INFLUENCE OF A CRUDE POLYSACCHARIDIC EXTRACT FROM LENTINULA EDODES ON PATULIN SYNTHESIS BY PENICILLIUM EXPANSUM AND ON THE ACTIVITY OF TWO BIOCONTROL YEASTS

The basidiomycetous edible fungus Lentinula edodes is very popular in Asia for its nutritional and medical properties. It produces lentinans, which are b-glucans displaying antioxidant, immuno- stimulating and anticancer effects. These polysaccharides have been reported to decrease the synthesis of mycotoxins by Aspergillus and Penicillium spp, possibly through the lentinanmediated stimulation of the antioxidant system of the toxigenic fungi. Wounds of stored apples are the main sites of penetration of Penicillium expansum, which synthesizes patulin in rotting fruits. Wounding of fruit tissues generates the reactive oxygen species superoxide anion (O2) and hydrogen peroxide (H2O2), which can cause oxidative stress to the yeasts used as biocontrol agents of postharvest diseases of fruits, thus hindering their timely colonization of wounds and their protection of apples from fungal pathogens. In this preliminary work, we report that the crude lentinan extracts from L. edodes strain CF23 caused an evident decrease in in vitro patulin synthesis by P. expansum and, in lab-scale experiments, enhanced the antagonistic activity of the biocontrol yeasts Cryptococcus laurentii LS28 and Rhodotorula glutinis LS11 against the same fungus on apple fruits. The influence of crude lentinans on ROS production by apple tissues and on the resistance of the biocontrol yeasts to oxidative stress is under assessment.