Microbial transformation of benzothiophenes, with carbazole as the auxiliary substrate, by Sphingomonas sp. strain XLDN2-5.
Benzothiophenes are a toxic and relatively recalcitrant fraction of coal-tar creosote. We investigated the co-metabolic transformation of benzothiophene (BT) and its derivatives by the carbazole (CA) degrader Sphingomonas sp. XLDN2-5, which is not able to grow on benzothiophenes as the sole carbon source. Among the benzothiophenes tested, BT, 2-methylbenzothiophene (2-MBT) and 5-methylbenzothiophene (5-MBT) were co-metabolically converted. For 3-methylbenzothiophene, there was complete inhibition of growth on CA. The common transformation products for BT, 2-MBT and 5-MBT are the corresponding sulfoxides and sulfones. For BT, several high-molecular-mass sulfur-containing aromatic compounds, including benzo[b]naphtho[1,2-d]thiophene, benzo[b]naphtho[1,2-d]thiophene-7-oxide, 6a,11b-dihydrobenzo[b]naphtho[1,2-d]thiophene, 6a,11b-dihydrobenzo[b]naphtho[1,2-d]thiophene-7-oxide, and a new product, 6,12-epithiobenzo[b]naphtho[1,2-d]thiophene, were detected by GC-MS. These high-molecular-mass products are thought to be generated from a Diels-Alder-type reaction. Investigations with a combination of GC and flame ionization detection showed that about 17 % of BT was transformed to benzo[b]naphtho[1,2-d]thiophene. Aerobic transformation of benzothiophenes to sulfoxides and sulfones can reduce their toxicity, and facilitate their biodegradation. However, the formation of the high-molecular-mass products, such as benzo[b]naphtho[1,2-d]thiophene, should be considered in the biodegradation of benzothiophenes.
Gai
Zhonghui
Z
Key Laboratory of Microbial Metabolism, Ministry of Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Yu
Bo
B
Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, PR China.
Wang
Xiaoyu
X
State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China.
Deng
Zixin
Z
Key Laboratory of Microbial Metabolism, Ministry of Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Xu
Ping
P
Key Laboratory of Microbial Metabolism, Ministry of Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
D001673:Biodegradation, Environmental; D002227:Carbazoles / Q000378:metabolism*; D003470:Culture Media; D008401:Gas Chromatography-Mass Spectrometry; D020578:Sphingomonas / Q000254:growth & development / Q000378:metabolism*; D013876:Thiophenes / Q000737:chemistry / Q000378:metabolism*
D002227:Carbazoles; D003470:Culture Media; D013876:Thiophenes; C088015:benzothiophene; C041514:carbazole