Enhanced Fiber Quality of Black Spruce (Picea mariana) Thermomechanical Pulp Fiber Through Selective Enzyme Application

Two different enzyme applications were applied to black spruce thermomechanical pulping (TMP) in an attempt to selectively enhance the physical properties of the resulting pulp. Past studies have revealed some application difficulties between pulp and enzymes. A new method of enzyme application including fiberizing the wood chips and cooling the fiberized material prior to enzyme application was employed to maximize the fiber surface area available for enzyme reaction and to obtain optimal enzyme reaction temperatures. Fiberized chips are chips that have been destructured in a converging screw chip press followed by low energy refining to produce extremely coarse fiber pulp. TMP pulps obtained from a control sample of whole wood chips, fiberized wood treated with water, and fiberized wood with two different enzyme applications were evaluated for specific refining energy and various physical properties. Scanning electron microscopy (SEM) in conjunction with image analysis techniques was used to determine fiber wall thickness, degree of fiber fibrillation, and percent surface disruption for selected trial pulps. One monocomponent pectinase enzyme evaluated in this work was found to significantly improve various physical properties and increase the specific surface area of the resulting pulp. The multicomponent more aggressive pectinase enzyme evaluated was determined to be less effective at enhancing physical properties than the less aggressive monocomponent enzyme. The new fiberizing application method employed prior to enzyme application was found to reduce the specific refining energy requirements by 7%. When evaluated at a constant freeness, the enzyme treatment in conjunction with the new application method was found to reduce specific refining energy by about 9%. The enzyme application had only minimal impact on energy requirements. The enzyme application did significantly enhance the tensile and tear index of the resulting pulp. Dramatic increases in the amount of fibrillation and fiber surface disruption were also found to result from specific enzyme action upon the fiber. The resulting fiber wall thickness was reduced as a result of the enzyme action as well. Results from this work reveal that selective enzyme application is an effective method for enhancing specific physical properties of TMP pulps.