| Summary: | Inhibition of α-glucosidase (EC 3.2.1.20) and β-galactosidase (EC 3.2.1.23) biosynthesis by phenolic compounds (phenol, 2-chlorophenol, 4-chlorophenol, 4-bromophenol and 3,5-dimethylphenol) in Escherichia coli, Bacillus and Pseudomonas species isolated from petroleum refinery wastewater was assessed. At sufficient concentrations, phenols inhibited the induction of α-glucosidase and β-galactosidase. The patterns of these toxic effects can be mathematically described with logistic and sigmoid dose-response models. The median inhibitory concentrations (IC50) varied among the phenols, the bacteria and enzymes. Quantitative structure–activity relationship (QSAR) models based on the logarithm of the octanol–water partition coefficient (log10Kow) were developed for each bacterium. The correlation coefficients varied between 0.84and 0.99 for the enzymes. The test results indicated α-glucosidase and β-galactosidase biosynthesis as important microbial indices for evaluation of toxicity of phenolic compounds.
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