Detection of chlorinated and brominated hydrocarbons by an ion sensitive whole cell biosensor

A microbial biosensor was formed by applying immobilized cells of Rhodococus sp. DSM 6344 to the surface of ion selective potentiometric electrodes. The bacterium contains the enzyme alkyl-halidohydrolase (EC 3.8.1.1), which transforms appropriate halogenated hydrocarbons into the corresponding alcohols and halogen ions, the latter being detectable by ion sensitive electrodes. Several matrices for immobilization (alginate, agarose, carrageenan, polyacrylamide, etc.) were tested, the most effective being the direct formation of a catalytic layer on the electrode surface by alginate gels.

Influence of the specific activity of the catalytic layer and the effect of temperature and pH on sensor performance were tested. Reproducible results were obtained within a time period of 5 min. Calibration with 1-chlorobutane and ethylenebromide showed a non-linear dependence and a good sensitivity, e.g. 0·22 and 0·04 mg/l, respectively. The relative standard deviation was determined as 7·8% by carrying out five consecutive experiments. The sensor can be stored at 277 K in dry form for 1 week and is easily rehydrated in calcium nitrate solutions.