Cellulase biocatalysis: key influencing factors and mode of action

Commercial interests have been escalating worldwide on cellulase enzymes, since it has enormous potentiality to process most abundant and eco-friendly celluloses and convert them into the renewable and sustainable energy, chemicals, fuels and materials. However, overcoming the cellulose recalcitrance and understanding accurate cellulase catalytic activities have been remaining as major technological challenges. Here we reviewed cellulose hierarchy as a primary focus for cellulase actions and highlighted open questions related to endo- and exo-type cellulases. Special importance has been paid to critically evaluate research efforts on enzyme-substrate interactions, processivity, synergism and mechanistic paradigm for cellulose depolymerizations. These understandings pave the way for enzyme based cellulose bioprocessing and further gains of fundamental science and improved methods for cellulase engineering. We hope the article is potentially important for the biologists, polymer specialists, industrialists and most of the scientists active in cellulose science and technology.