Abstract:
The present study employed bacterial consortium STK consisting of Zoogloea sp., Stenotrophomonas sp. and Mesorhizobium sp. to bioremediate pyrene contaminated soil in the presence or absence of biosurfactant. A 250 ml.-flask-containing soil slurry (1:0-1:12, soil:water) spiked with 1000 ppm pyrene was bioaugmented with STK consortium at 10 [superscript 8] cfu/ml and incubated for 1 week at room temperature with agitation rate of 200 rpm. It was found that at 1:4-1:12 ; soil:water STK consortium degraded pyrene to less than 1% within 7 days. Effect of surfactant addition to a 1:6 soil slurry (w/v) which included Brij 35, a nonionic surfactant, surfactin at 15x ACMC or Bacillus subtilis BBK-1 a surfactin producer (at 5-20 10 [superscript 7] cfu/ml) on pyrene-degrading ability of STK consortium was studied. All surfactants tested including B. subtilis BBK-1 showed no significant difference in enhancing pyrene degrading ability of STK indicating all surface active agents had no synergistic or positive effect toward pyrene degradation by STK. However, more than 99% pyrene was degraded in the presence of STK whereas 4-38% degradation was obtained from the control which STK was absent. Denaturing gradient gel electrophoresis (DGGE) of PCR amplified 16s rDNA revealed STK as dominant species in all the systems tested.