Isolation of Biphenyl and Polychlorinated Biphenyl-Degrading Bacteria and Their Degradation Pathway Young-Cheol Chang & Kazunori Takada & DuBok Choi & Tadashi Toyama & Ken Sawada & Shintaro Kikuchi Received: 4 April 2012 / Accepted: 11 March 2013 / Published online: 27 March 2013 # Springer Science+Business Media New York 2013 Abstract Four strains of biphenyl-degrading bacteria were isolated from a sewage and identified from the Rhodococcus genus (SK-1, SK-3, and SK-4) and Aquamicrobium genus (SK-2) by 16S rRNA sequence. Among these strains, strain SK-2 was most suitable for biphenyl degradation. When 0.65, 1.3, 2.6, or 3.9 mM of biphenyl was used, the biphenyl was completely degraded within 24 and 96 h of culture, respectively. However, in the case of 6.5 and 9.75 mM of biphenyl, the biphenyl degradation yields were about 80 % and 46.7 % after 120 h of culture, respectively. The isolated strains could degrade a broad spectrum of aromatic compounds including high-chlorinated polychlorinated biphenyl (PCB) congeners in the presence of biphenyl. In addition, strain SK-2 could utilize PCB congeners containing one to six chlorine substituents such as 2,2′,4,4′,5,5′-hexachlorobiphenyl. The PCB utiliza- tion rate by the strain SK-2 was increased compared to that of other PCB congener-utilizing bacteria. The four isolates metabolized 4-chlorobiphenyl to 4-chlorobenzoic acid and 2- hydroxy-6-oxo-6-(4′-chlorophenyl)-hexa-2,4-dienoic acid. These results suggest the isolated strains might be good candidates for the bioremediation of PCB-contaminated soil, espe- cially high-saline soils. Keywords Biphenyl . Polychlorinated biphenyl (PCB) . Biphenyl-degrading mechanism . Rhodococcus genus . Aquamicrobium genus Appl Biochem Biotechnol (2013) 170:381–398 DOI 10.1007/s12010-013-0191-5 Y.-C. Chang (*) : K. Takada : K. Sawada : S. Kikuchi Division of Applied Sciences, College of Environmental Technology, Graduate School of Engineering, Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585 Hokkaido, Japan e-mail: ychang@mmm.muroran-it.ac.jp D. Choi (*) Biotechnology Lab, BK Company R&D Center, Jeonbuk 579-879, Republic of Korea e-mail: choidubok@yahoo.co.kr D. Choi Department of Pharmacy, College of Pharmacy, Chungbuk National University, Cheongju 361-763, Republic of Korea T. Toyama Department of Research, Interdisciplinary Graduate School of Medical and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511, Japan