Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
2000-10-30
2003-01-14
Silverman, Stanley S. (Department: 1754)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C435S171000, C071S008000
Reexamination Certificate
active
06506956
ABSTRACT:
TECHNICAL FIELD
The present invention relates to fungi having dioxin degradability, to a method of using the fungi for degrading dioxins, to compost that contains the fungi, to a method for producing the compost, and to a method of using the compost for cultivating plants. More precisely, the invention relates to fungi capable of degrading dioxins having accumulated in the soil of farms and developed lands into harmless substances, to a method of using the fungi for degrading dioxins, to compost that contains the fungi, to an effective method for producing the compost, and to a method of using the compost for cultivating plants for agricultural crops, etc.
BACKGROUND ART
Dioxins are a type of harmful substances that are discharged in the nature from various facilities, appliances and others typically including incinerators for garbage and industrial wastes.
Known are various dioxins of different chemical structures, and 2,3,7,8-tetrachlorodibenzo-p-dioxin is the most typical. Living organisms could hardly degrade dioxins, and many of them absorbs dioxins. Through food chain, dioxins are finally accumulated and concentrated in animals, often causing malformation in the animal kingdom, and the problem with dioxins is now a grave object of public concern.
Various methods for preventing the generation of dioxins have been investigated and proposed. For example, a two-stage method of burning exhaust gas at high temperatures in automobiles and incinerators has been put into practical use. However, this is still insufficient for preventing the generation of dioxins. Dioxins having been discharged in air fall down on the earth along with rain and snow, and accumulate in soil. At present, no one knows an effective method for degrading dioxins into harmless substances.
Some recent studies are directed to biodegradation of chemical substances such as dioxins and others that are hardly degraded in the nature, and some reports say that lignin degrading enzymes produced by a type of microorganisms can degrade dioxins [BIO INDUSTRY, Vol. 15, No. 2, pp. 5-13 (1998); Chemistry, Vol. 52, No. 10, pp. 24-25 (1997)].
Relative to the degradation of dioxins by such microorganisms-derived lignin degrading enzymes, the reports precisely say that the lignin degrading enzymes produced by white rot fungi, which are in a group of wood-rotting fungi of the genus Basidiomycetes, have the ability to degrade various chemical substances including dioxins, further saying that the white rot fungi grow with a nutrient source of polysaccharides, cellulose and hemicellulose that are the essential ingredients of wood, and degrade lignin in wood depending on the energy from the nutrient source. Accordingly, in wooded regions where such white rot fungi live, dioxins having fallen down on the earth along with rain shall be degraded by lignin degrading enzymes produced by the white rot fungi.
In farms for agricultural crops, grass, etc., however, the soil is poor in cellulose and hemicellulose that are to be the nutrient source for white rot fungi. In addition, a large amount of microbicides and chemical fertilizers are often applied to the soil of such farms. Therefore, the environment of farms is not suitable for white rot fungi living therein. In some area of lands developed by civil engineering, trees and flowers are planted. However, the soil in the area is also poor in cellulose and hemicellulose, and its environment is not suitable for white rot fungi living therein.
Accordingly, dioxins will accumulate increasingly in such farms and developed lands, and the influence of the thus-accumulated dioxins on living organisms will be a more serious problem. In that situation, it is much desired to develop a technique effective for degrading the dioxins having accumulated in the soil of farms and developed lands into harmless substances to thereby renew the soil so that the renewed soil may have no negative influence on living organisms.
The present invention is to provide fungi having the ability to degrade dioxins that have accumulated in the soil where agricultural crops and others are cultivated into harmless substances, to provide compost that contains the fungi and a method of producing the compost, and to provide a method of using the compost for cultivating plants.
DISCLOSURE OF THE INVENTION
We, the present inventors have assiduously studied to solve the problems noted above, and, as a result, have found that, when a plant-derived organic material that contains lignin is used for producing compost and when the plant-derived organic material having been thermally fermented under a specific condition is inoculated with a specific type of fungi to be compost, then the resulting compost can degrade dioxins having accumulated in the soil of farms and others into harmless substances. On the basis of these findings, we have completed the present invention.
Specifically, the subject matter of the invention resides in the following:
1. Fungi having the ability to degrade lignin and belonging to the genera, Chaetomium, Penicillium and Schizophyllum, which have the ability to degrade dioxins.
2. A method of degrading dioxins, which comprises applying the fungi of above 1 to a dioxin-containing organic or inorganic substance in an amount of at least 1×10
2
cfu per gram of the dry weight of the substance.
3. A method of degrading dioxins by applying the fungi of above 1 to a dioxin-containing organic or inorganic substance, for which is used a material inoculated with the fungi.
4. Compost containing the fungi of above 1.
5. The method of degrading dioxins as in above 3, wherein the fungi-inoculated material is the compost of above 4.
6. A method for producing the compost of above 4 by fermenting a plant-derived organic material, which is characterized in that the plant-derived organic material contains lignin, and the plant-derived organic material having been thermally fermented in a process that includes a step of keeping it at a temperature falling between 65 and 100° C. for at least 2 hours is further fermented while being inoculated with at least one type of the fungi of above 1 at a temperature not higher than 65° C.
7. A method for producing the compost of above 4, wherein the plant-derived organic material is inoculated with the fungi of above 1 to such that the cell concentration in the inoculated material is at least 1×10
2
cfu per gram of the dry weight of the plant-derived organic material.
8. A method for producing the compost of above 4, wherein the plant-derived organic material is thermally fermented in the presence of a nitrogen fertilizer component-containing substance that serves as a fermentation promoter, in the initial stage of the process of thermophilic fermentation.
9. Compost having the ability to degrade dioxins, in which the cell concentration of the fungi of above 1 falls between 1×10
3
and 1×10
10
cfu per gram of the dry weight of the compost.
10. A method for cultivating plants, which comprises applying the compost of above 4 to the soil of farms or developed lands, and cultivating plants on the soil.
BEST MODES OF CARRYING OUT THE INVENTION
In the method of the invention for producing compost that has the ability to degrade dioxins, used is a lignin-containing, plant-derived organic material for the compost.
In general, weeds and vegetable refuse that can be fermented into compost within a short period of time are much used for the material for compost that serves as a soil improver or base manure. However, as not containing a large amount of lignin, they are unsuitable for the material for the compost of the invention. Even if used, they could not attain the intended effect of the invention. A lignin-containing, plant-derived organic material is suitable for the compost of the invention. Specific examples of the material are wood, bark, bamboo, corn stems, pulp, pulp wastes, etc. For their forms, wood chips and sawdust are preferred. Also preferred are bark, bamboo and corn stems having been cut into pieces to have a length of 200 mm or so; as well as t
Miyamoto Hideo
Suzuki Motoshi
Yuki Junichiro
Idemitsu Kosan Co. Ltd.
Nave Eileen E.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Silverman Stanley S.
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