Fiber modification with cellulases and hemicellulases

This research is comprised of several investigations concerning the relationship of cellulases and hemicellulases to cellulosic fibers used in the papermaking process. These enzymes systems have been shown to contain multiple active components, which synergistically degrade wood fibers. A principal requirement for working with enzyme systems is an accurate and convenient method for determining protein concentration. To evaluate methods currently available, cellulase components were purified from a commercial solution. The components separated in useful quantities were Cellobiohydrolase I (CBH-I), Endoglucanase I (EG-I), and Endoglucanase II (EG-II). The major component for hemicellulase activity, Endoxylanase (XYL), was purified from a commercial xylanase preparation. These components were used to compare assay methods for accuracy. The method judged most practical in terms of convenience and accuracy was the Bicinchonic Acid (BCA) assay.; One commercially viable use of enzymes is to improve drainage rates of recycled or other difficult to dewater stocks. This investigation compared drainage rates, strength properties, fiber length, and yield for several types of fiber, which had been treated with enzymes before or after refining. This was compared with drainage, fiber properties, and yield of pulps, which had been screened as an alternate method of drainage improvement. It was found that enzyme treatment prior to refining accelerated the rate of refining. Treatment after refining and screening improved drainage with little or no loss of strength. Enzyme treatments showed much lower yield loss than similar results achieved by screening.; Use of enzyme pretreatment on chips to reduce energy usage in mechanical pulping was also investigated. Cellulase enzymes were used to treat wood blocks of different wood species, which were subsequently pulped utilizing a specially designed single chip refiner to determine the power requirement difference. Environmental Scanning Electron Microscopy (ESEM) showed improved fibrillation and fiber bundle breakdown for both Red Maple and Southern Pine when the wood was enzyme treated prior to pulping. This did not result in significant macro-scale differences in freeness or power requirements. Enzyme treatment appeared to reduce the amount of oversized rejects in the pulp that could reduce the energy required for reject refining in mechanical pulp processes.