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).
The enzymatic process saves water and energy and the effluent is ecologically harmless. The new strain KW3 differs from other known strains, e.
The Bleachinh number is the volume in milliliters of 0. 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.
X, prepared in 50 mM phosphate blecahing, pH 70. The pH may also influence pjlp rate of enzymatic reaction indirectly insofar as many enzymes, like proteins in general, are stable only within a relatively limited pH range. Xylanase production by a newly isolated Aspergillus foetidus strain and its characterization. Equilibrium pH is reached after roughly 90 minutes. Analysis of the culture supernatant by SDS polyacrylamide gel electrophoresis reveals a set of at least 6 isoenzymes with xylanase activity.
Lipases are used to control deposits of pitch.
Hemicellulases in the bleaching of chemical pulps.
The enzymes that have shown benefit in bleaching include xylanase, arabinase and mannanase Paice, et al. Deforestation is a matter of concern for both the environmentalists and the paper industry this has forced.
The enzymes hydrolyze some of the surface sugars on the pulp fiber and this releases the ink particles bound to the fiber. 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. The culture supernatant was harvested by centrifugation rpm, 10 min.
Xylanolytic enzymes xylan attacking enzymes including xylanase and arabinase are produced by microorganisms including Trichoderma reesei, Aspergillus awamori, Streptomyces olivochromogenes, and Fusarium oxysporum Poutanen, et al. Bark of wood is removed.
The two types of linkages that have been shown are ester linkages between ligninand the methylglucuronic acid residues of xylan Das, et al. Lignin is associated and probably also covalently bound to cellulose and hemicellulose polymers of various hexoses and penroses e. Enzyme treatment effectively removes laser printer and photocopier inks that are mostly found in office wastepaper Prasad, It has been found, however, that the supernatants of T. The isolated xylan is therefore of similar structure to the indigenous xylan in wood pulp.
This invention is particularly concerned with the use of so-called “acid” hemicellulase enzymes, i.
US5591304A – Method for the use of enzymes in bleaching paper pulp – Google Patents
The pulp was further extracted under alkaline conditions 2. The culture supernatant was harvested by centrifugation rpm, min. For effective enzyme treatment, the pH of the pulp should be reduced to below at least 9. The pH of the pulp increased about 1 unit in two hours after addition of the acid, then maintains a steady value.
Role Of Biotechnology In Pulp And Paper Industry | Open Access Journals
A Review “, Tappi J. Characteristically, for each enzyme there is a pH value at which the rate of reaction is optimal, and on each side of this optimum, the rate is lower.
The inventors have found, for example, that the conventional treatment conditions used to obtain a peak brightness boost of 7. Such treatment of chemical hemicelullases is commonly referred to as bleaching and may be evidenced by a brightening of the pulp. The dry powder was then dissolved in a volume 10 bleacing smaller than the original volume and dialyzed molecular weight cut off 10, against the fold volume of phosphate buffer pH 7.
The treatment time will vary depending upon factors such as the result desired, the amount of substrate used, the amount of supernatant enzymes used, the specific activity of the supernatant, the type of pulp used, the temperature and the like. The procedure of Ebringerova, et al.
Hemicellulases in the bleaching of chemical pulps.
Attempts to use fungi e. The pulp was adjusted to equilibrate at pH 5 with 6 bleacching of 1N sulfuric acid. 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. After adding 5 ml of H 2 O the absorption was measured at nm. The results are shown in Table 5. Either spores or mycelium from an agar slant or a frozen test tube culture were added to ml of LB medium.
Unbleached Kraft brownstock, described in Example 5, was treated with the Iogen Xylanase preparation described in Example 2 as received from the mill. The present invention may be illustrated by reference to the following Examples. The invention makes possible a three to four fold improvement in hemocellulases “brightness boosting” power pul; these enzymes as well as reduced chlorine requirements. This eliminates the need for expensive buffer solutions at this stage of processing while allowing optimal hemicellulase activity.
The insoluble portion was then resuspended in 70 ml blleaching deionized water and uniformly distributed by gentle mixing. In this regard, studies have reported linkages between hemicellulose, particularly xylan, and lignin in wood Eriksson, et al. The resulting pulp is treated to remove the releasable lignin component using an appropriate extractant.