Effect Of Nonionic Surfactant And Shear Force On The Enzymatic Hydrolysis Of Lignocellulose And Its Mechanism

Producing cellulosic ethanol from lignocellulose by the process of enzymatic hydrolysis and fermentation is the effective method to solve energy crisis and relieve the environmental pollution.But,there still exist many problems in the process of enzymatic hydrolysis,including low efficiency and high enzyme loading.Adding nonionic surfactants in the process of enzymatic hydrolysis is one of the effective approaches to solve these problems.However,the performance of the additives that have been developed to enhance the enzymatic hydrolysis still can't reach the requirement of industrial manufacture.Therefore,researchers are working hardly to develop other nonionic surfactants with better performance.Understanding the mechanism of nonionic surfactants enhancing the enzymatic hydrolysis of lignocellulose can help to utilize them much more effectively.But the mechanism is still not very clear now.Effect of different nonionic surfactants on the enzymatic hydrolysis efficiency of lignocellulose was investigated.The structure of nonionic surfactants will affect its adsorbing configuration on lignin,the hydrophilicity of lignin,the enzymatic hydrolysis efficiency and the nonproductive adsorption of cellulase on lignin.Results showed that nonionic surfactants with larger molecular weight and has both separated hydrophilic and hydrophobic structures can adsorb more on lignin,and the adsorption layer was firmer and more compact.Meanwhile,it can form bigger steric hindrance on the surface of lignin,which can reduce the nonproductive adsorption of cellulase on lignin and improve enzymatic hydrolysis efficiency remarkably.Effect of nonionic surfactants on the enzymatic hydrolysis of lignocellulose and pure cellulose at different agitation rate was investigated.Results showed that the enhancement at high agitation rate was most significant,and the enhancement at low agitation rate was worse than that at high agitation rate.The cellulase would easily deactivate due to the shear force,and the deactivation degree was related to the cellulase concentration.The lower the cellulase concentration was,the severer the deactivation was.Besides,the cellulase would deactivate when exposed to the air-liquid interface.Because the force on the cellulase molecular exposed to air-liquid interface was unbalanced,which would lead to the unfolding of the cellulase.Nonionic surfactants can reduce the cellulase deactivation caused by shear force and air-liquid interface and,therefore,enhance the enzymatic hydrolysis of cellulose.Revealing the mechanism of how they act to enhance the enzymatic hydrolysis of lignocellulose is helpful for developing new cellulase with better performance and improving the utilization of lignocellulose.