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).

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From the results shown in Examples 1 and 2, the relative cellulase and xylanase activity for Applicants’ Iogen xylanase preparation is In the next unit operation, a series of rotary drum filters are used to wash the bulk of the weak black liquor away from the fibers. Method of digesting wood with an alkaline liquor by adding an acidic agent to precipitate dissociated lignin.

Hemicellulases in the bleaching of chemical pulps. – Semantic Scholar

For example, at high pH levels, a component in the black liquor may stabilize the enzyme and modify the properties of the substrate, thereby making it more susceptible to attack. However, very few enzyme systems have been found which selectively act on pulp in terms of not adversely affecting the cellulosic content of pulp.

The method of claim 2 wherein the enzyme preparation has a low cellulase content such that about FPU or less are added per ton of pulp. NCIM 59 in biobleaching of bagasse pulp.

Xylanase focuses in a band corresponding to an isoelectric point pI of 9. The chlorinated pulp is then washed before entering the alkaline extraction stage E. This invention is particularly concerned with the use of so-called “acid” hemicellulase enzymes, i.

The chlorine bleachjng usage was 0. An example of such a strain is T.

It reduces the overall energy requirements for mechanical process and reduces the quantum of chemicals for chemical pulping. Attempts to use fungi e. Hardwood and softwood Kraft pulp 2. In a further embodiment of this invention, as it may be applied to a mill with a flow sheet as outlined in FIG.

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High-level of xylanase production by the thermophilic Paecilomyces themophila J18 on wheat straw in solid-state fermentation. The same procedure as that for endo-xylanase was used except hemicellklases galactomannan Sigma No. This cellulase enzyme can have phlp undesirable effects on pulp qualities such as pulp strength. A number of microorganisms are known to make hemicellulase enzymes.

Cellulase enzymes are found on the gels at positions corresponding to lower pI levels. Residual enzymes are hemivellulases during drying of the paper. The amount of organochlorines discharged from a pulp mill is closely related to the bleaching process used bleacning, in particular, to the amount of chlorine used for bleaching. Lipase has been used to control pitch buildup. Conventional way of making paper pulp Bark of wood is removed.

The method of claim 6 wherein the cooking process is followed by an oxygen delignification process. Xylanase Activity To 0. The insoluble ih was then resuspended in 70 ml of deionized water and uniformly distributed by gentle mixing. This is the complete opposite of what it does at the normally preferred conditions of operation for enzyme treatment.

Enzymes control the properties of the pulp fiber and, therefore, the end product.

Hemicellulases in the bleaching of chemical pulps.

In bleacching, the new strain KW3 shows a resistance towards crystal violet which is considered atypical for Thermomonospora fusca. This makes the use of recycled paper as im viable option to reduce the number of trees needed to be cut to make paper. US USA en The pulp was adjusted to equilibrate at pH 5 with 6 ml of 1N sulfuric acid. Background of the Invention The starting point for making paper is wood.

The bleachign process may involve anywhere from one to thirteen stages. To our knowledge, this result is completely unexpected and no other enzyme system demonstrates these properties. The method of claim 5 wherein the enzyme preparation has a low cellulase content such that not more than about 2, FPU are added per ton of pulp. One of the biggest challenges facing the pulp and paper industry is to reduce the use of chlorine in the bleaching process.

In some instances, the pulp slurry may be so thick that it will take as long as 60 minutes for the pH of the free liquid in the pulp to stabilize.

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In one embodiment of this invention, the process is carried out using a xylanase enzyme lulp produced by the fungus Trichoderma reesei. By this lignin that binds the cellulose fibers are removed. The pulp was further extracted under alkaline conditions 2. Treatment with alkali is not used and this eliminates the need for subsequent bleaching with hydrogen peroxide. 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.

On binding to this site, the substrate hemicellulasea brought into close proximity to specific groups on the enzyme that cooperatively destabilize certain bonds in the substrate, making them more chemically reactive.

Enzymatic deinking work with old newsprint and office waste paper. The resulting pulp may then be further bleached by a chemical bleaching sequence to the desired brightness whereby substantial savings of chemicals are observed when compared to pulp bleached to the same brightness by the same sequence but without using the enzyme treatment.

Hemicellulases in the bleaching of chemical pulps.

After being washed with water, the cooked material contains 1. Oxygen bleached spruce Kraft pulp with a Kappa number of They save production costs and henicellulases formation of unwanted products during pulp bleaching process.

These treatment stages are known as the “brightening” stages because hemivellulases final product is the desired bright white pulp. The preferred range of pulp kappa numbers is between 20 and 40 for softwood and 10 to 20 for hardwood, however, the process of this invention can be applied to oxygen delignified pulps with even lower kappa numbers.

Determination of Kappa Number The Kappa number is the volume in milliliters of 0. The enzymes added should be from the class of hemicellulose degrading enzymes that have a pH optimum for hydrolysis between 3. Alternatively the crude enzyme preparation was lyophilised.