Reduction of Ochratoxin A by Proteolytic Activity of Oenococcus oeni
Gisselle R. Apud, Diego A. Sampietro, and Pedro
Adrián Aredes Fernández*
*Facultad de Bioquímica, Química y Farmacia – Universidad
Nacional de Tucumán (UNT) – CONICET, Ayacucho 471, San Miguel de
Tucuman/Tucumán/4000), Argentina (pedroaredes@conicet.gov.ar)
Ochratoxin A (OTA) is a mycotoxin with harmful effects on health. Its occurrence in grapes and wine is mainly caused by Aspergillus carbonarius and Aspergillus niger. OTA decontamination using microorganisms is a safe and environmentally friendly control method. Several acid lactic bacteria with a proteolytic system have the ability to hydrolyze OTA. This is possible because OTA is the only mycotoxin with a peptide bond in its molecular structure. We demonstrated that Oenococcus oeni, the major species found in wine during malolactic fermentation, express proteolytic and peptidasic activities on grape juice and wine proteins under stress conditions. The aim of this work was to determine the ability of the O. oeni RAM 11 proteolytic system to reduce OTA concentrations. O. oeni RAM 11 was grown in MRS broth supplemented with 15% (v/v) tomato juice (pH 4.8) at 28°C until its exponential growth phase (OD560 0.8). Harvested and washed cells were suspended in 0.05 M citrate buffer, pH 5.0, and incubated at 28°C for two hours. The supernatant was collected to assay proteolytic activity and OTA reduction. Proteolytic activity was determined using sterile grape juice as substrate and the amino acids released were measured by Doi using ninhydrin reagent. Additionally, the supernatant was supplemented with 10 μg/L commercial OTA and incubated at 28°C for four hours. The OTA concentration was determined by ELISA competitive method using the OTA Ridascreen-Fast kit (R-Biopharm, Germany). Proteolytic activity was evidenced with a value of 0.230 mmol/L. This activity reduced 3.25 μg/L OTA in four hours. Thus, the proteolytic system of O. oeni RAM 11 can reduce OTA concentration enough to reduce or eliminate this mycotoxin during malolactic fermentation.
Funding Support: CONICET
