Inhibition of β-galactosidase and α-glucosidase synthesis in petroleum refinery effluent bacteria by phenolic compounds

Abstract

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 dose-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.

Effect of Heavy Metals on β-galactosidase Activity in Marine Bacteria

“…C A is the absorbance of uninhibited control (without toxicant), T A is the absorbance of inhibited test (with different concentrations of toxicant), x is the concentration of metal ion, a is the uninhibited value of enzyme activity (100%), KI is dimensionless toxicity parameter; K i is the coefficient of inhibition [10].…”

“…Harvested cells were washed twice in deionized water and were standardized in a spectrophotometer to an optical density of 0.6 at 420 nm. The standardized cell suspensions were employed as inocula in the assay of the enzyme [10].…”

“…The method of Nweke and Okpokwasili [10] was employed with little modification. Small quantities of (0.1 ml) standardized cell suspensions were inoculated into sterile triplicate 20 ml screwcapped test tubes containing 1.9 ml Z-buffered (pH 7.0) nutrient broth-lactose medium (0.4 ml Z-buffer, 0.4 ml of nutrient broth and 0.1 ml of 0.4% w/v lactose and required volume of deionized water) supplemented with a specific concentration of heavy metal ion (0.001-200 mg/l).…”

“…The absorbance of ρnitrophenol solution produced was measured spectrophotometrically at 420 nm (λ max). The βgalactosidase activity was calculated relative to the control [10].…”

“…Sediments have diverse microbes which play important roles in aquatic ecosystem functions, such as ecological decontamination, biogeochemical cycles and recycling of organic matter [7,8,9]. β -galactosidase which catalyses the breakdown of lactose to glucose and then to galactose is an intracellular enzyme and its biosynthesis is induced by lactose or its derivatives [10]. Factors that affect metabolic actions (e.g.…”