Enzymatic dehalogenation of gas phase substrates with haloalkane dehalogenase

• Published in: Biotechnology and bioengineering 2000-08, Vol.69 (3), p.235-241
• Main Authors: Dravis, Bryan C., LeJeune, Keith E., Hetro, Amy D., Russell, Alan J.
• Format: Article
• Language: English
• Subjects: Air Pollutants - chemistry; Air Pollutants - metabolism; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of gaseous effluents; bioremediation; Biotechnology; Buffers; Butanes - metabolism; Catalysis - drug effects; Chromatography, Gas - methods; Environment and pollution; enzymes; Ethylamines - pharmacology; Fundamental and applied biological sciences. Psychology; gas phase; haloalkane dehalogenase; Halogens - metabolism; Hydrocarbons, Halogenated - chemistry; Hydrocarbons, Halogenated - metabolism; Hydrogen-Ion Concentration; Hydrolases - metabolism; Industrial applications and implications. Economical aspects; Kinetics; Propane - analogs & derivatives; Propane - metabolism; Rhodococcus - enzymology; Solubility; Static Electricity; Temperature; triethylamine; Water - metabolism
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/1097-0290(20000805)69:3<235::AID-BIT1>3.0.CO;2-D

Haloalkane dehalogenase is an enzyme capable of catalyzing the conversion of short‐chained (C2–C8) aliphatic halogenated hydrocarbons to a corresponding primary alcohol. Because of its broad substrate specificity for mono‐, di‐, and trisubstituted halogenated hydrocarbons and cofactor independence, haloalkane dehalogenases are attractive biocatalysts for gas‐phase bioremediation of pollutant halogenated vapor emissions. A solid preparation of haloalkane dehalogenase from Rhodococcus rhodochrous was used to catalyze the dehalogenation reaction of 1‐chlorobutane or 1,3‐dichloropropane delivered in the gas phase. For optimal gas‐phase dehalogenase activity, a relative humidity of 100%, aw = 1, was desired. With a 50% reduction in the vapor‐phase hydration level, an 80% decrease in enzymatic activity was observed. The enzyme kinetics for the gas‐phase substrates obeyed an Arrhenius‐“like” behavior and the solid haloalkane dehalogenase preparation was more thermally stable than its water‐soluble equivalent. Triethylamine was added to the gaseous reaction environment in efforts to increase the rate of reaction. A tenfold increase in the dehalogenase activity for the vapor‐phase substrates was observed with the addition of triethylamine. Triethylamine altered the electrostatic environment of haloalkane dehalogenase via a basic shift in local pH, thereby minimizing the effect of the pH‐reducing reaction product on enzyme activity. Both organic phase and solid‐state buffers were used to confirm the activating role of the altered ionization state. © 2000 John Wiley & Sons, Inc., Biotechnol Bioeng 69: 235–241, 2000.