REVIEW PAPER Cellulose is not just cellulose: a review of dislocations as reactive sites in the enzymatic hydrolysis of cellulose microfibrils Budi J. Hidayat • Claus Felby • Katja S. Johansen • Lisbeth G. Thygesen Received: 22 February 2012 / Accepted: 26 June 2012 / Published online: 4 August 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Most secondary plant cell walls contain irregular regions known as dislocations or slip planes. Under industrial biorefining conditions dislocations have recently been shown to play a key role during the initial phase of the enzymatic hydrolysis of cellulose in plant cell walls. In this review we chart previous publications that have discussed the structure of dislocations and their susceptibility to hydrolysis. The supramolecular structure of cellulose in disloca- tions is still unknown. However, it has been shown that cellulose microfibrils continue through dislocations, i.e. dislocations are not regions where free cellulose ends are more abundant than in the bulk cell wall. In more severe cases cracks between fibrils form at dislocations and it is possible that the increased accessibility that these cracks give is the reason why hydrolysis of cellulose starts at these locations. If acid or enzymatic hydrolysis of plant cell walls is carried out simultaneously with the application of shear stress, plant cells such as fibers or tracheids break at their dislocations. At present it is not known whether specific carbohydrate binding modules (CBMs) and/or cellulases preferentially access cellulose at disloca- tions. From the few studies published so far it seems that no special type of CBM is involved. In one case an endoglucanase was found to preferably bind to dislocations. Keywords Dislocations Á Hydrolysis Á Cellulases Á CBMs Abbreviations CBM Carbohydrate binding domain GH Glycoside hydrolase MFA Microfibril angle Introduction As an abundant and renewable resource cellulose has been the target of much research with the aim of processing biomass into fuels and chemicals. Sub- stantial achievements within microbiology, industrial enzymes and biomass processing have put the first pilot scale biorefineries on-line, but considerable research and development efforts are still needed in order to reduce process costs. A crucial step in the processing of cellulose is the enzymatic hydrolysis of glycosidic bonds between the glucose monomers of the cellulose chain. Irregular regions within the cell B. J. Hidayat (&) Á C. Felby Á L. G. Thygesen Faculty of Science, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Denmark e-mail: bjhi@life.ku.dk L. G. Thygesen e-mail: lgt@life.ku.dk K. S. Johansen Novozymes A/S, Krogshøjvej 36, 2880 Bagsværd, Denmark 123 Cellulose (2012) 19:1481–1493 DOI 10.1007/s10570-012-9740-2