Solid-state cultivation of Aspergillus oryzae using insoluble plant cell wall polysaccharides and expression analyses of plant polysaccharide degradation-related enzymes

Aspergillus oryzae produces multiple plant polysaccharide degradation-related enzymes, which make an important contribution to brewing and biotechnology. In this study, to clarify the mechanisms underlying the enzymatic degradation of plant cell wall polysaccharides by A. oryzae, we prepared insoluble plant cell wall polysaccharides from two plants, mung bean hypocotyls and Chinese chives, and used these as substrates for solid-state cultivation of this fungus. A. oryzae secretes numerous types of carbohydrate-active enzymes that are involved in the degradation of cellulosic and hemicellulosic polysaccharides among insoluble plant cell wall polysaccharides. Transcriptomic analyses revealed that genes encoding both characterized and uncharacterized carbohydrate-active enzymes were highly expressed in solid-state cultures using insoluble plant cell wall polysaccharides, indicating that these enzymes cooperatively degrade plant cell wall polysaccharides.