جستجوی مقالات مرتبط با کلیدواژه "laccase" در نشریات گروه "جنگلداری"

The aim of this study was to evaluate the effect of white rot fungus (Trametes versicolor (L.) Lloyd) on physical and mechanical properties of treated and untreated poplar wood (Populus deltoides Marshall and P. nigra L.). Heat treatment was used as wood modification. Heat-treated and untreated poplar wood specimens were evaluated after exposing to the white rot fungus for 16 weeks. The evaluated properties was included: laccase activity, mass loss, density changes, impact strength and compression strength parallel to grain due to thermal modification and also fungus efficiency. Evaluation of lacase activity showed more efficiency of this enzyme in controls in compared to modified specimens in which also caused more mass loss. In both two poplar wood species, thermal modification reduced the density and the impact strength of the specimens, but improved the compression strength parallel to grain. Evaluation of physical and mechanical properties of the specimens exposed to white rot fungus also showed that thermal modification limits efficiency of this fungus on both poplar wood species. As a result, the reductions in the studied physical and mechanical properties, including mass loss, density, compression strength parallel to grain, and impact strength, were significantly more pronounced in the control group than the modified specimens.

The recycling of different paper and paperboard products can supply the major shortage of cellulosic raw materials needed for the production of pulp and paper, and it can be important from the economic and environmental point of view. Using recycled pulp in papermaking reduces the quality of the final paper. Therefore, the use of enzyme pre-treatment separately or combined sequences as well as pulp bleaching can be effective in improving the quality properties of the final paper obtained from recycled pulp. This research was conducted with the aim of investigating the effect of enzyme pre-treatment with cellulase and laccase sequence on the bleachability of the resulting pulp with hydrogen peroxide, and the quality of the final pulp after bleaching system were investigated.

At first, the mixture of waste newspaper and magazine papers were deinked using enzyme pre-treatment (combined sequence of cellulase and laccase) as well as conventional chemical method. Enzymatic pre-treatment was done as experimental treatments C1L1 (cellulase usage: 0.1% and duration time: 10 minutes; laccase usage: 20u and duration time: 120 minutes), C1L2 (cellulase usage: 0.1% and duration time: 10 minutes; laccase usage: 40u and duration time: 120 minutes), C2L1 (cellulase usage: 0.1% and duration time: 20 minutes; laccase usage: 20u and duration time: 120 minutes) and C2L2 (cellulase usage: 0.1% and duration time: 20 minutes; laccase usage: 40u and duration time: 120 minutes) under specific process conditions. Also, control pulp (without adding chemicals or enzymes) and chemically deinked pulp samples were also prepared and then bleaching of deinked pulp was accomplished using hydrogen peroxide bleaching system including 2% hydrogen peroxide, 2% sodium hydroxide, 2% sodium silicate, 0.2% DTPA chelating agent and 0.1% magnesium sulfate in separate plastic bags under process conditions of 10% consistency, 70°C temperature and 2 hours in a water bath. At the end, the optical and strength characteristics of the bleached pulp were evaluated.

The results of the evaluation of bleached pulp with hydrogen peroxide after deinking with conventional method and also cellulase and laccase enzyme pre-treatment sequences showed that the use of enzyme pre-treatment in deinking improves the overall performance of the hydrogen peroxide bleaching process and resulted in the papers with better optical and strength characteristics after bleaching compared to pulp pre-deinked by conventional chemical method. C2L2 and C2L1 pre-treatments in combined enzymatic treatments after bleaching with hydrogen peroxide led to an improvement in brightness by 11.12% (increase of about 5 units) and 9.5% (increase of about 4 units), respectively. In these pretreatments, the whiteness of the paper increased by 31.92% and 24.54% (an increase of about 9 and 6 units), respectively. Also, the yellowness of the paper decreased by 40.19% and 44.25%, respectively, and the opacity of the paper reduced by 37.74% and 23.97%, respectively. Also, in experimental runs of C2L1 and C2L2, the paper tensile index increased 29.17% and 35.64%, respectively (40.64 Nm/g and 38.7 Nm/g, respectively), breaking length enhanced by 64.42% and 99%, respectively (5.92 km and 4.89 km), and the paper burst index also increased by 70.85% and 92.37% (3.81 mN.m2/g and 4.29 kPa.m2/g), respectively. The tear indices of paper in these runs were determined on average about 6.82 mN.m2/g and 6.62 mN.m2/g, which are a little lower compared to the chemically deinked pulp after bleaching, but in the pretreatment with the combined sequence C2L1, the tear index of paper was almost equivalent to that of chemically deinked pulp.

Paper made of recycled fibers has less strength compared to virgin fibers due to the multiplicity of recycling. Several solutions have been proposed to solve this problem consist of specialized enzymes application. While the applications of enzymes in the pulp and paper industry is still in the research and development stage, but some of them have pioneered the technology to operate. There are various methods to increase recycled fiber bonding and improves the paper strength. Oxidant enzymes such as cellulase and laccase are one of the methods that could accelerate delignification. Laccase-mediator system has the greatest effect on increasing of paper strength according to previous studies. Common Low molecular weight of mediator such as ABTS or HBT are the best non-phenolic lignin oxidizing that have been used yet. In order to increase the strength of recycled paper the effect of laccase treatment on old corrugated container (OCC) pulp was investigated in this study. OCC pulp was obtained from headbox of recycled paper factory in the north of Iran (Afrang Noor), and then was fractionated by Bauer-McNett classifier. HBT mediator was selected to treatment of OCC pulp by laccase. The pulp was treated by the enzyme in the adjusted conditions including consistency: 2%, pH: 5, reaction time: 2 hours, and reaction temperature: 60 °C in dosing levels of 0.005%, 0.01% , and 0.015 % based on oven-dried weight of pulp. Handsheet making and characteristic measurement carried out by TAPPI test methods and also statistical analysis was conducted using completely randomized design. Fiber classification result showed that fines constitute about 31% of weight of the pulp. There are significant differences at 1% level among the pulp strength properties of OCC which treated with laccase enzyme. Tensile and burst indices significantly were increased compared to the control using 0.005% of laccase. Multiple Duncan test showed that the average of these two indices by using 0.005% and 0.015% laccase (based on O.D. weight of pulp) had no significant difference and placed in the same statistical group. The variation trend of tear index unlike the other indices was observed and concora medium test (CMT) decreased at all levels of the treatments. OCC pulp treated with 0.005% laccase-HBT (based on O.D. weight of pulp) is recommended according to the important role of tensile and burst strength in test liner for packaging industry. Due to decreasing of Concora medium test (CMT) by the enzyme, laccase application is not suitable for making corrugated paper.

The efficiency of Oxidation Processes, Enzymatic treatment, and combined enzymatic/chemical sequences on color remediation of CMP pulp mill effluent was investigated. Two kinds of fungal enzymes; Laccase (EC: 1.10.3.2) from Terametes Versicolor and Versatile Peroxidase (EC: 1.11.1.7) from Bjerkandera adusta were chosen and applied. Also, the effect of external mediator on the enzyme based degradations was studied. It was found that both VP from Bjerkandera adusta and Laccase from Terametes versicolor decolorized the deep brown effluent to a clear light yellow solution. It has been found that, concomitant use of enzymes and photo-Fenton process produces a considerable effect on color remediation. The data analysis of sequence treatment indicated that, chemical treatment after the enzymatic stage (photo-Fenton as a post treatment unit) yield a better performance for the CMP effluent. It has been found that, concomitant use of enzymes and photo-Fenton process produces a considerable effect on color remediation. The data analysis of sequence treatment indicated that, chemical treatment after the enzymatic stage (photo-Fenton as a post treatment unit) yield a better performance for the CMP effluent.