Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Reexamination Certificate
2001-03-14
2003-11-25
Lilling, Herbert J. (Department: 1651)
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
C588S253000
Reexamination Certificate
active
06653119
ABSTRACT:
TECHNICAL FIELD
The present invention relates to white rot fungi having the activity of efficiently decomposing dioxins, as well as a method for decomposing dioxins by using the white rot fungi. In more detail, the present invention relates to a method for decomposing dioxins in incineration ash by using white rot fungi and crude extracellular enzymes from the white rot fungi.
BACKGROUND ART
It has been said that dioxins are the most hazardous poison generated by human activities ever. It has strong toxicity resulting in carcinogenesis, weight loss, thymus atrophy, skin disorders, hepatic disorders, teratogenicity, etc. Because the compounds are chemically stable, there are also environmental concerns about their accumulation. The environmental dispersion of dioxins generated during waste incineration has become a serious problem worldwide. Dioxins are grouped into several categories based on their chemical structures. There are 70 or more known isomers of polychlorinated dibenzo-p-dioxins (PCDDs). This category contains 2,3,7, 8-tetrachlorodibenzo-p-dioxin (2,3,7, 8-T
4
CDD), which is known to be highly toxic. 2,3,7,8-T
4
CDD shows extremely high acute toxicity, having a LD
50
value of 0.6 to 2.0 &mgr;g/kg for guinea pigs. Other dioxins are also known, which include polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs), both having several isomers.
Dioxins are generated mainly by incineration. The source includes nonindustrial waste incineration, industrial waste incineration, metal refining, petroleum additives (lubricating oil), cigarette smoke, recycled black-liquor boilers, incineration of wood and discarded material, auto emissions, etc. Dioxins are also generated in the bleaching process of bleached kraft-pulp production, in the process of manufacturing agricultural chemicals such as PCNB, and such processes. Among them, the incineration of non-industrial waste is estimated to generate about 80% of the total dioxin output. For example, more than 4000 gTEQ of dioxin is produced annually in Japan due to non-industrial waste incineration.
Industrially advanced nations are already taking measures to legally regulate dioxin release by restricting the dioxin concentration released from incinerators. Even in the mechanical aspect, the combustion efficiency of incinerators, and the treatment of released gases have.been improved, producing effective results. However, dioxins already released into the environment have polluted the soil, and leachates have been polluted by fly ash and also by incineration ash buried at final disposal sites. These dioxin pollutions are serious problems and dioxin-decomposing countermeasures should be taken immediately.
In recent years, bioremediation is gaining the spotlight as a means for eliminating pollutants that have been released into the environment. Bioremediation is a technology by which environmental pollutants are processed using microbial functions, finally converting pollutants into non-toxic substances such as carbonic acid gas, water, inorganic salt, and such. Bioremediation is further divided into biostimulation and bioargumentation. The former is the means of enhancing the functional activity of microorganisms present in the polluted environment by adding nutrient salts, improving aeration, etc. The latter is the means of introducing microorganisms having a cleaning function into the polluted environment.
Microbial decomposition of dioxin is divided into three classes depending on the type of microorganism or enzyme used, namely, (1) aerobic decomposition by bacteria, (2) reductive dechlorination by anaerobes, and (3) decomposition by Basidiomycetes.
Only a few research reports exist regarding the decomposition by bacteria. Recently, a series of evaluations were done on the genus Sphingomonas. Wittich et al. screened strains capable of growing in the presence of dibenzo-p-dioxin (DD) and dibenzofuran (DF) as a unique carbon source and succeeded in the isolation of the Sphingomonas sp. RW1 strain (Wittich, R. et al., Appl. Environ. Microbiol., 1992, 58, 1005-1010; H. -A. Arfmann et al., Appl. Environ. Microbiol., 1997, 63, 3458-3462) and HH69 strain (Harms, H. et al., Appl. Environ. Microbiol., 1995, 61, 2499-2505). RW1 strain was capable of decomposing chloro- and dichloro-substituted dioxins, but could not decompose further-substituted dioxins. The decomposition products obtained were salicylic acid, catechol, and chlorinated compounds thereof (Wilkes, H. et al., Appl. Environ. Microbiol., 1996, 62, 367-371). In addition to these studies, there are reports on the decomposition of dioxins such as dibenzofuran and dibenzo-p-dioxin by utilizing aerobic bacteria such as the genus Pseudomonas and the genus Alcaligenes (G. Schreiner et al., Chemosphere, 1997, 34, 1315-1331). There are also some reports on dioxin decomposition by anaerobic microorganisms (P. Adriaens etal., Environ. Sci. Technol., 1995, 29, 2252-2260; J. E. M. Beurskensetal., Environ. Toxicol. Chem., 1995, 14, 939-943). For example, these include the dechlorination of heptachlorodibenzo-p-dioxin (HpCDD) to hexachlorodibenzo-p-dioxin (HxCDD) as well as the conversion from 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) to dichlorodibenzo-p-dioxin (2-CDD) by anaerobic microorganisms within sludge (Wittich, R. et al., Appl. Microbiol. Biotechnol., 1998, 49, 489-499). However, there are concerns of more toxic compounds being generated during the decomposition processes. In addition to these microorganisms, others capable of decomposing dioxins have been identified (Hammer et al., Appl. Environ. Microbiol., 1998, 64, 2215-2219).
Bumpus et al. have suggested that a white rot fungus,
Phanerochaete chrysosporium
, which belongs to Basidiomycetes, might be capable of decomposing several types of persistent substances (Bumpus, J. A. et al., Science, 1985, 228, 1434-1436). Since the publication of this report, many researchers have been interested in the decomposition of environmental pollutants by white rot fungi, and thus, there are many reports concerning this matter. However, reports on decomposition of dioxins are small in number. Valli et al. found that the decomposition was markedly enhanced when 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) was treated with
P. chrysosporium
in a medium having a poor nitrogen source. Based on this finding, the authors deduced that the lignin-decomposing enzyme system participates in dioxin decomposition (Valli, K. et al., J. Bacteriol., 1992, 174, 2131-2137). DD was further treated with lignin peroxidase (LiP), obtaining an ether-linkage cleavage product (Joshi, D. et al., Biochem., 1994, 33, 10969-10976). However, it is questionable that LiP would act on a compound having more than two chloro-substitutions.
The present inventors have previously reported that the YK-624 strain of the white rot fungus
Phanerochaete sordida
is capable of decomposing dioxins such as polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) (Takada, S. et al., Appl. Environ. Microbiol., 1996, 62, 4323-4328). It is known that white rot fungi are capable of decomposing various environmental pollutants such as chlorophenol, chloroaniline, PCBs, a variety of agricultural chemicals, aromatic hydrocarbon compounds, nitro compounds, dyes, and so on in addition to dioxins. Accordingly, attention is being given to the fungus as a useful and key organism for environmental cleanup. However, in order to practically use the method of white rot fungus-mediated dioxin decomposition, it is necessary to discover a white rot fungus strain having a high dioxin-decomposing activity. Such strains should further be able to decompose not only particular types of dioxins, but also a variety of dioxins contained in incineration ash, etc. Even when the activity of decomposing dioxin is recognized in a test tube, it is necessary to construct new systems for decomposing dioxins present in wastes such as incineration ash, etc. Thus, when it comes to the practical use of dioxin decomposition by white rot fungi, many problems remain
Kondo Ryuichiro
Sakai Kokki
Wakao Koichi
Bio Remediation Technologie, Inc.
Lilling Herbert J.
Shanks & Herbert
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