Chemistry: molecular biology and microbiology – Enzyme – proenzyme; compositions thereof; process for... – Hydrolase
Patent
1993-09-21
1997-03-11
Wax, Robert A.
Chemistry: molecular biology and microbiology
Enzyme , proenzyme; compositions thereof; process for...
Hydrolase
435 691, 4352521, 4352523, 4352543, 435278, 536 232, 935 14, 935 28, 935 66, 935 68, 935 69, C12N 942, C12N 1556, C12N 1580
Patent
active
056100485
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of PCT/DK92/00099 filed Mar. 27, 1992, which is incorporated herein by reference.
The invention comprises a xylanase, a corresponding recombinant DNA sequence, a vector, a transformed host, a method for production of the xylanase, an agent containing the xylanase, and a use of the agent.
Xylan, a major component of plant hemicellulose, is a polymer of D-xylose linked by .beta.-1,4-xylosidic bonds. Xylan can be degraded to xylose and xylo-oligomers by acid or enzymatic hydrolysis. Enzymatic hydrolysis of xylan produces free sugars without the by-products formed with acid (e.g. furans).
There are currently five major applications for xylanases; 1) enzymatic breakdown of agricultural wastes for production of alcohol fuels; 2) enzymatic modification of animal feeds or feed components or addition to animal feeds for in vivo breakdown of the hemicellulose fraction; 3) use as a baking agent; 4) manufacturing of dissolving pulps yielding cellulose; and 5) bio-bleaching of wood pulp. [Detroym R. W. In: Organic Chemicals from Biomass, (CRC Press, Boca Raton, Fla., 1981) 19-41.; Paice, M. G., and L. Jurasek. J. Wood Chem. Technol. 4: 187-198.; Pommier, J. C., J. L. Fuentes, G. Goma. Tappi Journal (1989): 187-191.; Senior, D. J., et al., Biotechnol. Letters 10 (1988):907-912.]
The pulp and paper industry is using xylanase compositions in the bleaching process to enhance the brightness of bleached pulps, to decrease the amount of chemicals used in the bleaching stages, and to increase the freeness of pulps in the recycled paper process [Eriksson, K. E. L., Wood Science and Technology 24 (1990); 79-101.; Paice, M. G., R. Bernier, and L. Jurasek, Biotechnol. and Bioeng. 32 (1988): 235-239.; Pommier, J. C., J. L. Fuentes, and G. Goma, Tappi Journal (1989): 187-191.]
Kraft pulping, a process widely used in the pulp and paper industry, involves the alkaline sulfate cooking of pulp to remove 90-98% of the lignin. The remaining 2-10% of lignin gives the pulp a dark brown color which has the tendency to darken in UV light or by oxidation. In order to obtain a white pulp for high quality paper, the brown color is removed by a multi-stage bleaching process using chemicals, e.g. chlorine, chlorine dioxide, ozone, oxygen or hydrogen peroxide.
Presently, there is much concern about the environmental impact of the chemicals generated from the bleaching process. Enzymes can aid in the removal of lignin from the pulp without any harmful side products. Reports show that lignin in wood is linked to xylan [Eriksson, O., et al., Wood Sci. Technol. 14 (1980); 267.; Takashi, N., and T. Koshijiima, Wood Sci. Technol. 22 (1988); 177-189]. By a limited hydrolysis of the xylan a greater release of lignin occurs during bleaching. Thus, by enzymatically treating the pulp prior to bleaching the amount of bleaching chemicals needed would in turn decrease. [Viikari, L., et al., Proceedings of the 3rd International Symposium on Biotechnology in the Pulp and Paper Industry (1986); 67.]
According to the technical literature, good results have been obtained by means of fungal preparations from Trichoderma [Paice, M. G., L. Jurasek, J. Wood Chem. Technol. 4 (1989): 187-198.; Senior, D. J., et al., Biotechnol. Letters. 10 (1988): 907-912], which require pH adjustment of the wood pulps below pH 6.0.
A Trichoderma xylanase preparation, Pulpzyme.TM. HA (commercially available from Novo Nordisk A/S) can be used for delignification of kraft pulps at pH 5-7. At 50.degree. C. and pH higher than 7, the enzyme shows only little effect.
Also a Bacillus pumilus xylanase preparation, Pulpzyme HB (commercially available from Novo Nordisk A/S) can be used for delignification of Kraft pulps at pH 5-7. At 50.degree. C. and pH higher than 7, the enzyme shows only little effect.
Humicola insolens xylanases have been described (Yoshioka, H. et al., Agric. Biol. Chem. 43(3) (1981) 579-586). In the crude preparation they have a pH-optimum of 6.0 and a temperature optimum of 60.degree. C. At pH 9 they
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Dalb.o slashed.ge Henrik
Halkier Torben
Heldt-Hansen Hans P.
Pedersen Lars S.
Schulein Martin
Lambiris, Esq. Elias J.
Moore William W.
Novo Nordisk A S
Wax Robert A.
Zelson Esq. Steve T.
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