Immobilization of recombinant Trametes versicolor aflatoxin B1-degrading enzyme (TV-AFB1D) with montmorillonite for absorption and in situ degradation of aflatoxin B1.

Abstract

Aflatoxin B₁ is a highly carcinogenic and teratogenic substance mainly produced by toxin-producing strains such as Aspergillus flavus and Aspergillus parasitic. The efficient decomposition of aflatoxin is an important means to reduce its harm to humans and livestock. In this study, Trametes versicolor aflatoxin B₁-degrading enzyme (TV-AFB₁D) was recombinantly expressed in Bacillus subtilis (B. subtilis) 168. MMT-CTAB-AFB₁D complex was prepared by the immobilization of TV-AFB₁D and montmorillonite (MMT) by cross-linking glutaraldehyde. The results indicated that TV-AFB₁D could recombinantly express in engineered B. subtilis 168 with a size of approximately 77 kDa. The immobilization efficiency of MMT-CTAB-AFB₁D reached 98.63% when the concentration of glutaraldehyde was 5% (v/v). The relative activity of TV-AFB₁D decreased to 72.36% after reusing for 10 times. The content of AFB₁ in MMT-CTAB-AFB₁D-AFB₁ decreased to 1.1 µg/g from the initial 5.6 µg/g after incubation at 50 °C for 6 h. The amount of 80.4% AFB₁ in the MMT-CTAB-AFB₁D-AFB₁ complex was degraded by in situ catalytic degradation. Thus, the strategy of combining adsorption and in situ degradation could effectively reduce the content of AFB₁ residue in the MMT-CTAB-AFB₁D complex.