Waste Shiitake (Lentinula edodes) mushroom medium, a lignocellulosic aglicultural residue, was evaluated as a fermentable substrate. 87% of the fermentable sugars remained in the waste mushroom medium. The sugar yield of the waste mushroom medium (46.3%) was higher than that of raw mushroom medium (20.3%) after 48 h of enzymatic saccharification by Meicelase because L. edodes changed wood structure. These results indicated that the waste mushroom medium is a suitable substrate for fermentation. Next, the efficient ethanol production using steam explosion pretreatment was studied. After 30 h of simultaneous saccharification and fermentation (SSF) using Meicelase and Saccharomyces cerevisiae AM12, 20.0 g/L ethanol was produced from 100 g/L water-insoluble residue of the waste mushroom medium treated at a steam pressure of 20 atm and a steaming time of 5 min. This corresponded to an ethanol yield of 77.0% of the theoretical, i.e. 14.7 g of ethanol obtained from 100 g of waste mushroom medium.
