Preliminary study on the condition for liquefaction and saccharification of Dioscorea zingiberensis powder for ethanol fermentation

The tubers of Dioscorea zingiberensis are abundant in starch and can be used for ethanol fermentation. The properties of liquefaction and saccharification were investigated under mild conditions. Adding water to the powder of the tubers at first, and heating to a certain temperature, then adding α-amylase to the slurry and holding the temperature for certain time, after that, falling the temperature to 60℃ and adjusting the pH value, then adding glucoamylase and holding temperature in order to let starch transform to glucose completely. The results of single factor tests show that the optimal liquefaction conditions are that the size of Dioscorea zingiberensis particle >60 mesh, ratio of materials to water is 1∶5(m/m), the amount of α-amylase 10 U/g, 90℃ holding 30 min, and the optimal saccharification conditiones are as follows: pH 4.0～4.5, the amount of glucoamylase 60 U/g, 60℃ holding 90 min. The results suggest that the conversion of starch in Dioscorea zingiberensis using enzyme is feasible and effective.