Screening, identification and degradation efficiency evaluation of zearalenone-degrading bacteria

Abstract: [Objective] To screen efficient and practical zearalenone (ZEN) degrading strains and to preliminarily explore their degradation mechanism and degradation effect. 【Methods】 Using ZEN as the sole carbon source, strains were screened from moldy feed and soil samples. The strains were identified through morphological observation and 16S rDNA sequencing analysis. The correlation between strain growth rate and ZEN degradation rate was analyzed using culture time as a variable. The degradation activity of the strains was preliminarily analyzed and located by measuring the degradation rates of different active components and ZEN after inactivation treatment. The extraction effects of ammonium sulfate precipitation (ammonium sulfate saturation of 30%, 40%, 50%, 60%, 70%, and 80%) and tannin-polyethylene glycol (tannin concentrations of 2, 5, 10, 15, and 20 mg/mL; polyethylene glycol concentrations of 6, 8, 10, 12, and 14 mg/mL) on the crude degrading enzyme were compared. The molecular weight of the target active protein was determined by SDS-PAGE gel electrophoresis. Finally, the moisture content of moldy corn flour was adjusted using the strains and crude enzyme solution to determine the ZEN degradation effect. [Results] The experimental strain XJ-140 was screened and identified as *Bacillus amyloliquefaciens*. This bacterium could degrade 93.75% of ZEN (2 μg/mL) after 24 h of culture. Strain XJ-140 primarily degraded ZEN using extracellular enzymes, supplemented by cell wall adsorption. The ZEN degradation rates of the crude enzyme extracted by the ammonium sulfate precipitation method (60% ammonium sulfate saturation) and the tannin-polyethylene glycol method (optimal tannin concentration 10 mg/mL, optimal polyethylene glycol concentration 10 mg/mL) were 37.14% and 51.49%, respectively, with the tannin-polyethylene glycol method showing better extraction performance. The molecular weight of the target active protein is preliminarily estimated to be 61 kDa or 28 kDa. Furthermore, both the fermentation broth and crude enzyme solution of strain XJ-140 were able to degrade ZEN in moldy corn flour. 【Conclusion】The screened strain XJ-140 degrades ZEN through extracellular enzymes, and has a certain removal effect on ZEN-contaminated corn flour in practical applications.