Biodegradation of phenol by new strain of thermophilic bacteria

In the field of hazardous wastewater treatment the attention is focused on aromatic hydrocarbons because of their widespread presence in wastewater from petroleum refineries and petrochemical industries. Phenols are among the most hazardous contaminants in refinery wastewater and they are the most difficult to remove. Many techniques have been used in the past few years for removal of phenols. Biological treatment has proved to be the most promising and economical method for this purpose. Recent researches have shown that native microorganisms are more effective than commercial type. In this study, batch experiments were carried out to evaluate the biodegradation of phenol by thermophilic bacteria using free and immobilized cells at different conditions. This strain was isolated from the soil close to Tehran oil refinery which was characterized as Nocardia otitidiscaviarum. The bacteria were activated and gradually acclimatized to high concentrations of phenol of up to 1000 mg/l. The experimental results indicated that the biodegradation ability of this isolated strain is highly affected by temperature, pH, initial phenol concentration and abundance of the biomass. The biodegradation rate by free cells is optimized at 50 ºC, pH of 7 and phenol concentration of 600 mg/l. The higher phenol concentrations inhibited the biomass and reduced the biodegradation rate. However, the isolated strain still has the ability of degrading phenol at the concentration of 1000 mg/L. Cells acclimated to phenol can be adsorbed on the external surface the Monolith as the support where they grow to form a network of large filaments. Exponentially-growing cells were adsorbed faster than their stationary-phase counterparts. Immobilization resulted in a remarkable enhancement of the respiratory activity of cells and a shorter lag phase preceding the active phenol degradation.

کلیدواژه ها:

Biodegradation ، Immobilization ، Monolith ، Phenol ، Thermophile