Distribution of chlorophenolic compounds, from a pulp mill, in Lake Bonney, South Australia

Water and sediment samples from Lake Bonney (south-eastern South Australia) were collected at various distances from the effluent discharge point of a sulfite-based pulp mill and analysed for chlorophenolic compounds. The period of sample collection (July 1991 to January 1992) occurred during a time when bleaching process of the mill was being converted from using molecular chlorine to using hydrogen peroxide. In water samples, the major chlorophenolic compounds detected were 2,4,6-trichlorophenol, tetrachlorocatechol and chlorinated guaiacols. In sediment samples, the major chlorophenolic compounds detected were chlorinated guaiacols and chlorinated catechols. The concentrations of these compounds in lake water generally decreased over the sampling period, corresponding to the decrease in use of molecular chlorine. Concentrations in sediment decreased with increasing distance from the discharge point. The presence of chlorinated guaiacols in water and sediment at a site 17 km from the effluent discharge point indicated that these compounds degrade slowly in the lake. The presence of the chlorinated catechols in sediments at localities where these compounds were not detected in the water suggests that de-0-methylation of adsorbed chlorinated guaiacols occurs and/or that there is preferential adsorption of chlorinated catechols to sediment.

Purification and properties of chlorocatechol 1,2-dioxygenase from Alcaligenes denitrificans BRI 6011

The specific activity of chlorocatechol 1,2-dioxygenase from Alcaligenes denitrificans BRI 6011 was found to be maximal in the early logarithmic growth phase. The enzyme was purified from cultures at mid-log phase of growth using ammonium sulfate fractionation, and phenyl-Sepharose and DEAE-Sepharose chromatography. The protein gave a single band by SDS polyacrylamide gel electrophoresis with an apparent molecular weight of 33 000, and the temperature and pH optima were 30 °C and 7.5, respectively. Catechol, 3-chlorocatechol (3-CC), 4-CC, 3,4-dichlorocatechol (3,4-DCC), 3,5-DCC, 3,6-DCC, 3-methylcatechol (3-MC), and 4-MC served as substrates for the enzyme. The Vmax values for the dichlorocatechols were similar, while those for the monochlorinated and methylated catechols were higher. The Km values for all the chlorinated catechols were typically below 1 μM, while those for catechol and the methylated catechols were above 10 μM.Key words: chlorocatechol 1,2-dioxygenase, Alcaligenes denitrificans, purification, characterization, chlorobenzoic acid degradation.