Conversion of coffee residue waste into bioethanol with using popping pretreatment

Coffee residue waste (CRW), which is produced after coffee extraction for coffee powder and instant coffee preparation, is a primary industrial waste. In this study, the use of CRW for bioethanol production was evaluated. The carbohydrate content of CRW was analyzed for fermentable sugars such as glucose, galactose, and mannose, which can be fermented by Saccharomyces cerevisiae. Pretreatment at a pressure of 1.47 MPa for 10 min with popping pretreatment was required to increase enzymatic hydrolysis. CRW was well hydrolyzed following popping pretreatment at 1.47 MPa. The enzymatic conversion rate of CRW to fermentable sugars was 85.6%. Ethanol concentration and yield (based on sugar content) following enzymatic hydrolysis after simultaneous saccharification and fermentation were 15.3 g/L and 87.2%, respectively.