Characterization of a Trametes versicolor aflatoxin B1-degrading enzyme (TV-AFB1D) and its application in the AFB1 degradation of contaminated rice in situ

Aflatoxin B(1) (AFB(1)) contaminates rice during harvest or storage and causes a considerable risk to human and animal health. In this study, Trametes versicolor AFB(1)–degrading enzyme (TV–AFB(1)D) gene recombinantly expressed in engineered E. coli BL21 (DE3) and Saccharomyces cerevisiae. The TV–AFB(1)D enzymatic characteristics and AFB(1) degradation efficiency in contaminated rice were investigated. Results showed that the size of recombinant TV-AFB(1)D expressing in E. coli BL21 (DE3) and S. cerevisiae was appropriately 77 KDa. The kinetic equation of TV-AFB(1)D was y = 0.01671x + 1.80756 (R(2) = 0.994, K(m) = 9.24 mM, and V(max) = 553.23 mM/min). The Kcat and Kcat/K(m) values of TV-AFB(1)D were 0.07392 (s(−1)) and 8 M(−1) s(−1), respectively. The AFB(1) concentration of contaminated rice decreased from 100 μg/ml to 32.6 μg/ml after treatment at 32°C for 5 h under the catabolism of TV-AFB(1)D. S. cerevisiae engineered strains carrying aldehyde oxidase 1 (AOX1) and Cauliflower mosaic virus 35 S (CaMV 35 S) promoters caused the residual AFB(1) contents, respectively, decreased to 3.4 and 2.9 μg/g from the initial AFB(1) content of 7.4 μg/g after 24 h of fermentation using AFB(1)-contaminated rice as substrate. The AFB(1) degradation rates of S. cerevisiae engineered strains carrying AOX1 and CaMV promoters were 54 and 61%, respectively. Engineered S. cerevisiae strains integrated with TV-AFB(1)D expression cassettes were developed to simultaneously degrade AFB(1) and produce ethanol using AFB(1)-contaminated rice as substrate. Thus, TV-AFB(1)D has significant application potential in the AFB(1) decomposition from contaminated agricultural products.