Potential of yeast antagonists on invitro biodegradation of ochratoxin A

Six antagonistic yeast strains were screened initially for their ability to degrade Ochratoxin A (OTA) in liquid medium amended with OTA (7.5 μg ml−1) and different concentrations of yeast cells at 30 °C. Highest OTA degradation was observed when the yeast cell concentration used at 1 × 108 cells/ml ranging from 7.8 to 84%. Out of six yeast strains, three strains [Metschnikowia pulcherrima (MACH1), Pichia guilliemonodii (M8) and Rhodococcus erythropolis (AR14)] were selected for further studies. In preliminary studies yeast strains were evaluated for their ability to degrade OTA at different temperature regimes (10, 15, 20, 25, 30 and 35 °C) and found that 30 °C was the optimum temperature for yeast growth and highest OTA degradation ranging from 10.4 to 83.5%. These three strains were further evaluated to test their potential on OTA degradation using different concentrations of OTA (5 and 10 μg ml−1) only at 30 °C. Three strains showed more or less same results with that of 7.5 μg ml−1 concentration ranging from 7.5 to 81%. The three yeast antagonists were further tested to confirm either degradation or cell wall adsorption of OTA at different time intervals. Among the strains, MACH1 effectively degraded the OTA (>80%) at 30 °C after 15 days incubation compared to other strains tested and few amounts of OTA adsorption was observed in the yeast cell wall. LC–MS studies revealed that no by-product like α-OT or Phenylalanine was found during the degradation process. Therefore, further studies are needed to understand the mechanism of action of these yeast strains during OTA degradation.