BIODEGRADATION OF PHENOL BY FREE AND IMMOBILIZED CELLS OF A NOVEL Pseudomonas sp. NBM11

Abstract

In the present study, a pure culture of bacterium (Pseudomonas sp. Strain NBM11) was isolated from the soil sample from a site contaminated with medical wastes and wastewater. The isolated strain can degrade up to 1000 mg/L of phenol completely. It was observed that temperature, pH and initial concentration of phenol play key roles in determining the rate of phenol degradation. The isolated strain exhibited the maximal degradation of the substrate within a range of pH 6.8 to 7.2 and an incubation temperature between 30 ºC and 32 ºC. It was found that by increasing the concentration of phenol, the lag phase gets extended due to the inhibitory nature of phenol. The kinetic parameters such as µ_max (maximum specific growth rate), K_s (half-saturation coefficient) and K_i (substrate inhibition constant) were estimated as 0.184 1/h, 7.79 mg/L and 319.24 mg/L, respectively, by fitting the growth kinetics data to the Haldane model of substrate inhibition. The bacterial strain was immobilized in alginate beads and its phenol degradation efficiency was observed to increase many fold. The immobilized cells were found to be used efficiently for seven cycles consecutively without any decrease in their efficiency.

Keywords:
Pseudomonas sp.; Immobilization; Calcium alginate; Acinetobacter calcoaceticus; Phenol Biodegradation