With increasing concerns about the global warming issue mainly caused by the huge amount of carbon dioxide released into the atmosphere and dwindling oil supplies urge people to change the situation that fuels and chemicals are heavily dependent on fossil feedstocks.Therefore,clean and renewable energy,such as fuel ethanol should be utilized.Currently,the techniques of fuel ethanol production using lignocellulosic biomass have attracted much attention.A key to converting lignocellulosic biomass to fuel ethanol is effectively producing fermentable sugars through hydrolysis of polysaccharides from the biomass.At present,either acid or enzymatic hydrolysis processes are used to obtained fermentable sugars.Compared with acid hydrolysis,though enzymatic hydrolysis is milder and more specific,it requires pretreatment to improve enzymatic digestibility.Pretreatment is usually preformed by energy intensive physical methods,high temperature and pressure or the use of a chemical solvent.It could prolonged reaction times,increased cost of enzymatic reaction and increased of environment pollution.Instead,acid hydrolysis is a simple,direct and efficient method to hydrolyze polysaccharides from biomass into fermentable sugars.