Unbleached Hardwood Kraft Pulp Research Articles

Ergosterol and Its Metabolites Induce Ligninolytic Activity in the Lignin-Degrading Fungus Phanerochaete sordida YK-624.

White-rot fungi are the most important group of lignin biodegraders. Phanerochaete sordida YK-624 has higher ligninolytic activity than that of model white-rot fungi. However, the underlying mechanism responsible for lignin degradation by white-rot fungi remains unknown, and the induced compounds isolated from white-rot fungi for lignin degradation have never been studied. In the present study, we tried to screen ligninolytic-inducing compounds produced by P. sordida YK-624. After large-scale incubation of P. sordida YK-624, the culture and mycelium were separated by filtration. After the separation and purification, purified compounds were analyzed by high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance. The sterilized unbleached hardwood kraft pulp was used for the initial evaluation of ligninolytic activity. Ergosterol was isolated and identified and it induced the lignin-degrading activity of this fungus. Moreover, we investigated ergosterol metabolites from P. sordida YK-624, and the ergosterol metabolites ergosta-4,7,22-triene-3,6-dione and ergosta-4,6,8(14),22-tetraen-3-one were identified and then chemically synthesized. These compounds significantly improved the lignin-degrading activity of the fungus. This is the first report on the ligninolytic-inducing compounds produced by white-rot fungi.

Sustainable high-yield lignocellulosic fibers and modification technologies educing softness and strength for tissues and hygiene products for global health

Unbleached hardwood kraft pulp was treated with a non-ionic surfactant to decrease the concentration of a hydration shell by dislodging hard-to-remove water through a targeted reduction in surface tension. Energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry techniques were used to investigate and evaluate these fiber-surfactant interactions. Scanning electron microscopeimages were taken to observe the change in the morphology from the surfactant treatment. The surface tension was measured by using pendant drop tests, which reduced from 71.46 mN/m to ∼ 49–51 mN/m for different pretreatment techniques and hence, reduced the pulling force exerted by the liquid bridge water on the fibers by 28–31%. This consequently led to reduced fiber collapse, and the surfactant-treated fibers showed higher bulk and softness without a concomitant sacrifice of mechanical properties. The scanning electron microscopeimages confirmed a more cylindrical fiber structure and showed an unaffected fiber–fiber interaction because of which the tensile strength was not compromised with the increase of bulk. The surfactant-treated fibers showed better recovery or spring back, i.e. a return to their original form after compression relative to the untreated fibers. Therefore, it was possible to make tissue papers with higher bulk, softer hand-feel, and a higher absorbing capacity, without reducing the tensile strength by simple and green processes involving chemical and mechanical modifications.

Influence of pulp bleaching and compatibilizer selection on performance of pulp fiber reinforced PLA biocomposites

ABSTRACTThis article focuses on the effect of pulp bleaching and emerging commercial compatibilizers on physical performance of pulp fiber reinforced poly(lactic acid) (PLA) biocomposites. Industrially bleached and unbleached hardwood kraft pulp fibers are treated with several additive types, and compounded with PLA to fiber content of 30 wt %. After injection molding, the produced biocomposites are evaluated by their mechanical performance and fiber–matrix adhesion. For selected materials, fiber surface and fiber properties are reflected to composite performance by analyzing the compositions, dimensions, and lignin coverage of original fibers, as well as fiber dispersion and dimensions after melt processing. As a conclusion, unbleached kraft pulp fibers provide significant improvement in physical properties of PLA/pulp fiber composites. Of the screened compatibilizers, epoxidated linseed oil has a clear positive effect on performance when bleached kraft pulp fibers are used. The improvements correspond to enhanced fiber–matrix adhesion and differences in remaining fiber length distributions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47955.

Accumulation of sugar from pulp and xylitol from xylose by pyruvate decarboxylase-negative white-rot fungus Phlebia sp. MG-60

Phlebia sp. MG-60 is a white-rot fungus that produces ethanol with high efficiency from lignocellulosic biomass without additional enzymes. Through engineering of this powerful metabolic pathway for fermentation in Phlebia sp. MG-60, chemical compounds other than ethanol could be produced. Here, we demonstrate sugar accumulation from unbleached hardwood kraft pulp and conversion of xylose to xylitol by pyruvate decarboxylase (pdc)-negative Phlebia sp. MG-60. We isolated Phlebia sp. strain MG-60-P2 from protoplasts to unify the protoplast phenotypes of the regenerated strains. Homologous recombination achieved a stable pdc-knockout line, designated KO77. The KO77 line produced traces of ethanol, but accumulated xylitol from xylose or glucose from unbleached hardwood kraft pulp. These metabolic changes in the pdc-knockout strain reflect the potential of metabolic engineering in Phlebia sp. MG-60 for direct production of chemical compounds from lignocellulosic biomass.

Direct Fungal Production of Ethanol from High-Solids Pulps by the Ethanol-fermenting White-rot Fungus Phlebia sp. MG-60

A white-rot fungus, Phlebia sp. MG-60, was applied to the fermentation of high-solid loadings of unbleached hardwood kraft pulp (UHKP) without the addition of commercial cellulase. From 4.7% UHKP, 19.6 g L-1 ethanol was produced, equivalent to 61.7% of the theoretical maximum. The highest ethanol concentration (25.9 g L-1, or 46.7% of the theoretical maximum) was observed in the culture containing 9.1% UHKP. The highest filter paper activity (FPase) was observed in the culture containing 4.7% UHKP, while the production of FPase in the 16.5% UHKP culture was very low. Temporarily removing the silicone plug from Erlenmeyer flasks, which relieved the pressure and allowed a small amount of aeration, improved the yield of ethanol produced from the 9.1% UHKP, which reached as high as 37.3 g L-1. These results indicated that production of cellulase and ensuing saccharification and fermentation by Phlebia sp. MG-60 is affected by water content and benefits from a small amount of aeration.

All-cellulose composites from unbleached hardwood kraft pulp reinforced with nanofibrillated cellulose

In the present work, nanofibrillated cellulose (NFC) from bleached eucalyptus pulp was prepared, characterized and used as reinforcement in an unbleached eucalyptus fiber matrix. First, the NFC was fabricated through TEMPO-mediated oxidation and characterized for the degree of polymerization, water retention value, cationic demand and carboxyl content. Intrinsic mechanical properties were also calculated by applying the rule of mixtures, which determines the coupling (f c) and efficiency factor (η e) of cellulose nanofibrils within the matrix. The results showed that the average intrinsic tensile strength and Young’s modulus of NFC are estimated to be 6,919 MPa and 161 GPa, respectively. After characterization, the NFC was used as reinforcement in the preparation of biocomposites in the form of paper handsheets, which were physically and mechanically analyzed. The presence of NFC induced an increase in the density of biocomposites and significant enhancement of the mechanical properties as well as an important reduction in porosity. Finally, f c and η e were determined from the mean intrinsic properties.

Direct ethanol production from cellulosic materials by the hypersaline-tolerant white-rot fungus Phlebia sp. MG-60

White-rot fungus Phlebia sp. MG-60 was identified as a good producer of ethanol from several cellulosic materials containing lignin. When this fungus was cultured with 20g/L unbleached hardwood kraft pulp (UHKP), 8.4g/L ethanol was produced after 168h of incubation giving yields of ethanol of 0.42g/g UHKP, 71.8% of the theoretical maximum. When this fungus was cultured with waste newspaper, 4.2g/L ethanol was produced after 216h of incubation giving yields of ethanol of 0.20g/g newspaper, 51.1% of the theoretical maximum. Glucose, mannose, galactose, fructose and xylose were completely assimilated by Phlebia sp. MG-60 with ethanol yields of 0.44, 0.41, 0.40, 0.41 and 0.33g/g of sugar respectively. These results indicated that Phlebia sp. MG-60 was a good candidate for bioethanol production from cellulosic materials.

Novel blend of biorenewable wet-end paper agents

Recent studies have shown potential for a designed biorefinery product, polylactic acid (PLA), to increase the strength-to-weight ratio of paper produced from conventional kraft pulp and kraft pulp made from hot-water extracted hardwoods (biorefinery pulp). These results indicated that, after surface-treatment with 2 % PLA (per ovendry [o.d.] fiber basis), paper made from sugar maple biorefinery pulp could be equivalent to or even greater in strength than paper made from sugar maple conventional kraft pulp, while retaining its higher bulk. In the current study, we present the results of reinforcement of the pulps with PLA applied in the wet-end in combination with a known environmentally friendly dry strength agent, cationic starch. The preliminary results obtained with amylopectin-based starch of relatively high nitrogen content (starch B) were encouraging since strength, including wet strength and stretch, of paper reinforced with a blend of 0.5% starch B and 0.5% PLA was higher than strength of paper reinforced with 1% starch B. Moreover, based on the compatible strengths of paper reinforced with 0.6 % PLA-starch B blend (1/5) and of paper reinforced with 1% starch B, we hypothesize that there is a synergistic effect of PLA and starch B on tensile strength of paper. The hypothesis was tested using pulps of different lignin content (Norway spruce thermomechanical pulp [TMP], hardwood unbleached kraft pulp, and softwood bleached kraft pulp). Tensile strength increased for papers made from these pulps. The effect was pronounced in the case of lignin-rich pulps, where tensile strength in the presence of 0.6% PLA-starch blend (1/5) exceeded that in the presence of 1% starch B. This result is in accordance with a higher attraction of lignin-rich fibers to hydrophobic PLA and indicates a promising approach in increasing strength-to-weight ratio of paper made from relatively hydrophobic pulps like TMP or unbleached kraft pulp. Accordingly, paper made from unbleached hardwood kraft pulp with 0.6% PLA-starch B blend (1/5) exhibited an improved resistance to water penetration.

Binding affinities of different metal ions to unbleached hardwood kraft pulp

No abstract available

Oscillatory Flow Mixer for Pulp Bleaching

This paper reports the results of an investigation on the use of oscillatory baffled column as a mixer for pulp bleaching. Unbleached hardwood kraft pulp was bleached using hydrogen peroxide. Variables studied were oscillation frequency, oscillation amplitude, and pulp consistency. The mixing process was achieved by oscillating pulp suspension in a periodically baffled column at a certain frequency and amplitude. The mixing quality of pulp bleaching was quantified using mixing index. The results showed that mixing quality improved with oscillation frequency and amplitude, but decreased with pulp consistency. This typical device is very promising as a mixer for pulp bleaching.

Bleaching of kraft pulp by a commercial lipase: Accessory enzymes degrade hexenuronic acids

The potential of a commercial lipase for bleaching kraft pulp was investigated. Enzymatic treatment of hardwood and softwood kraft pulps before and after oxygen delignification resulted in a significant reduction of kappa number and hexenuronic acid content. Pretreatment of unbleached hardwood kraft pulp followed by a DE bleaching sequence gave the same kappa number as a control sequence but with considerably less chlorine dioxide. Two enzyme fractions containing high accessory enzyme activities were purified by size exclusion chromatography. These fractions demonstrated a high bleaching efficiency as well as a high selectivity, with a significant reduction in sugar released in the filtrate compared to commercial xylanase bleaching. This work provides the first evidence that the accessory enzymes from a commercial enzyme preparation can degrade hexenuronic acids and bleach kraft pulp.

Surface Characterization of Softwood and Hardwood Kraft Pulp Fibers from Different Stages in a Bleaching Sequence

Pulp samples from a softwood kraft pulp line and a hardwood kraft pulp line were used to study how the chemical surface composition of different kraft pulp fibers are modified as the fibers are processed in the fiber line. The pulps were bleached according to the following sequence: OQ(OP)(ZQ)(OP). Three different surface analyzing techniques were used and compared to each other in order to determine the content of lignin and extractives on the fiber surfaces. The three techniques studied were electron spectroscopy for chemical analysis (ESCA), ESCA in combination with mercurization of the lignin, and mechanical peeling of the outer part of the fiber surface followed by standard chemical analyzing techniques. All analyzing techniques show that the surface coverage by lignin and extractives is higher compared with that of the bulk of the fibers. Standard ESCA, that uses both the theoretical and the measured values of the O/C ratio and C1 carbon content, in most cases gives the highest values on the surface coverage by lignin on both softwood and hardwood kraft pulp fibers, followed by the mercurization and mechanical peeling techniques. More extractives are detected on all kraft pulp fiber surfaces when standard ESCA is used as compared to the mechanical peeling technique. The obtained results indicate that the mercurization technique in combination with ESCA analysis is a good alternative for surface analysis of kraft pulp fibers. However, further investigations are needed to support this recommendation. Standard ESCA indicates that the surface lignin on both unbleached softwood and hardwood kraft pulp fibers has lower reactivity in an oxygen delignification stage as compared to the bulk lignin. In opposite, the mercurization technique and the mechanical peeling technique indicate similar reactivity of bulk and surface lignin towards oxygen. Furthermore, all ESCA techniques show that the decrease in surface coverage by lignin and total lignin content of both softwood and hardwood pulp fibers is low in the last hydrogen peroxide bleaching stage. Oxygen delignification is most efficient in removing surface extractives on both softwood and hardwood pulps and adsorption of surface extractives occurs after the ozone bleaching stage on all pulp samples.

Studies on hypersaline-tolerant white-rot fungi III: biobleaching of unbleached kraft pulp by hypersaline-tolerant manganese peroxidase from a marine white rot isolate, Phlebia sp. MG-60

A marine white rot isolate, Phlebia sp. MG-60, secreted lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase under different sea salt incubation conditions. Its MnP production was strongly enhanced by adding 3% sea salts, and the MnP showed high tolerance to sea salts and NaCl. The crude enzyme secreted at 3% sea salt concentration by Phlebia sp. MG-60, in which the main component was MnP (cMnP), was then used to bleach unbleached hardwood kraft pulp (UKP) in vitro. The pulp was brightened 11 points by 4 U of cMnP, and the kappa number was decreased 6 points when only 0.5 mM H2O2 was added continuously. When 0.5 mM H2O2 (1.22 mg H2O2 /g pulp) was added at the initial bleaching, the pulp brightness increased 6 points with a dosage of 4 U of cMnP. When crude MnPs were employed to bleach UKP with organic-free model white-water instead of the Milli Q water usually used, the pulp was brightened 10 and 13 points by 4 and 20 U of cMnP, respectively, and 5 and 6 points by 4 and 20 U of MnP, respectively, of Phanerochaete chrysosporium.

Biomechanical Pulping and Bioble aching Using White Rot Fungus IZU-154

White rot fungus IZU-154, which more extensively and selectively degrades wood lignin than other fungi, was applied to mechanical pulping process and bleaching process for unbleached kraft pulp.The fungal treatment of coarse hardwood and softwood mechanical pulp with IZU-154reduced refiningenergyrequirements by about 2/3 and 1/3, respectively, and improved pulp strength properties. Combinedfungal and chemical bleaching process could significantly reduce the total effective chlorine andthe pollution load of waste liquors in comparison with the conventional bleaching process. Furthermore, unbleached hardwood kraft pulp (HWKP) was biobleached with partially purified manganese peroxidase (MnP) which plays the most important role in biobleaching of HWKP by white rot fungi. The totaleffective chlorine required to obtain a pulp of 85% brightness by chlorine-basedchemical bleaching afterrepeated MnP treatments was reduced to 70% for HWKP compared to the conventional bleachingprocess without introducing MnP treatments.

Change in oxidation state of manganese atoms in kraft pulp during biological bleaching with white-rot fungusPhanerochaete sordida YK-624

Change in the oxidation state of manganese atoms in unbleached hardwood kraft pulp (UKP) during the biological bleaching of UKP withPhanerochaete sordida YK-624 was determined by the electron spin resonance (ESR) method. The spectrum of Mn(II), which reveals hyperfine splitting, was not observed in the ESR analysis of UKP, but the spectrum for manganese dioxide was observed. After fungal treatment of UKP withP. sordida YK-624, the spectrum of Mn(II) was detected. The reduction of manganese dioxide was triggered by the increase in NADPH-dependent ferrireductase activity. It is concluded that the manganese dioxide dominant in UKP was reduced byP. sordida YK-624 to Mn(II), which stimulates the production and function of manganese peroxidase.

Role of Tween 80 in biobleaching of unbleached hardwood kraft pulp with manganese peroxidase

The role of Tween 80 in biobleaching of unbleached hardwood kraft pulp (HWKP) with manganese peroxidase (MnP) was investigated. Among the surfactants (e.g., Tween 80, Tween 20, CHAPSO) the most significant brightness increase was obtained with Tween 80. Tween 80 and Tween 20 exhibited several effects, such as dispersion of degraded lignin and activation of MnP, that partly contributed to the brightening of HWKP during MnP treatment. However, these characteristics did not explain the most appreciable effect on the brightness increase by Tween 80. Lipid peroxidation of surfactants during MnP biobleaching was determined by measuring the peroxide value (POV). The order of the POV increase was consistent with that of the brightness increase of pulp during MnP treatment in the presence of various surfactants or linolenic acid. However, radicals and peroxides derived from lipid (linolenic acid) peroxidation by lipoxidase hardly brightened the HWKP by themselves. These results suggested that Tween 80 was peroxidized by Mn(III), and that Mn(III) and lipid peroxidation of Tween 80 synergistically brightened HWKP.

A new xylanase from a Trichoderma harzianum strain.

A new xylanase (XYL2) was purified from solid-state cultures of Trichoderma harzianum strain C by ultrafiltration and gel filtration. SDS-PAGE of the xylanase showed an apparent homogeneity and molecular weight of 18 kDa. It had the highest activity at pH 5.0 and 45 degrees C and was stable at 50 degrees C and pH 5.0 up to 4 h xylanase. XYL2 had a low Km with insoluble oat spelt xylan as substrate. Compared to the amino acid composition of xylanases from Trichoderma spp, xylanase XYL2 presented a high content of glutamate/glutamine, phenylalanine and cysteine, and a low content of serine. Xylanase XYL2 improved the delignification and selectivity of unbleached hardwood kraft pulp.

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

Kraft pulp was delignified using laccase produced by the white rot fungus Trametes versicolor immobilized in solid support under specific conditions. The stability tests showed that this enzyme was stable for 6 h at 55 degrees 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 degrees C and pH 8.0 followed by alkaline extraction and ECF bleaching sequences.

Bleaching of Hardwood Kraft Pulp with Manganese Peroxidase from Phanerochaete sordida YK-624 without Addition of MnSO(inf4)

In vitro bleaching of an unbleached hardwood kraft pulp was performed with partially purified manganese peroxidase (MnP) from the fungus Phanerochaete sordida YK-624 without the addition of MnSO(inf4) in the presence of oxalate, malonate, or gluconate as manganese chelator. When the pulp was treated without the addition of MnSO(inf4), the pulp brightness increased by about 10 points in the presence of 2 mM oxalate, but the brightness did not significantly increase in the presence of 50 mM malonate, a good manganese chelator. Residual MnP activity decreased faster during the bleaching with MnP without MnSO(inf4) in the presence of malonate than in the presence of oxalate. Oxalate reduced MnO(inf2) which already existed in the pulp or was produced from Mn(sup2+) by oxidation with MnP and thus supplied Mn(sup2+) to the MnP system. The presence of gluconate, produced by the H(inf2)O(inf2)-generating enzyme glucose oxidase, also improved the pulp brightness without the addition of MnSO(inf4), although treatment with gluconate was inferior to that with oxalate with regard to increase of brightness. It can be concluded that bleaching of hardwood kraft pulp with MnP, using manganese originally existing in the pulp, is possible in the presence of oxalate, a good manganese chelator and reducing reagent.

Bleaching of Hardwood Kraft Pulp with Manganese Peroxidase Secreted from Phanerochaete sordida YK-624

In vitro bleaching of an unbleached hardwood kraft pulp was performed with manganese peroxidase (MnP) from the fungus Phanerochaete sordida YK-624. When the kraft pulp was treated with partially purified MnP in the presence of MnSO(4), Tween 80, and sodium malonate with continuous addition of H(2)O(2) at 37 degrees C for 24 h, the pulp brightness increased by about 10 points and the kappa number decreased by about 6 points compared with untreated pulp. The pulp brightness was also increased by 43 points to 75.5% by multiple (six) treatments with MnP combined with alkaline extraction. Our results indicate that in vitro degradation of residual lignin in hardwood kraft pulp with MnP is possible.