Progress and Research Needs of Plant Biomass Degradation by Basidiomycete Fungi

Abstract

Basidiomycete fungi are efficient organisms for conversion and degradation of plant biomass. This is due to combination of their extracellular enzymes and chemical reactions targeted to plant cell wall degradation. Wood- and litter-decomposing white rot fungi have unique ability to degrade and even mineralize all polymeric components of plant cell walls, including aromatic lignin, which makes them promising candidates for biotechnological applications using plant biomass as feedstock. Rapidly increasing whole genome sequence data has revealed the content of plant biomass modification related genes in different basidiomycete species. Comparative genome analyses have enlightened evolutionary events that have led to development of different fungal plant cell wall decay strategies, which are reflected in nuances detected between basidiomycete rot types and life styles in nature. However, basidiomycete genomes harbour a large number of genes encoding proteins with unknown functions, which remains to be characterized to fully understand the degradation process. In addition, fungal aromatic metabolism of plant biomass-derived compounds has gained relatively little attention, although aromatic metabolic enzymes specifically acting on lignin structures would provide interesting options for biotechnological use. Still, low production levels of basidiomycete enzymes in commonly used ascomycete or bacterial host organisms often hamper their use in biotechnological applications. Another aspect that is in its infancy in basidiomycetes and restricts the use of their full potential is understanding of the regulatory systems driving the production of plant biomass-degrading enzymes. In this chapter, recent developments in basidiomycete research with respect to plant biomass conversion will be discussed.