Enzymatic Conversion of Waste (Rice Husk) into Fermentable Sugar through Diluted Acid Pretreatment

Abstract

The enzymatic production of fermentable-sugar from rice husk was examined using diluted sulfuric-acid as a pretreatment medium. In this study, 10 g of rice husk were separately pretreated with 0.5 M, 1.0 M and 1.5 M sulfuric acid at different time interval of 2-24 hours, prior to saccharification by cellulase-enzyme at 37°C and pH of 4.5. Then the quantity of monosaccharide produced was determined spectrophotometrically. After two hours of pretreatment, the 1.5 M H2SO4 pretreated samples yielded 88.05 mg/g (39.11%) of glucose, 1.0 M H2SO4  pretreated samples yielded 68.4 mg/g (30.38%), and 0.5M H2SO4 pretreated samples yielded 68.7 mg/g (30.51%) respectively, when compared with the un-pretreated sample (20.4 mg/g). However, after two hours, the production of glucose significantly reduced with increase time, except with 1.0 and 0.5 M H2SO4 pretreated sample which significantly increase at 4-hours (82.5 and 76.5 mg/g respectively). The result suggests that sulfuric acid enhances the release of fermentable-sugar, and that the yield is dependent on the concentration of acid and the time of treatment. The reduction in glucose yield over time as shown in the results could be due to the ability of the acid to liberate sugar which may be washed off during the washing process to remove the acid prior to the hydrolysis by enzyme.