Screening and Identification of Zearalenone-Degrading Bacteria and Preliminary Extraction of Zearalenone-Degrading Enzyme
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Abstract:
A zearalenone (ZEN)-degrading bacterial strain was screened from soil using the enrichment culture method. ZEN was coated onto an inorganic salt medium as the sole carbon source in the initial screening, and the degradation rate of ZEN in the fermentation broth of the strain was used as the evaluation index in the second screening. The strain with the highest degradation rate was named A.lwoffi.Haut.1, which showed a degradation rate of 93.54% after co-incubation with 5 μg/mL ZEN in the fermentation broth for 48 h at 37 ℃. The strain was identified through 16S rDNA gene sequencing analysis, physiological and biochemical experiments, and observation of colony morphology, followed by the preliminary localization of its degradation active substances. Finally, the effectiveness of the tannic acid-polyethylene glycol and salt precipitation methods for crude ZEN-degrading enzyme extraction in cell-free supernatant was tested. A.lwoffi.Haut.1 was identified as a strain of Acinetobacter lwoffii. The highest ZEN-degradation rate of A.lwoffi.Haut.1 in cell-free supernatant was 82.31%, which decreased to 20.10%, 41.67%, and 18.68% after treatment with heat, protease K, and protease K+SDS, respectively, thus indicating that extracellular enzymes were the main degradation active substances. The degradation rate of the crude enzyme solution extracted using 15 mg/mL of tannic acid and 10 mg/mL of polyethylene glycol solution was 64.33%, and that using salt precipitation with 60% ammonium sulfate was only 20.30%. Therefore, the tannic acid-polyethylene glycol method was highly effective for the extraction of degradation enzymes. This study provides a research basis for investigating the bacterial degradation mechanism of ZEN and a new research material for ZEN biodegradation.
