Development of a microbial bioassay for chlorinated and brominated hydrocarbons

A microbial assay for the determination of halogenated organic hydrocarbons in water samples was developed using cells of a Rhodococcus strain. Bacterial cells containing the enzyme alkyl-halidohydrolase (E.C. 3.8.1.1.) were immobilized in alginate gel by forming small beads which were added to the sample solution. On contact with halogenated hydrocarbons the enzyme liberated halogen ions which were detected by ion sensitive potentiometric chloride or bromide electrodes. In order to achieve a quick result, the change in EMF was recorded for an interval of 5 min and correlated to the contents of halogenated hydrocarbons (kinetic principle). The detection limit for chlorinated and brominated aliphatic hydrocarbons was below 50 μg 1−1 and 10 μg 1−1, respectively; the relative standard deviation was 5.5%. The influence of temperature, pH, several inorganic salts and metal ions was studied.