the food and feed industries, as well as for establishing high-efficiency green strategies for AFB1 degradation. In this study, an AFB1-degrading strain HS-1 was isolated and identified as Bacillus paramycoides, and the active component responsible for AFB1 degradation was localized in the supernatant. Following heat treatment, the supernatant was evaluated for its AFB1 degrading capacity, showing that it achieved nearly complete degradation of 2 μg/mL AFB1 after 48 h reaction at 70 ℃ and pH 11. This implies the presence of an alkaline enzyme with excellent thermostability whose activity can be enhanced after high-temperature treatment. A thermostable alkaline CotA laccase with AFB1-degrading capacity was further identified from the B. paramycoides HS-1 genome. Under optimal conditions (80 ℃, pH 8, and 10 mmol/L methyl syringate as a mediator), this enzyme achieved 93.94% degradation of 2 μg/mL AFB1 after 12 h reaction. This research expands the resource pool of AFB1-degrading enzymes and provides a scientific foundation for the development of efficient and heat-resistant AFB1-degrading enzyme preparations.

Key words: Bacillus paramycoides; aflatoxin B1; CotA laccase; thermostability