HEMICELLULASES IN PULP BLEACHING PDF

Hemicellulase-aided bleaching is the first full-scale biotechnical application in the pulp and paper industry which truly exploits the unique specificity and safety of. () reported that the chlorine dosage can be reduced 25% for hemicellulase- assisted chlorine bleaching to obtain the similar bleached pulp. Paice et al. Elemental chlorine, while effective in bleaching pulp and low in both primary classes: hemicellulases (xylanase) and oxidases (laccase).

Author: Felmaran Molmaran
Country: Moldova, Republic of
Language: English (Spanish)
Genre: Technology
Published (Last): 19 October 2005
Pages: 373
PDF File Size: 14.60 Mb
ePub File Size: 13.91 Mb
ISBN: 991-3-47029-934-7
Downloads: 96734
Price: Free* [*Free Regsitration Required]
Uploader: Zulkizragore

Residual enzymes are deactivated during drying of the paper. A process for the bleaching of a kraft pulp, a hardwood pulp or a softwood pulp in order to reduce the lignin content thereof which process includes the steps of: This, in turn, leads to a significantly reduced chlorine requirement to bleach pulp. The region of an enzyme that specifically interacts with the substrate is called the active site. Sodium hydroxide is added to the pulp to remove the residual reaction products that were not solubilized in the acidic chlorination stage but readily dissolve in an alkaline medium.

WO Pedensen et al.

Typical measurements of pulp pH over time after acidification are shown in Table 3. Mannanase enzymes are made by Trichoderma and Aspergillus sp. These slurries are so thick as to make pH measurement by the usual method i.

Social factors like poverty, literacy, corporate spending are the factors behind low level consumption. Process for high consistency oxygen delignification of alkaline treated pulp followed by ozone delignification.

Hemicellulases in the bleaching of chemical pulps. – Semantic Scholar

Enzymatic deinking work with old newsprint and office waste paper. After being washed with water, the cooked material contains 1. Oxidative enzyme such as laccase is also used for reducing costs hemicfllulases pulp mills.

  KNAUF WANDSYSTEME PDF

This result is not surprising, because black liquor contains many aromatic and sulfide compounds that would be expected to be detrimental to enzyme activity. It is preferred in the practice of this invention that the specific cellulase content of the enzyme preparation contemplated be very low so that not more than about 10, FPU of cellulase activity is added per ton of pulp see Examples 1 and 2and more preferably about 2, FPU or even about FPU or less per ton of pulp.

WO Zamost et al. Enzyme hemicellulsaes involved in cellulose hydrolysis by the rot fungus Sporotrichum pulverulentum. This invention preferably concerns the use of xylanase or other hemicellulase enzymes that have pH optima for hydrolysis of below 6.

The results are shown in FIG. In one embodiment of this invention, the process is carried out using a xylanase enzyme preparation produced by the fungus Trichoderma reesei.

This eliminates the need for expensive buffer solutions at this stage of processing while allowing optimal hemicellulase activity. They save production costs and prevents formation of unwanted products during pulp bleaching process. Enzyme treatment effectively removes laser printer and photocopier inks that bleeaching mostly found in office wastepaper Prasad, It is a primary objective of this invention to provide a means to overcome the deleterious effect of Kraft black liquor on enzyme processes for pulp bleaching.

The enzymatic process saves water and energy and the effluent is ecologically harmless.

US5591304A – Method for the use of enzymes in bleaching paper pulp – Google Patents

X, prepared in 50 mM phosphate buffer, pH 7 0. Pulp bleaching using enzymes Biobleaching Chlorine is used for bleaching process which has a huge polluting potential.

  HIGROMAS CEREBRALES PDF

Biotechnology, silviculture, trees and other bioresources can be used to enhance the properties required in cellulose fibers Buschle-Diller and Ren. Catalog X in the following manner. The results are shown in Table 5. A process according to claim 1 wherein the enzyme system further comprises a mannanase. In mechanical pulping, debarked logs are forced through rotating toothed steel discs.

The two types of linkages that have been shown are ester linkages between ligninand the methylglucuronic acid residues of xylan Das, et al. At this point, the fibers are in a solution of dissolved lignin and pulping chemicals, hemicellulasees dilute or weak black liquor.

The data show that, by using the enzyme, considerably less active chlorine is needed to reach the same brightness level than with common bleaching sequences. Pulp that did not receive enzyme treatment was brought through the procedure, except enzyme was not added.

Role Of Biotechnology In Pulp And Paper Industry | Open Access Journals

Bleached fibers need be rinsed only once. The issues to be addressed in future are: For effective enzyme treatment, the pH of the pulp should be reduced to below at least 9.

A further preferred enzyme system also contains mannanase and other enzymatic components of T. Lignin fragments, resin acids, and other low molecular weight compounds which are released during chipping and pulping can be used to generate value-added products.

Equilibrium pH is reached after roughly 90 minutes.