Mill usage and mechanistic studies of xylanase to enhance bleaching

This chapter discusses the mill usage and mechanistic studies of xylanase to enhance bleaching. Xylanase aided bleaching is the most widely used example of biotechnology in actual mill operations. About 20 bleached kraft mills in Canada, Finland, the US, and other countries use xylanase on a continuous basis. Xylanase is added to the pulp prior to bleaching. The enzyme does not bleach, brighten, or (for the most part) delignify the pulp. The mills use xylanase to decrease costs, decrease chlorine dioxide usage, increase pulp brightness, decrease effluent discharges, or obtain any of several other benefits. All of these benefits are obtained with low capital costs. The five important areas of xylanase treatment in a bleach plant includes (1) pulp susceptibility, (2) enzyme selection, (3) mixing and dispersion, (4) reaction conditions, and (5) bleach plant control. The potential for improving benefits in a mill is by increasing the understanding of selectivity and other aspects of the mechanisms of xylanase in bleaching offers.