title: Biodegradation kinetics of trans-4-methyl-1-cyclohexane carboxylic acid.
abstract: Naphthenic acids are a complex mixture of organic compounds which naturally occur in crude oil. Low molecular weight components of the naphthenic acids are known to be toxic in aquatic environments and there is a need to better understand the factors controlling the kinetics of their biodegradation. In this study, a relatively low molecular weight naphthenic acid compound (trans-isomer of 4-methyl-1-cyclohexane carboxylic acid) and a microbial culture developed in our laboratory were used to study the biodegradation of this naphthenic acid and to evaluate the kinetics of the process in batch cultures. The initial concentration of trans-4-methyl-1-cyclohexane carboxylic acid (50-750 mg l(-1)) did not affect the maximum specific growth rate of the bacteria at 23 degrees C (0.52 day(-1)) to the maximum biodegradable concentration (750 mg l(-1)). The maximum yield observed at this temperature and at a neutral pH was 0.21 mg of biomass per milligram of substrate. Batch experiments indicated that biodegradation can be achieved at low temperatures; however, the biodegradation rate at room temperature (23 degrees C) and neutral pH was 5 times faster than that observed at 4 degrees C. Biodegradation at various pH conditions indicated a maximum specific growth rate of 1.69 day(-1) and yield (0.41 mg mg(-1)) at a pH of 10.
authors.affiliation: Division of Environmental Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. janice.paslawski@usask.ca
authors.forename: Janice C
authors.initials: JC
authors.lastname: Paslawski
authors.forename: John V
authors.initials: JV
authors.lastname: Headley
authors.forename: Gordon A
authors.initials: GA
authors.lastname: Hill
authors.forename: Mehdi
authors.initials: M
authors.lastname: Nemati
mesh_terms: D001673:Biodegradation, Environmental; D002264:Carboxylic Acids / Q000378:metabolism; D003509:Cyclohexanecarboxylic Acids / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D002264:Carboxylic Acids; D003509:Cyclohexanecarboxylic Acids; D014874:Water Pollutants, Chemical; C044895:cyclohexanecarboxylic acid; C046170:naphthenic acid