Structural features of cellulosic materials in relation to enzymic hydrolysis

The susceptibility of cellulose to enzymatic hydrolysis is determined largely by its accessibility to extracellular enzymes secreted by or bound on the surface of cellulolytic microorganisms. Direct physical contact between these enzymes and the cellulosic substrate molecules is an essential prerequisite to hydrolysis. Since cellulose is an insoluble and structurally complex substrate, this contact can be achieved only by diffusion of the enzymes from the organism into the complex structural matrix of the cellulose. Any structural feature that limits the accessibility of the cellulose to enzymes by diffusion within the fiber will diminish the susceptibility of the cellulose of that fiber to enzymatic degradation. In this review, the influence of eight such structural features have been discussed in detail.