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This study investigated the synergistic effects of formamidine sulfinic acid (FAS) bleaching and cationic additives on mixed waste paper (MWP) quality. MWP was chemically deinked and bleached with hydrogen peroxide (H2O2) or FAS at concentrations of 1–4%. Cationic starch and cationic polyacrylamide (CPAM) were applied as dry-strength additives at 1–3%. FAS bleaching at 4% dosage outperformed H2O2, improving brightness by 17% and reducing yellowness by 56%. CPAM showed superior performance in enhancing paper strength properties compared to cationic starch, with an optimal concentration of 2% for both additives. Surface charge analysis demonstrated effective fiber negative charge neutralization by both additives, with CPAM exhibiting higher efficiency. Field emission scanning electron microscopy (FESEM) confirmed significant improvements in fiber surface characteristics, particularly with 2% CPAM and 4% FAS combination. Water retention value decreased with additive application, potentially improving dewatering efficiency. Results indicate that combining FAS bleaching with optimized CPAM dosage can significantly enhance recycled paper quality, potentially narrowing the gap between recycled and virgin pulp properties. [ABSTRACT FROM AUTHOR]

This study investigates the role of secondary condensates in the pulp and paper industry's journey to minimize its water footprint. The integration of secondary condensates, traditionally less explored in bleaching processes, is examined for its potential in reducing freshwater demand. Condensates with different organic content (chemical oxygen demand, COD) and their mixtures were tested as washing liquid after the alkaline extraction stage (EP) of eucalyptus globulus kraft pulp and compared to hot water. Two subsequent chlorine dioxide stages were applied to evaluate the impact of the washing liquid COD on pulp properties and chemicals consumption. Despite its higher organic content, the condensates can be used as a partial or total substitute for hot water without substantial compromises in the pulp properties, such as brightness, reversion, and viscosity. The calculated correlation between ClO2 consumption and COD in the washing liquid can be applied for assessing economic and environmental trade-offs, providing a roadmap for optimizing processes and reducing environmental impacts. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Xylanases are the main biocatalysts used for the reduction of the xylan backbone from hemicellulose, randomly splitting off β‐1,4‐glycosidic linkages between xylopyranosyl residues. Xylanase market has been annually estimated at 500 million US Dollars and they are potentially used in broad industrial process ranges such as paper pulp biobleaching, xylo‐oligosaccharide production, and biofuel manufacture from lignocellulose. The highly stable xylanases are preferred in the downstream procedure of industrial processes because they can tolerate severe conditions. Almost all native xylanases can not endure adverse conditions thus they are industrially not proper to be utilized. Protein engineering is a powerful technology for developing xylanases, which can effectively work in adverse conditions and can meet requirements for industrial processes. This study considered state‐of‐the‐art strategies of protein engineering for creating the xylanase gene diversity, high‐throughput screening systems toward upgraded traits of the xylanases, and the prediction and comprehensive analysis of the target mutations in xylanases by in silico methods. Also, key molecular factors have been elucidated for industrial characteristics (alkaliphilic enhancement, thermal stability, and catalytic performance) of GH11 family xylanases. The present review explores industrial characteristics improved by directed evolution, rational design, and semi‐rational design as protein engineering approaches for pulp bleaching process, xylooligosaccharides production, and biorefinery & bioenergy production. [ABSTRACT FROM AUTHOR]

The aim of this study was the experimental demonstration and assessment of a novel lignocellulose biorefinery (LCB) for the integration of beech wood-based products as platform and fine chemicals. The process sequence included organosolv pulping followed by pulp bleaching, hydrothermal conversion of hemicellulose to xylose and its purification, fermentation of xylose to malic acid, and base-catalyzed lignin depolymerization (BCD). The resulting products were dissolving pulp, phenolic BCD-oligomers, and malic acid. The state of the art for these technologies is their experimental proof of concept and validation at a laboratory- and pilot-scale and has a technology readiness level (TRL) of 3–4. By integrating and optimizing the single-process steps into one LCB, the TRL could be increased to 5. Based on the findings of the experimental studies, a LCB converting 50,000 dry metric tonnes ( = ̂ 38.7 MW) of beech wood annually was simulated with Aspen Plus. Mass and energy balances showed that 14,616 dry metric tonnes of dissolving pulp, 5174 dry metric tonnes of BCD-oligomers, and 4077 dry metric tonnes of malic acid annually could be produced. The total energy efficiency is 40.3%. The calculation of specific production costs demonstrated the marketability of dissolving pulp (1350 €/t) and BCD-oligomers (2180 €/t), whereas malic acid (4750 €/t) is not yet competitive. Environmental assessment showed reduced greenhouse gas (GHG) emissions from the production of BCD-oligomers and malic acid and higher GHG emissions from the production of dissolving pulp compared with the reference products. In total, the examined LCB would contribute to the mitigation of global warming. [ABSTRACT FROM AUTHOR]

Chromophores, colored substances of rather high stability that reduce brightness, are present in all kinds of cellulosic products, such as pulp, fibers, aged cellulosic material, and even in very low concentrations in highly bleached pulps. Thus, they are the prime targets of industrial pulp bleaching. In this study, the three cellulosic key chromophores 2,5-dihydroxy-1,4-benzoquinone (DHBQ, 1), 5,8-dihydroxy-1,4-naphthoquinone (DHNQ, 2), and 2,5-dihydroxyacetophenone (DHAP, 3) were bleached with ozone at pH 2 resembling industrial conditions (Z-stage). Bleaching kinetics were followed by UV/Vis spectrophotometry. The chemical structures of the degradation products were analyzed using NMR spectroscopy as well as GC/MS and confirmed by comparison with authentic reference compounds. The main, stable intermediates in the ozonation reactions have been elucidated by employing ozone not in excess but roughly stoichiometric amounts: mesoxalic acid (4) from DHBQ (1), rhodizonic acid (5) from DHNQ (2), and hydroxy-[1,4]-benzoquinone (8) from DHAP (3). As the final products at a large excess of ozone, a complex mixture of carboxylic acids (C1 to C4) was obtained, with the C4 acids being formed by subsequent condensation of smaller fragments (malonic acid and mesoxalic acid) rather than directly as ozonation products. At shorter reaction times and lower ozone excess, some aldehydes and ketones (C2 and C3) were contained in addition. The mixture of the degradation products was not completely stable but tended to undergo further changes, such as decarboxylation and condensation reactions. The reaction mechanisms of degradation by ozone, intermediate formation and re-condensation are described and discussed. [ABSTRACT FROM AUTHOR]

Present study deals with the extraction and isolation of microcrystalline cellulose (MCC) from date palm fruit bunch stalk (DPFS) of date palm tree (Phoenix dactylifera L.) through integrated chemical method. To facilitate comparative study, each DPFS-treated, DPFS-pulp and DPFS-MCC samples were produced through respective bleaching, alkaline and acid hydrolysis treatments. The obtained samples were characterized in aspects of structural, morphological, elemental, crystallinity and thermal properties. From physicochemical analysis, fourier transform infrared ray (FTIR) and X-ray diffraction (XRD) showed the improved cellulose crystalline structure from DPFS-treated to DPFS-MCC. Morphology analysis revealed that the isolated DPFS-pulp and DPFS-MCC samples had microfibrillar structure, which achieved through the fibre disintegration by a series of chemical treatments. Moreover, the rigidity was also found the highest for isolated DPFS-MCC with 79.4% crystallinity degree. Further, the DPFS-MCC sample manifested better thermal properties for its high weight loss (84.15%), low residual weight (15.44%) and high decomposition temperature (364.2 °C) compared to the other fibre samples. Also, the DSC analysis showed the thermal behaviour which is in line with the thermal decomposition of those fibre samples. Therefore, in view of the overall result, the isolated DPFS-MCC could act as potential filler for reinforcing polymeric materials in composite field of applications. [ABSTRACT FROM AUTHOR]

2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ, 1) is the most prominent representative of cellulosic key chromophores, which occur almost ubiquitously in all types of aged cellulosics. The degradation of DHBQ by chlorine dioxide under conditions of industrial pulp bleaching ("D stage") was studied, i.e. in moderately acidic medium (pH 3) at temperatures between 50 and 90 °C. The degradation in the presence of excess ClO2 generates rhodizonic acid (RhA, 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone, 2) as a secondary chromophore which is even more stable and more potent as a chromophore than the starting DHBQ, especially in the form of its salts. At least a threefold ClO2 excess is needed for complete DHBQ consumption. The reaction from DHBQ to RhA involves pentahydroxybenzene (PHB, I) as an intermediate which is either readily further oxidized to RhA by excess ClO2 or slowly reconverted to DHBQ in the absence of ClO2. The RhA yield after 30 min reaction time had a maximum of 83% at a DHBQ/ClO2 molar ratio of 1:5, and decreased with increasing ClO2 charge, reaching 38% at a DHBQ/ClO2 ratio of 1:8 and above. Degradation of DHBQ by ClO2 is 42 times faster than that of RhA (50 °C, pH 3). RhA is present in aqueous medium in the form of its dihydrate, 2,3,5,5,6,6-hexahydroxycyclohex-2-ene-1,4-dione, which contains two pairs of geminal diols at C-5 and C-6. At pH 5 and above it forms an aromatic C6O62− dianion, so that the RhA salts are very stable. These salts are intensively colored, not only the ones with transition metal cations, but also those with monovalent (Na+, K+) and especially divalent (Ca2+, Mg2+) main group metals, and usually have very low solubility so that they precipitate on the pulp fibers. It was demonstrated that the inferior ClO2-bleachability of some pulps is due to the conversion of DHBQ into colored RhA and its respective salts. [ABSTRACT FROM AUTHOR]

Background: Xylanases are considered one of the most important enzymes in many industries. However, their low thermostability hampers their applications in feed pelleting, pulp bleaching, and so on. The main aim of this work was to improve the thermostability of Trichoderma ressei xylanase 2 (Xyn2) by introducing disulfide bonds between the N-terminal and α-helix and the β-sheet core. Results: In this work, two disulfide bonds were separately introduced in the Xyn2 to connect the N-terminal and α-helix to the β-sheet core of Xyn2. The two disulfide bonds were introduced by site-directed mutagenesis of the corresponding residues. The half-life of the mutants Xyn2C14–52 (disulfide bond between β-sheets B2 and B3) and Xyn2C59–149 (disulfide bond between β-sheets A5 and A6) at 60°C was improved by approximately 2.5- and 1.8-fold compared to that of the wild type Xyn2. In addition, the enzyme's resistance to alkali and acid was enhanced. Conclusion: Our results indicated that the connection of the N-terminal and α-helix to the β-sheet core is due to the stable structure of the entire protein.

Aims: The utilization of micro‐organisms in pulp and paper industries has proved biobleaching technology as an environmentally friendly alternative to the conventional approach. In this paper, the effect of actinobacterial fermentation broth on pulp biobleaching has been investigated. Methods and Results: Actinobacterial colonies were isolated from lignocellulose‐rich soil samples and screened for xylanase production and bleaching activity. The most efficient isolate in bleaching activity showed 100% similarity to Streptomyces rutgersensis. Pulp treatment with 5‐day fermentation broth of this strain showed up to 7% increase in brightness (30°C for 6 h, pH (5–7)) compared to untreated (control) pulp. Also, after 60 min biotreatment, significant reduction (12·5%) in consumption of bleaching chemicals was achieved to obtain final brightness of 55%. Conclusion: Actinobacterial fermentation broth can be considered as a rich source of effective biobleaching agents which may be considered as environmental friendly and cost‐effective technique in comparison with traditional method. Significance and Impact of the Study: Our findings showed ability of S. rutgersensis UTMC 2445 in bleaching chemomechanical paper pulp. Also, two strains of Saccharothrix, a rare actinobacterium, with biobleaching activity were introduced. In the proposed method, there is no need to use purified enzymes, and biobleaching process can be done using the fermentation broth. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Kraft pulps from acacia hybrid, Acacia mangium of 8 years old and Acacia auriculiformis of 6, 8 and 10 years old were pre-treated with oxygen, peroxyformic acid and acid treatment prior to bleaching. The kappa number reduction was 52-63% by oxygen delignification, 31-35% by peroxyformic acid (PFA) pre-treatment and 11-13% by acid pre-treatment. Oxygen delignified pulp required less chlorine dioxide charge to reach target brightness. At the consumption of 30 kg ClO2/ton of pulp, the pulp brightness reached to 65-71% for the untreated pulp, 81-85% for the oxygen delignified pulp, 81-82% for the PFA treatment and 79-80% for acid pre-treated pulp. COD load in bleached effluent was much lower in oxygen delignified pulp. Cold alkali extraction of unbleached and oxygen delignified pulps was also carried out with varying alkali charge to remove hexenuronic acid (HexA) from the pulp. Xylan removal from the pulp was insignificant and resulted in no removal of HexA. Acid pretreatment removed 55.7% to 17.8% HexA from acacia hybrid, 57.5% to 16.3% from A. auriculiformis of 10 years and 58.6% to 20.1% from A. auriculiformis of 6 years old, resulting in improved final pulp brightness.

Graphical abstract Abstract Immobilized enzyme holds considerable potential for industrial applications. In this study, a thermostable xylanase from Geobacillus thermodenitrificans X1 was subjected to carrier free immobilization to generate xylanase cross-linked enzyme aggregates (Xy-CLEAs). Xy-CLEAs were prepared by using overnight precooled (at −20 °C) acetone as precipitant and glutaraldehyde (GA) as the cross-linker. A reaction time of 2 h, GA (0.01% v/v), protein concentration (1.67 mg/mL), 2 h precipitation time and protein to precipitant ratio of 1:10 were found to be the optimum conditions for Xy-CLEAs preparations. Morphological and structural characterization of CLEAs revealed their spherical shape with a diameter of 200–250 nm. In comparison to free xylanase, the immobilized xylanase had high relative activity at a diverse temperature and pH range. Thermostability and pH stability was also improved after immobilization of xylanase. CLEAs of xylanase proved to be commercially reliable as they retained 53.5% activity after being reused till six cycles and 86% activity after storage at 4 °Cfor 8 weeks. [ABSTRACT FROM AUTHOR]

The enzyme involved in hexenuronic acid (HexA) removal from kraft pulp was identified in Paenibacillus sp. strain 07. Extracellular and intracellular enzymes of Paenibacillus sp. were assessed for their hexenuronosyl-xylotriose (∆X3) degradation activity. First, ∆X3 was obtained from hardwood kraft pulp by enzymatic hydrolysis using three commercial enzymes. Crude extracellular and intracellular enzyme fractions were obtained from Paenibacillus cultures cultivated in 0.5% (w/v) birch wood xylan as the sole carbon source. The ∆X3-degrading activities of the enzyme fractions were measured by hydrolysis assays in sodium acetate buffer containing ∆X3 substrate (pH 6) at 50 °C. The reaction products were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection. The enzyme fractions displayed different chromatogram patterns. After treatment with the intracellular enzyme fraction, the chromatograms displayed xylose and hexenuronosyl xylobiose (∆X2) peaks. The chromatogram patterns of the extracellular fraction assays indicated xylose, xylotriose, and ∆X2 production. Thus, the intracellular enzymes of Paenibacillus can hydrolyze the xylosidic linkages at the reducing ends of ∆X3, whereas a specific extracellular enzyme can hydrolyze HexA. This enzyme is potentially applicable to HexA removal during bio-bleaching.

A newly identified ligninolytic Rhodococcus strain (Rhodococcus sp. T1) was isolated from forestry wastes (Trabzon/Turkey). The DyP type peroxidase of Rhodococcus sp. T1 (DyPT1) was cloned, characterized and paper treated for industrial applications. Molecular weight of the protein was about 38 kDa. The kinetic parameters were 0.94 mM and 1417.53 µmol/min/mg for Km and Vmax, respectively. The enzyme was active at the temperature range of 25-65 °C and optimum temperature was 35 °C, enzyme was stable up to 6 days at room temperature. Optimum pH of the DyPT1 was 4.0 and it was stable between pH 4.0-6.0 up to 8 days at room temperature. Effects of some metal ions, Hemin, and some chemical agents on DyPT1 were determined. Hemin has implemented protective effects on the stability and the activity of the enzyme in long time periods when added into growing medium. DyPT1 was applied to eucalyptus kraft pulp for analyzing the bleaching efficiency, physical and optical tests of the manufuctared paper were carried out. Application of lignin peroxidase to kraft pulp caused a decrease of 5.2 units for kappa number and an increase from 52.05 to 64.18% in the delignification rate. [ABSTRACT FROM AUTHOR]

Abstract: 5,8-Dihydroxy-[1,4]-naphthoquinone (DHNQ) is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the degradation of DHNQ by chlorine dioxide at moderately acidic (pH 3) conditions, corresponding to the conditions of industrial bleaching (“D stage”). The degradation involves three major pathways. As initial reaction, a hydrogen transfer from DHNQ to chlorine dioxide via a PCET mechanism occurs to form a radical DHNQ· and chlorous acid. DHNQ· is then attacked by water to give a pentahydroxynaphthalene radical PHN· that is stabilized by strong delocalization of the non-paired electron into its aromatic ring. PHN· immediately disproportionates to give the observable intermediate 1,2,4,5,8-pentahydroxynapththalene (I), which was comprehensively confirmed by NMR and MS (path A). In the presence of excess ClO2, I is immediately further oxidized into acetic acid, glycolic acid, oxalic acid and CO2 as the final, stable, and non-colored products (path C). In the absence of excess ClO2, elimination of water from I regenerates DHNQ (path B), so that at roughly equimolar DHNQ/ClO2 ratios ClO2 is fully consumed while a major part of DHNQ is recovered. To avoid such DHNQ “recycling” under ClO2 consumption—and to completely degrade DHNQ to colorless degradation products instead—ClO2 must be applied in at least fivefold molar excess relative to DHNQ.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: A chemical bleaching process of paper pulps gives off excessive amount of chlorinated organic wastes mostly released to environment without exposing complete bioremediaton. Recent alternative and eco‐friendly approaches toward pulp bleaching appear more responsive to environmental awareness. Here we report, direct use of a recombinant Bacillus subtilis bacterium for pulp bleaching, endowed with three ligninolytic enzymes from various bacteria. In addition, efficient bleaching performance from glutathione‐S‐transferase (GST) biocatalyst tested for the first time in pulp bleaching applications was also achieved. Simultaneous and extracellular overproduction of highly active GST, laccase, and lignin peroxidase catalysts were also performed by Bacillus cells. Both enhanced bleaching success and improved delignification rates were identified when enzyme combinations tested on both pine kraft and waste paper pulps, ranging from 69.75% to 79.18% and 60.89% to 74.65%, respectively. Furthermore, when triple enzyme combination applied onto the papers from pine kraft and waste pulps, the best ISO brightness values were identified as 66.45% and 64.67%, respectively. The delignification rates of pulp fibers exposed to various enzymatic bleaching sequences were comparatively examined under SEM. In conclusion, the current study points out that in near future, a more fined‐tuned engineering of pulp‐colonizing bacteria may become a cost‐effective and environmentally friendly alternative to chemical bleaching. [ABSTRACT FROM AUTHOR]

Abstract: 2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) and 5,8-dihydroxy-[1,4]-naphthoquinone (DHNQ) are two key chromophores which are almost ubiquitous in cellulosic materials. Their fate under conditions of alkaline peroxide bleaching (P stage) has been established previously, but the intermediacy of cyclic peroxides, which so far had only been postulated, remained an open issue. By means of 17O NMR spectroscopy, additionally supported by other NMR techniques, it was demonstrated that both DHBQ and DHNQ form cyclic peroxides as primary intermediates in the reaction with hydrogen peroxide under alkaline conditions. These intermediates are subsequently further degraded to products already known. The experimental confirmation of the cyclic peroxides is an important step in the understanding of reaction mechanisms in pulp bleaching chemistry. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Endo-1, 4-β-xylanase is an enzyme that depolymerises xylan, a major component of lignocellulose. The economic utilization of lignocellulosic biomass as a feedstock for the production of fuel and chemicals would represent a paradigm shift in industrial carbon utilization, allowing sustainable resources to replace the non-renewable energy resources like petroleum. However, lignocellulose is a highly recalcitrant material that is extremely difficult to depolymerize. Many microorganisms possess repertoires of enzymes which act synergistically to decompose various components of lignocellulosic biomass into simple sugars. Biomass-utilizing organisms are widely distributed within different species of archaea, bacteria, fungi, protists, plants, and animals. These organisms possess numerous lignocellulolytic enzymes that can hydrolyze cellulose, hemicelluloses, or lignin. The present paper gives a detailed account of strategies for production, purification and application of microbial xylanases. Conversion of lignocellulose into fermentable sugars and subsequent conversion into bioethanol has been discussed in the present paper. [ABSTRACT FROM AUTHOR]

Chlorine bleaching technology (C process, CEH process, H process and theirs combination), which was identified as a primary formation source of PCDD/Fs, is still widely used by the vast majority of Chinese non-wood pulp and paper mills (non-wood PMs). The purpose of this study was to provide information and data support for further eliminating dioxin for non-wood PMs in China, and especially to evaluate the PCDD/Fs release reduction for those mills converting their pulp bleaching processes from CEH to ECF. The PCDD/Fs concentrations of the bleached pulp and bleaching wastewater with ECF bleaching were in the ranges of 0.13–0.8 ng TEQ kg −1 , and 0.15–1.9 pg TEQ L −1 , respectively, which were far lower than those with CEH process, indicating that the ECF process is an effective alternative bleaching technology to replace CEH in Chinese non-wood PMs to reduce dioxin release. The release factor via flue gas of the alkali recovery boiler in Chinese non-wood PMs was first reported to be 0.092 μg TEQ Ad t −1 in this study. On the assumption that pulp bleaching processes of all Chinese non-wood PMs were converted from CEH to ECF, the annual release of PCDD/Fs via the bleaching wastewater and bleached pulp would be reduced by 79.1%, with a total of 1.60 g TEQ. [ABSTRACT FROM AUTHOR]

Hexeneuronic acids (HexA) are a major cause of discoloration (yellowing/brightness reversion) in pulps from xylan-containing wood, being generated from the xylan's 4- O-methylglucuronic acid residues. The HexA-derived chromophores, whose identification and structure confirmation have been described in the previous part of this series (Rosenau et al. in Cellulose, 2017), were subject to conditions of peroxide bleaching, i.e. treatment with hydrogen peroxide in alkaline medium. These chromophores, ladder-type oligomers of mixed aromatic-quinoid and mixed furanoid-benzoid character, are degraded relatively quickly to one major product, 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ), and a minor component, 2,5-dihydroxyacetophenone (DHA). These two compounds, which have already been identified as two of the three key chromophores (besides 5,8-dihydroxy-[1,4]-naphthoquinone, DHNQ) in aged cellulosics, are potent chromophores themselves and are subsequently more slowly degraded to non-colored degradation products, according to pathways already described in previous parts of this series. The occurrence of DHBQ and DHA in the bleaching treatment of the HexA-derived chromophores establishes the link between HexA chemistry and the key chromophore classes of residual chromophores found in aged cellulosic materials. [ABSTRACT FROM AUTHOR]

By applying increasing amounts of ozone (Z stage bleaching) on eucalyptus oxygen-delignified pulps, it was observed that both lignin and hexenuronic acids (HexA) are attacked early during the treatment. While the HexA were progressively removed, however, the oxidized lignin tended to stay in the pulp. An acidic stage (A stage) at pH 3 and a temperature of 90 to 95°C removed a high proportion of the HexA, which eventually reduced the ozone requirement. In spite of the negative impact of the A stage on the DP of cellulose, totally chlorine-free sequences containing A led to pulps of higher viscosity. Increasing the temperature in A to 120°C did not seem to have an effect other than increasing the rate of the hydrolysis reactions. A very efficient metal removal was observed when a chelating agent was added in A (AQ). Some trials showed that splitting the Z stage in a ZEZE-like process (E for alkaline extraction) minimized the impact on pulp viscosity, and that AQPZE-like sequences can reach a quality comparable to some commercial elemental chlorine free (ECF) pulps.

This paper reports high level production of a cellulase-free xylanase using wheat bran, a cost-effective substrate, under submerged fermentation by alkalophilic Bacillus subtilis ASH. Production of xylanase was observed even at alkaline pH up to 11.0 and temperature 60 °C, although the highest enzyme titer was recorded at neutral pH and 37 °C. The enzyme production under optimized fermentation was 1.5-fold greater than under unoptimized conditions. Pre-treatment of unbleached pulp of 10% consistency with crude xylanase (6 IU/g o.d. pulp) at 60 ºC for 2 h increased the final brightness by 4.9%. The enzyme treatment reduced the chlorine consumption by 28.6% with the same brightness as in the control. A reduction in kappa number and increase in viscosity was observed after enzyme pre-treatment. Scanning electron microscopy revealed loosening and swelling of pulp fibers. The strength properties viz. grammage, fiber thickness, beating degree, tensile index, breaking length, tear index and double fold of the treated pulp were improved as compared to the control pulp. This study reveals the potential of B. subtilis ASH xylanase as a biobleaching agent for the paper and pulp industry.

Optimum conditions to run the P Mo stage for bleaching eucalyptus kraft pulp were 90 ºC, pH 3.5, 2 h, 0.1 kg/t Mo and 5 kg/t H2O2. The P Mo stage efficiency increased with decreasing pH (1.5-5.5) and increasing temperature (75-90 ºC), time (2-4 h), and hydrogen peroxide (3-10 kg/t) and molybdenum concentration (0.1-0.4 kg/t). The implementation of the P Mo stage, as replacement for the A stage, decreased total active chlorine demand of the OAZDP sequence by 6 kg/t to reach 90% ISO, both in laboratory and mill scale. Such practice resulted in decreased bleaching chemical costs to produce fully bleached pulp of 90% ISO.

Crude xylanase preparations from Penicillium corylophilum, Aspergillus niger and Trichoderma longibrachiatum were used to treat Eucalyptus kraft pulp, prior to chlorine dioxide and alkaline bleaching sequences. The enzyme pretreatment improved brightness and delignification of non-delignified and oxygen-bleached samples of eucalyptus kraft pulp. Xylanase preparations from T. longibrachiatum and P. corylophilum were more effective to reduce pulp kappa number. A small reduction in viscosity was obtained when the oxygen-bleached pulp was treated with xylanase preparation from A. niger. For all enzyme samples, the best release of chromophoric material from the pulp was at 237 nm. The enzyme preparation from P. corylophilum was responsible for the highest release of reducing sugar at a dosage interval of 10-20 IU/g dry weight pulp. Scanning electron microscopy studies of oxygen-bleached pulp after xylanase treatment revealed morphological changes, including holes, cracks, filament forming and peeling.Amostras de xilanases de extratos brutos de Penicillium corylophilum, Aspergillus niger e Trichoderma longibrachiatum foram utilizadas no branqueamento de polpa kraft de eucalipto antes das seqüências alcalina e dióxido de cloro. O pré-tratamento enzimático melhorou a alvura e o processo de deslignificação de amostras de polpa kraft de eucalipto não-tratada e tratada com oxigênio. Amostras de xilanases de T. longibrachiatum e P. corylophilum foram mais efetivas na redução do número kappa da polpa. A polpa tratada com oxigênio sofreu uma pequena redução na sua viscosidade quando incubada com amostra de xilanase de A. niger. Para todas as amostras de xilanases, a maior liberação de cromóforos da polpa foi a 237 nm. A amostra de xilanase de P. corylophilum liberou maior quantidade de açúcar redutor da polpa, utilizando dosagem de 10-20 UI/g de peso seco da polpa. Estudos de microscopia eletrônica de varredura revelaram várias alterações morfológicas da polpa tratada com oxigênio tais como a formação de buracos, rachaduras e filamentos.

An oxygen delignified eucalyptus kraft pulp was bleached by applying a catalytic amount of a tertiary amine, 1,4-diazabicyclo[2,2,2]octane, and hypochlorous acid at varying pH, temperature, and time. The bleaching filtrate was analyzed for chloroform and AOX and the pulp for residual lignin, hexenuronic acid, and OX. In comparison with chlorine dioxide bleaching, the novel catalytic bleaching (pH < 6) generated only traces of chloroform and low contents of AOX and OX. Separate catalytic oxidations of authentic hexenuronic acid showed that it was a major precursor of chloroform. The results demonstrate a practical way to reduce organochlorine formation in pulp bleaching and provide new understanding on the reaction pathways that yield chloroform. [ABSTRACT FROM PUBLISHER]

BACKGROUND Organoperoxyl radicals generated from unsaturated fatty acids can initiate lignin degradation reactions. RESULTS Manganese peroxidase ( MnP, EC 1.11.1.13) produced by the basidiomycete Ceriporiopsis subvermispora and biomimetic systems were explored to produce organoperoxyl radicals for lignin degradation of eucalypt wood and unbleached kraft pulps. Treatment of milled-wood with MnP-, Mn3+- or Fe2+-linoleic acid systems transformed the lignin structure and released water-soluble low molar mass aromatic fragments. Lignin transformations initiated by MnP were the most intense. Residual lignins from MnP- or Mn3+-treated wood exhibited diminished yields for thioacidolysis monomers and increased carboxyl content, suggesting β-O-4 and Cα-Cβ cleavage followed by side chain oxidation. MnP-based biobleaching of eucalypt kraft pulp corresponded to savings of 3.7 kg ClO2 ton−1 pulp during elemental chlorine free ( ECF) bleaching to 88-90% brightness. Another interesting characteristic of the MnP-treated pulp was a slightly higher drainage before refining, suggesting that this pulp would require less energy during drying in industrial processes. CONCLUSION Lignin was degraded in vitro by the action of MnP and biomimetic systems initiating lipid peroxidation reactions. Application of the most reactive system, based on MnP, provided savings of 3.7 kg ClO2 ton−1 pulp during ECF bleaching to 88-90% ISO brightness. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]