A Kinetic Study On Enzymatic Hydrolysis Of Rice Straw Pretreated With Ultrasound-assisted

With the energy and environmental problems in the world getting worse and worse,fuel ethanol production from lignocellulosic materials is an important alternative to solve these problems and maintain social suastainable development. There are a lot of researches on the pretreatment and enzymatic hydrolysis of lignocellulosic materials,but most researches are focus on the traditional methods of pretreatment and enzymatic hydrolysis of lignocellulosic materials.The research on the pretreatment and enzymatic hydrolysis of rice straw as the lignocellulosic materials via ultrasound technology has not been reported to our knowledge.Pretreament of any lignocellulosic biomass is crucial before enzymatic saccharification.In this work, the effect of pretreatment with or without ultrasound-assisted(120 W/30 min) to the composition of rice were investigated.The results showed that in comparison with the unpretreated rice straw, the content of hemicelluloses and lignin are respectively 14.86%,5.88% by the alkali pretreatment; 11.08%,5.14% by the ultrasound-assisted alkali pretreatment;11.85%,6.3% by the acid pretreatment;9.73%,5.94% by the ultrasound-assisted acid pretreatment.For the remove of hemicelluloses and lignin,ultrasound-assisted pretreatment was more efficient than pretreatment without ultrasound. We aslo established a simplified kinetic model for the complicated saccharification process.The validity of the model developed was confirmed by its successful simulation of the time courses of glucose during the saccharification.The results showed that ultrasound-assisted pretreatment exerted an inapparent effect on the ultimate conversion of substrate T∞and the competitive product inhibition constants KI,while an obviously effect on the apparent rate constant k and apparent Michaelis KM.The result is as follows:the values of K is respectively 15.30 h-1,21.32 h-1,13.40 h-1,15.42 h-1;the values of KM is respectively 17.55 g·L-1,14.14 g·L-1,15.29 g·L-1,15.80 g·L-1;the values of K1 is respectively 2.31 g·L-1,2.08 g·L-1,1.81 g·L-1,1.85 g·L-1.Ultrasound-assisted pretreatment can decreases the crystallinity of lignocellulose destroying the intermolecular hydrogen bonding effectively and improves the degradation rate of lignin and the saccharification rate of zymohydrolysis availably.