Supramolecular Structure - A Key Parameter for Cellulose Biodegradation Diana Ciolacu, * 1 Florin Ciolacu, 2 Valentin I. Popa 2 Summary: Three different cellulosic substrata, like microcrystalline cellulose, cotton cellulose and spruce dissolving pulp, were chosen for biodegradation. The kinetics of the enzymatic hydrolysis of these celluloses by Trichoderma reesei, has been inves- tigated. The experiments proved the fact that both the morphological structure and the crystalline one are crucial to the process and the ratio of the reactions. In addition, in order to obtain the most accessible cellulose substratum it was studied the biodegradation of cellulose allomorphs of spruce dissolving pulp. The insoluble cellulose fraction remaining after enzymatic hydrolysis was examined by X-ray diffraction method and it was established the degree of crystallinity and the average crystallite size. The enzymatic degradation is also proved by the decrease in the degree of polymerization of hydrolyzed samples. Keywords: biodegradation; cellulose; degree of polymerization (DP); enzymes; wide-angle X-ray scattering (WAXS) Introduction Cellulose, the most abundant component of plant biomass, is found in nature almost exclusively in plant cell walls, although it is produced by some animals (e.g., tunicates) and a few bacteria. [1,2] Cellulose is synthe- sized in nature as individual molecules (linear chains of glucosyl residues) which undergo self-assembly at the site of bio- synthesis. [3] The enzymatic degradation of cellulose [b(1–4)-linked glucose] is of large biological and economical importance. Cellulose biodegradation studies empha- sized the importance of improved cellulosic technologies and better cellulolytic enzymes for conversion of biomass to easily fermen- table compounds such as glucose. [4–8] Cellu- lose biodegradation studies have been generally oriented upon physiological char- acteristics of cellulolytic microorganisms and also on biochemical properties of the enzymes synthesized by them. [9–11] More- over, the enzymatic chain cleavage has received attention by significant contribu- tion to elucidation of cellulose structure, as well as characterization of cellulose deri- vatives. [12] Enzymatic degradation of crys- talline polysaccharides is difficult to study because the insoluble substrate is not amenable to straightforward biochemical analysis and soluble intermediate oligosac- charide products are degraded fast and, therefore, difficult to detect. Thus, usually the only detectable products during degra- dation of cellulose are mono-, di-, and trisaccharides, which are typical end pro- ducts. [13–16] This is the reason that there are only a few studies on the relation between the fine structure of cellulose and its biodegradability. [17–20] The effect of the variety of physical structures adopted by the cellulose molecules in its different crystalline forms on biodegradation was not yet investigated in detail. In this paper the effect of polymorphism on the biode- gradability of cellulose, was evaluated. In addition, the relative importance of differ- ent structural parameters on the enzymatic Macromol. Symp. 2008, 272, 136–142 DOI: 10.1002/masy.200851220 136 1 ‘‘Petru Poni’’ Institute of Macromolecular Chemistry, Grigore-Ghica Voda Alley, 41A, 700487 Iasi, Romania E-mail: dciolacu@icmpp.ro 2 Faculty of Industrial Chemistry, ‘‘Gh. Asachi’’ Tech- nical University of Iasi, Bv. Dimitrie Mangeron, 71 A, 700050 Iasi, Romania Copyright ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim