Biochemical characterization and application of glycoside hydrolases from Lentinula edodes

Abstract

<i>Lentinula edodes</i> (shiitake) is a white-rot fungus that can break down plant cell wall carbohydrates including cellulose, hemicellulose, and pectin by glycoside hydrolases (GHs). Among these, degradation of pectin has been suggested to be important for the initial stages of wood decay. We purified and characterized a pectin-degrading enzyme from <i>L. edodes</i> (LePG28A) that has endotype polygalacturonase activity. The enzyme showed synergistic action with oxalic acid in the degradation of calcium polygalacturonate gel, indicating that oxalic acid has a role in the chelation of calcium ions from pectic substrates. The cell walls of fungi such as <i>L. edodes</i> are constructed mainly from chitin and β-1,3/1,6-glucans. Therefore, fungi also produce GHs associated with cell wall polysaccharides. Lentinan is aβ-1,3/1,6-glucan with physiological activities that are found in fresh <i>L. edodes</i> fruiting bodies. Lentinan content in mushrooms decreases rapidly during post-harvest storage due to the actions ofβ-1,3-glucanases. We developed a shiitake mushroom strain with high lentinan content through the downregulation ofβ-1,3-glucanase EXG2.