Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Treating animal or plant material or micro-organism
Patent
1994-03-22
1995-03-07
Naff, David M.
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Treating animal or plant material or micro-organism
435278, 435200, D21C 100, D21C 300, C12N 924
Patent
active
053957652
DESCRIPTION:
BRIEF SUMMARY
This application is a continuation of PCT/DK92/00300 filed Oct. 14, 1992, the contents of which are incorporated herein by reference.
TECHNICAL FIELD
This invention relates to novel enzymes. More specifically, the invention provides novel xylanases obtainable from strains belonging to the genus Rhodothermus. The invention also relates to the use of the xylanases in the treatment of lignocellulosic pulp.
BACKGROUND ART
Xylan, a major component of plant hemicellulose, is a polymer of D-xylose linked by beta-1,4-xyiosidic 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).
Major applications for xylanases are enzymatic breakdown of agricultural wastes for production of alcohol fuels, enzymatic treatment of animal feeds to release free pentose sugars, manufacturing of dissolving pulps yielding cellulose, and bio-bleaching of wood pulp [Detroyrn 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. Gorna., 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 chlorine 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. Bemier, and L. Jurasek, Biotechnol. and Bioeng. 32 (1988):235-239.; Pommier, J. C., J. L. Fuentes, and G. Gorna, 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 95% of the lignin. The remaining 5% of lignin gives the pulp a dark brown colour 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 colour is removed by a multi-stage bleaching process using chlorine and/or chlorine dioxide.
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 active chlorine 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].
SUMMARY OF THE INVENTION
Recently novel thermophilic bacteria named Rhodothermus have been isolated from an alkaline hot spring in Iceland [Alfredsson, G. A.; Kristjansson, J. K.; Hjorleifsdottir, S.; Stetter, K. O. (1988): Rhodothermus marinus, gen.nov., sp.nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland; J. Gen. Microbiol. 134; 299-306]. We have now found that these bacteria produce highly thermostable xylanolytic enzymes with good stability in a broad pH range.
Accordingly, in its first aspect, the invention provides xylanases having activity at temperatures of from below 60.degree. to above 100.degree. C., a relative activity of more than 50% in the interval of from pH 5 to pH 8 after incubation for 5 minutes at 65.degree. C., a relative temperature stability at 80.degree. C. of more than 80% after incubation at pH 7 for 3 hours, being capable of hydrolysing birchwood xylans, and having immunochemical properties identical or partially identical to those of a xylanase derived from the strain ATCC 43812, or the strain ATCC 43813, or the strain DSM 4252.
In another aspect, the invention pr
REFERENCES:
patent: 4966850 (1990-10-01), Yu et al.
Eriksson et al., Wood Sci. Technol., 14: 267-279, 1980.
Abstract of Japanese Patent No. JP 60-58070 published Apr. 4, 1985.
Alfredsson et al., J. of Gen. Microbiology, vol. 134, pp. 299-306.
Detroy R. W., Organic Chemicals from Biomass, pp. 19-41 (1981).
Paice et al., J. Wood Chem., Technol., vol. 4, No. 2, pp. 187-198 (1984).
Pommier et al., Tappi Journal, pp. 187-191 (1989).
Paice et al., Biotech. & Bioengineering, vol. 32, pp. 235-239 (1988).
Chen et al., Biotech. Letters, vol. 10, No. 12, pp. 913-918 (1988).
Takahashi et al., Wood Sci. Technol., vol. 22, pp. 177-189 (1988).
Eriksson et al., Wood Sci. Technol., vol. 24, pp. 79-101 (1990).
Viikari et al., Proceedings 3rd Int'l Symposium on Biotech in Pulp & Paper Industry, pp. 67-69 (1986).
Anker Lisbeth
Dahlberg Leif A. L.
Holst Olof P.
Lowney Karen A.
Meller Mike
Naff David M.
Novo Nordisk A S
Zelson Steve T.
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