During the bioconversion of lignocellulose, enzymatic hydrolysis of cellulose to produce glucose is a key step. However, it also has become a bottle-neck for effective bioconversion of lignocellulosic biomass to fuels or chemicals. A large amount of works have demonstrated that addition of non-ionic surfactant during enzymatic hydrolysis of pretreated lignocelluloses can effectively improve the cellulose conversion thus reducing the enzyme loading. In this paper, the effects of non-ionic surfactant on enzymatic hydrolysis of pure cellulose and pretreated lignocellulose are reviewed comprehensively. The relationships of the structural features of substrate, hydrolysis conditions and cellulase formulation with the action of surfactant are discussed. Corresponding mechanisms are analyzed in terms of the adsorption of cellulases and the synergism of the cellulase components. However, the current research progress has not clearly elucidated the mechanisms for the effects of non-ionic surfactant on cellulose hydrolysis. It is proposed that to deeply understand the mechanism, further researches should be focused on systematically investigating the relations of substrate structure, hydrolysis conditions with the actions of non-ionic surfactant to the enzymatic hydrolysis of cellulose. Microscopically, the interactive actions and forces between surfactant and substrate, surfactant and cellulase enzymes should be investigated from the atomic and molecular levels. The thermodynamic and kinetic behaviors of enzymatic hydrolysis of cellulose with addition of surfactant should also be illustrated.

Contents
1 Introduction
2 Effects of surfactant on enzymatic hydrolysis of pure cellulose and mechanism
2.1 Factors influencing the action of surfactant
2.2 Mechanism for the action of surfactant on pure cellulose hydrolysis
3 Effects of surfactant on enzymatic hydrolysis of pretreated lignocellulose
3.1 Effects of substrate structural features
3.2 Effects of hydrolysis conditions
4 Mechanisms for the action of surfactant on lignocellulose hydrolysis
4.1 Effects of surfactant on substrate structure
4.2 Effects of surfactant on enzyme stability
4.3 Effects of surfactant on the interaction between enzyme and substrate
5 Conclusion