Toxicity of ochratoxin A in aBrevibacillus brevis — Growth inhibition assay

Ochratoxin A (OTA) is a nephrotoxic, carcinogenic and immunosuppressive mycotoxin. It can be detoxified by various microorganisms, e.g. different yeast strains, via metabolisation into ochratoxin α (OTα). Within this study a growth inhibition assay was developed to compare the toxicity of OTA and its degradation product OTα. As an indicator organismBrevibacillus brevis was used. The assay was performed in microtiterplates. Growth inhibition was determined by comparing the optical density values ofBrevibacillus brevis cultures grown in medium supplemented with OTA/OTα and OTA/OTα-free medium, respectively.It could be shown thatB. brevis is sensitive to OTA (EC100=0.5 mg/L±0.03 mg/L), which is not the case for its metabolite OTα. Therefore this bioassay is a useful tool to show the detoxification of OTA to OTα by microbial degradation.