A Transition from Cellulose Swelling to Cellulose Dissolution by o-Phosphoric Acid:Evidence from Enzymatic Hydrolysis and Supramolecular Structure

摘要

Cellulose is the primary product of photosynthesis in terrestrial environments,and the most abundant renewable polymer produced in the biosphere (e.g.,approx 100 billion dry tons/year).Cellulose,a common material in plant cell walls,is a linear condensation polymer consisting of D-anhydroglucopyranose joined together by beta-1,4-glucosidic bonds with a degree of polymerization (DP) from 100 to 20 000.Adjacent anhy-droglucose molecules are rotated 180 deg with respect to their neighbors,and coupling of adjacent cellulose molecules by extensive hydrogen bonds and van der Waals forces results in a parallel alignment and a crystalline structure,which produces a straight,stable heterogeneous supramolecular structure and low accessibility to chemicals and cellulases.In nature,cellulose is very stable with a half-life of 5-8 million years for beta-l,4-glucosidic bonds at 25 deg C.Much faster cellulose degradation mediated by cellulase is a very important biological process to return carbon sediments to the atmosphere and would offer promises for the production of biobased products and bioenergy from cellulosic materials.