Dynamics of cork mycobiota throughout stopper manufacturing process: from diversity to metabolite

Abstract

Cork, the continuous layer of outer bark of the Quercus suber L. tree, has physical and chemical properties that are unique. Portugal possesses 33 % of the world’s cork oak forests and accounts for approximately half of total global cork production. The manufacture of cork discs (or stoppers) comprises several stages, including two boiling stages, during which slabs of cork are steeped in boiling water. In days following the boiling the humidity of the slabs decreases and they become completely covered in a white mycelium of Chrysonilia sitophila until the cork achieves a certain water activity level (ca 0.9 aw). Below this level other fungal species (e.g. Penicillium, Aspergillus or Trichoderma) can germinate and shift the fungal colonization of the cork slabs. The two main objectives of the research described in the presented PhD thesis are (1) a taxonomic identification of the mycobiota present in cork slabs throughout the manufacture of cork discs, and (2) an investigation into the chemical compounds, which can give unfavourable properties to the cork, produced by these fungi.(...)