Abstract
White-rot fungi are the only organisms capable of completely decomposing wood, and their industrial use is expected to expand for the conversion of agricultural waste and unused biomass into resources. Cell walls are important structures that protect cells from the external environment, but many aspects of the cell wall structure of basidiomycetes, including white-rot fungi, remain unclear. In this study, we developed a method for labeling cell walls polysaccharides with fluorescent probes and succeeded in visualizing the cell wall polysaccharide structure of the white-rot fungus Pleurotus ostreatus. The results of cell wall staining in Aspergillus oryzae, an ascomycete fungus, with P. ostreatus, suggest that there may be differences between ascomycetes and basidiomycetes in terms of the localization of cell wall glucans. In addition to development of cell wall staining techniques, a strain with a disruption of the gene pkac2, which is predicted to be involved in the regulation of multiple cell wall synthesis-related genes, was isolated to modify the cell wall structure of P. ostreatus. The Δpkac2 strain not only had a reduced amount of β-glucan in the cell wall, but also did not form pellets, enabling high-density culture in liquid medium. The wood-degrading enzyme production capacity of the Δpkac2 strain was evaluated, and it was found to have high cellulase and xylanase production capacity. These results indicate that the Δpkac2 strain can be efficiently cultured in liquid medium and will be a good candidate for the industrial production of wood-degrading enzymes.
