Study of fungal and bacterial laccases for the reduction of ochratoxin A content in model wine

Abstract

Ochratoxin A (OTA) is a mycotoxin produced by several filamentous fungi infecting grape bunches (Penicillium and Aspergillus spp.), this toxin pass to must when grapes are crushed and later it is found in wine. Following the evaluations of the toxicity of OTA, European Commission Regulations have been promulgated introducing upper limits for OTA concentrations in various commodities (cereals, cereal products, dried vine fruit, coffee, wine, grape juice, baby foods and dietary foods for special medical purposes). The use of fungal (Plerotus eryngii, Pleurotus pulmonarius and Trametes versicolor), and bacterial (Streptomyces coelicor) laccases permits to decrease Ochratoxin A, and other mycotoxins in buffer systems containing various natural and artificial redox mediators. Recently several laccases from lactic acid bacteria of wine and other foods have been isolated, identified and characterized. The aim of this research was to study the effect of synthetic and natural mediators on the degradation of Ochratoxin A (OTA) using laccases from Botrytis cinerea (fungal) and lactic acid bacteria. Studies were carried out in acetate buffer and model wine and evaluated the effect of different oenological factors (pH, SO2 and ethanol content). Quantification of OTA was accomplished by LC-QTOF analysis. Results showed that fungal and bacterial laccases alone were not effective in decreasing OTA content and the presence of redox mediators was required to achieve some reduction of OTA concertation, both in buffer and model wine.  Monomeric flavanols catechin and epicatechin were the most effective mediators among those assayed, followed by ferulic acid. Caftaric acid and the flavonols quercetin and quercetin-3-O-rutinoside were almost ineffective as mediators. SO2 at a concentration of 30 mg/L was able to completely prevent OTA degradation. These preliminary results confirmed the activity of laccase enzymes against ochratoxin A and provide knowledge on the effects of natural redox mediators suggesting new biological alternative strategies to eliminate undesirable substances present in wine.