DETERMINATION OF DEGRADATION POTENTIAL OF INDIGENOUS MICROORGANISMS FOR TOLUENE

Abstract

Toluene is a cyclic monoaromatic hydrocarbon which is extensively used as an industrial solvent. It is among the major environmental pollutants in petroleum contaminated sites. Environmental and public health effects of toluene due to soil and water contamination requires remedial measures. It has been categorized as hazardous chemical on EPA list of priority pollutants. Biodegradation offers the most viable solution for remediation of petroleum contaminated sites. Present study was carried out to isolate the bacterial strains capable of degrading toluene efficiently. A total of thirteen toluene degrading bacteria were isolated from petroleum contaminated soil by enrichment culture technique. Mineral salt medium (MSM) having toluene as a sole carbon source was used to investigate the growth of isolated strains. Acclimatization study was carried out to screen out potential toluene degraders on the basis of optical density measured at 600 nm. Out of thirteen isolates, only four isolates showed efficient growth at different concentrations (15, 30, 45 and 60 mg/L) of toluene with maximum optical density of 0.85. Identification of potential strains was done by 16S rRNA gene sequencing process which identified strains as Ochrobactrum anthropi, Ochrobactrum intermedium, Enterobacter cloacae and Pseudomonas aeruginosa. Bench scale bioreactor system was established for biodegradation of toluene and its percentage removal was determined by using UV-visible Spectrophotometer. At 60 mg/L of toluene concentration, degradation efficiency of individual strains and consortium was found to be 62.9, 58.7, 72.1, 81.1 and 88.4 % respectively within 72 hours which indicated that efficiency enhanced when consortium of four isolates was used. A phylogenetic tree was developed by using MEGA 4 program to explore the lineage of potential toluene degraders. This study may play an important role in onsite bioremediation of petrochemical industrial waste.