Ethanol producedfromrenewablebiomass,suchaslignocellulosicfeedstock,isoneofthealternative energy resourcesthatcanbeenvironmentallyfriendly.However,physicalandchemicalbarrierscaused by thecloseassociationofthemaincomponentsoflignocellulosicbiomass,aswellasstarch,hinderthe hydrolysisofcelluloseandhemicelluloseinlignocelluloseaswellasamylaseandamylopectininstarch to fermentablesugars.Oneofthemaingoalsofpretreatmentforenzymatichydrolysisistoincreasethe enzyme accessibilityforimprovingdigestibilityofcelluloseandstarch.Ultrasoundirradiationappliedto cellulosic materialsandstarch-basedfeedstockwasfoundtoenhancetheefficiency ofhydrolysisand subsequentlyincreasethesugaryield.Priorresearchconductedonapplyingultrasonictechnologyfor cellulose andstarchpretreatmenthasconsideredavarietyofeffectsonphysicalandchemical characteristics,hydrolysisefficiency andethanolyield.Thispaperreviewstheapplicationofultrasound irradiation tocelluloseandstarchpriortoandduringhydrolysisintermsofsugarandethanolyields. It alsoaddressescharacteristicssuchasaccessibility,crystallinity,degreeofpolymerization,morpholo- gical structure,swellingpower,particlesizeandviscosityasinfluenced byultrasonictreatment.
