Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of...
Reexamination Certificate
1999-08-23
2002-09-17
Naff, David M. (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
C210S600000, C210S605000, C210S610000, C424S093100, C435S252100, C435S262500
Reexamination Certificate
active
06451580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a technique of enrichment of decomposing bacteria which can be used to treat soil polluted by organic contaminants, such as agricultural chemicals, particularly to prevent groundwater pollution caused by agricultural chemicals in soil and a technique of isolating the decomposing bacteria by utilizing the enriching technique, and more particularly to techniques of these kinds which make it possible to drastically reduce time required for the enrichment or isolation of the decomposing bacteria.
2. Prior Art
To maintain today's agricultural production, agricultural chemicals cannot be dispensed with, and to conserve flora in golf courses or the like as well, agricultural chemicals are used in large quantities. On the other hand, there is a concern that agricultural chemicals work as contaminants to have undesirable effects on the environment, especially to be a pollution source of groundwater. To eliminate this threat, it is desired to develop a technique of effectively preventing agricultural chemicals from remaining or spreading in the environment as contaminants after they have served their functions.
A great variety of microorganisms on the order of billions/1 g live in soils, and among these microorganisms there are not a few decomposing bacteria which are capable of decomposing organic compounds serving as functional skeletons in a lot of agricultural chemicals, thereby defusing the organic compounds or eliminating the same from the environment. Therefore, it is possible to thereby eliminate contaminants, such as agricultural chemicals or the like, from the environment by exploiting such capabilities of the decomposing bacteria. Generally, however, under natural conditions, decomposing bacteria capable of decomposing or degrading specific kinds of organic compounds are too thinly populated to effectively prevent contaminants from remaining or spreading in the environment. Therefore, a method of selectively enriching such decomposing bacteria and isolating the same from soil and thereafter applying the same to soil again is considered to be powerful means for preventing groundwater pollution by soil contaminated by organic compounds, such as agricultural chemicals and the like.
The method of selective enrichment/isolation of specific kinds of bacteria from diverse soil-inhabiting bacteria includes a soil percolation technique in which a column or the like is filled with soil containing inhabiting decomposing bacteria to form an enrichment soil layer, and inorganic salt medium, which contains only contaminants, such as agricultural chemicals, as solo carbon and nitrogen sources, is continuously circulated through the enrichment soil layer, whereby a specific kind of decomposing bacteria, that is, decomposing bacteria which are capable of using the carbon or nitrogen source contained in the inorganic salt medium for assimilation are selectively enriched for isolation. In the case of the above conventional soil percolation technique, generally a time period of one half to one year is required to enrich and isolate decomposing bacteria for practical use, which is a large impediment encountered in putting to practical use a groundwater pollution control technique and a soil cleanup technique using decomposing bacteria.
SUMMARY OF THE INVENTION
The present invention has been made under these circumstances, and its object is to provide a method of enriching decomposing bacteria which is capable of realizing bacteria-enriching/isolating speeds required high enough to put to practical use the groundwater pollution control technique using decomposing bacteria, and a method of isolating the decomposing bacteria by using the enriching method.
This invention is based on the following new finding: It is possible to improve the above soil percolation technique by adding an artificial microhabitat having a specific characteristic to an enrichment soil layer and thereby largely enhance the speed of enrichment of decomposing bacteria and the speed of isolation of the same from the soil.
According to the study of the present inventors, it has been found that if a porous material having an infinite number of micropores, such as charcoal, is fragmented to pieces of approximately several mm to ten and several mm in size such that the same can be handled with ease and at the same time has a large effective surface area, and then the fragmented porous material is mixed into an enrichment soil layer as an artificial microhabitat, decomposing bacteria can be effectively enriched and isolated over a time period of three weeks to three months, although they are slightly different depending on the kind of a contaminant and the kind of bacteria decomposing the contaminant. Such high-speed enrichment and isolation are not only far more excellent than the conventional methods requiring a time period of one half to one year, but also can sufficiently meet requirements for putting to use the technique of controlling pollution of groundwater by using the, decomposing bacteria.
Such high-speed enrichment and isolation is considered to be enabled by the following mechanism: First, the artificial microhabitat formed of the porous material efficiently adsorbs contaminants, that is, carbon and nitrogen sources, contained in an inorganic salt medium, into its infinite number of micropores mainly by hydrophobic adsorption to decompose bacteria. Further, under preferred conditions provided by the micropores of the artificial microhabitat, the decomposing bacteria can actively proliferate and be active in the micropores. These factors cooperate so that the decomposing bacteria in the micropores efficiently decompose or degrade the contaminants efficiently adsorbed in the micropores. As a result, the high-speed enrichment can be realized. In other words, by using the artificial microhabitat, the contaminants per se can be collected with efficiency in the artificial microhabitat, and moreover the artificial microhabitat can promote the growth of the decomposing bacteria, thereby enabling the high-speed enrichment of the bacteria. This also works effectively when artificial microhabitats containing enriched decomposing bacteria are used in farms and golf courses as a material for prevention of groundwater pollution, realizing a more efficient groundwater control capability.
In isolating decomposing bacteria through enhanced enrichment of the same, it goes without saying that the above-described mechanism works, but further, high-speed isolation of the decomposing bacteria is realized by isolating operations effectively carried out through the fact that enriched decomposing bacteria can be easily taken out from soil in the form of a treatable artificial microhabitat, and that by using the microhabitat, it is possible to easily inoculate the taken-out bacteria in new artificial microhabitats, and further that by circulation, it is possible to purify and enrich the bacteria in the artificial microhabitat.
One of the conditions for effectively activating the above-described mechanism is that a porous material as artificial microhabitats has a greater adsorptivity for adsorbing organic contaminants than a target soil.
According to the study of the present inventors, a more preferable condition of the porous material is that it has an adsorption coefficient (K
f
) larger than scores of times and at the same time smaller than thousands of times as large as that of a soil used for an enrichment soil layer. Such a condition is substantially equivalent to a condition that the porous material has a specific surface area larger than approximately 50 m
2
/g and at the same time smaller than about 600 m
2
/g.
The reason for making these conditions preferable is related to the above-described mechanism. That is, if a porous material has an adsorptivity larger than required, it is impossible to cause adsorption of organic contaminants such that the decomposing bacteria are capable of effectively using the contaminants, more specifically, it is impossib
Takagi Kazuhiro
Yoshioka Yuuichi
Naff David M.
National Institute for Agro-Environmental Sciences Independent A
Rader & Fishman & Grauer, PLLC
Ware Deborah K.
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