Preparation of recombinant Kluyveromyces lactis agents for simultaneous degradation of two mycotoxins.

Aflatoxin B 1 (AFB 1 ) and zearalenone (ZEN) are widely distributed in corns, peanuts, and other cereals, causing serious threat to food safety and human health. As shown by our previous studies, the recombinant yeast strain Kluyveromyces lactis GG799(pKLAC1-ZPF1) had the ability of degrading AFB 1 and ZEN simultaneously. In this work, the agent preparation process was optimized for K. lactis GG799(pKLAC1-ZPF1), and the storage conditions of the prepared yeast agents were investigated, for obtaining the products with high storage activities and potent mycotoxin degradation efficiency. The optimal preparation process was as follows: centrifugation at 6000 rpm for 15 min for collection of the yeast cells, spray drying with the ratio of protective compounds to yeast cells at 3:1 (w/w) and then stored at - 20 °C. Simultaneous degradation tests of AFB 1 and ZEN were performed using the supernatants of reactivated yeast agents after three months of storage, and the degradation ratios for AFB 1 and ZEN in reaction system 1 (70.0 mmol/L malonic buffer, pH 4.5, with 1.0 mmol/L MnSO 4 , 0.1 mmol/L H 2 O 2 , 5.0 μg/mL AFB 1 and ZEN, respectively) were 48.2 ± 3.2% and 34.8 ± 2.8%, while that for ZEN in reaction system 2 (50.0 mmol/L Tris-HCl, pH 7.5, with 5.0 μg/mL AFB 1 and ZEN, respectively) was 30.1 ± 2.7%. Besides, the supernatants of reactivated yeast agents degraded more than 80% of AFB 1 and 55% of ZEN in contaminated peanuts after twice treatments. Results of this work suggested that the optimized process for K. lactis GG799(pKLAC1-ZPF1) was with high value for industrial applications.