02269naa a2200205 a 450000100080000000500110000800800410001910000170006024500430007726000090012052016670012965000190179665000160181565000200183165000230185165300160187470000170189070000200190777301360192717984462017-03-28       1998    bl ---       0--  u    #d1 aDURAN, N. L.  aThe dehalogenation kinetics of CFC-11.  c1998  aThe kinetics of biodegradation provides an objective basis for evaluation the fate of contaminants and their persistence in the environment. Information about degradation rates is very important from the bioremediation standpoint. The objective of this study was to determine the kinetic parameters for the dehalogenation of CFC-11 to HCFC-21, previously reported by our laboratory. Batch experiments were performed using an enriched mixed culture of sulfate-reducing bacteria that originated from groundwater samples obtained from aquifer contamined with CFC-11 and other halogenated aliphatic compunds. When substrate depletion curves with initial concentrations of 1.6uM were analyzed, good linearity was obtained when fitted to the Henri-Michaelis-Menten equation. The kinetic parameters associated with the microbial dehalogenation of CFC-11 to HCFC-21 were calculated by linear regression to be Km=1.29uM and Vm=0.598 uM h-1. The first-order rate constant (k1) was determined to be 4.6 x 10-2h-1. An acute toxicity effect was observed at 8.34uM CFC-11, while concentrations below 0.04uM were biologically unavailable. Since the availability of electron acceptors has been known to affect the flow of electrons required for reductive dehalogenation reactions, alternative electron acceptors were tested. It was found that only sulfate supported the dehalogenation reaction while sulfite and thiosulfate did not. The addition of sulfate-reducing inhibitors, selenate or molybdate, to an actively degrading sulfate-grown culture inhibited the dehalogenation reaction. A model is proposed for the mechanism of electron flow patterns in the reduction of CFC-11.  abiodegradation  axenobiotics  aBiodegradação  aSubstancia Tóxica  aXenobiotico1 aSMITH, G. B.1 aNUNES, V. da S.  tIn: LATIN AMERICAN BIODEGRADATION & BIODETERIORATION SYMPOSIUM, 3., 1998, Florianopolis. Anais... Florianopolis: UFSC, 1998. p.1-5.