High concentrations of fatty acids affect the lipase treatment of softwood thermomechanical pulps

Triglycerides, a major class of wood extractives, contribute to the colloidal pitch that initiates pitch deposits. Because industrial or pilot-scale treatments with lipolytic enzymes to reduce triglyceride concentrations in pulp have not been successful in North America, we investigated such treatments at a laboratory scale. Different batches of industrial softwood chemithermomechanical pulps (CTMP) were treated with a range of concentrations of two commercial lipases: Resinase A 2X (Novo Nordisk AG) and Lipidase 10 000 (American Laboratories Inc.). A pilot-scale thermomechanical pulp (TMP) made from the same wood as the CTMP, but without the sodium hydrosulfite used in the CTMP, was also treated with the lipases. While triglycerides decreased in all the pulp treatments, the extent of their hydrolysis varied according to the ratio of triglyceride to the fatty/resin acid fraction. As this ratio can vary significantly in softwood TMP and CTMP, the success of industrial treatments of softwood mechanical pulps by commercial lipases may be related to variations in this ratio. Supporting this, adding linoleic acid to an extractives-free pulp that was spiked with olive oil reduced lipase activity by up to 55%. Received: 7 August 1997 / Received last revision: 8 December 1997 / Accepted: 14 December 1997     

Modification of high-lignin softwood kraft pulp with laccase and amino acids

This study demonstrates the potential of laccase-facilitated grafting of amino acids to high-lignin content pulps to improve their physical properties in paper products. Research studies have recently reported that increases in anionic fiber charge can improve strength properties of paper. In an effort to increase carboxylic acid groups, we developed a unique two-stage laccase grafting protocol in which fibers were initially treated with laccase followed by grafting reactions with amino acids. The bulk acid group content was measured, and a variety of amino acids including glycine (Gly), phenylalanine (Phe), serine (Ser), arginine (Arg), histidine (His), alanine (Ala), and aspartic acid (Asp) were examined. The effects of optimizing laccase dose, and amino acid structures, on fiber modification chemistry were studied. Histidine provided the best yield of acid groups on pulp fiber, and was used for the preparation of handsheets for physical strength testing. Laccase-histidine treated pulp showed an increase in strength properties of the resulting paper.     

Evaluating laccase-facilitated coupling of phenolic acids to high-yield kraft pulps

In an effort to alter the physical properties of high-yield kraft, fibers were treated at high consistency (20%) with laccase and syringic, vanillic, or 4-hydroxybenzoic acid. Treatment with laccase and 4-hydroxybenzoic acid resulted in a 20-point increase in kappa number and a 100% increase in bulk acid groups. ESCA analysis of the treated and untreated pulp revealed that the laccase-grafted fibers had a two-fold enrichment in acid groups, strongly suggesting a laccase-facilitated coupling of 4-hydroxybenzoic acid to the fiber surface. A model system consisting of lignin-coated cellulosic fibers was developed to determine changes to the lignin structure during laccase grafting. ³¹P NMR analysis of lignin from the model system revealed an increase in acid groups with a concomitant decrease in phenolic hydroxyl groups.     

Residual lignin studies of laccase-delignified kraft pulps

The delignification of chemical pulps with laccase and -hydroxybenzotriazole was explored employing a pre- and post-O₂ delignified softwood draft pulp. The delignification properties of laccase were shown to be improved with -hydroxybenzotriazole was used as a mediator instead of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid). Analysis of the structure of residual lignin before and after laccase/ -hydroxybenzotriazole treatment indicated that the biobleaching system oxidizes the phenolic component of lignin and that the residual lignin is demethylated and significantly enriched in carboxylic acid groups.     

Treatment of recycled kraft pulps with Trichoderma reesei hemicellulases and cellulases

Effects of recycling ECF-bleached softwood kraft pulp on pulp properties were evaluated in the laboratory. The tensile strength, fiber flexibility and WRV lost during drying of the pulp were recovered by refining between the cycles which, however, resulted in deteriorated drainage properties. The recycled pulps were treated with purified Trichoderma reesei cellulases and hemicellulases and the changes in fiber properties due to enzymatic treatments were characterized. The endoglucanases (EG I and EG II) significantly improved pulp drainage already at low dosage levels, and EG II was found to be more effective at a given level of carbohydrate solubilization. Combining hemicellulases with the endoglucanase treatments increased the positive effects of the endoglucanases on pulp drainage. However, as a result of the endoglucanase treatments a slight loss in strength was observed. Combining mannanase with endoglucanase treatments appeared to increase this negative effect, whereas the impact of xylanase was not significant. Although the drainage properties of the pulps could be improved by selected enzymes, the water retention capacity of the dried hornified fibers could not be recovered by any of the enzymes tested.     

Use of acid-tolerant xylanase for bleaching of kraft pulps

A xylanase from Aspergillus kawachii, active at pH 2.0–2.5, was found to be suitable for improvement of bleachability. Due to the low working pH of the xylanase, the metal cations were also removed and thus the metal removal stage using chelating agents could be omitted. The use of acid-tolerant xylanase is especially beneficial prior to ozone or chlorine dioxide bleaching stages due to the minimization of pH adjustment steps during bleaching.     

Biobleaching of Eucalyptus globulus kraft pulps: comparison between pulps obtained from exploded and non-exploded chips

The aim of this work was to evaluate the response to biobleaching of steam exploded kraft pulps and to compare the results with the controls. For this end, a laccase-mediator treatment using commercial laccase (Novozyme 51003) and a natural mediator (acetosyringone) were assayed, followed by alkaline extraction and hydrogen peroxide stages.Our approach resulted in exploded biobleached pulps with lower kappa number and improved optical properties compared to controls, even after subjecting pulps to accelerated ageing. Additionally, use of hydrogen peroxide was reduced. The LMS (laccase-mediator system) had a smaller impact on the properties of the bleached pulps and on hydrogen peroxide consumption than the steam explosion process did.     

Biological bleaching of kraft pulps by white-rot fungi and their enzymes

Abstract: The use of white-rot fungi, especially Trametes versicolor and isolate IZU-154, to delignify and brighten kraft pulps is reviewed. The fungal treatments are effective but slow; the responsible enzymes are being studied with a view to accelerating the process. Manganese peroxidase, or laccase with a co-substrate, can demethylate and partially solubilize the lignin in pulps, mimicking the early steps of the fungal delignification.     

Modification of high-lignin kraft pulps with laccase. Part 2. Xylanase-enhanced strength benefits

The effects of xylanase pretreatment of high lignin content softwood (SW) kraft pulp on subsequent pulp treatment with laccase in combination with gallic acid were investigated. Although xylanase pretreatment was ineffective in enhancing the laccase-facilitated biografting of gallic acid to kraft fibers, it was beneficial for subsequent treatment with laccase exclusively. Treating pulp fibers with xylanase followed by laccase provided a collective 25% and 46% increase in dry and wet tensile strength properties, respectively.     

Investigation of lignin-carbohydrate complexes in kraft pulps by selective enzymatic treatments

The occurrence of covalent bonds between residual lignin and polysaccharides in birch and pine kraft pulps was investigated by specific enzymatic treatments. Pure enzymes degrading cellulose, xylan and mannan were used both separately and in combination. Comparison of the molar masses of polysaccharides and lignin in the orginal pulps and in the residual pulps after enzymatic treatments showed that residual lignin in birch kraft pulp is linked at least to xylan. A minor portion may also be linked to cellulose. In pine kraft pulp some of the residual lignin appears to be linked to cellulose, glucomannan and xylan. The linkages between lignin and cellulose and hemicelluloses may be either native or formed during pulp processing. The results also provided new information on the synergistic action of cellulose- and hemicellulose-degrading enzymes on pulp fibres. The synergism appears to be mainly due to the structure of the pulp fibres, with different layers of cellulose sheets, hemicelluloses and lignin. On the other hand the results also provided information about fibre structure. The degradation of xylan clearly enhanced the action of enzymes on cellulose, suggesting that xylan partially covers the cellulose. A similar phenomenon was not observed in the simultaneous hydrolysis of glucomannan and cellulose. However, the results suggest that glucomannan does interact with cellulose, possibly by non-covalent linkages. Received: 8 July 1998 / Received revision: 7 October 1998 / Accepted: 11 October 1998     

Exogenous carnitine application augments transport of fatty acids into mitochondria and stimulates mitochondrial respiration in maize seedlings grown under normal and cold conditions

This study aimed to investigate whether exogenous application of carnitine stimulates transportation of fatty acids into mitochondria, which is an important part of fatty acid trafficking in cells, and mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions. Cold stress led to significant increases in lipase activity, which is responsible for the breakdown of triacylglycerols, and carnitine acyltransferase (carnitine acyltransferase I and II) activities, which are responsible for the transport of activated long-chain fatty acids into mitochondria. While exogenous application of carnitine has a similar promoting effect with cold stress on lipase activity, it resulted in further increases in the activity of carnitine acyltransferases compared to cold stress. The highest activity levels for these enzymes were recorded in the seedlings treated with cold plus carnitine. In addition, these increases were correlated with positive increases in the contents of free- and long-chain acylcarnitines (decanoyl-l-carnitine, lauroyl-l-carnitine, myristoyl-l-carnitine, and stearoyl-l-carnitine), and with decreases in the total lipid content. The highest values for free- and long-chain acylcarnitines and the lowest value for total lipid content were recorded in the seedlings treated with cold plus carnitine. On the other hand, carnitine with and without cold stress significantly upregulated the expression level of citrate synthase, which is responsible for catalysing the first reaction of the citric acid cycle, and cytochrome oxidase, which is the membrane-bound terminal enzyme in the electron transfer chain, as well as lipase. All these results revealed that on the one hand, carnitine enhanced transport of fatty acids into mitochondria by increasing the activities of lipase and carnitine acyltransferases, and, on the other hand, stimulated mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions.     

Patterns of plasma fatty acids in rat models with adenovirus infection

Adenoviral vectors are among the most promising vectors available for human gene therapy. However, the use of recombinant adenoviral vectors, including replicationcompetent adenovirus (RCA), raises a variety of safety concerns in relation to the development of new therapies based on gene therapy. To examine how organic compounds change in rat plasma following the injection of adenovirus, beta-galactosidase expressing recombinant adenovirus (designated rAdLacZ) or RCA, we investigated the content of fatty acids (FAs), which are important biochemical indicators in pathological conditions. Pattern recognition analysis on the level of FAs in rat plasma is described for the visual discrimination of adenovirus infection groups from normal controls. Plasma FAs from four control rats (normal group), and from four rats with rAdLacZ infection and six rats with RCA infection (the two abnormal groups), were examined by gas chromatography-mass spectrometry in selected ion monitoring modes as their tert-butyldimethylsilyl derivatives. In total, 20 FAs were positively detected and quantified. The results of the Studentos t-test on the normal mean of two abnormal groups, the levels of three FAs (p< 0.05) from rAdLacZ group and eleven FAs (p < 0.05) from RCA group were significantly different. When star symbol plotting was applied to the group mean values of 20 FAs after normalization to the corresponding normal mean values, the resulting eicosagonal star patterns of the two infected groups were distorted into similar shapes, but were distinguishable from each other. Thus, these approaches will be useful for screening and monitoring of diagnostic markers for the effects of infection following the use of adenoviral vectors in gene therapy.     

Assessment of various commercial enzymes in the bleaching of radiata pine kraft pulps

Four xylanase preparations that are commercially available, namely Cartazyme from Sandoz, Ecopulp from Alko-ICI, Irgazyme from Ciba-Genencor and Pulpzyme HB from Novo Nordisk, were tested in bleaching experiments of kraft pulps from Pinus radiata. The main objective of this study was to optimize a reduction in the consumption of chlorine dioxide in the bleaching sequences C₉₀/D₁₀E_oDED, C₇₀/D₃₀E_oDED and D₁₀₀EDED. Enzymatic treatments led to savings of ClO₂ between 3.5 and 3.9 kg per air-dried tons (ADT) in the three bleaching sequences, without affecting the target brightness of the pulps. In these assays, some minor although reproducible differences in the performance of the enzymes were observed. In most cases, xylanase treatment partially affected the beatability of the pulps, measured as the number of revolutions in the PFI mill required to reach the same tensile index as the respective controls.     

Differences in cellular fatty acids and lipid composition inClostridium pasteurianum under nitrogen-and non-nitrogen-fixing conditions

Clostridium pasteurianum total cellular saturated fatty acids increased through its growth cycle from 81% to 91% but varied significantly in the composition under nitrogen- and non-nitrogen-fixing conditions. During ammonia-assimilating growth, palmitic acid decreased from 67.7% to 43.5% by late log while marked increases in shorter chain saturated fatty acids (C_15:0 and below) and a long chain saturated C_22:0 occured. In contrast, under N₂-fixing growth conditions, palmitic acid increased from 45.5% to 84.3% by late log, representing nearly the total amound of saturated fatty acids found inC. pasteurianum. The total cellular lipid concentration decreased as the culture aged. irrespective of the nitrogen sources; however, the phospholipid concentration increased significantly during N₂-fixing growth as compared with a 50% decrease during ammonia-assimilating conditions. The implication of these differences and possible role of palmitic acid and phospholipids inC. pasteurianum nitrogen fixation process are discussed.