Effluent decontamination by the ibuprofen-mineralizing strain, Sphingopyxis granuli RW412: Metabolic processes

Genetic Characterization of the Ibuprofen-Degradative Pathway of Rhizorhabdus wittichii MPO218

“…In addition to the ipf region described above, we have identified two other DNA regions involved in IBU utilization. One of the regions, involved but not essential for growth using IBU, is involved in the metabolism of propionyl-CoA, supporting the proposal that propionyl-CoA is a by-product of IBU degradation ( 15 , 17 , 19 ). The other region is also found on pIBU218 but is far from the ipf region and is essential for allowing growth using IBU.…”

“…Thus, while Ibu-2 accumulates a yellow intermediate while growing with IBU as the sole carbon and energy source, neither RW412 nor MPO218 develop any coloration under the same conditions. In addition, the doubling time of MPO218 growing on IBU was substantially shorter than that of RW412, around 3 h for MPO218 versus the 16 h described for RW412 ( 16 , 17 ). Murdoch et al ( 15 , 19 ) and Aguilar-Romero et al ( 17 ) have analyzed the metabolic pathway of ibuprofen biodegradation at the biochemical level showing that, in the first step, a CoA ligase binds coenzyme A to ibuprofen, which is then attacked by a dioxygenase system to form a dihydrodiol, which thereafter is cleaved by a retro-aldolase into propionyl-CoA and 4-isobutylcatechol.…”

“…In addition, the doubling time of MPO218 growing on IBU was substantially shorter than that of RW412, around 3 h for MPO218 versus the 16 h described for RW412 ( 16 , 17 ). Murdoch et al ( 15 , 19 ) and Aguilar-Romero et al ( 17 ) have analyzed the metabolic pathway of ibuprofen biodegradation at the biochemical level showing that, in the first step, a CoA ligase binds coenzyme A to ibuprofen, which is then attacked by a dioxygenase system to form a dihydrodiol, which thereafter is cleaved by a retro-aldolase into propionyl-CoA and 4-isobutylcatechol. According to gas chromatography-mass spectrometry (GC-MS) metabolite analysis by Murdoch et al ( 19 ), 4-isobutylcatechol should subsequently be attacked by an extradiol-2,3 dioxygenase and a dehydrogenase to produce 2-hydroxy-5-isobutylhexa-2,4-dienoic acid.…”

“…Several studies have shown a toxic effect on aquatic and soil organisms exposed to IBU concentrations equivalent to those found in the environment ( 2 , 12 – 14 ), so improving wastewater treatment processes to eliminate this pollutant is a priority. Although several microorganisms capable of biodegrading IBU have been isolated to date, the metabolic pathways of this biodegradation and their genetic bases remain poorly understood ( 2 , 15 – 17 ). Although ibuprofen seems to be biodegradable, the fact that it is detected in such large amounts in the environment, and that it is detected in wastewater treatment plant (WWTP) effluents, indicates that there must be environmental factors limiting its biodegradation ( 2 , 7 , 11 , 18 ).…”

“…Within the Sphingomonadaceae family, three different strains sharing the same set of genes related to IBU biodegradation have been independently isolated worldwide. The ipf cluster, first described in the Sphingomonas ibu-2 strain by Murdoch et al ( 15 , 19 ), has been found highly conserved at the DNA level in two different strains, Rhizorhabdus wittichii MPO218 ( 16 ) (formerly Sphingomonas wittichii [ 20 ]) and Sphingopyxis granuli RW412 ( 17 ). Both MPO218 and RW412 carry the ipf genes on a large plasmid ( 16 , 17 ) that, in the case of the plasmid pIBU218 carried by R. wittichii strain MPO218, has been shown to be conjugative ( 16 ).…”