Biodegradation of Phenolic Pollutants in Industrial Wastewater Using Selected Bacterial Isolates

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Fadlalla, Zeinab Fadlalla Ahmed
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University of Khartuom
The overall aim of this study was to assess the potentiality of some bacterial isolates as well as their oxidative enzymes as degrading agents of phenolic compounds. Nine bacterial isolates, recovered from different industrial wastewater, were cultured on mineral salt mediam containing 200 mg/L phenol for 12 hours at 37°C. Three isolates (F, H, I) which showed complete degradation (100%) of phenol were morphologically and biochemically characterized then cultured, separately, in broth medium for 12 hours at different pH values (5-10), different temperatures (20- 45°C) and different glucose concentrations (0.0, 0.25 and 0.50%). The three isolates showed high removal percentages of phenol at pH7.0, temperature 30°C and 0.25% glucose concentration. Crude phenol oxidase enzyme was extracted from each of the three isolates. The enzymatic and specific activities as well as the optimum temperature and pH value were determined using spectrophotometeric technique. The ability of the extracted enzymes to degrade the phonolic pollutants was tested on four industrial and three synthetic wastewater samples. The specific activity of phenol oxidase from isolate I was twice higher than that of isolate F. The extracted enzymes were active over a wide range of pH (4 – 10) and temperature (20 – 60°C) values with optimum pH value of 7.0 and optimum temperature of 30°C. The calculated Km values for phenol oxidases from bacterial isolates F, H and I were 0.41, 0.26 and 0.17 mM phenol, respectively while the Vmax values were 0.21, 0.31 and 0.24 ΔA/min in the same order. Km value of phenol oxidase from isolate I (0.17 mM phenol) was very low indicating a high enzymatic affinity towards phenol. After incubating the extracted enzymes with the collected industrial wastewater samples for 75 min, almost phenol was completely degraded. When assaying the enzymes with in vitro wastewaters, Enzymes were able to degrade or oxidize at least 10 different phenolic compounds. In conclusion, the bacterial isolates, or their oxidase enzymes, could be potentially used for biodegradation of phenolic pollutants in industrial wastewaters.
Biodegradation, Phenolic Pollutants, Industrial Wastewater, Selected Bacterial Isolates