Characteristics of a microbial assay for the detection of halogenated hydrocarbons using cells of an actinomycete-like organism as a biological component

Abstract

Cells of an Actinomycete-like bacterium, strain GJ70, with the ability to degrade several haloalkanes were used as a biological component in a discontinuous microbial bioassay for the detection of 1,3-dichloropropene and 1,2-dibromoethane in water. The cells were entrapped in different matrices such as calcium alginate, carrageenan, chitosan, polyacrylamide-hydrazide and chitosan-carboxymethyl cellulose; the specific dehalogenating activity of the immobilized cells was highest with the two last matrices. By the addition of small beads of immobilized cells to a stirred sample solution and by the use of an ion selective electrode (ISE) for the quantification of enzymatically released halogen ions, the concentration of halogenated hydrocarbons could be estimated by determining the change of electrode potential within a period of 5 min. The detection limits for 1,3-dichloropropene and 1,2-dibromoethane were below 100 μg/l and 25 μg/l, respectively; the relative standard deviation was < 10%. In addition, several chlorinated and brominated hydrocarbons were converted by the bacterial cells at a reduced rate e.g. 1,2-dibromopropane, 1-bromoethane, 1,5-dichloropentane, etc. Moreover, temperatures of between 20 and 40°C did not affect the enzymatic activity of the cells, and a pH of between at 5 and 9 had little influence. Several organic substances and non-metabolizable compounds did not affect the conversion, whereas some heavy metal ions acted as inhibitors.