Phenotypic traits underlying wound competence of postharvest biocontrol yeasts and degradation of mycotoxins by these microorganisms.

We had previously shown that wound competence of postharvest biocontrol agents (BCAs) acting against wound pathogens of apples relies on resistance of these microorganisms to reactive oxygen species (ROS: superoxide anion, O2-• and hydrogen peroxide, H2O2), generated by the fruit tissue as a consequence of wounding. In this work we report the in vitro comparison of the enzyme activities deactivating ROS (superoxide dismutase, SOD and catalase, CAT) and the antioxidant potential of culture filtrates of two biocontrol yeast strains displaying lower (Rhodothorula glutinis LS11) and higher (Cryptococcus laurentii LS28) wound competence and antagonistic activity. The more efficient antagonist LS28 showed significantly higher SOD and CAT activities and higher antioxidant potential of its culture filtrate. Recently, EU has released regulations (472/2002 and 1425/2003) setting the highest tolerable levels of the mycotoxins Patulin and Ochratoxin A (OTA), which contaminate apple-based food products and wine, as a consequence of infections by Penicillium expansum and Aspergillus carbonarius on apples and grape, respectively. Two BCAs of our collection (strain LS11 and Aureobasidium pullulans LS30) are able to degrade in vitro Patulin and OTA, respectively. Further, strain LS11 shows active reduction of Patulin also in vivo, i.e. in apples artificially infected by P. expansum.