Rhizoremediation of fuel oil by Vetiveria zizanioides in association with Kocuria sp. no. MU1 and Micrococcus luteus WN01

Abstract

Pot experiments were conducted to determine the rhizoremediation potential of Vetiveria zizanioides in association with bacteria isolated from the oil-polluted area, in fuel oil degradation. The analysis of fuel oilcontaminated soil from Udonthani Province, Thailand, revealed 23 isolates based on their partial 16S rDNA sequences. Among these, only 6 isolates could grow on fuel oil MSM medium. Fuel oil biodegradability assay was performed with the six isolates and the established oil degrader strain Micrococcus luteus WN01. The results showed that M. luteus WN01 and Kocuria sp. MU01 utilized the fuel oil at maximal percentages (86.06% and 63.12%, respectively). Hence, they were chosen as inoculated bacteria in fuel oil-contaminated soil planted with vetiver grass, in 5 treatments:control, natural attenuation, rhizoremediation, bioaugmentation, and phytoremediation. The results revealed that plants in association with M. luteus WN01 or Kocuria sp. MU01 showed significant increases in total biomass, shoot height and root length, with higher relative growth rates. A significant decrease (> 50%) in total petroleum hydrocarbon (TPHs) concentration in soil, with the highest percentage of removal (50.25%), was observed in rhizoremediation with M. luteus WN01 after 45 days of treatment. Moderate percentages of removal (37-47%) were shown in rhizoremediation with Kocuria sp. MU01, bioaugmentation and phytoremediation. Natural attenuation exhibited the lowest percentage of removal (20.8%). These results suggested that mutual benefits between vetiver grass and bacteria M. luteus WN01 or Kocuria sp. MU01 can enhance the rhizoremediation of petroleum hydrocarbon contaminated soil.