Lentinan degradation in the Lentinula edodes fruiting body during postharvest preservation is reduced by downregulation of the exo-β-1,3-glucanase EXG2.

Lentinan from Lentinula edodes fruiting bodies (shiitake mushrooms) is a valuable β-glucan for medical purposes based on its anticancer activity and immunomodulating activity. However, lentinan content in fruiting bodies decreases after harvesting and storage due to an increase in glucanase activity. In this study, we downregulated the expression of an exo-β-1,3-glucanase, exg2, in L. edodes using RNA interference. In the wild-type strain, β-1,3-glucanase activity in fruiting bodies remarkably increased after harvesting, and 41.7% of the lentinan content was lost after 4 days of preservation. The EXG2 downregulated strain showed significantly lower lentinan degrading activity (60-70% of the wild-type strain) in the fruiting bodies 2-4 days after harvesting. The lentinan content of fresh fruiting bodies was similar in the wild-type and EXG2 downregulated strains, but in the downregulated strain, only 25.4% of the lentinan was lost after 4 days, indicating that downregulation of EXG2 enables keeping the lentinan content high longer.