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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The unique structures of the active sites of enzymes provide this specificity and not only allow favorable binding of specific substrates but also exclude the unfavorable binding of many substances that are not hemciellulases.
In addition, the new strain had the following biochemical properties typical for Thermomonospora fusca: A process according to claim 1 wherein the pulp is chemical pulp.
It was found that the relevant pH for the enzyme reaction appears to be the pH at which the pulp blexching. A process bbleaching to claim 1 which comprises the further process step of: After 2 hours time the pulp suspension was filtered through a Whatman No.
The purpose of this process, known as kraft pulping, is to separate the wood chips into individual fibers and to substantially dissolve the lignin portion of the wood.
The process of this invention overcomes a critical and heretofore unrecognized problem that has reduced the effectiveness hemicellulasfs enzymes in a conventional pulp mill bleachery. 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.
US5591304A – Method for the use of enzymes in bleaching paper pulp – Google Patents
The present invention relates to an improved method for using enzymes in the processing hemciellulases paper pulp to boost the efficiency of the bleaching process. Not surprisingly, residual black liquor is deleterious to the action of xylanase enzymes.
Process for producing a pulp suitable for papermaking from nonwood fibrous materials. 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. To avoid these problems, the liquor was squeezed out of a sample of the pulp and the pH of this liquor measured.
The key challenges are poor and technology obsolete, lacking ability in achieving economy scale and lack of skilled labor http: Process for high consistency oxygen delignification of alkaline treated pulp followed by ozone delignification.
A deinking process involving sodium hydroxide, flocculants, dispersants and surfactants is used widely currently.
Role Of Biotechnology In Pulp And Paper Industry | Open Access Journals
This is the relevant pH for the invention, and is the pH referred to in the following examples. This technology can hemidellulases combined with various types of kraft pulping processes and bleaching sequences. Biotechnology has positively impacted on: The extent of delignification and bleachability of the pulp may be indicated by the Kappa number.
Equilibrium pH is reached after roughly 90 minutes.
The isolated xylan is therefore of similar structure to the indigenous xylan in wood pulp. It has previously been found that these enzymes do not work well on the partially washed brownstock that is typical of commercial Kraft pulp mills.
In the present invention, a high level of brightness boosting activity is achieved at pH levels previously taught by Novo to inactivate the enzymes. For effective enzyme treatment, the pH of the pulp should be reduced to below at least 9. The inventors have found, for example that belaching results using Trichoderma xylanase are three times better at pH 7.
The enzymes added should be from the class of hemicellulose degrading enzymes that have a pH optimum for hydrolysis between 3.
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The pH of the pulp increased about 1 unit in two hours after addition of the acid, then maintains a steady value. The enzyme dose indicated was the activity measured under standard conditions Example 2.
In chemical pulping, a majority of the lignin is removed from wood pulp e. Genetically engineered microorganisms and bleachong can displace many of the environmentally adverse practices used in pulp processing http: Enzymes differ most strikingly from ordinary chemical catalysts in their substrate specificity and catalytic efficiency. These slurries are so thick as to make pH measurement by the usual method i. 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 i features hereinbefore set forth and as fall within the scope of the invention.
Wood chips are debarked and then fed into a digester where they are cooked in a concentrated solution of sodium hydroxide and sodium sulfide. The resulting samples were then centrifuged to remove insoluble substrate and assayed for the total amount of reducing sugar as xylose released bleacbing the reaction bleavhing the DNS method.
After enzyme treatment, each sample of pulp was washed with 3.
Paper is manufactured from pulp by sulphite and sulphate process. Applicants have further discovered that enzyme hfmicellulases with a pH optima for hydrolysis of below 6.
Hemicellulases in the bleaching of chemical pulps.
However, the treatment with chlorine is undesirable from an environmental standpoint because the resulting effluents contain a large number of toxic compounds e. Germgard, Paperi ja Puu, 4: Fungal and enzyme pitch degradation products are used in some TMP Gehlhoff, and sulfite mills Fleet et al. Studies on the solid-state production of thermostable endoxylanases from Thermoascus aurantiacus: Treatment with alkali is not used and hemicelluulases eliminates the need for subsequent bleaching with hydrogen peroxide.
The pH optima for enhancing bleaching with xylanase of around 5. Pulp bleaching using enzymes Biobleaching Chlorine is used for bleaching process which has a huge polluting potential. Paice, Biotechnology and Bioengineering, Enzymes control the properties of the pulp fiber and, therefore, the end product.