Pulp bleaching using laccase from trametes versicolor under high temperature and alkaline conditions

Kraft pulp was delignified using laccase produced by the white rot fungusTrametes versicolor immobilized in solid support under specific conditions. The stability tests showed that this enzyme was stable for 6 h at 55°C and pH 8.0, allowing its use under pH and temperature conditions very close to those used in industrial bleaching. In this work, unbleached hardwood Kraft pulp was submitted to prebleaching using 2 U laccase/g pulp basis. Reaction time, temperature, and pH of the enzymatic treatment were investigated. Good results regarding Kappa number reduction, selectivities, and high viscosities were obtained when prebleaching was performed for 1 h at temperature of 55©C and pH 8.0 followed by alkaline extraction and ECF bleaching sequences.

     

Sulfur-free dissolving pulps and their application for viscose and lyocell

In this study, the concept of multifunctional alkaline pulping has been approved to produce high-purity and high-yield dissolving pulps. The selective removal of hemicelluloses was achieved by either water autohydrolysis (PH) or alkaline extraction (E) both applied as pre-treatments prior to cooking. Alternatively, hemicelluloses were isolated after oxygen delignification in a process step denoted as cold caustic extraction (CCE). Eucalyptus globulus wood chips were used as the raw material for kraft and soda-AQ pulping. In all process modifications sulfur was successfully replaced by anthraquinone. By these modifications purified dissolving pulps were subjected to TCF bleaching and comprehensive viscose and lyocell application tests. All pulps met the specifications for dissolving pulps. Further more, CCE-pulps showed a significantly higher yield after final bleaching. Morphological changes such as ultrastructure of the preserved outer cell wall layers, specific surface area and lateral fibril aggregate dimension correlated with the reduced reactivity towards regular viscose processing. The residual xylan after alkali purification depicted a lower content of functional groups and a higher molecular weight and was obviously entrapped in the cellulose fibril aggregates which render the hemicelluloses more resistant to steeping in the standard viscose process. Simultaneously, the supramolecular structure of the cellulose is partly converted from cellulose I to cellulose II by the alkaline purification step which did not influence the pulps reactivity significantly. Nevertheless, these differences in pulp parameters did not affect the lyocell process due to the outstanding solubility of the pulps in NMMO. Laboratory spinning revealed good fiber strength for both, regular viscose and lyocell fibers. The high molecular weight xylan of the CCE-treated pulps even took part in fiber forming.     

Characterization and sources of extractable organochlorine in white sucker downstream from bleached kraft pulp mills

Organochlorine, obtained by extraction with hexane–acetone mixture (3?:?1) of fillets of white sucker (Catostomus commersoni) sampled downstream of pulp mills and in a reference river, was characterized by gel-permeation chromatography, transesterification, neutron activation analysis, and gas chromatography with halogen-sensitive detection. It was found that over 78% of the extractable organochlorine (EOCl) is of relatively high molecular weight (>～350). Chlorinated fatty acids account for 43–80% of EOCl in the high-molecular-weight portion, while chlorobenzenes, chlorinated pesticides, and polychlorinated biphenyls account for 4–55% of EOCl in the low-molecular-weight portion. Though undetectable in reference fish, three particular chlorinated fatty acids, i.e. threo-5,6-dichlorotetradecanoic, threo-7,8-dichlorohexadecanoic and threo-9,10-dichlorooctadecanoic acids, are characteristic of EOCl from fish collected downstream of bleached kraft pulp mills using chlorine-based bleaching, representing about 30% of total EOCl, of which threo-5,6-dichlorotetradecanoic acid alone accounts for 60–70%. It is thus evident that, among chlorinated compounds discharged from bleached kraft pulp mills, threo-9,10-dichlorooctadecanoic acid, presumably generated in chlorine-based bleaching processes, is the most bio-accumulative in fish and can be biodegraded by fish into dichlorohexadecanoic and dichlorotetradecanoic acids, presumably via β-oxidative metabolism. These three compounds were also identified in suspended solids isolated from biologically treated final effluent discharged from a bleached pulp mill using 50% ClO₂ substitution, thus confirming the effluent-related source for downstream fish. The finding also suggests that β-oxidation of dichlorooctadecanoic acid may also be operative in micro-organisms.     

A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine (Pinus sylvestris) wood. Part I: lipophilic compounds

The wood resin in Scots pine (Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm(-1). Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at approximately 1650 cm(-1) due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.     

Analysis of impurities occurring in a totally chlorine free-bleached Kraft pulp

A set of impurities (specks) occurring in a TCF (totally chlorine free)-bleached Kraft pulp of Eucalyptus globulus wood was studied. The impurities were Soxhlet extracted with acetone, and the extracts subsequently analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) using high-temperature capillary columns. The lipophilic fraction isolated from E. globulus wood extractives was also analyzed for comparison. The composition of the acetone extracts was very similar to that of E. globulus wood. Fatty acids, steroid hydrocarbons, sterols, steroid ketones and sterol esters, arising from E. globulus wood extractives survived the cooking and bleaching processes and accumulated in the pulp. On the other hand, the residue left after acetone extraction was studied by pyrolysis–GC–MS. The results indicated that it was composed of small particles of polyisoprene rubber. In conclusion, the speck impurities studied here seems to be composed of two different moieties, a lipophilic part arising from wood extractives and a core of small particles of synthetic polymers (polyisoprene rubber).     

A precise study on the feasibility of enzyme treatments of a kraft pulp for viscose application

The development of efficient process steps to convert paper-grade to dissolving pulps was investigated as part of the work programme to improve the process economics. The challenge of pulp refinement comprises the selective removal of hemicelluloses and the precise adjustment of the pulp viscosity, while maintaining the reactivity of the pulp as required for viscose application. The purpose of this study was to investigate the effects of various enzyme treatments on a commercial oxygen-delignified Eucalyptus globulus paper-grade kraft pulp in the course of a total chlorine free bleaching sequence in combination with refining techniques following the principle of Modified Kraft Cooking (Sixta et al. 2007). The objectives were to assess its applicability as viscose pulp besides the reduction of chemical consumption in alkaline and ozone bleaching steps by means of xylanase pre-treatment and the controlled adjustment of final pulp viscosity utilizing endoglucanase post-treatment. Xylanase pre-treatment combined with cold caustic extraction at reduced alkalinity efficiently removed the hemicelluloses from the pulp and clearly increased the pulp brightness by extensive removal of hexenuronic acid side chains. The xylanase pre-treated pulp showed increased reactivity towards xanthation and high viscose dope quality in terms of particle content. The dependence of cellulose chain scission on the applied endoglucanase concentration was analyzed in detail, and this allowed precise viscosity reduction as well as reactivity increase. The differently treated pulps, with and without xylanase pre-treatment, were of very narrow molecular weight distribution and the quality of the spun fibers were very similar to those viscose fibers from commercial dissolving pulps.     

Determination of Chlorophenols in Wastewater with Methyl Chloroformate Derivatization,Solid Phase Extraction,and Gas Chromatography–Mass Spectrometry

The determination of chlorophenols in wastewater with methyl chloroformate derivatization, solid phase extraction, and gas chromatography–mass spectrometry is reported. In order to employ this combined solid phase derivative extraction method, quantitative extraction was performed by the introduction of 100 mL of sample in 1.0 mol L^?1 sodium hydroxide into a column containing 500 mg of packed resin at a flow rate of 1.0 mL/min. The chlorophenols were retained and derivatized quantitatively in the column by the introduction of 0.25 mL of methyl chloroformate. The derivatized analytes were eluted with 5.0 mL of hexane before the effluent was dried under a stream of nitrogen. The dried solution was diluted to a volume of 50 µL with hexane followed by analysis by gas chromatography–mass spectrometry. The preconcentration parameters were optimized and under these conditions: limits of detection from 0.010 to 0.423 µg L^?1, a preconcentration factor of 2500, and precision values from 4.8 to 7.7% as the relative standard deviation were obtained. The method was employed for the analysis of water samples and the recoveries of the analytes were between 76 and 103%.     

Development of rigid biporous polymeric adsorbent for protein chromatography

Summary A novel biporous poly (glycidyl methacrylate-triallyl isocyanurate-divinylbenzene) resin (denoted as Resin C) was prepared byin-situ co-polymerization with both superfine granules of sodium sulfate and the solvents toluene and n-heptane as porogenic agents. This material is based on a novel porogenic mode of a combination of both solid granules and solvents. The properties of Resin C were characterized, and then compared with both Resin A (where only solvents as porogen) and Resin B (where only solid granules are used as porogen). The biporous resin showed good mechanical performance, high dynamic adsorption capacity and column efficiency at high flow-rates. These factors indicate the biporous resin as a promising adsorbent for high-speed protein separation by chromatography.     

Gas chromatographic determination of pollutants in the chlorination and caustic extraction stage effluent from the bleaching of a bamboo pulp

The gas chromatographic detection and quantitative determination of various chlorophenolics as well as resin and fatty acids have been carried out in the chlorination and caustic extraction stage effluents generated in the laboratory by bleaching a bamboo pulp. A number of chlorinated phenols, catechols, guaiacols, syringaldehydes and resin acids as well as non-chlorinated saturated and unsaturated fatty acids together with resin acids have been detected. The concentration of various compounds detected have also been compared with the reported (96)LC(50) values.     

Bleach Enhancement of Mixed Wood Pulp by Xylanase–Laccase Concoction Derived Through Co-culture Strategy

Mixed enzyme preparation having both xylanase and laccase activity was evaluated for its bleach enhancing ability of mixed wood pulp. The enzyme was produced through co-cultivation of mutant Penicillium oxalicum SAU_E-3.510 and Pleurotus ostreatus MTCC 1804 under solid-state fermentation. Bleaching of pulp with mixed enzyme had resulted into a notable decrease in kappa number and increased brightness as compared to xylanase alone. Analysis of bleaching conditions had denoted that 8 IU g⁻¹ of mixed enzyme preparation (xylanase/laccase, 22:1) had led into maximal removal of lignin from pulp when bleaching was performed at 10% pulp consistency (55 °C, pH 9.0) for 3 h. An overall improvement of 21%, 8%, 3%, and 5% respectively in kappa number, brightness, yellowness, and viscosity of pulp was achieved under derived bleaching conditions. Process of enzymatic bleaching was further ascertained by analyzing the changes occurring in polysaccharide and lignin by HPLC and FTIR. The UV absorption spectrum of the compounds released during enzymatic treatment had denoted a characteristic peak at 280 nm, indicating the presence of lignin in released coloring matter. The changes in fiber morphology following enzymatic delignification were studied by scanning electron microscopy.     

Fast analysis of relative levels of dehydroabietic acid in papermaking process waters by on-line sample enrichment followed by atmospheric pressure chemical ionisation-mass spectrometry (APCI-MS)

Resin acids are considered to be significant contributors to the toxicity of pulp mill effluents. Traditionally, the analysis of these acids is performed by liquid–liquid extraction followed by gas chromatography. This paper describes a method suitable for monitoring the relative concentration levels of the main resin acid component, dehydroabietic acid (DHAA), in process waters by atmospheric pressure chemical ionisation-mass spectrometry (APCI-MS). This method was further improved, first by testing different precolumns for on-line sample clean-up and then by developing the APCI-MS analysis of the analytes trapped in the precolumn (i.e., solid-phase extraction column). The external standard, internal standard, and response factor methods were compared. The curve profiles of the results obtained with the above determinations were very similar to each other. This finding suggested that the rapid APCI-MS method, using a selected ion monitoring (SIM) technique, is a potential tool for monitoring relative concentration levels of DHAA. The technique is also recommended for rapid and simple monitoring of DHAA as well as of other resin acids, and their derivatives, such as their chlorinated analogues, in various aquatic environmental samples.     

Pulp Enhancement of Oil Palm Empty Fruit Bunches (OPEFBs) via Biobleaching by Using Xylano-Pectinolytic Enzymes of Bacillus amyloliquefaciens ADI2

The present work reports the biobleaching effect on OPEFB pulp upon utilisation of extracellular xylano-pectinolytic enzymes simultaneously yielded from Bacillus amyloliquefaciens ADI2. The impacts of different doses, retention times, pH, and temperatures required for the pulp biobleaching process were delineated accordingly. Here, the OPEFB pulp was subjected to pre-treatment with xylano-pectinolytic enzymes generated from the same alkalo-thermotolerant isolate that yielded those of higher quality. Remarkable enhanced outcomes were observed across varying pulp attributes: for example, enzyme-treated pulp treated to chemical bleaching sequence generated improved brightness of 11.25%. This resulted in 11.25% of less chlorine or chemical consumption required for obtaining pulp with optical attributes identical to those generated via typical chemical bleaching processes. Ultimately, the reduced consumption of chlorine would minimise the organochlorine compounds found in an effluent, resulting in a lowered environmental effect of paper-making processes overall as a consequence. This will undoubtedly facilitate such environmentally-friendly technology incorporation in the paper pulp industry of today.     

Analysis of pitch deposits produced in kraft pulp mills using a totally chlorine free bleaching sequence

Two organic deposits accumulated in a Kraft pulp mill during pulping of Eucalyptus globulus wood and throughout a TCF (totally chlorine free) bleaching sequence were characterized. One deposit was collected after cooking and an oxygen delignification stage while the other was collected after bleaching with hydrogen peroxide. The deposits were Soxhlet extracted with acetone, and the extracts redissolved in chloroform and subsequently analyzed by gas chromatography (GC) and GC-mass spectrometry (MS) using short and medium length high temperature capillary columns, respectively. On the other hand, the insoluble residues left after the acetone extraction were analyzed by Curie-point flash pyrolysis-GC-MS and by pyrolysis-methylation-GC-MS. The compounds identified in the deposits arise from the E. globulus wood lipophilic extractives that survive the pulping and bleaching processes. Triglycerides were completely hydrolyzed during the Kraft cooking and the fatty acids dissolved. Steroids (alcohols, hydrocarbons, ketones and esters) and waxes were the main components in the deposit collected after the oxygen delignification stage. After the bleaching with hydrogen peroxide, content of the waxes were reduced and fatty acids appeared. High amounts of fatty acids salts were also identified in the deposit collected after the oxygen stage, and in minor amounts in the deposit collected after hydrogen peroxide bleaching. In contrast, this deposit was mainly made up of high amounts of lignin-derived phenolic moieties.     

13C CPMAS NMR investigations of cellulose polymorphs in different pulps

In order to obtain information about the crystallinity and polymorphs of cellulose, and the occurrence of hemicelluloses in pulp fibers, wood cellulose, bacterial cellulose, cotton linters, viscose, and celluloses in different pulps were investigated by solid state ¹³C CPMAS NMR spectroscopy. A mixed softwood kraft pulp and a dissolving-grade pulp were treated under strongly alkaline and acidic conditions and the effect on cellulose crystallinity was studied. The presence of different crystalline polymorphs of cellulose and the amounts of hemicelluloses are considered.     

Ultrasound-Assisted Extraction of Humic Substances from Peat: Assessment of Process Efficiency and Products’ Quality

Results of efficiency of obtaining humic substances (HSs) from peat in traditional alkaline extraction (TAE) and ultrasound-assisted alkaline extraction (UAAE) are presented. The influence of the duration of the process and ultrasound intensity on the efficiency of extraction of humic acids (HAs) and fulvic acids (FAs) extraction was determined. The composition of the fulvic acid fraction was examined depending on the type of eluent used. Fulvic acids were divided into fractions using columns packed with DAX-8 resin. For this process, 0.1 M NaOH and 0.5 M NH₃∙H₂O were used as eluents. For the quality assessment of specific fulvic acids fractions, spectroscopic methods (UV-Vis and FTIR) were used. Ultrasound had a positive effect on HS extraction efficiency, especially in increasing the amount of a desired hydrophobic fraction of fulvic acids (HPO). However, a negative effect of the excessive prolongation and ultrasound intensity (approximately 400 mW∙cm⁻²) on the extraction efficiency of HPO eluted with 0.1 M NaOH solution was observed. Using peat as a raw carbon material for the HS extraction process can be used as an alternative industrial application of peat. UAAE may be considered as an alternative method to TAE, which provides a higher efficiency in HS isolation from peat.     

Separation of phenolic acids from sugarcane rind by online solid‐phase extraction with high‐speed counter‐current chromatography

Sugarcane rind contains some functional phenolic acids. The separation of these compounds from sugarcane rind is able to realize the integrated utilization of the crop and reduce environment pollution. In this paper, a novel protocol based on interfacing online solid‐phase extraction with high‐speed counter‐current chromatography (HSCCC) was established, aiming at improving and simplifying the process of phenolic acids separation from sugarcane rind. The conditions of online solid‐phase extraction with HSCCC involving solvent system, flow rate of mobile phase as well as saturated extent of absorption of solid‐phase extraction were optimized to improve extraction efficiency and reduce separation time. The separation of phenolic acids was performed with a two‐phase solvent system composed of butanol/acetic acid/water at a volume ratio of 4:1:5, and the developed online solid‐phase extraction with HSCCC method was validated and successfully applied for sugarcane rind, and three phenolic acids including 6.73 mg of gallic acid, 10.85 mg of p‐coumaric acid, and 2.78 mg of ferulic acid with purities of 60.2, 95.4, and 84%, respectively, were obtained from 150 mg sugarcane rind crude extracts. In addition, the three different elution methods of phenolic acids purification including HSCCC, elution–extrusion counter‐current chromatography and back‐extrusion counter‐current chromatography were compared.     

Determination of fatty acid methyl esters derived from algae Scenedesmus dimorphus biomass by GC–MS with one‐step esterification of free fatty acids and transesterification of glycerolipids

Algae can synthesize, accumulate and store large amounts of lipids in its cells, which holds immense potential as a renewable source of biodiesel. In this work, we have developed and validated a GC–MS method for quantitation of fatty acids and glycerolipids in forms of fatty acid methyl esters derived from algae biomass. Algae Scenedesmus dimorphus dry mass was pulverized by mortar and pestle, then extracted by the modified Folch method and fractionated into free fatty acids and glycerolipids on aminopropyl solid‐phase extraction cartridges. Fatty acid methyl esters were produced by an optimized one‐step esterification of fatty acids and transesterification of glycerolipids with boron trichloride/methanol. The matrix effect, recoveries and stability of fatty acids and glycerolipids in algal matrix were first evaluated by spiking stable isotopes of pentadecanoic‐2,2‐d₂ acid and glyceryl tri(hexadecanoate‐2,2‐d₂) as surrogate analytes and tridecanoic‐2,2‐d₂ acid as internal standard into algal matrix prior to sample extraction. Later, the method was validated in terms of lower limits of quantitation, linear calibration ranges, intra‐ and inter‐assay precision and accuracy using tridecanoic‐2,2‐d₂ acid as internal standard. The method developed has been applied to the quantitation of fatty acid methyl esters from free fatty acid and glycerolipid fractions of algae Scenedesmus dimorphus .     

Separation of α‐ from β‐arylalanines by nickel nitrilotriacetate chromatography

A method is described to separate α‐ from β‐arylalanines by ligand exchange chromatography on a nickel nitrilotriacetate agarose column with UV monitoring of the effluent. Separate mixtures containing an α‐ and β‐arylalanine pair (1 mg of each) were individually loaded onto the nickel resin pre‐equilibrated with the mobile phase at room temperature, and the amino acids were eluted from the column with a gradient from pH 12.0–8.0. The β‐arylalanines eluted first, followed by the α‐isomers. The four α/β‐amino acid pairs tested were well separated with baseline resolution. An aliquot of each fraction was chemically treated to derivatize the amino acids to their N‐acyl methyl ester analogs, and their identities were confirmed by GC/MS analysis. The sample recovery was quantitative (>98%), and the column matrix was very resilient, as demonstrated by consistent separation of the solutes after ～100 preparative cycles.     

Potential of Thermo and Alkali Stable Xylanases from Thielaviopsis basicola (MTCC-1467) in Biobleaching of Wood Kraft Pulp

Thermo- and alkali-stable xylanases produced from Thielaviopsis basicola (MTCC-1467) on low-cost carbon source like rice straw were evaluated for their potential application in biobleaching of wood kraft pulp. Enzyme treatment at retention time of 240?min with 20?IU/gm of dried pulp resulted in ~85.2?% of reduction in kappa number. When compared to control, 110.8, 93, and 72.2?% of enhancement in brightness (percent International Organization of Standardization), whiteness, and fluorescence, respectively, were observed for enzyme-treated pulp. Spectroscopic analysis showed significant release of chromophoric compounds from enzyme-treated pulp. Furthermore, scanning electron microscope studies of unbleached and enzyme bleached pulp revealed the effectiveness of enzymatic treatment. The enzyme-treated pulp subjected to later stages of chemical bleaching resulted in 16?% decrease in chlorine consumption along with considerable reduction in chemical oxygen demand percentage (14.5?%) level of effluent. Various pulp properties like fiber length, fiber width, burst strength, burst index, tear strength, tear index, tensile strength, and breaking length were also significantly improved after enzyme treatment when compared to control.     

Direct determination of resin and fatty acids in process waters of paper industries by liquid chromatography/mass spectrometry

Liquid chromatography/mass spectrometry (LC/MS)-based methods were developed for the analysis of 10 resin acids and five fatty acids in process waters of paper industries. No fragmentation of target compounds was observed using atmospheric pressure chemical ionization (APCI) with negative ionization. The [M - H](-) ion permitted the individual quantification of fatty and aromatic resin acids, whereas the non-aromatic resin acids presented a single and common ion at m/z 301. Separation with two columns of different polarity permitted peak confirmation. The method that used a C(8) column with 2-propanol in the mobile phase allowed a certain separation and identification of the non-aromatic resin acids, whereas the method using a C(18) column provided detection limits 10-fold lower for fatty acids. Limits of detection were 0.10 ng for all compounds. Direct sample introduction was compared with liquid-liquid extraction, with similar recoveries (70-101%). Whereas slightly lower detection limits were obtained with liquid-liquid extraction, better reproducibility was observed for direct sample introduction. Resin and fatty acids were determined in process waters of several paper industries. Palmitic, dehydroabietic and non-aromatic resin acids were encountered in most water samples, at levels between 22 and 403 micro g l(-1). LC/MS with direct sample introduction was found to be a good alternative to traditional liquid-liquid extraction and gas chromatography for the analysis of such compounds since no derivatization was required and sample manipulation was minimal.