Exo-metabolome of some fungal isolates growing on cork-based medium

Abstract

Fungal species colonize the cork slabs during the manufacturing of cork stoppers process. The most important fungal species that colonizes cork slabs immediately after boiling is Chrysonilia sitophila. Other fungal species may germinate replacing the C. sitophila mycelium on the cork slabs when the slabs’ water activity decreases below 0.9. The possible production of exo-metabolites or volatile compounds by some fungal species during the post-boiling stage was verified in pure cultures using three different media compositions. The results suggest that no deleterious exo-metabolites or mycotoxins are produced by the studied fungal species, both in cork medium or in cork medium added with C. sitophila extracts. However, the addition of C. sitophila extract to the cork medium enhanced the growth of the other studied fungal isolates and altered the respective exo-metabolome profile, leading to the assumption that in their natural habitat, the late cork colonizers like Penicillium spp. and Aspergilus spp. could take advantage from an earlier C. sitophila development as a result of its metabolism and/or mycelium remains. Fungal successions may thus not only be a function of time and substrate, but also they can be dependent of the remains of former colonizers. In fact, the production of the exo-metabolites by the studied fungal isolates suggests that, under the used experimental conditions, they appear to play an important role in fungal interactions amongst the cork mycoflora.