Biological Bleaching of Chemical Pulps

Abstract

Use of biotechnology in pulp bleaching has attracted considerable attention and achieved interesting results in recent years. Enzymes of the hemicellulolytic type, particularly xylan-attacking enzymes, xylanases are now used commercially in the mills for pulp treatment and subsequent incorporation into bleach sequences. The aims of the enzymatic treatment depend on the actual mill conditions and may be related to environmental demands, reduction of chemical costs or maintenance or even improvement of product quality. The use of oxidative enzymes from white-rot fungi, that can directly attack lignin, is a second-generation approach, which could produce larger chemical savings than xylanase but has not yet been developed to the full scale. It is being studied in several laboratories in Canada, Japan, the U.S.A. and Europe. Certain white-rot fungi can delignify kraft pulps increasing their brightness and their responsiveness to brightening with chemicals. The fungal treatments are too slow but the enzyme manganese peroxidase and laccase can also delignify pulps and enzymatic processes are likely to be easier to optimize and apply than the fungal treatments. Development work on laccase and manganese peroxidase continues. This article presents an overview of developments in the application of hemicellulase enzymes, lignin-oxidizing enzymes and white-rot fungi in bleaching of chemical pulps. The basic enzymology involved and the present knowledge of the mechanisms of the action of enzymes as well as the practical results and advantages obtained on the laboratory and industrial scale are discussed.

Statistical optimization of alkaline xylanase production from Streptomyces violaceoruber under submerged fermentation using response surface methodology

“…Xylanase (endo-β-1,4-xylanase) and β-xylosidase (β-D-xyloside xylohydrolase) the main constituents of the xylanolytic enzyme system, convert xylan into a more readily fermentable form [1][2][3] . In recent years, interest in xylanases has increased markedly due to their usage in the pulp and paper industry 1,[4][5][6][7] . Other potential applications include the clarification of fruit fi juices and wine, the extraction of plant oil, coffee and starch, the production of oligosaccharides and improvement of the nutritional value of animal feed 2,[8][9][10] .…”

Structural modification of eucalypt pulp lignin in a totally chlorine-free bleaching sequence including a laccase-mediator stage

“…Their oxidoreductases have high redox potential, and may be applied for delignifying and bleaching of paper-grade pulps (Bajpai 2004). Ligninolytic peroxidases were investigated as agents for environmentally sound bleaching of pulps, together with laccases (Paice et al 1995).…”

Exploitation of for the Heterologous Production of Cellulases and Hemicellulases

“…The largest group (about 65%) is technical enzymes used in the detergent, textile, leather and pulp and paper industry, second by food enzymes (about 27%), followed by enzymes used in the animal feed industry (about 6%) [2,3,[15][16][17][18][19]. Xylanases found applications in the baking industry by modifying cereal flours [20], improvement in the nutritional value of animal feeds for ruminants (cattle and sheep) [21] and monogastrics (chickens and pigs) [22,23], and the pre-bleaching of pulp for paper making [24]. Xylanases and cellulases (together with pectinases) are used for the clarification of wine and fruit juice [25], liquefying of fruits and vegetables for the making of puree and the treatment of textiles [26,14].…”