Development of Enzymatic Microtoxicity Test for the Toxicity Assay of Chlorophenolic Compounds

Enzymes are proteins that serve as catalysts of biological reactions in the animal, plant, and microbial cells. They are quite specific concerning with regard to their substrates. Enzymes lower the activation energy and increase the rate of biochemical reactions. According to the type of reaction catalyzed, enzymes are currently subdivided into six classes, namely oxidoreductases, hydrolases, transferases, lyases, isomerases, and ligases. The effects of toxic chemicals and chlorophenolic compounds on enzyme activity are determined by fast, useful, and simple enzymatic methods. These methods can be carried out in low volumes and automatically using equipment such as a spectrophotometer, fluorometer and scintillation counters. In this study, a new microtoxicity test was developed with the use of the fungal and bacterial β-galactosidase enzyme. In the toxicity experiments, the effects of 2,4,6-trichlorophenol (2,4,6 TCP), 2,4-dichlorophenol (2,4 DCP) and 4-chlorophenol (4 CP) over the β-galactosidase enzyme activity were investigated. In this study, the bacterial and fungal β-galactosidase enzyme was found to be effective in determining the detoxification of some chlorinated phenolic compounds, 2,4,6-TCP, 2,4-DCP, and 4-CP, through the treatment with laccase enzyme. The inhibitor effect of toxic compounds on the activity of the β-galactosidase enzyme was examined. As a result of the studies, 61% inhibition for 2,4,6-TCP, 58% inhibition for 2,4-DCP and 47% inhibition for 4-CP was observed. Mikrotoxicity test system developed in our laboratory which works principally based on inactivation of β-galactosidase activity by toxic chlorinated phenolics, was used for toxicity detection. Data obtained from microtoxicity tests have shown that the dechlorination of chlorinated phenolics with laccase has resulted in the loss of toxic potentiality of these chemicals to a substantial extent. We thought that this study is to be an important contribution to bioremediation science and environmental technology with a new biotechnological approach.

The Performance of Four Different Mineral Liners on the Transportation of Chlorinated Phenolic Compounds to Groundwater in Landfills

The aim of this study was to investigate the efficiency of four different mineral liners (clay, bentonite, kaoline, and zeolite) which could be utilized to prevent the transport of phenolic compounds to groundwater through alternative liner systems. Four laboratory-scale HDPE reactors with 80 cm height and 40 cm inner diameter were operated for a period of 180 days. Results indicated that the transport of mono- or dichlorophenols is significantly prevented by the liner systems used, while the transport of highly chlorinated phenolic compounds cannot be prevented by the landfill liner system effectively. Highly chlorinated phenolic compounds in groundwater can be found in higher concentrations than the leachate, as a result of the degradation and transformation of these compounds. Thus, the analysis of highly chlorinated phenolic compounds such as 2,4,6-TCP, 2,3,6-TCP, 3,4,5-TCP, and PCP is of great significance for the studies to be conducted on the contamination of groundwater around landfills.