Biological degradation of toluene by indigenous bacteria Acinetobacter junii CH005 isolated from petroleum contaminated sites in India

The bacterium Acinetobacter junii was isolated from petroleum-contaminated site in India and tested for its efficiency in degradation of toluene under aerobic condition. Within pH range 4-9, the optimum pH for toluene biodegradation was found to be 7.5. With increase in time, there was enhancement in degradation of toluene. Pure culture of Acinetobacter junii was able to degrade 69, 73 and 80% of 150, 100, and 50 ppm toluene, respectively, within 72 h at 37 degrees C. Simultaneous growth and degradation of toluene by the bacterium indicated the utilization of toluene as carbon source. After 72 h of treatment, toluene biodegradation was nearly stable. Scanning electron microscopic characterization of bacterial cells treated with toluene revealed the changes in surface morphology. Some of the cylindrical cells of bacterium got transformed into ovoid and spherical shape to escape the toluene toxicity. Degradation intermediates were identified by gas chromatography-mass spectroscopy. The major intermediate compounds identified after toluene degradation by bacteria were 1-isopropenyl-4-methyl-1,3-cyclohexadiene; 1,3-Cyclohexadiene; 2-methyl-5-(1-methylethyl); 4-methoxycarbonyl-4-butanolide; and vinyl (2E,4E)-2,4-hexadienoate, which are less-toxic in nature. The degradation of toluene into non-toxic intermediate compounds as well as the growth in the presence of toluene presents the suitability of Acinetobacter junii in biofiltration of toluene-containing petroleum waste.