Identification and functional characterization of a novel amidohydrolase involved in ochratoxin A degradation by Acinetobacter baumannii HAU425.

Ochratoxin A (OTA) is a widespread mycotoxin calling for the development of effective strategies for its decontamination. In this study, a highly efficient OTA-degrading bacterium Acinetobacter baumannii HAU425 was isolated from soil with ochratoxin α (OTα) as the degradation product. The identification of OTA hydrolase from strain HAU425 was carried out by combining genome mining with gene cloning and heterologous expression technologies. A novel amidohydrolase Amse was found to show OTA hydrolase activity, which could achieve 93 % OTA degradation in 5 min. Amse shared low amino acid sequence identity (38-43 %) with other previously reported OTA hydrolases. More impressively, Amse retained 72 % of its maximum activity at 20 °C. The deletion of Amse gene did not affect the growth of strain HAU425, but led to 60 % reduction of OTA degradation by the strain. Moreover, the addition of Amse at 5 μg mL could degrade 87 % of 5 ng mL of OTA in grape juice at 20 °C within 3 h, while retaining the quality of grape juice. These findings shed new light on OTA biodegradation mechanism and the utilization of enzymes for detoxifying OTA in fruit products.