Effects of commercial cellobiohydrolase treatment on fiber strength and morphology of bleached hardwood pulp

Development of fiber strength properties and morphological changes on the surface of bleached hardwood kraft pulp after treatment with commercial cellobiohydrolase (CBH) was evaluated. Tensile and tear indices showed no significant effect of the treatment. The treatment resulted in reduction of wet zero-span strength, while the dry zero-span values increased. The decrease in wet zero-span values was most likely caused by preferential action of CBH on structurally irregular zones in the fiber wall coupled with greater sensitivity of wet zero-span testing towards the localized fiber defects. The fracture zone of the wet zero-span tested samples was imaged by scanning electron microscopy (SEM). Visual observation revealed differences in fiber fracture between treated and control samples. The straighter and cleaner fractures of the treated sample could be attributed to the localized hydrolytic action of CBH. Visual analysis of the treated fiber surface morphology by SEM showed an increase of more visible fiber wall dislocations, particularly on fibers of smaller diameter. The increased presence of the fiber dislocation correlates with the decrease in the wet zero-span values of treated samples.