Pretreatment Of Kraft Pulp Research Articles

Production and purification of xylanase from alkaliphilic Bacillus licheniformis and its pretreatment of eucalyptus kraft pulp

Abstract Xylanases from bacterial sources have potential applications in various industrial processes. In the present study, the effect of enzymatic pre-treatment on pulp bleaching has been investigated using purified xylanase from alkaliphilic Bacillus licheniformis strain Alk-1. The xylanase produced by present isolate while growing on wheat bran was purified to homogeneity by 5.84-fold purification with ~15.97% recovery by anion exchange chromatography using DEAE-cellulose. The estimated molecular weight of the xylanase was ~46 kDa. The optimal pH and temperature for xylanase activity were pH 9.0 and 60 °C, respectively. The enzyme showed good activity retention (80%) after 1 h incubation at 60 °C and pH 9.0. Enzyme activity was stimulated by Ca2+, Fe2+ and Mg2+ and inhibited by Cd2+, Hg2+ and Cu2+ at 2 mM and 10 mM conc. For xylan, the enzyme gave a Km value of 5.26 mg/mL and Vmax value of 433 μM/min/mg proteins when the reaction was carried out at 60 °Cand pH 9.0. Pre-treatment of kraft pulp with xylanase showed 19% reduction in kappa number, compared to control pulp, after 2 h treatment. The SEM and FTIR analysis of xylanase-treated pulp revealed significant morphological and structural changes on pulp fibres. GC-MS analysis of filtrates from control and xylanase-treated pulps showed variation in the presence of different plant-derived organic compounds. The present work finds potential application in paper production by making it cleaner and ecofriendly process.

Characterization of a NewProvidenciasp. Strain X1 Producing Multiple Xylanases on Wheat Bran

Providencia sp. strain X1 showing the highest xylanase activity among six bacterial isolates was isolated from saw-dust decomposing site. Strain X1 produced cellulase-free extracellular xylanase, which was higher in wheat bran medium than in xylan medium, when cultivated at pH 8.0 and 35°C. Zymogram analysis of crude preparation of enzymes obtained while growing on wheat bran and birchwood xylan revealed the presence of seven and two distinct xylanases with estimated molecular weight of 33; 35; 40; 48; 60; 75; and 95 kDa and 33 and 44 kDa, respectively. The crude xylanases were produced on wheat bran medium and showed optimum activity at pH 9.0 and 60°C. The thermotolerance studies showed activity retention of 100% and 85% at 40°C and 60°C after 30 min preincubation at pH 9.0. It was tolerant to lignin, ferulic acid, syringic acid, and guaiacol and retained 90% activity after ethanol treatment. The enzyme preparation was also tolerant to methanol and acetone and showed good activity retention in the presence of metal ions such as Fe2+, Mg2+, Zn2+, and Ca2+. The crude enzyme preparation was classified as endoxylanase based on the product pattern of xylan hydrolysis. Pretreatment of kraft pulp with crude xylanases for 3 h at 60°C led to a decrease in kappa number by 28.5%. The properties of present xylanases make them potentially useful for industrial applications.

Family-10 and family-11 xylanases differ in their capacity to enhance the bleachability of hardwood and softwood paper pulps.

Enzyme-aided bleaching of softwood and hardwood kraft pulps by glycosyl hydrolase family-10 and -11 xylanases and a family-26 mannanase was investigated. The ability to release reducing sugar from pulp xylan and to enhance bleachability is not a characteristic shared by all xylanases. Of the six enzymes tested, two xylanases belonging to family 11 were most effective at increasing bleachability and improving final paper brightness. None of the enzymes had a deleterious effect on pulp fibre integrity. The efficiency of individual xylanases as bleach enhancers was not dependent on the source microorganism, and could not be predicted solely on the basis of the quantity or nature of products released from pulp xylan. Cooperative interactions between xylanase/xylanase and xylanase/mannanase combinations, during the pretreatment of softwood and hardwood pulps, were investigated. Synergistic effects on reducing-sugar release and kappa number reduction were elicited by a combination of two family-10 xylanases. Pretreatment of kraft pulp with mannanase A from Pseudomonas fluorescens subsp. cellulosa and any one of a number of xylanases resulted in increased release of reducing sugar and a larger reduction in kappa number than obtained with the xylanases alone, confirming the beneficial effects of family-26 mannanases on enzyme-aided bleaching of paper pulp.

Influence of sodium sulfate on the pretreatment of kraft pulp with nitrogen dioxide

Influence of sodium sulfate on the pretreatment of kraft pulp with nitrogen dioxide

Influence of Oxygen During Pretreatment of Kraft Pulp with NO2

Abstract Large additions of O2 during the pretreatment of modified or industrial kraft pulp with NO2 under conditions which favored an autocatalytic generation of NO2 from produced and added HNO3 led to a decreased viscosity after a subsequent oxygen bleaching, If the comparison was made at high kappa numbers. The difference was less apparent when the oxygen bleaching was extended. The yield of pulp at a given kappa number was reduced by large O2 additions. An Increased yield of nitric acid contributed to these effects. Hydrogen cyanide and ammonia were produced during the pretreatment in reactions between lignin and generated nitrogen oxides. Addition of O2 led to decreased yields of these products.

Short communication: Removal of reactor gas during pretreatment of kraft pulp with NO2 before oxygen bleaching

Short communication: Removal of reactor gas during pretreatment of kraft pulp with NO₂ before oxygen bleaching

Formation of Nitric Acid During Pretreatment of Kraft Pulp with Nitrogen Dioxide and Oxygen

Abstract During pre treatment of unbleached kraft pulp with 1-4Z nitrogen dioxide in the presence of oxygen 50–86 mole percent of the nitrogen dioxide was converted to nitric acid. The conversion was suppressed at high temperature and consistency and by a decreased addition of nitrogen dioxide. In most experiments the proportion of nitric acid decreased with an increased duration of the treatment although nitric acid was produced. The results confirm that nitrogen dioxide is regenerated in a reaction cycle and show that nitric acid serves as a source of nitrogen dioxide.

Treatment of wood pulp with nitrogen dioxide before oxygen bleaching

Pretreatment of kraft pulp with nitrogen dioxide and oxygen before conventional oxygen bleaching with magnesium sulfate as protector leads to markedly decreased lignin contents after a given duration of the oxygen bleaching. An increased temperature during the pretreatment favours the delignification. The most striking effect of the pretreatment is that it leads to a suppressed rate of depolymerization of the cellulose during the oxygen bleaching.