Document qm045gqMDMDxOEd30yDnNem6M

Oxidation of Polychlorinated Biphenyls by Achromobacter pCB by H. Ahmed' ind D. D. Focht DtjMUMini of Soil Science and Agricultural Engineering IInivenity of California, Riverside, Calif. Polychlorinated biphenyls (FCBs) have been used extensively In various conmerclal products since the 1920's. The widespread ' occurrence of these chemicals has been documented by Rlsebrough et al. (2). Despite the extensive usage of FCBs, data pertain ing to the longevity of these chemicals In soil and water are un available. We had reported previously that certain mono and dlchlarlnated biphenyls were degraded readily by a species of Achromobacter pCB isolated from sewage effluent (1). It Is the Intention of this Investigation to study the biodegradation of other Isomers of FCBs with 2 to 5 chlorine atems. MATERIALS AND MEIHCOS The following chemicals were purchased from Analabs, Inc., North Haven, Connecticut: 2,3-dlchloroblphenyl (2,3-DCB), 2.4- dlehloroblphenyl (2,9-DCB), 3,`t-dlchloroblphenyl (3,4-DCB), 3.5- dlchloroblphenyl (3,5-DCB), 3,3'-dlchloroblphenyl (3,3'-OCB), 3,5,2'-trlchloroblphenyl (3,<(,2'-tCB), 2,3,2',3'-tetrachlarobl- phenyl (P.S^'.S'-TCB), 2,5.3',|t'-tetrachlaroblphenyl (2,5,3'>*'TCBJ and 2,3,`1,5,6-pentachloroblphenyl (2,3,`t5,6-PCB). Resting cell suspensions of Achronobacter pCB grown on p-chloroblphenyl (pCB) were tested for their ability to metabo lise 2,3-DCB, 2.H-DCB, 3.K-DCB, 3,5-DCB, 3.3'-DCB, 2,3,2',3'-TCB. 2.5,3'.`t'-TCB, arid 2,3,t,5,6-PCB. Cultural, mancmetrlc, and analytical techniques used In this study have been described previously (1). RESULTS AN) DISCUSSION Mancmetrlc studies Indicated that with the exception of 2,5>3',4'-TCB, all the above listed FCBs were oxidized by bacteria (Town on pCB. Except far a brief lag observed In the degradation of 3i3'-DCB, all other FCBs were oxidized without lag. The results are given In Figures 1 and 2. The mancmetrlc data also suggested that 2,3-DCB, 2,4-DCB, 3,`MXB, 3,5-DCB, and 3,5-DCB were oxidised to an appreciable extent by pure cultures of Achronobacter pCB; 2,3,2',3'-TCB and 2,3,9,5,6-FCB were oxidized only slightly. The high degree of oxidation of dlchlarlnated biphenyls In which one of the biphenyl rings was I------------------------------------------ " Present address: Department of Health, 313 North Figueroa, Lob Angeles, California 90012 n feUetla af tavlreaaeatal Caatsalaeiiaa Tailealetp, Vaf. II, Ha. t O l bp ffat^M-Varlac Haw Vask. Im. MQNS 069351 1 H moles o x y g e n /ji moles substrate pigOT 2. Coddatlcn of tri, tetra, and penta chloroblphenyl. 2 C 2 ( </> O *-- Plpire 1. Oxldatlcn of dlchlOToblpheny'la. cc Oj Vi N. 1 o) unsubstituted may be due to the preferential degradation of the unsubstituted ring as noted by the extent of oxidation between 3,3'-OCB and all other dlchloroblphenyls having one unsubstituted ring. Even 2,3,H,5,6-PCB was oxidized ccnparably to 2,3,2',3'-TCB and more than 2,5,3',H'-TCB. The Warburg flask contents were withdrawn upon ccnpletlon of the experiments--as determined by the return of respiration rate to that of endogenous--and centrifuged to obtain clear supernatant solutions. Hie supernatant solutions were assayed for liberation of chloride and were analyzed.spectrophotcmetrlcally to obtain absorption maxima of produots that might have accimilated during .. degradation. The absorption maxima of the substrates and the Intermediates are shown In Table 1. TABLE 1 Oxygen uptake and absorption maxima (l max) of substrates and products Substrate Oxygen uptaket 1 max of substrate X max of products < -- ' 2,3-Dlchloroblphenyl 2,4-Dlchloroblphenyl 3 4-Wchloroblphenyl 3,5-Dlchloroblphenyl 3,3'-01ohlaroblphenyl 3*4,2' -TM.chlorobiphenyl 2,3*2*,3'-Tetrachloro- biphenyl 2,5,3' ,9'-Tetrachloro- - biphenyl 2,3,1,5,6-Pentachlaro- biphenyl 2.25 2.25 3.HO 2.75 a.6o 1.00 0.5 0 0.5 . 265 235 265 235 265 290*, 280, 235 265 290, 280*. 235 265 H00, 235 265 400, 290, 235 265 320, 280 265 265 265 280 tmaoles oxygeivtonoles substrate shoulder only - Jhaanuch as the bacterium was unable to dehalogenate any of the chlorinated biphenyls, as noted by the absence of chloride In all supernatants, It appears likely that Increasing chlorine substitution renders the biphenyl molecule more resistant to microbial attack as the mancmetrlc results further Indicate. REFERBJCES (1) AH, M., and EOCHT, D. D., Can. J. Microbiol. (In Press). (2) RISEBRCKMH, R.W., REICHE, P., PEAKAU., D.B., HEKMAN, S.O., arxl KmVB), M.N. Mature 220, 1098 (1968). n MUMS 084353