Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues – Scleroproteins – e.g. – fibroin – elastin – silk – etc.
Reexamination Certificate
2000-03-01
2003-11-18
Low, Christopher S. F. (Department: 1653)
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
Scleroproteins, e.g., fibroin, elastin, silk, etc.
C530S355000, C530S842000, C530S418000, C530S422000, C530S423000, C514S002600, C073S073000, C106S900000
Reexamination Certificate
active
06649740
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention relates to compositions and methods of use for soil amendments and bioremediation. More particularly, the invention relates to compositions and methods of use of hydratable keratin and keratin hydrogels as soil amendments and nutrient sources for bioremediation.
2. Description of Related Art
Keratin is a protein characterized by the prevalence of cysteine which, when crosslinked, render most keratins insoluble and environmentally robust in that they are resistant to hydrolysis and dissolution. Nitrogen release from unmodified poultry feathers has been reported as being too slow for use as a greenhouse fertilizer (Williams and Nelson, 1992). But, production of a feather meal by pressurized steam treatment, which breaks disulfide bonds, results in an increased rate of nitrogen mineralization (Hadas and Kautsky, 1994; Choi and Nelson, 1996). Feather meal also releases organic sulfur as plant available SO
4
2−
(Wainwright et al., 1985). The availability of nitrogen may also be enhanced by microbial action by composting keratin material. Fertilizers have also utilized keratin materials after complete hydrolysis to component amino acids. Chelates of such amino acids have been used as trace element fertilizers (Baolin et al., 1995). Mineral-organic fertilizers have also been prepared by mixing minerals with keratin hydrolyzates.
A possible limitation on crude keratin fertilizer preparations is that it may enrich the soil with keratolytic fungi which may be pathogenic to man and animals (Wainwright et al., 1985). Leather meal as a keratin source is also problematic because of the possibility of incorporating tanning agents such as chromium. Feather meal is malodorous, but can be made odor-free and more easily composted by autoclave treatment (Choi and Nelson, 1996).
An adequate supply of water is essential for plant survival and control of soil hydration is required for optimal plant growth. A number of soil moisture systems require a monitoring system that regulates an external water supply. Examples of such systems are disclosed in U.S. Pat. Nos. 4,796,654 and 4,182,357. These systems require a considerable amount of equipment, which will in turn require maintenance. U.S. Pat. No. 5,814,123 discloses the addition of humectants to enhance soil water retention. A humectant is a compound or material that has an avidity for water and will promote the retention of water in the soil. However, under some circumstances such a compound may compete with plants for the moisture retained in the soil. There is a continuing need for materials that can both enhance water holding capability and promote the retention of the moisture content of soil.
Bioremediation of soil utilizes microorganisms to degrade environmental contaminants such as hydrocarbons and halogenated chemicals. The rate and extent of microbial degradation is limited by the availability of nutrients in the contaminated soil. Without added nutrients, the microbial degradation of environmental contaminants can take an undesirably long time. Even with a nutrient supply, in situ bioremediation can be a prolonged process and preferred characteristics of microbial nutrient sources are that they are long acting, resistant to leaching, and biodegradable such that undesirable residues from the nutrient source are not left in the remediated soil. Groundwater is also amenable to bioremediation and permeable bio-active barriers are used to act as in situ bioremediation filters (Sutherson, 1997). Desirable characteristics for such barrier constituents are water permeability and a non-leachable nutrient source for support of a microbial population.
Physical barriers are also used in containment of environmental contaminants. Hair has been proposed as a physical adsorbent for the remediation of oil spills. Keratin preparations have also been disclosed as adsorbents for heavy metals (Japanese Patent Abstracts JP53042281, JP4281856). Natural sorbents, including keratin, have been used as physical sorbents for heavy oil in bioremediation studies (Setti et al., 1999). The use of sorbents increased the rate of n-alkane degradation, possibly due to the formation of a water/cell/oil/sorbent interphase. Natural sorbents are preferred because of their biodegradability.
SUMMARY
The present invention provides a soil amendment comprising a chemically modified oxidized keratin that upon hydration forms a hydroge. The keratin hydrogel can increase the water retention properties of soil and provide a source of organic and inorganic nutrients. The hydrogel can also support the remediation of contaminated soil and groundwater by adsorbing environmental toxins and/or providing a nutrient source for microorganisms capable of degrading the environmental toxins.
In the context of the present invention, the term “hydratable keratin” and “hydratable keratin material” is a keratin or keratin material that when hydrated forms a hydrogel.
One aspect of the present invention is a soil amendment composition comprising an oxidized keratin hydrogel. The oxidized keratin includes sulfonate groups and is associated with one or more metal ion species. “Association” and “associated” are defined in regard to the interaction between oxidized keratin and metal ion species as including both ionic bonds, that is heteropolar bonds between a negative anion and a positive cation, and chelates, wherein a metal is bonded to another molecule by a covalent bonding process or a coordination based on the donation of a free electron pair of one atom. It is believed that the predominant bonding is ionic and involves the sulfonic acid residues of the oxidized keratin. In the practice of preferred embodiments of the invention, one may select any suitable metal ion depending on the particular application, or the particular needs of the soil to be treated. For example, soils that are depleted in potassium or other plant nutrients, or that may be depleted in a cation or metal such as iron or zinc, for example, useful for microbial growth would be treated with a soil amendment that contained one or more of those metals or cations. In preferred embodiments, the one or more metal ions or cations associated with the oxidized keratin may include, but are not limited to potassium, sodium, copper, zinc, manganese, magnesium, iron, calcium and combinations of these.
The keratin source for the soil amendment composition may be any suitable source of keratin, either a soft keratin or a hard keratin, and would include keratin derived from animal or human hair, feathers, leather, skin, fur, animal hooves, animal or human nails, beaks, claws, scales, feet and horns, and is preferably a keratin that includes oxidizable amino acids such as cystines. In certain embodiments, the soil amendment may also further comprise a preservative such as an antifungal agent. Preservatives for use in the practice of the invention would include, but are not limited to tetraalkylammonium hydroxide, glutaraldehyde or formalin, and in certain preferred embodiments tetraalkylammonium hydroxide is used.
The soil amendment keratin hydrogel composition may be made by the process comprising oxidizing disulfide bonds in a keratin material with an oxidizing agent to obtain a keratin solid having sulfonic acid residues. Any suitable oxidizing agent may be used in the practice of the invention, including, but not limited to hydrogen peroxide, alkali peroxides, peracids, perborates, percarbonates, persulfates, hypochlorite or chlorine dioxide, with hydrogen peroxide or peracetic acid being the most preferred for certain embodiments. The oxidized keratin solid is separated and mixed with a water-miscible solvent containing one or more metal ion or cationic species such that the one or more metal ions or cationic species become associated with the oxidized keratin solid. The water-miscible solvent may contain up to about 20 volume percent of water. The water-miscible solvent is substantially removed and the oxidized keratin is hydrated to form a hydrogel. Any suitable water miscible solven
Blanchard Cheryl R.
Siller-Jackson Arlene J.
Smith Robert Allen
Timmons Scott F.
Van Dyke Mark E.
Kam Chih-Min
Keraplast Technologies Ltd.
Low Christopher S. F.
Vinson & Elkins L.L.P.
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