Characteristics of Cotton Cellulose Depolymerized by a Brown-Rot Fungus, by Acid, or by Chemical Oxidants

Summary Wood decay fungi of the brown-rot type destroy the strength of wood before significant weight loss occurs.This is due to extension depolymerization of the cellulose. Evidence indicates that enzymes cannot gainaccess to the cellulose in wood and that the depolymerizing agent might be oxidative. Our objectiveshere were to gain information about the nature of the agent by characterizing pure cellulose that hadbeen depolymerized by a brown-rot fungus (BR) and to compare its characteristics with those of cellulosedepolymerizcd by acid (A). by Fenton’s reagent (Fe 2+ + H 2 O 2 ) (F), or by periodic acid/bromine/water(P). All four types of depolymerized cellulose exhibited molecular size characteristics indicating that de-polymerization was due to cleavages within the noncrystalline regions. Carbonyl contents of the sampleswere similar, from 1.4 to 1.9 per cellulose molecule. Carboxyl contents were 0.44, 0.00, 0.24, and 7.38per molecule for samples BR, A, F, and P, respectively; uronic acids were absent except for a trace insample P. On complete acid hydrolysis the samples gave the expected amounts of glucose, except forsample P, which contained nonglucosyl moietics that did not contain carbonyl or carboxyl groups detectedby our analytical procedures. With theglucose in the acid hydrolysates we found glyceric, crythronic,ararbonic, and gluconic acids in samples BR and F, and crythronic acid in sample P. Our results indicatethat the brown-rotted cellulose resembles sample F more than samples A or P.