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Complete degradation of polychlorinated biphenyls by a combination of ultraviolet and biological treatments
JOURNALOF FERMENTATION ANDBIOENGINEERWG Vol. 81, No. 6, 573-576. 1996
Complete Degradation of Polychlorinated Biphenyls by a Combination of Ultraviolet and Biological Treatments MINORU SHIMURA,‘* TAKAO KOANA,’ MASAO FUKUDA,2 AND KAZUHIDE KIMBARA’ Environmental Biotechnology Laboratory, Railway Technical Research Institute, Z-8-38 Hikaricho, Kokubunji, Tokyo 185l and Department of Bioengineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 94@-21,2 Japan Received 14 July 1995/Accepted 26 February 1996
A method combining ultraviolet (UV) irradiation followed by microbial treatment was successfully applied to the efficient and complete degradation of polychlorinated biphenyls (PCBs). By UV irradiation, most PCB congeners in a methanol solution were transformed into lesser chlorinated compounds containing less than three chlorines. The resultant UV-irradiated PCBs were then subjected to microbial degradation by Pseudomonas akaligenes TK102, resulting in their complete degradation within a week. [Key words: polychlorinated
biphenyl,
ultraviolet
irradiation,
biological
degradation,
Pseudomonas
alcaligenes]
Polychlorinated biphenyls (PCBs) are a family of compounds produced by the direct chlorination of biphenyl, in which 1 to 10 chlorine atoms can be attached to the biphenyl molecule. PCBs are chemically and thermally stable and are used for many industrial purposes. However, PCBs have been steadily released into the environment and are now recognized to be widespread pollutants around the world. Although the industrial sale of PCBs has been prohibited in many countries since the early 197Os, PCBs are still detected at low levels in almost all environmental samples. It is also the case that huge amounts of PCBs have been stocked for safe treatment, and it is estimated that half a million tons of PCBs and PCB-contaminated wastes are still remain to be treated (1). For the disruption of PCBs, three general approaches are conceivable: incineration, chemical treatment and biological treatment (2). Incineration has been commonly used, but this method is postulated to produce more toxic compounds such as polychlorinated dibenzofurans and polychlorinated dibenzodioxins. Chemical treatment, such as by a base-catalyzed dechlorination process, may also give rise to unknown secondary metabolites which are mutagenic in Salmonella strain TA98 (3). Ultraviolet (UV) treatment is known to dechlorinate PCBs partially (4). Biological treatment, i.e., aerobic degradation and anaerobic dechlorination of PCBs, has been well documented (5-l 1). Reductive dechlorination of highly chlorinated congeners was demonstrated in aquatic sediments, but the process is slow and difficult to control (12). Oxidative degradation by aerobic bacteria has been well studied for lower chlorinated congeners with less than four chlorines (Fig. 1). Here, we report on the successful development of a method that combines UV irradiation for highly chlorinated PCBs followed by biological treatment for the resultant lesser chlorinated PCBs. To investigate dechlorination by UV irradiation, PCBs were transferred into screw-capped quartz glass cells (13 x 13 x 58 mm) and exposed to UV irradiation (5 mW/cm2) at room temperature. After irradiation, the reaction solution was analyzed by a gaschromatograph
(type 5890 series II; Hewlett Packard Co., Palo Alto, CA, USA) equipped with an Ultra-2 capillary column (length, 50 m; diameter, 0.22 mm; thickness, 0.33 pm) using a mass selective detector (10). When a 2-ml methanol solution of 20,ng/ml of 2,5, 2’,5’-tetrachlorobiphenyl was exposed to UV light for 6 h, 8 peaks appeared in the gaschromatograph analysis (Fig. 2). Mass spectra of the peaks revealed that these were mono-, di-, tri- and tetra-chlorobiphenyls. After 23-h irradiation, only mono- and di-chlorinated biphenyls appeared along with biphenyl. Chlorines at the ortho positions were found to be preferentially eliminated, indicating that UV irradiation is a favorable treatment prior to biological treatment, since PCB congeners with chlorines at the ortho positions are known to be recalcitrant to biological degradation (9, 13, 14). KCSOO, a commercial PCB mixture containing tetrato octa-chlorobiphenyls, is extensively used in electrical transformers, and is stored in large amounts by electrical and railway companies in Japan. We therefore studied the degradation of KCSOO. When a 2-ml methanol solution of 500/1g/ml KC500 was exposed to UV light for 26 h, most peaks decreased as much as 95% (Table 1). PCB congeners with four to eight chlorines were transformed into less chlorinated compounds, such as 3chlorobipheny1, 4-chlorobiphenyl, 3,4-dichlorobiphenyl, 3,4’-dichlorobiphenyl, and 4,4’dichlorobiphenyl (Fig. 3). The presence of a biphenyl peak indicated that some congeners were completely dechlorinated. However, further UV irradiation over 26 h was not effective for dechlorination of the di-chlorinated congeners produced. Titanium oxide is known to enhance dehalogenation by UV irradiation, but its effect
FIG. 1. Catabolic pathway for the aerobic biodegradation biphenyl and chlorobiphenyls.
* Corresponding author. 573
of
514
SHIMURA
ET AL.
J. FERMENT.BIOENG.,
TABLE Number of substitution
Peak no.
1.
Analysis of the dechlorination of KC500 by UV irradiation % decrease
Congener identification
3h
18 20 21 22 24 25 28 31
2,5/s 2,4,4’ 3,4,2’ 2,3,4 2,3,3’ 2,3,4’ 2,5,2’,5’ 2,6,3’,5’ 2,4,2’,5’ 2,3,2’,5’ 2,6,3’,4’ 2,3,4,2’ 2,3,6,4’
33 34 35 36 37 38 39 41 42 43 44 45
2,4,5,4’ 2,3,5,2’,6’ 2,5,3:4’ 3,4,5,2’ 2,4,5,2’,6’ 2,4,3’,4’ 2,3,4,3’ 2,3,6,2’,4’ 2,3,3’,4’ 2,3,4,4’ 2,3,6,2’,3’ 2,3,5,2’,5’ 2,4,5,2’,5’ 2,3,5,2’,4’ 2,4,5,2’,4’ 2,4,5,2’,3’ 2,3,4,5,2’ 2,3,4,2’,5’ 2,3,4,6,4’ 2,3,5,3:5’ 2,3,4,2:4’ 2,3,6,2’,3’,6’ 3,4,3’,4’ 2,3,6,3’,4’
5,6
46 47 48 49 52 53 54
Sh
15 h
26h
(-624) (- 122) (-509) (-36) (- 105) (- 139) (-5;
(-732) (-110) (-518) (-29) (-112) (-77) t-1;
47 100 74 100 71 93 97 96
88 100 97 100 97 99 100 100
(-15) (- 136) 43 c-l;
(-lo:‘,
33 59 66 73 69 100 21
73 57 26 62 39 85 90 88 100 43
95 93 99 96 99 100 89 100 99 97 100 98
99 99 100 100 100 100 98 100 100 100 100 99
2 ,3 ,5 ,6 92’,5’ 2,3,5,2’,3:6’ 3,4,5,2’,5’ 2,3,4,6,2’,5’ 2,4,5,3’,4’ 2,3,6,2’,4’,5’ 2 ,3 ,4 ,5 ,3’ 2 ,3 ,5 ,6 ,2’,3’ 2,3,4,5,2’,6’ 2 ,3 ,4 15 ,4’ 2,4,5,2’,4:5’ 2,3,4,2’,3:6’ 2,3,4,3’,4’ 2 93 ,4 95 12’,5’
31 14 83 20 50 78 58
67 55 85 7.5 80 93 88
100 100 100 100 100 100 100
100 100 100 100 100 100 100
697
56 57 58 59 60 63 64 66 67
2 ,3 I4 ,5 ,2’,4’ 2 ,3 ,4 >6 >2:3:6’ 2,3,4,2’,4’,5’ 2,3,5,6,3’,4’ 2,3,4,6,3’,4’ 2 >3 75 ,6 ,2’,3:5’ 2 93 ,4 ,6 ,2’,4:5’ 2,4,5,3:4:5’ 2 ,3 f4 ,5 ,2’,3:6’ 2 ,3 ,4 ,5 t6 >2’,4’ 2 ,3 ,5 ,6 ,2’,3:4’
77 64 84 74 72 39 78 57 39
92 86 94 91 90 80 92 90 81
100 100 100 100 100 100 100 100 100
100 100 100 100 100 100 100 100 100
798
68 69 70 71 72 73 75 77 78 80 82
2,3,4,5,6,2’,3’ 2,3,4,5,3’,4’ 2 ,3 I4 ,5 96 I2’33’ 2 I3 14 ,5 ,2’,3’,5’ 2,3,4,5,6,3’,5’ 2 ,3 14 ,5 ,2’,4’,5’ 2 ,3 75 I6 ,3’,4’,5’ 2 93 94 96 ,3’,4,,5’ 2 ,3 ,4 >5 ,2’,3’,4’ 2 ,3 t5 ,6 .2’,3:4:5’ 2 ,3 ,4 ,5 ,2’,3:4:6’ 2 3 4 5 6 2’,4’,5’ 2 ,3 t4 ,5 ,6,2’,3’,4’ ’ ’ ’ ’ ’ 2,3,4,5,2’,3’,4:5’
85 15 34 75 31 100 100 100 74 68 90
96 77 79 94 75 100 100 100 95 100 100
100 100 100 100 100 100 100 100 100 100 100
100 100 100 100 100 100 100 100 100 100 100
374
475
2,5,3’,5’
Numbers in parentheses show that these congeners increased in amount during UV irradiation.
on a biological system is unknown (15). Hence, as we planned to utilize microorganisms to degrade the remaining congeners in the PCB solution, we did not use titanium oxide during the UV irradiation. The UV-irradiated PCBs were then subjected to the biological treatment. The strain TK102 used in this study was isolated from soil by enrichment culture with biphenyl as a sole carbon source. TK102 is a gram-negative bacterium, identified as Pseudomonas alcaligenes by the National Collections of Industrial and Marine Bacteria Limited (Aberdeen, UK). UV-irradiated KC500 was concentrated j-fold by evaporation and an aliquot of one quarter was added to a 5-ml culture of P. alcaligenes TK102 containing
3 mg/ml of biphenyl. The final concentration of UVtreated KC500 was 125 pg/ml. An autoclaved cell suspension of P. alcaligenes TK102 (121”C, 15 min) was used as a control. The culture was incubated at 30°C with reciprocal shaking (1OOrpm). After incubation for one week, PCBs were extracted and analyzed. As shown in Fig. 3, the UV-irradiated PCBs were completely degraded (Fig. 3D). Thus, the combination of UV irradiation followed by microbial treatment resulted in the efficient and complete degradation of PCBs. This method can be utilized for the actual treatment of PCBs. We thank Dr. John F. Quensen III for advice on the construc-
VOL. 81, 19%
NOTES
575
100 ,
B 7
10
20
30
40
So
60
Retention time (miu) FIG. 2. UV irradiation of 2,5,2’,5’-tetrachlorobiphenyl. The chromatographs show the results of 60min (A), 360min (B), and 23 h (C) UV irradiation, respectively. Biphenyl (8) and six congeners, 2,5,3’-trichlorobiphenyl(2), 2,5,2’-trichlorobiphenyl(3), 3,3’-dichlorobiphenyl (4), 2,3’-dichlorobiphenyl (5), 2,5-dichlorobiphenyl (6) and m-chlorobiphenyl(7), were observed after UV irradiation of 2,5,2’,5’tetrachlorobiphenyl (1).
2
03 10
Ii 20
30
40
so
60
Retention time (ma)
REFERENCES
FIG. 3. Degradation of KC500 by UV irradiation and subsequent biological treatment. KC500 (A) was irradiated under UV light for 5 h (B), and 26 h (C). UV-irradiated PCB samples were treated in a culture of P. ulcaligenesTK102 (D). Peaks 1: biphenyl; 2: o-chlorobiphenyl; 3: m-chlorobiphenyl; 4: p-chlorobiphenyl; 5: 2,2’-, 2,6-dichlorobiphenyl; 6: 2,4-, 2,5-dichlorobiphenyl; 7: 2,3’-dichlorobiphenyl; 8: 2,4’-, 2,3-dichlorobiphenyl; 9: 3,5-dichlorobiphenyl; 10: 2,6,2’-trichlorobiphenyl; 11: 3,4-dichlorobiphenyl; 12: 3,4’-dichlorobiphenyl; 13: 2,5,2’-trichlorobiphenyl; 14: 4,4’-dichlorobiphenyl; 15: 2,6,3’-, 2,3,6’-trichlorobiphenyl; 16: 2,3,2’-, 2,4,6-trichlorobiphenyl; 17: 3,5,2’-trichlorobiphenyl; 18-82: listed in Table 1.
1. Furukawa, K.: Microbial degradation of polychlorinated biphenyls (PCBs), p. 33-57. 1n Chakrabarty, A.M. (ed.), Biodegradation and detoxification of environmental pollutants. CRC Press, Boca Raton, FL. (1982). 2. Carpenter, H. B.: PCB sediment decontamination-technical/ economical assessment of selected alternative treatments. EPA report, EPA/600/2-86/112 (1986). 3. DeMarini, D. M., Iiouk, V. S., Koroel, A., and Rogers, C. J.: Effect of a base-catalyzed dechlorination process on the genotoxicity of PCB-contaminated soil. Chemosnhere. 24.I 17131720 (i992). Herring, J. L., Haanan, E. J., and Bills, D. D.: UV irradiation of Aroclor1254. Bull. Environ. Contam. Toxicol.. I 8.I 153-157 (1972). Ahmed, M. and Focht, D. D.: Degradation of polychlorinated biphenyls by two species of Achromobacter. Can. J. Microbiol., 19, 47-52 (1973). Furuknwa, K.: Microbial metabolism of polychlorinated biphenyls. Studies on the reletive dagradability of polychlorinated biphenyl components by Alcalogenes sp. J. Agric. Food. Chem., 42, 543-548 (1976). Kikuchi, Y., Yasukouchi, Y., Nagata, Y., Fukuda, M., and Takagi, M.: Nucleotide sequence and functional analysis of the meta-cleavage pathway involved in biphenyl and polychlorinated
biphenyl degradation in Pseudomonas sp. strain KKSIM. J. Bacterial., 176, 4269-4276 (1994). 8. Kimbara, K., Hashimoto, T., Fukuda, M., Koana, T., Takagi, M., Oiski, M., and Yano, K.: Isolation and characterization of a mixed culture that degrades polychlorinated biphenyls. Agric. Biol. Chem., 52, 2885-2891 (1988). 9. Seto, M., Kiibara, K., Shimura, M., Hatta, T., Fukuda, M., and Yano, K.: A novel transformation of polychlorinated biphenyls by Rhodococcus sp. RHAl. Appl. Environ. Microbiol., 61, 3353-3358 (1995). 10. Quensen HI, J. F., Boyd, S. A., and Tiedje, J. M.: Dechlorination of four commercial polychlorinated biphenyl mixtures (Aroclors) by anaerobic microorganisms from sediments. Appl. Environ. Microbial., 56, 2360-2369 (1990). 11. Ye, D., Quensen III, J. F., Tiedje, J. M., and Boyd, S. A.: Evidence for puru dechlorination of polychlorobiphenyls by methanogenic bacteria. Appl. Environ. Microbial., 61, 21662171 (1995). 12. Brown, J. F., Jr., Bedard, D. L., Brennan, M. J., Caruahan, J. C., Feng, H., and Wagner, R. E.: Polychlorinated biphenyl dechlorination on aquatic sediments. Science, 236, 709-712 (1987). 13. Bedard, D. I;., Untermau, R., Bopp, L. H., Breaoan, M. J.,
tion of our analytical system and Dr. Gouri Mukerjee for critical reading of the manuscript.
576
SHIMURA ET AL.
Haberl, M.L., and Johnson, C.: Rapid assay for screening and characterizing microorganisms for the ability to degrade polychlorinated biphenyls. Appl. Environ. Microbial., 51, 761768 (1986). 14. Bedard, D. L., Haberl, M. L., May, R. J., and Brennan, M. J.: Evidence for novel mechanisms of polycholorinated biphenyl
J. FERMENT. BIOENG.. metabolism in Alculigenes eutrophus H850. Appl. Environ. Microbial., 53, 1103-1112 (1987). 15. Carey, J. H., Lawrence, J., and Tosine, H. M.: Photodechlorination of PCB’s in the presence of titanium dioxide in aqueous suspensions. Bull. Environ. Contam. Toxicol., 16, 697-701 (1976).
Complete Degradation of Polychlorinated Biphenyls by a Combination of Ultraviolet and Biological Treatments MINORU SHIMURA,‘* TAKAO KOANA,’ MASAO FUKUDA,2 AND KAZUHIDE KIMBARA’ Environmental Biotechnology Laboratory, Railway Technical Research Institute, Z-8-38 Hikaricho, Kokubunji, Tokyo 185l and Department of Bioengineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 94@-21,2 Japan Received 14 July 1995/Accepted 26 February 1996
A method combining ultraviolet (UV) irradiation followed by microbial treatment was successfully applied to the efficient and complete degradation of polychlorinated biphenyls (PCBs). By UV irradiation, most PCB congeners in a methanol solution were transformed into lesser chlorinated compounds containing less than three chlorines. The resultant UV-irradiated PCBs were then subjected to microbial degradation by Pseudomonas akaligenes TK102, resulting in their complete degradation within a week. [Key words: polychlorinated
biphenyl,
ultraviolet
irradiation,
biological
degradation,
Pseudomonas
alcaligenes]
Polychlorinated biphenyls (PCBs) are a family of compounds produced by the direct chlorination of biphenyl, in which 1 to 10 chlorine atoms can be attached to the biphenyl molecule. PCBs are chemically and thermally stable and are used for many industrial purposes. However, PCBs have been steadily released into the environment and are now recognized to be widespread pollutants around the world. Although the industrial sale of PCBs has been prohibited in many countries since the early 197Os, PCBs are still detected at low levels in almost all environmental samples. It is also the case that huge amounts of PCBs have been stocked for safe treatment, and it is estimated that half a million tons of PCBs and PCB-contaminated wastes are still remain to be treated (1). For the disruption of PCBs, three general approaches are conceivable: incineration, chemical treatment and biological treatment (2). Incineration has been commonly used, but this method is postulated to produce more toxic compounds such as polychlorinated dibenzofurans and polychlorinated dibenzodioxins. Chemical treatment, such as by a base-catalyzed dechlorination process, may also give rise to unknown secondary metabolites which are mutagenic in Salmonella strain TA98 (3). Ultraviolet (UV) treatment is known to dechlorinate PCBs partially (4). Biological treatment, i.e., aerobic degradation and anaerobic dechlorination of PCBs, has been well documented (5-l 1). Reductive dechlorination of highly chlorinated congeners was demonstrated in aquatic sediments, but the process is slow and difficult to control (12). Oxidative degradation by aerobic bacteria has been well studied for lower chlorinated congeners with less than four chlorines (Fig. 1). Here, we report on the successful development of a method that combines UV irradiation for highly chlorinated PCBs followed by biological treatment for the resultant lesser chlorinated PCBs. To investigate dechlorination by UV irradiation, PCBs were transferred into screw-capped quartz glass cells (13 x 13 x 58 mm) and exposed to UV irradiation (5 mW/cm2) at room temperature. After irradiation, the reaction solution was analyzed by a gaschromatograph
(type 5890 series II; Hewlett Packard Co., Palo Alto, CA, USA) equipped with an Ultra-2 capillary column (length, 50 m; diameter, 0.22 mm; thickness, 0.33 pm) using a mass selective detector (10). When a 2-ml methanol solution of 20,ng/ml of 2,5, 2’,5’-tetrachlorobiphenyl was exposed to UV light for 6 h, 8 peaks appeared in the gaschromatograph analysis (Fig. 2). Mass spectra of the peaks revealed that these were mono-, di-, tri- and tetra-chlorobiphenyls. After 23-h irradiation, only mono- and di-chlorinated biphenyls appeared along with biphenyl. Chlorines at the ortho positions were found to be preferentially eliminated, indicating that UV irradiation is a favorable treatment prior to biological treatment, since PCB congeners with chlorines at the ortho positions are known to be recalcitrant to biological degradation (9, 13, 14). KCSOO, a commercial PCB mixture containing tetrato octa-chlorobiphenyls, is extensively used in electrical transformers, and is stored in large amounts by electrical and railway companies in Japan. We therefore studied the degradation of KCSOO. When a 2-ml methanol solution of 500/1g/ml KC500 was exposed to UV light for 26 h, most peaks decreased as much as 95% (Table 1). PCB congeners with four to eight chlorines were transformed into less chlorinated compounds, such as 3chlorobipheny1, 4-chlorobiphenyl, 3,4-dichlorobiphenyl, 3,4’-dichlorobiphenyl, and 4,4’dichlorobiphenyl (Fig. 3). The presence of a biphenyl peak indicated that some congeners were completely dechlorinated. However, further UV irradiation over 26 h was not effective for dechlorination of the di-chlorinated congeners produced. Titanium oxide is known to enhance dehalogenation by UV irradiation, but its effect
FIG. 1. Catabolic pathway for the aerobic biodegradation biphenyl and chlorobiphenyls.
* Corresponding author. 573
of
514
SHIMURA
ET AL.
J. FERMENT.BIOENG.,
TABLE Number of substitution
Peak no.
1.
Analysis of the dechlorination of KC500 by UV irradiation % decrease
Congener identification
3h
18 20 21 22 24 25 28 31
2,5/s 2,4,4’ 3,4,2’ 2,3,4 2,3,3’ 2,3,4’ 2,5,2’,5’ 2,6,3’,5’ 2,4,2’,5’ 2,3,2’,5’ 2,6,3’,4’ 2,3,4,2’ 2,3,6,4’
33 34 35 36 37 38 39 41 42 43 44 45
2,4,5,4’ 2,3,5,2’,6’ 2,5,3:4’ 3,4,5,2’ 2,4,5,2’,6’ 2,4,3’,4’ 2,3,4,3’ 2,3,6,2’,4’ 2,3,3’,4’ 2,3,4,4’ 2,3,6,2’,3’ 2,3,5,2’,5’ 2,4,5,2’,5’ 2,3,5,2’,4’ 2,4,5,2’,4’ 2,4,5,2’,3’ 2,3,4,5,2’ 2,3,4,2’,5’ 2,3,4,6,4’ 2,3,5,3:5’ 2,3,4,2:4’ 2,3,6,2’,3’,6’ 3,4,3’,4’ 2,3,6,3’,4’
5,6
46 47 48 49 52 53 54
Sh
15 h
26h
(-624) (- 122) (-509) (-36) (- 105) (- 139) (-5;
(-732) (-110) (-518) (-29) (-112) (-77) t-1;
47 100 74 100 71 93 97 96
88 100 97 100 97 99 100 100
(-15) (- 136) 43 c-l;
(-lo:‘,
33 59 66 73 69 100 21
73 57 26 62 39 85 90 88 100 43
95 93 99 96 99 100 89 100 99 97 100 98
99 99 100 100 100 100 98 100 100 100 100 99
2 ,3 ,5 ,6 92’,5’ 2,3,5,2’,3:6’ 3,4,5,2’,5’ 2,3,4,6,2’,5’ 2,4,5,3’,4’ 2,3,6,2’,4’,5’ 2 ,3 ,4 ,5 ,3’ 2 ,3 ,5 ,6 ,2’,3’ 2,3,4,5,2’,6’ 2 ,3 ,4 15 ,4’ 2,4,5,2’,4:5’ 2,3,4,2’,3:6’ 2,3,4,3’,4’ 2 93 ,4 95 12’,5’
31 14 83 20 50 78 58
67 55 85 7.5 80 93 88
100 100 100 100 100 100 100
100 100 100 100 100 100 100
697
56 57 58 59 60 63 64 66 67
2 ,3 I4 ,5 ,2’,4’ 2 ,3 ,4 >6 >2:3:6’ 2,3,4,2’,4’,5’ 2,3,5,6,3’,4’ 2,3,4,6,3’,4’ 2 >3 75 ,6 ,2’,3:5’ 2 93 ,4 ,6 ,2’,4:5’ 2,4,5,3:4:5’ 2 ,3 f4 ,5 ,2’,3:6’ 2 ,3 ,4 ,5 t6 >2’,4’ 2 ,3 ,5 ,6 ,2’,3:4’
77 64 84 74 72 39 78 57 39
92 86 94 91 90 80 92 90 81
100 100 100 100 100 100 100 100 100
100 100 100 100 100 100 100 100 100
798
68 69 70 71 72 73 75 77 78 80 82
2,3,4,5,6,2’,3’ 2,3,4,5,3’,4’ 2 ,3 I4 ,5 96 I2’33’ 2 I3 14 ,5 ,2’,3’,5’ 2,3,4,5,6,3’,5’ 2 ,3 14 ,5 ,2’,4’,5’ 2 ,3 75 I6 ,3’,4’,5’ 2 93 94 96 ,3’,4,,5’ 2 ,3 ,4 >5 ,2’,3’,4’ 2 ,3 t5 ,6 .2’,3:4:5’ 2 ,3 ,4 ,5 ,2’,3:4:6’ 2 3 4 5 6 2’,4’,5’ 2 ,3 t4 ,5 ,6,2’,3’,4’ ’ ’ ’ ’ ’ 2,3,4,5,2’,3’,4:5’
85 15 34 75 31 100 100 100 74 68 90
96 77 79 94 75 100 100 100 95 100 100
100 100 100 100 100 100 100 100 100 100 100
100 100 100 100 100 100 100 100 100 100 100
374
475
2,5,3’,5’
Numbers in parentheses show that these congeners increased in amount during UV irradiation.
on a biological system is unknown (15). Hence, as we planned to utilize microorganisms to degrade the remaining congeners in the PCB solution, we did not use titanium oxide during the UV irradiation. The UV-irradiated PCBs were then subjected to the biological treatment. The strain TK102 used in this study was isolated from soil by enrichment culture with biphenyl as a sole carbon source. TK102 is a gram-negative bacterium, identified as Pseudomonas alcaligenes by the National Collections of Industrial and Marine Bacteria Limited (Aberdeen, UK). UV-irradiated KC500 was concentrated j-fold by evaporation and an aliquot of one quarter was added to a 5-ml culture of P. alcaligenes TK102 containing
3 mg/ml of biphenyl. The final concentration of UVtreated KC500 was 125 pg/ml. An autoclaved cell suspension of P. alcaligenes TK102 (121”C, 15 min) was used as a control. The culture was incubated at 30°C with reciprocal shaking (1OOrpm). After incubation for one week, PCBs were extracted and analyzed. As shown in Fig. 3, the UV-irradiated PCBs were completely degraded (Fig. 3D). Thus, the combination of UV irradiation followed by microbial treatment resulted in the efficient and complete degradation of PCBs. This method can be utilized for the actual treatment of PCBs. We thank Dr. John F. Quensen III for advice on the construc-
VOL. 81, 19%
NOTES
575
100 ,
B 7
10
20
30
40
So
60
Retention time (miu) FIG. 2. UV irradiation of 2,5,2’,5’-tetrachlorobiphenyl. The chromatographs show the results of 60min (A), 360min (B), and 23 h (C) UV irradiation, respectively. Biphenyl (8) and six congeners, 2,5,3’-trichlorobiphenyl(2), 2,5,2’-trichlorobiphenyl(3), 3,3’-dichlorobiphenyl (4), 2,3’-dichlorobiphenyl (5), 2,5-dichlorobiphenyl (6) and m-chlorobiphenyl(7), were observed after UV irradiation of 2,5,2’,5’tetrachlorobiphenyl (1).
2
03 10
Ii 20
30
40
so
60
Retention time (ma)
REFERENCES
FIG. 3. Degradation of KC500 by UV irradiation and subsequent biological treatment. KC500 (A) was irradiated under UV light for 5 h (B), and 26 h (C). UV-irradiated PCB samples were treated in a culture of P. ulcaligenesTK102 (D). Peaks 1: biphenyl; 2: o-chlorobiphenyl; 3: m-chlorobiphenyl; 4: p-chlorobiphenyl; 5: 2,2’-, 2,6-dichlorobiphenyl; 6: 2,4-, 2,5-dichlorobiphenyl; 7: 2,3’-dichlorobiphenyl; 8: 2,4’-, 2,3-dichlorobiphenyl; 9: 3,5-dichlorobiphenyl; 10: 2,6,2’-trichlorobiphenyl; 11: 3,4-dichlorobiphenyl; 12: 3,4’-dichlorobiphenyl; 13: 2,5,2’-trichlorobiphenyl; 14: 4,4’-dichlorobiphenyl; 15: 2,6,3’-, 2,3,6’-trichlorobiphenyl; 16: 2,3,2’-, 2,4,6-trichlorobiphenyl; 17: 3,5,2’-trichlorobiphenyl; 18-82: listed in Table 1.
1. Furukawa, K.: Microbial degradation of polychlorinated biphenyls (PCBs), p. 33-57. 1n Chakrabarty, A.M. (ed.), Biodegradation and detoxification of environmental pollutants. CRC Press, Boca Raton, FL. (1982). 2. Carpenter, H. B.: PCB sediment decontamination-technical/ economical assessment of selected alternative treatments. EPA report, EPA/600/2-86/112 (1986). 3. DeMarini, D. M., Iiouk, V. S., Koroel, A., and Rogers, C. J.: Effect of a base-catalyzed dechlorination process on the genotoxicity of PCB-contaminated soil. Chemosnhere. 24.I 17131720 (i992). Herring, J. L., Haanan, E. J., and Bills, D. D.: UV irradiation of Aroclor1254. Bull. Environ. Contam. Toxicol.. I 8.I 153-157 (1972). Ahmed, M. and Focht, D. D.: Degradation of polychlorinated biphenyls by two species of Achromobacter. Can. J. Microbiol., 19, 47-52 (1973). Furuknwa, K.: Microbial metabolism of polychlorinated biphenyls. Studies on the reletive dagradability of polychlorinated biphenyl components by Alcalogenes sp. J. Agric. Food. Chem., 42, 543-548 (1976). Kikuchi, Y., Yasukouchi, Y., Nagata, Y., Fukuda, M., and Takagi, M.: Nucleotide sequence and functional analysis of the meta-cleavage pathway involved in biphenyl and polychlorinated
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