Production, purification and characterization of Bacillus sp. GRE7 xylanase and its application in eucalyptus Kraft pulp biobleaching

Abstract

Production of extracellular xylanase from Bacillus sp. GRE7 using a bench-top bioreactor and solidstate fermentation (SSF) was attempted. SSF using wheat bran as substrate and submerged cultivation using oat-spelt xylan as substrate resulted in an enzyme productivity of 3,950 IU g À1 bran and 180 IU ml À1 , respectively. The purified enzyme had an apparent molecular weight of 42 kDa and showed optimum activity at 70°C and pH 7. The enzyme was stable at 60-80°C at pH 7 and pH 5-11 at 37°C. Metal ions Mn 2+ and Co 2+ increased activity by twofold, while Cu 2+ and Fe 2+ reduced activity by fivefold as compared to the control. At 60°C and pH 6, the K m for oat-spelt xylan was 2.23 mg ml À1 and V max was 296.8 IU mg À1 protein. In the enzymatic prebleaching of eucalyptus Kraft pulp, the release of chromophores, formation of reducing sugars and brightness was higher while the Kappa number was lower than the control with increased enzyme dosage at 30% reduction of the original chlorine dioxide usage. The thermostability, alkali-tolerance, negligible presence of cellulolytic activity, ability to improve brightness and capacity to reduce chlorine dioxide usage demonstrates the high potential of the enzyme for application in the biobleaching of Kraft pulp.

One-step purification and characterization of cellulase-free xylanase produced by alkalophilic Bacillus subtilis ash

“…However, it was higher than 5.5 kDa as observed by Bastawde (4). In contrast, some workers documented a higher molecular weight than that observed in the present study (5,19,20,38,39). Low molecular weight xylanases are preferred for commercial application in paper and pulp industry as they penetrate throughout the pulp fibres more effectively to hydrolyze xylan making the fiber structure more permeable to extraction of lignin by chemicals (21).…”

“…It is produced by bacteria (11,19,37,41), fungi (29,34,41), actinomycetes (33) and yeast (26). Recently, interest in xylanase has markedly increased due its wide variety of biotechnological applications such as pre-bleaching of pulp, improving the digestibility of animal feed stocks, modification of cereal-based stuffs, bioconversion of lignocellulosic material and agro-wastes to fermentable products, clarification of fruit juices and degumming of plant fibers (15,21,44) etc.…”

Cloning, Expression, and Characterization of an GHF 11 Xylanase from Aspergillus niger XZ-3S

“…Applications of xylanases began in the 1980s in the preparation of animal feed, and later developed to the pulp and paper, food, brewing and textile industries. Since then the demands for xylanases have increased dramatically, covering a wide range of industrial fields [5][6][7].…”

Microbial Xylanases and Their Industrial Applications as Well as Future Perspectives: A Review

“…This activity has applications in the food and paper-making industries, along with uses in agriculture and for human health. It is produced by bacteria (Kiddinamoorthy et al, 2008;Sanghi et al, 2007), fungi Sharma and Sharma, 2013), actinomycetes (Ninawe et al, 2007) and yeast (Liu et al, 1998). Recently, interest in xylanase has markedly increased due to its wide variety of biotechnological applications such as pre-bleaching of pulp, improving the digestibility of animal feed stocks, modification of cereal-based stuffs, bioconversion of lignocellulosic material and agro-wastes to fermentable products, clarification of fruit juices and degumming of plant fibers Virupakshi et al, 2005) etc.…”