BACTERIA SCREENING FOR OCHRATOXIN A BIODEGRADATION POTENTIAL

Ochratoxin A (OTA) is frequently found as a contaminant of foods and animal feed across the world. Also, OTA is considered as a potentially carcinogenic substance and has been associated to the development of several pathologies in animals and humans. Several detoxification methods have been investigated for mycotoxins in foods and feed through the years. Nevertheless, only few are currently accepted, and most of strategies are based on the application of adsorbents in animal feed. Degradation of mycotoxins by selected microorganisms has proven to represent a practical and advantageous approach, since it excludes the presence of chemical residues and minimizes nutritional losses in the treated product. Thereon, the objective of this study was to evaluate the detoxifying potential of 107 bacterial strains, previously isolated from maize (30), soil (23), and salami (54), against OTA. Initially, Aspergillus sclerotioniger CECT 20583 was grown in tryptic soy broth (TSB) for OTA production. HPLC quantification has identified a concentration of 677 ppb in the culture after sterilization by filtration. Then, 0.5 mL of the OTA solution was transferred to 1.5 mL microtubes along with 0.4 mL of fresh TSB and 0.1 mL of either bacterial inoculum. The inoculum preparation consisted of fresh cultures of bacteria – maize and soil isolates incubated for 24 h at 30 °C in brain heart infusion (BHI) broth, and salami isolates for 24 h at 37 °C in de Man, Rogosa and Sharpe (MRS) broth – diluted to 0.5 McFarland scale with TSB. Microtubes were then incubated in shaker at 50 rpm for 24 h at the respective above-mentioned temperatures. After incubation, tubes were centrifuged in MiniSpin® at 13400 rpm for 10 min. Supernatants were syringe-filtered (0.22 µm) and directly injected in HPLC for OTA quantification. Compared to initial OTA concentration, there were significant reductions in most of the analyzed samples. Among results, 5, 7, and 7 strains isolated from maize, soil, and salami, respectively, promoted reductions equal or greater than 30%, being 2 strains able to reduce the OTA 677 ppb initial concentration to 28 and 119 ppb. Identification of active strains and biochemical essays will be further performed to verify the pathways of OTA degradation. In that way, specific isolated enzymes or the microorganism itself might be purified for the application in foods and animal feed.