Isolation and Characterization of Sphingopyxis sp. Q841: A New Zearalenone- Degrading Strain.

Zearalenone (ZEN) is a mycotoxin exhibiting estrogenic activity that poses a considerable risk to human health. In this study, a ZEN-degrading bacterium isolated from soil was identified as Sphingopyxis sp. and designated strain Q841. Q841 completely degraded 5 mg/L of ZEN within 4 h in mineral medium. It showed the highest activity within the tested ranges (25-37°C, pH 4.0-9.0), with optimal activity at pH 9.0 and 37°C. Assays of degradation efficiency in different fractions indicated that the ZEN-degrading activity was mainly associated with intracellular components rather than with the extracellular fraction. LC-TOF-MS/MS analysis identified the major degradation product as 1-(3,5-dihydroxyphenyl)-6'-hydroxy-1'-undecen-10'-one, a compound previously reported to be non-estrogenic. A candidate hydrolase responsible for ZEN degradation, designated ZenQ, was identified through BLASTp analysis of proteins predicted from the Q841 genome, and its optimal catalytic conditions were determined to be 45°C and pH 8.0. In practical assessment using naturally contaminated distillers dried grains with solubles, treatment with Q841 reduced ZEN from 1.2 mg/kg to 0.28 mg/kg, below the EU feed safety limit of 500 µg/kg. These findings demonstrate that Sphingopyxis sp. Q841 possesses remarkable potential for ZEN biodegradation.