Isolation, Identification of Bacillus siamensis DY3123 and Its Degradation Effect on Aflatoxin B1

Abstract:

[Objective] This study aimed to screen out a microbial strain capable of degrading aflatoxin B₁ (AFB₁) and decipher the degradation mechanism. [Method] With coumarin as the sole carbon source, AFB₁-degrading strains were isolated and screened from the larval gut of Monochamus alternatus (Coleoptera: Cerambycidae), and the degradation mechanism for AFB₁ was investigated. [Result] After primary screening and re-screening, a strain with the degradation rate reaching 94.71% for AFB₁ was obtained, and this strain was identified as Bacillus siamensis (B. siamensis) DY3123. The results of experiments on the degradation of AFB₁ by different cellular components indicated that the main active substances responsible for degrading AFB₁ were from the cell-free culture supernatant of B. siamensis DY3123, which showed the optimum degradation performance at 80 ℃ and pH 8.0 after 36 h. Cu²⁺ improved the degradation activity of the cell-free supernatant, while Zn²⁺, Mg²⁺, and Fe³⁺ exerted inhibitory effects. In addition, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (methyl thiazolyl tetrazolium, MTT) assay was employed to examine the effects of the degradation products on the viability of lymphocytes, which indicated that the degradation products had no significant impact on cell viability. [Conclusion] The findings lay a foundation for the application of B. siamensis DY3123 in the food and animal feed industry.