Microwave-Assisted Organic Acid Hydrolysis of Corncob in Bioethanol Production

The microwave-assisted hydrolysis of carbohydrate from corncob using acetic acid was investigated by response surface methodology. The sequence of variables affecting total reducing sugar concentration in the hydrolyzate was the ratio of corncob to acid solution > acid concentration > microwave heating time. The highest 84.2 g/L glucose concentration was obtained by 0.5 M acetic acid concentration with 0.40:1 corncob to acid solution ratio at 900 W microwave power for 10 min. The hydrolyzate prepared from the optimal hydrolysis condition was fermented by 8%w bakery yeast with pH 5.25 at 28°C for 62 h to achieve the optimum ethanol concentration of 32.2 g/L. This proposed that microwave-assisted organic acid hydrolysis is potential for producing fermentable sugars, and suggested that a two-step process for the ethanol is the satisfied production because of low cost, save energy consumption and friendly to environment.