title: Biodegradation of 2,4,5-trichlorophenol by aerobic microbial communities: biorecalcitrance, inhibition, and adaptation.
abstract: Chlorinated aromatic compounds challenge our environment and wastewater treatment processes due to their biorecalcitrance and inhibition. In particular, 2,4,5-trichlorophenol (TCP) seems to demonstrate greater resistance to biodegradation than other trichlorophenols and is a known uncoupler of the electron transport chain, although little work addresses this compound specifically. Here, we investigate the biorecalcitrance, inhibition, and adaptation to 2,4,5-trichlorophenol by aerobic mixed microbial communities. We show that 2,4,5-trichlorophenol is strongly resistant to biodegradation at concentrations greater than 40 microM, demonstrates inhibition to respiration in direct proportion to 2,4,5-trichlorophenol concentration (with 50% inhibition projected near 85 microM 2,4,5-trichlorophenol), and does not sustain biomass in continuous reactors, even when all input 2,4,5-trichlorophenol is degraded. Communities showed consistent adaptation patterns to 2,4,5-trichlorophenol at concentrations of 10 microM and 20 microM, but these patterns diverged at concentrations greater than 40 microM. Finally, thermodynamic approximations were used to estimate the yield of 2,4,5-trichlorophenol as 0.165 gVSS/gCOD, a low value that partially explains why biodegradation of 2,4,5-trichlorophenol did not sustain the biomass. In particular, we estimated that the minimum concentration to support steady-state biomass (S (min)) is approximately 180 microM, a value much larger than the 40-microM concentration that is strongly resistant to biodegradation. Thus, readily biodegradable concentrations of 2,4,5-trichlorophenol are too low to sustain the biomass that biodegrades it.
authors.affiliation: Department of Chemical Engineering, Northwestern University, Evanston, IL 60208, USA. michael.marsolek@asu.edu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Marsolek
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Kirisits
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D000222:Adaptation, Physiological; D000332:Aerobiosis; D001419:Bacteria / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002733:Chlorophenols / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D010100:Oxygen / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D002733:Chlorophenols; C009534:2,4,5-trichlorophenol; D010100:Oxygen