Mushrooms (white-rot basidiomycetes) such as Pleurotus ostreatus have multipurpose potential as they can create renewable alternatives for unsustainable materials such as plastics, meats, and leather by utilizing lignocellulosic biomass which is otherwise difficult and unsustainable to recycle. To develop such alternative materials efficiently using mushrooms, it is necessary to understand the structure and biosynthesis of mushroom cell walls.
Firstly, fractionation of the cell wall based on the alkali solubility of its components, and quantification of sugars, revealed the amount of constituent sugars in each fraction is much different from that of ascomycete fungi. Notably, content of α-glucan is much lower while β-glucan content is higher in P. ostreatus. The cell wall structure was visualized by confocal microscopy using α-glucan and β-glucan specific fluorescent probes with chitin staining by calcofluor white for P. ostreatus and the ascomycete Aspergillus nidulans. Imaging analysis revealed that the outermost layer of the cell wall is covered by β-glucan with occasional small α-glucan particles in P. ostreatus, whereas in A. nidulans it is covered with α-glucan. In P. ostreatus, the α-glucan layer was observed after β-glucanase treatment. These results indicated that there are big cell wall structure differences between ascomycete and basidiomycete fungi.
Therefore, we are starting to analyze cell wall polysaccharide synthases and transcription factors involved in the cell wall integrity signal transduction pathway in P. ostreatus. In this process, the modification of important mycelial characteristics for mushroom material was succeeded. Our studies demonstrate targets to improve hyphal structures for developing mushroom-based alternative materials.