Estimation of kinetic parameter for the biotransformation of three-ring azaarenes by the phenanthrene-degrading strain Sphingomonas sp. LH128.
We examined the biotransformation of several azaarenes to get information on their rate of removal from contaminated soil by cometabolic degradation. Acridine, 9-methyl-acridine, phenanthridine, benzo[f]quinoline, and benzo[h]quinoline were found to be cometabolized by phenanthrene-degrading Sphingomonas sp. strain LH128. The transformation of acridine and benzo[h]quinoline was shown to be inhibited at relatively high concentrations (24.9 mg/L and 58.2 mg/L, respectively). Maximum biotransformation rates (Vmaxs), Michaelis-Menten half saturation constants (Kms), and biotransformation constants (k1s) were estimated for acridine, phenanthridine, and benzo[f]quinoline and ranged from 14.0 to 26.1 mg/g total protein/h for Vmax, 0.57 to 2.9 mg/L for Km, and 4.9 to 30.8 L/g total protein/h for k1. For 9-methyl-acridine only, a k1 of 0.6 L/g total protein/h was estimated and for benzo[h]quinoline, the highest biotransformation rate measured was 6.8 +/- 0.4 mg/g total protein/h. To our knowledge, this is the first effort to determine both Vmax and Km kinetic parameters describing the biotransformation of phenanthrene- and anthracene-analogue azaarenes. The results show that the rate of removal of azaarenes from contaminated soil will probably be rather high, although accumulation of metabolites can be expected.
Department of Environmental and Toxicological Chemistry (IBED/MTC), University of Amsterdam, Nieuwe Achtergracht 166, 1018WV Amsterdam, The Netherlands.
René
R
van Herwijnen
Chris
C
de Graaf
Harrie A J
HA
Govers
John R
JR
Parsons
D001372:Aza Compounds / Q000378:metabolism*; D001711:Biotransformation; D004787:Environmental Pollution / Q000517:prevention & control*; D006575:Heterocyclic Compounds, 3-Ring / Q000378:metabolism*; D007700:Kinetics; D012044:Regression Analysis; D012988:Soil Microbiology; D020578:Sphingomonas / Q000378:metabolism*
D001372:Aza Compounds; D006575:Heterocyclic Compounds, 3-Ring