Abstract
Electron microscopical studies of changes in cotton fiber microstructure, after ex posure of the fibers to the cellulase in filtrates prepared from cultures of Myrothecium verrucaria, showed evidence of the transverse, jagged cuts into the cellulose structure previously seen by cytical microscopy. The degradation appeared localized in areas along the length of the fiber which were not related to any recognized component of fiber structure. Micrographs of fragmented, degraded fibers showed etching of the macro- fibrils of the sheets of secondary wall and a sharpening of the image of the individual microfibrils. Continued enzyme attack produced smaller fragments and hydrocellulose- like particles. Measurements of changes in tensile strength, swelling in alkali, and in glucose yield were correlated with changes in microstructure. The extent of fiber degradation by cellulolytic culture filtrates was limited and could be continued only if fibers were swollen between filtrate exposures. No evidence of damage to the cellulose structure was seen which could not be explained hy hydrolysis at the β-1,4-glucosidic linkage.
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