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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For example, at high pH levels, a pklp in the black liquor may stabilize the enzyme and modify the properties of the substrate, thereby making it more susceptible to attack. Removal of lignin can be achieved in many ways. Application of xylanase from alkaliphilic thermophilic Bacillus sp.
Hemicellulases in the bleaching of chemical pulps. – Semantic Scholar
The pH was adjusted to equilibrate at various levels between 5 and 8. WO Pedensen et al. For industrial use, however, it would be a significant advantage if enzymes bbleaching available which are active over a wide pH-range, especially pH and at a higher temperature.
Clearly, these alternatives incur significant costs. Enzymes used for de-inking Recycled paper fibers has to undergo deinking process to remove whatever ink that gets fused on to the paper during printing. Because of the finite time for diffusion of acid into the fibers, the pH rises over time. Because Kraft brownstock usually has a pH in excess of 9, Novo suggests that the pH of the pulp be adjusted to 5 to 6 for xylanase treatment. Since they are proteins and work under mild condition of temperature and pH, their use is restricted to various stages at pulping level and bleaching level.
In this regard, studies have reported linkages between hemicellulose, particularly xylan, and lignin in wood Eriksson, et al. Hemicellukases systems are catalytic, highly selective, and operable under mild temperature and pressures.
USA – Method for the use of enzymes in bleaching paper pulp – Google Patents
At this point, the fibers are in a solution of dissolved lignin and pulping chemicals, called dilute or weak black liquor. A ReviewTappi J. They may include, but are not limited to: Year of fee payment: The region of an enzyme that specifically interacts with the substrate is called the active site.
Topics Discussed in This Paper. Germgard, Paperi ja Puu, 4: In fact, the preferred optimum is in a range normally believed to lead to rapid enzyme inactivation. Determination of Kappa Number The Kappa number is the volume in milliliters of 0. Biotechnological techniques like molecular biology, enzymes engineering, genetic engineering genomics, proteomics, metabolomics and bioinformatics etc. Pulp Treatment Hardwood and softwood Kraft pulp 2. Modification of xylanases to increase thermophilicity, thermostability and alkalophilicity.
In the enzymatic process, cellulase and hemicellulase enzymes are mixed with the paper pulp. Such extractants essentially solubilise the affected lignin component and suitable extractants include but are not limited to bases such as alkali metal hydroxides EBleachjng, dioxane, acetone, and alcohol.
The enzyme boosted the brightness of the bleached pulp by 3 ISO points, as compared to 8 ISO points with pH 5 enzyme treatment on well-washed pulp. Analysis of the culture supernatant by SDS polyacrylamide gel electrophoresis reveals a set of at least 6 isoenzymes with xylanase activity.
In this preferred embodiment, the invention relates to enzyme preparations wherein the total cellulase activity added to the pulp is not more than about 10, filter paper units FPU of cellulase per ton of pulp using the IEA standard filter paper assay see Example 2.
The amount of acid should be chosen so that the pH of the brownstock slurry will stabilize at roughly 7. After being washed with water, the cooked material contains 1. X, prepared in 50 mM phosphate buffer, pH 70.
US5591304A – Method for the use of enzymes in bleaching paper pulp – Google Patents
A lower Kappa number is desirable as it indicates that a smaller amount of lignin is present. The most common method for producing strong pulp that is light in color for high bleahcing paper is the Kraft process. Thermostable hemicellulases from Bacillus steanothermophilus for pulp bleaching. These treatment stages are known as the “brightening” stages because the final product is the desired bright white pulp.
Cook, Pulp and Paper Canada, Accordingly, the Novo teachings of ways to deal with contaminating cellulase are therefore irrelevant to this embodiment. The method of claim 12 wherein b and bleachinf addition of the enzyme are conducted substantially simultaneously. The partially washed fiber, or brownstock, is then stored in bleacging high density brownstock tank, screened, washed again, and then pumped into a storage tank to await bleaching.
The preferred enzyme system comprises xylanase. Glucomannan is found primarily in softwood.
All of the enzyme treatments by VTT and Paice, et al. It has been found, boeaching accordance with this invention, that the enzyme systems of Thermomonospora strains comprising at least one hemicellulase acting enzyme can be used to selectively treat a variety of pulps at a high temperature and under alkaline conditions, whereby the lignin content is reduced while the cellulosic content of the pulp remains substantially unaffected.
Role Of Biotechnology In Pulp And Paper Industry
The pH has a marked influence on the rate of enzymatic reactions. While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification and that this application is intended to cover any variation, uses or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention.
The influence of pH on enzymatic reactions may involve several different types of bleachjng. The Kappa number is the volume in milliliters of 0. The method of claim 5 wherein the pH of the fiber slurry pulp is stabilized at between approximately 7.
VTT reported that treatment of pulp with hemicellulases from Aspergillus awamori and Streptomyces olivochromogenes increased the brightness of the pulp after bleaching by up to 5 ISO points Viikari, et al. There are strong attractive non-covalent forces between the active site and a substrate, and enzymes may be thought to act by “attracting” the substrate into the site, where the extraordinarily unique structural transformations hemicellklases the substrate occur.