Ochratoxin A (OTA) is widely found in food and feed products as a mycotoxin contaminant. It is produced by Penicillium species and several Aspergillus species. The identification OTA detoxification microorganisms is believed to be the best approach for decontamination. In this study, we isolated ASAG1, a bacterium with the ability to degrade OTA effectively, from grain depot-stored maize. A 16S rDNA sequencing approach was used to identify this strain as Bacillus amyloliquefaciens ASAG1. The degradation of OTA was detected in both medium and cell-free extracts after incubation with a culture of B. amyloliquefaciens ASAG1 cells. Subsequently, a hydrolysed enzyme (carboxypeptidase) related to the enzymatic conversion of OTA was cloned from the B. amyloliquefaciens ASAG1 genome. Using the Escherichia coli Expression System, we successfully expressed and purified this carboxypeptidase. When this enzyme was incubated with the engineered recombinant E. coli cells, the concentration of OTA was dramatically degraded. Our data therefore indicate that the carboxypeptidase produced by B. amyloliquefaciens ASAG1 is likely responsible for the biodegradation of OTA.
Keywords: Bacillus amyloliquefaciens; biocontrol; carboxypeptidase; ochratoxin A.