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 3,5dimethylphenol) 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

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... response models. The median inhibitory concentrations (IC 50 ) varied among the phenols, the bacteria and enzymes. Quantitative structure-activity relationship (QSAR) models based on the logarithm of the octanol-water partition coefficient (log 10 K ow ) 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. Inibição de β-galactosidase e síntese de α-glicosidase em bactérias de efluente de refinaria de petróleo por compostos fenólicos RESUMO A inibição da biossíntese da α-glicosidase (CE 3.2.1.20) e da β-galactosidase (3.2.1.23) por compostos fenólicos (fenol, 2-clorofenol, 4-clorofenol, 4-bromofenol e 3,5-dimetilfenol) nas espécies Escherichia coli, Bacillus e Pseudomonas isoladas de efluentes de refinarias de petróleo foi avaliada. Em concentrações suficientes, os fenóis inibiram a indução da αglicosidase e β-galactosidase. O comportamento desses efeitos tóxicos pode ser descrito matematicamente com modelos de logística e sigmóide dose-resposta. A mediana da concentração inibitória (IC50) variou entre os fenóis, as bactérias e enzimas. Modelos da relação quantitativa de estrutura-atividade (QSAR) baseados no logaritmo do coeficiente da partição octanol-água (log 10 K ow ) foram desenvolvidos para cada bactéria. Os coeficientes de correlação variaram entre 0.84 e 0,99 para as enzimas. Os resultados dos testes indicaram a biossíntese da α-glicosidase e da β-galactosidase como importantes índices microbianos para avaliação da toxicidade de compostos fenólicos. Palavras-chave: Toxidade; compostos fenólicos; QSAR; bactéria de resísuduo líquido. NWEKE, C. O.; OKPOKWASILI, G. C. Inhibition of β-galactosidase and α-glucosidase synthesis in petroleum refinery effluent bacteria by phenolic compounds. 50 CONCLUSION This study has shown that induction of α-glucosidase and β-galactosidase enzymes in Escherichia coli, Bacillus and Pseudomonas species could be inhibited by phenolic compounds to levels dependent on octanol-water partition coefficient. Thus, the organisms may serve as convenient indices for assessment of toxicity of environmental pollutants and by extrapolation, the risk assessment of industrial wastes.