PROCESS FOR THE DEGRADATION OF COAL TAR CONSTITUENTS BY WHITE ROT FUNGI

Abstract: A process for degrading coal tar or polycyclic aromatic constituents thereof using lignin degrading oxygenase fungal enzymes and hydrogen peroxide. The fungus is preferably living and is most preferably a white rot fungus such as Phanerochaete chrysosporium. The process provides a means for the treatment of coal tar wastes.

Description: PROCESS FOR THE DEGRADATION OF COAL TAR CONSTITUENTS BY WHITE ROT FUNGI Cross-Reference to Related Application This application is a continuation-in-part of application Serial No. 702,944 filed February 19, 1985. Background of the Invention (1) Summary of the Invention The present invention relates to a process for the degradation of polycyclic aromatic compounds found in coal tar mixtures. In particular the present invention relates to the biodegradation of coal tar. (2) Prior Art Most microorganisms are not able to cause complete biodegradation of polycyclic aromatic compounds. A few species of bacteria and fungi are able to cause extensive degradation of relatively simple polycyclic aromatic compounds (biphenyl and naphthalene, for example) On the other hand, polyaromatic compounds such as benzo(a)pyrene, a compound composed of five aromatic rings is resistant to biodegradation by most, but not all microorganisms and is acknowledged to be a persistent environmental pollutant. Although some microorganisms are able to degrade certain polycyclic aromatic compounds, their usefulness in icrobial waste treatment systems is often limited for the following reasons: (1) degradation' i often not extensive, that is to say degradation does not „ always proceed to carbon dioxide as an end product of metabolism; (2) some metabolites may be even more toxic than the parent compound and as environmentally persistent and (3) many microorganisms used in waste treatment systems are not able to degrade a wide variety of organopollutants, and thus mixtures of microorganisms ofte have to be used instead of a single species. The ability of a microorganism to degrade a broad spectrum of organopollutants is important in the treatment of sites contaminated with coal tar, a complex mixture of aromatic and polycyclic aromatic compounds that are by-products of the coking and coal gasification industries. For years coal tar wastes have been deposited in unlined dump sites where they have contaminated soils and ground water. The problem is to use microorganism to degrade the constituents found in coal tar. Objectives It is therefore an objective of the present invention to provide a process for the microbial degradation of the constituents of coal tar and polycyclic aromatic constituents thereof. Further, it is an objective of the present invention to provide a process which is simple and economical. These and other objectives will become increasingly apparent by reference to the following description and to the drawings. In The Drawings Figures 1 and 2 are graphs showing the ability of a white rot fungus (i.e. Phanerochaete chrysosporium) to mineralize representative l^C-labeled compounds which are found in coal tar. General Description The present invention relates to a process for biodegrading coal tar or constituents thereof. The process comprises mixing of coal tar or polycyclic aromatic constituents found in coal tar with white rot fungi and appropriate nutrients under aerobic conditions. The mixture may also be supplemented by providing additional lignin degrading oxidases and hydrogen peroxide. The coal tar constituents, including polycyclic aromatic compounds, are degraded to carbon dioxide. Specifically this invention relates to the ability of white rot fungi (e.g. Phanerochaete chrysosporium) to degrade normally hard-to-degrade polycyclic aromatic compounds found in coal tar. At the same time * easier-to-degrade organopollutants such as single aromatic ring compounds will also be degraded by white rot fungi. Furthermore, because -*- 4 Cθ2 has been fou to be the ultimate degradation product in all cases teste it is apparent that any potentially toxic intermediates from the degradation of the coal tar are also degraded. The process is very non-specific and capable of completel degrading a wide variety of organic molecules and thus is well suited for treatment of coal tar contaminated materials. Furthermore, because degradative enzymes are secreted by white rot fungi, treatment systems can consis of adding large amounts of these enzymes to effect initia oxidative degradation of the pollutants in the coal tar. Supplemental enzyme treatment can also take place in the presence of white rot fungi or other microorganisms. Specific Description Example 1 Because coal tar is a complex mixture containin well over 50 compounds, it was necessary to select representative compounds for evaluation. If these compounds are degraded, the rest will be degradable. The compounds studied and the reasons for their selection are listed below: (1) p-cresol - This monocyclic aromatic compound is an abundant component found in coal tar. It i relatively water soluble and, therefore, represents a majo threat to ground water. This compound is representative o one (1) ring compounds found in coal tar and is relatively easily degraded. It is noted that degradation of p-cresol alone by P. chrysosporium has been demonstrated by others. (2) 2-methylnaphthalene - This compound is an abundant component found in coal tar. It is slightly wate soluble, and, therefore a threat to ground water. This compound, along with naphthalene makes up greater than 70% of the organopollutants in some coal tar contaminated site This compound is representative of two ring polycyclic compounds found in coal tar. It is noted that degradation of this compound by . chrysosporium has not been reported by others. (3) phenanthrene - This polycyclic compound is found in coal tar and is representative of a suspect carcinogenic compound. This compound is representative of three ring compounds found in coal tar. It is noted that degradation of this compound by P. chrysosporium has not been reported by others. (4) benzo(a)pyrene - This polycyclic aromatic compound is found in coal tar and is representative of a carcinogenic compound. It is very difficult to degrade in the environment and is representative of five ring compounds found in coal tar. It is noted that the inventors were the first to demonstrate degradation of this compound by _. chrysosporium. The degradation of various 14 C-labeled coal tar constituents, i.e. p-cresol, phenanthrene, benzo(a)pyrene and 2-methylnaphthalene was accomplished separately in cultures of P_. chrysosporium as shown in Figures 1 and 2. Degradation, as assayed by -*- 4 Cθ2 evolution was monitored for thirty (30) days at which time supplemental glucose was added and degradation was monitored for another 30 days (60 days total) . Each compound was incubated in aqueous culture as described by Bu pus f et al. in U.S. application Serial No. 702,944 filed February 19, 1985. The culture medium was nutrient nitrogen deficient and was composed of 56 mM glucose, 1.2 mM ammonium tartrate, 20 mM dimethyl succinate buffer, pH 4.2-4.3. Cultures (10 ml) also contained trace amounts of thiamine and minerals as described by Kirk, T.K. et al. Arch. Microbiol. 117, 277-285 (1977). The initial concentration of - L4 C-p-cresol, l 4 C-2-methylnaphthalene and l 4 C-phenanthrene was 5 nmoles/culture. The initial concentration of ^ C-benzo(a)pyrene was 1.25 nmoles/culture. Evolution of l4 Cθ2 from each coal tar constituent was monitored as described by Kirk et al. and in Serial No. 702,944. As can be seen from Figures 1 and 2, the representative compounds are degraded up to the percentage levels indicated. The medium can be supplemented with mor nutrient medium including particularly an additional carbo source and the process reinitiated until the degradation i complete. As can be seen 2-methylnaphthalene is the most difficult to degrade and will therefore require more repeated treatments. The carbon source can be glucose, cellulose or any other compound which provides energy to the white rot fungus. The culture media for enabling the white rot fungus to degrade coal tar or derivatives thereof are well known to those skilled in the art. The process can be performed in the field or in a reaction vessel where large amounts of liquid are used. It is preferred to use a reaction vessel to prevent leaching into the ground water. It is intended that the foregoing description b only illustrative and that this invention be limited only by the hereinafter appended claims.

Claims: WE CLAIM: -1- A process for degrading a coal tar or a constituent thereof which comprises: (a) providing the coal tar or a polycyclic aromatic constituent thereof mixed with fungal enzymes containing a lignin degrading oxygenase and with hydrogen peroxide under aerobic conditions; and (b) degrading the coal tar or polycyclic aromatic constituents thereof to carbon dioxide. -2- The process of Claim 1 wherein the enzymes and hydrogen peroxide are provided by a fungus along with a carbon source enabling degradation of the coal tar or constituents thereof by the fungus. -3- The process of Claim 2 wherein the fungus is living. -4- The process of Claim 3 wherein the fungus is a white rot fungus. -5- The process of Claim 2 wherein the fungus has been grown in a culture medium containing a minimal nutrient nitrogen level. -6- The process of Claim 7 wherein the culture media includes a source of carbon, thiamine and minerals for the fungus. -7- The process of Claim 6 wherein the source of carbon is glucose. -8- The process of Claim 6 wherein the source of carbon is a carbohydrate. -9- The process of Claim 1 wherein the coal tar is mixed with soil from the environment and wherein the soil is mixed with the fungal enzymes and hydrogen peroxide. -lO¬ The process of Claim 9 wherein the soil is mixe with a fungus as the source of the fungal enzymes and hydrogen peroxide. -11- The process of Claim 1 performed in a reaction vessel.

Inventors: AUST STEVEN D, BUMPUS JOHN A, AUST, STEVEN, D., BUMPUS, JOHN, A.
Applicants: UNIV MICHIGAN, MICHIGAN STATE UNIVERSITY
Application year: 1987
Main classification: C02F3
IPC codes: B09C1, C02F3