Ochratoxin A degrading enzymes of Stenotrophomonassp. 043-1a

Ochratoxin A is a secondary metabolite that acts as a mycotoxin and is produced by Aspergillus, Penicillium, and other fungal species. It is a threat to animal and human health due to nephrotoxic, carcinogenic, and genotoxic properties and its widespread incidence in agricultural products. To reduce this threat, biological remediation processes are of growing interest. The aerobic gram-negative bacterium Stenotrophomonassp. 043-1a, isolated from soil, was previously shown to degrade ochratoxin A into the non-toxic ochratoxin α and l-phenylalanine (Schatzmayr et al. 2002). However, the enzyme or enzymes catalyzing this reaction in this strain remained elusive. Here, we report the targeted purification of Stenotrophomonassp. 043-1a lysate via ammonium sulfate precipitation, size-exclusion chromatography, and hydrophobic interaction chromatography to identify the ochratoxin A degrading enzymes by subsequent peptide fragment fingerprinting. The metallo-dependent hydrolase Chr1_3858681_3267 and a member of the peptidase S9 family, Chr1_3858681_771, were shown to degrade ochratoxin A. This was, to our knowledge, the first report of an ochratoxin A degrading enzyme from the peptidase S9 family.