Degradation of chlorothalonil through a hydrolytic dehalogenase secreted from Bacillus subtilis WB800
2015
Meng, Chao | He, Qin | Huang, Jun-Wei | Cao, Qin | Yan, Xin | Li, Shun-Peng | Jiang, Jian-Dong
To achieve the secretory expression of chlorothalonil hydrolytic dehalogenase (Chd), the chd gene was cloned into the vector pP43NMK under the control of the P43 promoter and the NprB signal peptide-encoding sequence and extracellularly expressed in the protease-deficient strain Bacillus subtilis WB800. The optimization of Chd production in submerged culture through Plackett-Burman and Box-Behnken designs enhanced the activity of Chd from 6.80 to 14.50 U l−1 and the protein expression amount from 1.93 μg ml−1 to 5.65 μg ml−1. The obtained Chd catalyzed a hydroxyl substitution at the 4-chlorine atom of chlorothalonil to form 4-hydroxy-trichloroisophthalonitrile, which is more soluble in water and easier to remove from the surface of vegetables. Six types of vegetables classified by the edible organ were selected for the chlorothalonil enzymatic degradation assay. After enzymatic reaction for 120 min, almost all of the 25 mg kg−1 chlorothalonil on cherry tomatoes was removed, approximately 82% of the 45 mg kg−1 chlorothalonil on lactuca sativa was removed, and approximately 40%–67% of the chlorothalonil on all other vegetables was removed. Moreover, the chlorothalonil eluted from the vegetables could be degraded to <1 mg l−1 after 3 h. The results of the present study demonstrated the potential of Chd to clean up chlorothalonil residue on the surfaces of vegetables.
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