Extracellular enzymes secreted in the mycelial block of Lentinula edodes during hyphal growth

Abstract

Abstract Lentinula edodes (shiitake mushroom) is one of the most widely cultivated edible mushrooms and is primarily cultivated using sawdust medium. While there have been improvements in the cultivation technology, the mechanism of mycelial block cultivation, such as mycelial growth and enzymatic sawdust degradation, has not been clarified. In this study, the mycelium was elongated longitudinally in the bottle sawdust culture for 27 days. The cultivated sawdust medium was divided into three sections (top, middle, and bottom parts), and the enzymatic activities of each part were analyzed. In the bottom part of the medium, amylase, pectinase, fungal cell wall degradation enzyme (β-1,3-glucanase, β-1,6-glucanase, and chitinase), and laccase activities were higher than in other parts, indicating that these enzymes are produced from the tip region and have important roles for mycelial spread and nutrient uptake. Proteins with the laccase activity were purified from the bottom part of the medium, and a laccase was identified as Lcc13. On the other hand, lignocellulose degradation enzymes, such as endoglucanase, xylanase, and manganese peroxidase were highly secreted in the top part. The results indicate that the principal sawdust degradation occurs after mycelial colonization.