Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Patent
1993-06-25
1995-01-03
Michl, Paul R.
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
523128, 523124, 435171, 4352541, C08J 1100, C08K 500, C12P 104, C12N 100
Patent
active
053787382
DESCRIPTION:
BRIEF SUMMARY
INDUSTRIAL FIELD
The present invention relates to a method for decomposing plastic and a decomposing agent therefor as well as a biodegradable plastic.
Therefore, the present invention not only makes greater contribution to the disposal of plastic waste which is now drawing serious social concern, but also proposes the elucidation of the decomposing mechanism thereof and the designing of a biodegradable plastic.
BACKGROUND OF THE INVENTION
Polyolefin plastic has been considered non-biodegradable conventionally, and it has been known that only about 1% of polyethylene as a polyolefin plastic is decomposed after 10-year bacterial treatment (Journal of Applied Polymer Science, 35, 1288-1302 (1988)).
Also, it is known a method for decomposing polyamide plastic by means of a bacterium (Flavobacterium sp. K172) (Agr. Bio Chem., 39 (6), 1219-1223(1975); Hakkoukougakukaishi, 60(5), 363-375(1982)). However, all of these conventional methods concerning polyamide plastic are classified in the method for treating water-soluble, low-molecular nylon 6 oligomer (molecular weight of about 2,000 or less). Thus, water-insoluble, high-molecular nylon (molecular weight of about 10,000 or more) cannot be decomposed with these methods.
It has been known a biodegradable composition which has been modified for ready biological attack by dispersing starch in a thermoplastic synthetic resin (Japanese Patent Laid-open No. Sho 49-55740). In the biodegradable composition, however, it is only the starch particle that is decomposed biologically, whereas the synthetic resin cannot be decomposed. That is, the composition is just degraded when the starch particle is not any more decomposed, so the synthetic resin still remains.
For the disposal of plastic waste, the rapid decomposition of plastic waste of itself is an issue of significance. Therefore, such objective cannot be achieved by the conventional methods, as is apparently shown in what has been described above.
Under such current technical circumstances, the present invention has been performed for the objective to prevent plastic pollution. The present invention has been carried out for the objective to provide a method for efficiently decomposing plastic of itself which has never been substantially decomposed by the conventional methods and to provide a plastic suitable for such decomposition method.
DISCLOSURE OF THE INVENTION
The present inventors have made investigation so as to achieve the aforementioned objectives, and have thus focused their attention to biological treatment by means of a variety of bacteria from the respect of preventing secondary pollution. However, the inventors have recognized the need of conceptual innovation concerning microbial selection, culturing condition, treating condition and the like because they have not been able to achieve the primary objective. Thus, they have made reinvestigation.
By selecting Basidiomycetes as a microorganism, it has been found in accordance with the present invention that enzymes generated from Basidiomycetes cannot act on non-hydrophilic plastic but can act on plastic mixed or coated with a hydrophilic property imparting-substance which can then impart wettability to the plastic whereby the enzymes can sufficiently decompose the plastic of itself.
As to polyolefin plastic in particular, polyolefin plastic after hydrophilic treatment is subjected to bacterial treatment under conditions without supplement of nitrogen source and/or carbon source as essential nutrients for bacterial growth or treatment which conditions are totally contrary to conventional state of the art. It has been found that Basidiomycetes can efficiently decompose polyolefin plastic. Thus, the present invention has been achieved. In the present Specification, polyolefin plastic is often referred to as polyethylene hereinbelow.
BEST MODE OF CARRYING OUT THE INVENTION
Polyethylene, nylon, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polyester and the like are included in plastic and these are decomposable.
These types of plast
REFERENCES:
patent: 4016117 (1977-04-01), Griffin
patent: 5118725 (1992-06-01), Suominen
Deguchi Tetsuya
Nishida Tomoaki
Takahara Yoshimasa
DeWitt LaVonda
Kabushiki Kaisha Kobe Seiko Sho
Michl Paul R.
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