Screening and characterization of a salt-tolerant aflatoxin B₁-degrading strain isolated from Doubanjiang, a Chinese typical red pepper paste

Abstract

Aflatoxin B₁ (AFB₁) is a carcinogenic mycotoxin present in many foods, posing a serious human health problem. Oriental high-salt fermented foods are highly susceptible to AFB₁ contamination due to their production process and condition. Therefore, it is necessary to isolate microbial resources that can remove AFB₁ in a high-salt condition. In the current study, forty-nine salt-tolerant microorganisms with the ability to remove AFB₁ were isolated from Doubanjiang, a Chinese typical high-salt red pepper paste. Among them, Bacillus velezensis AD8 had the highest removal rate of AFB₁. The AFB₁ removal activity of B. velezensis AD8 was mainly attributed to culture supernatant, and it was sensitive to sodium dodecyl sulfate (SDS) or/and proteinase-K treatment, which indicated that extracellular enzyme contributed to the degradation of AFB₁. The optimal incubation time, pH value and NaCl concentration of the initial medium for degradation of AFB₁ by the B. velezensis AD8 were investigated. In addition, the AFB₁ concentration had no significant effect on degradation activity. The addition of nitrogen source, Mg²⁺ and Mn²⁺ stimulated degradation rate, whereas addition of carbon source, Zn²⁺ and Fe²⁺ inhibited degradation. Thus, B. velezensis AD8 might be a potential candidate to degrade AFB₁ in high-salt food matrices.

Keywords:
aflatoxin B₁ (AFB₁); biodegradation; salt tolerance; Bacillus velezensis AD8