BLEACHING ENZYMES WORLD PULP&PAPER 48 Man has used enzymes since the first batches of beer, wine and cheese were made thousands of years ago. Our bodies use enzymes for the digestion of food amongst a myriad of other things to survive and to grow. In 1833 Anselme Payen was the first to discover an enzyme. Eduard Buchner received a Nobel prize in 1907 for his discovery of “cell free fermentation,” which was in fact the use of an enzyme. The first commercial enzymes were produced by Röhm in 1914 for the detergent industry. This trypsin enzyme, isolated from animals, degraded proteins and was used as a detergent. It proved to be so powerful compared with traditional washing powders that German housewives’ suspicions were aroused by the small size of the original package, so the product had to be reformulated and sold in larger packages(1). It has only been in the last 30 years that the paper industry has stepped into the arena. Enzymes are proteins which act as catalysts in either accelerating or influencing specific chemical reactions. They are derived from living organisms, yet they themselves are not living. They do not reproduce, nor are they capable of mutation. They can be deactivated under certain conditions and can be destroyed under other conditions. Typically, most enzymes are destroyed at temperatures around 115oC (220oF) into innocuous organic materials. The first commercial enzymes were produced by Röhm in 1914 for the detergent industry The concept of using enzymes for the bleaching of pulp is not new. With the advent of ECF (elemental chlorine free) bleaching in the late 1990s, the industry quickly realized that bleaching with chlorine dioxide was much more expensive and adopted the use of various technologies such as oxygen delignification and acid pretreatment in an effort to reduce chlorine dioxide usage. To reduce chlorine dioxide usage further, investigation began into the commercial viability of using enzymes in the bleaching of pulp. During the late 1980s and into the early 1990s, mill trials had already begun using xylanase enzymes in an effort to reduce the amount of chlorine dioxide used in bleaching. The industry encountered issues in that, in order for the enzymes to work, a very narrow operational band of pH and temperature had to be maintained over a period of 1-3 hours in order for the enzymes to be effective. Unfortunately, the required conditions were not native to the typical pulp mill, so extensive pH and temperature control strategies had to be employed. It was in the pH control that the bulk of the difficulties were encountered as the typical pH at the end of the brownstock washing system was somewhere between 9.0-11.5. By Thomas Holm, Global Market Development Manager, Pulp, Buckman Bleaching Enzymes – Back from the Drawing Board Figure 1. Impact of Vybrant® 701 on XDED yield - pH 9.0