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Benefits-Sharing in the National Parks
Environmental Impact Statement

What sort of Research Might Lead to Benefits-Sharing

An example of an enzyme discovered in a Yellowstone microorganism that has practical uses in agriculture, industry, and human food production.

Xylanase from Acidothermus cellulolyticus

Enzymes are biological catalysts produced by all living things .The enzyme named xylanase (pronounced zy-la-nase) deconstructs plant structural material by breaking down hemicellulose, a major component of the plant cell wall. Plant cell walls are necessary to prevent dehydration and maintain physical integrity. They also act as a physical barrier to attack by plant pathogens. In nature, some plant consumers or pathogens use xylanase to digest or attack plants. Many microorganisms produce xylanase, but mammals do not. Some herbivorous insects and crustaceans also produce xylanase.

Xylanase has been extracted from many different fungi and bacteria. It is commonly used in animal feeds, paper production, and food production.

Over 70 U.S. patents have been issued for various xylanase sources, uses, or production methods. There are additional xylanase producers and users who do not hold patents. One of the patented methods of producing xylanase relies on a microorganism discovered in Yellowstone National Park, Acidothermus cellulolyticus.

Discovery and Study of Acidothermus cellulolyticus

This microorganism was discovered in Yellowstone in the early 1980s and introduced to the scientific community in 1986. The scientists who discovered this previously unknown microorganism were bioprospectors. They were searching for a microorganism that could help convert biomass into alcohol for fuel. The scientific team inoculated culture tubes with 1 ml samples of mud and decaying wood from several thermal features in Norris Geyser Basin in Yellowstone. Twelve slightly different microorganism strains survived in the culture tubes. Those that showed the most promising cellulolytic (the ability to break down cellulose) abilities were cultured further. Three strains were chosen for intensive study. Each colony of bacteria was separated and grown under a variety of conditions. The selective conditions applied during enrichment and isolation (growth of the organisms) ensured that the surviving strains were those most suitable for the bioprospectors' needs. A single strain was selected as the "type strain" and a living sample was deposited in the American Type Culture Collection for safekeeping and to facilitate its distribution to other scientists for further study.

In the next few years, researchers began to look at the enzymes in this microbe. The scientists who published an article in 1989 about a cellulase discovered in Acidothermus cellulolyticus applied for a U.S. patent for that cellulase in the same year, and the patent was issued in 1992. Nine more U.S. patents have been issued for various enzyme production methods directly related to A. cellulolyticus.

 Practical Uses of Xylanase

The earliest U.S. patent for a method of xylanase production was issued in 1979 for an enzyme mixture used as an animal feed additive for dairy cattle. Xylanase has since proven useful in many ways:

  1. Biobleaching paper pulp. Paper producers need to retain cellulose while removing the lignin from paper pulp. The classic way to perform this operation is to add chlorine-based bleaches to the pulp. Xylanase breaks the hemicellulose chains that are responsible for the close adherence of lignin to the cellulose network. There is thus a reduced need for bleach to remove the loosened lignin. When the bleach used is chlorine-based, the use of xylanase leads to a reduction in organo-chlorine pollutants such as dioxin from the paper making process. In addition, chlorine-free bleaching (such as peroxide or ozone bleaching) can achieve brighter results with the addition of xylanase. Because xylanase does not harm cellulose, the strength of the paper product is not adversely affected.
  2. Improving animal feed. Adding xylanase stimulates growth rates by improving digestibility, which also improves the quality of the animal litter. For example, chicken feed based on wheat, rye, and many other grains is incompletely digested without added enzymes. These grains tend to be too viscous in the chicken's intestine for complete digestion. Xylanase thins out the gut contents and allows increased nutrient absorption and increased diffusion of pancreatic enzymes in the digesta. It also changes hemicellulose to sugars so that nutrients formerly trapped within the cell walls are released. The chickens get sufficient energy from less feed. The barn is cleaner because the feed is more thoroughly digested so the chicken waste is drier and less sticky. In addition, chicken eggs are cleaner because the excrement in the laying area is drier. In a sense, the addition of xylanase to animal feed pre-digests that feed.
  3. Making bread fluffier and keeping it fresh longer. Added xylanase modifies wheat flour arabinoxylans and can result in a loaf with more than 10% greater volume. Crumb softness after storage is also improved.
  4. Aiding in separation of wheat or other cereal gluten from starch.
  5. Increasing juice yield from fruits or vegetables. Xylanase aids in the maceration (chewing up) process. In addition, added xylanase can reduce the viscosity of the juice, improving its filterability.
  6. Extracting more fermentable sugar from barley for making beer, as well as processing the spent barley for animal feed. In both cases, xylanase has the ability to break hemicellulose down into sugars. In addition, added xylanase can reduce the viscosity of the brewing liquid, improving its filterability.
  7. Improving silage (or enhanced fermentative composting). Treatment of forages with xylanase (along with cellulase) results in better quality silage and improves the subsequent rate of plant cell wall digestion by ruminants. There is a considerable amount of sugar sequestered in the xylan of plant biomass. In addition to converting hemicellulose to nutritive sugar that the cow or other ruminant can digest, xylanase also produces compounds that may be a nutritive source for the ruminal microflora.
  8. Improve degradability of plant waste material (for instance, agricultural wastes) thereby reducing organic waste disposal in landfill sites.
  9. Improve the cleaning ability of detergents that are especially effective in cleaning fruit and vegetable soils and grass stains.
  10. Fuel-alcohol production. Xylanase decreases the viscosity of the mash and prevents fouling problems in distilling equipment.
  11. Improve the extraction of oil from oil-rich plant material such as corn-oil from corn embryos.
  12. Improve retting of flax fibers. Retting is the decomposition of the outer stem of the flax plant necessary before the fibers are processed into linen.

Practical Sources of Xylanase

  • Many of species of fungi. Genera known to produce xylanase include Aspergillus, Disporotrichum, Penicillium, Neurospora, Fusarium, Neocallimastix, Trichoderma, Coniothyrium, etc.
  • A number of species of bacteria, some from extreme environments (hot, alkaline, etc.) which makes them more suitable for industrial environments.
  • Transgenic (recombinant) bacteria, fungi, or yeast transformed with genes from other microorganisms.
  • Transgenic Brassica napus (canola) has also been invented. The meal produced from this canola can be used as an animal feed supplement (Canola meal is the protein-rich residue left after the production of canola oil).

Another example of park-based research that might lead to a benefits-sharing agreement is found at Carlsbad Caverns National Park in New Mexico. Read an article about this research in the National Park Service's 2000 Natural Resource Year in Review.

References:

Mohagheghi, A. "Isolation and characterization of Acidothermus cellulolyticus gen. nov., sp. nov., a new genus of thermophilic, acidophilic, cellulolytic bacteria." International Journal of Systematic Bacteriology 36, no. 3 (1986): 435-443.

Tucker, M.P, Mohagheghi, A., Grohmann, K., and Himmel, M.E. "Ultra-thermostable cellulases from Acidothermus cellulolyticus: comparison of temperature optima with previously reported cellulases." Biotechnology 7 (1989): 817-820.

update on 11/23/2009  I   http://nature.nps.gov/benefitssharing/xylanase.cfm   I  Email: Contact Us
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