3 NATIVE CELLULOSE-DEPOLYMERIZING ENDOGLUCANASES FROM SOLID-SUBSTRATECULTURES OF THE BROWN-ROT FUNGUS MERULIPORIA (SERPULA) INCRASSATA

Three extracellular cellulose-depolymerizing enzymes from cotton under going decay by the brown rot fungus Meruliporia (Serpula) incrassata w ere isolated by anion exchange and hydrophobic interaction chromatogra phies. Depolymerization was detected by analyzing the changes in the m olecular size distribution of cotton cellulose by high performance siz e-exclusion chromatography. The average degree of polymerization (DP; number of glucosyl residues per cellulose chain) was calculated from t he size-exclusion chromatography data. The very acidic purified endogl ucanases, Cel 25, Cel 49, and Cel 57, were glycosylated and had molecu lar weights of 25,200, 48,500, and 57,100, respectively. Two, Cel 25 a nd Cel 49, depolymerized cotton cellulose and were also very active on carboxymethyl cellulose (CMC). Cel 57, by contrast, significantly dep olymerized cotton cellulose but did not release reducing sugars from C MC and only very slightly reduced the viscosity of CMC solutions. Mole cular size distributions of cotton cellulose attacked by the three end oglucanases revealed single major peaks that shifted to lower DP posit ions. A second smaller peak (DP, 10 to 20) was also observed in the si ze-exclusion chromatograms of cotton attacked by Cel 49 and Cel 57. Un der the reaction conditions used, Cel 25, the most active of the cellu lases, reduced the weight average DP from 3,438 to 315, solubilizing a pproximately 20% of the cellulose. The weight average DP values of cot ton attacked under the same conditions by Cel 49 and Cel 57 were 814 a nd 534; weight losses were 9 and 11%, respectively.