Conjunction of Vetiveria zizanioides L. and oil-degrading bacteria as a promising technique for remediation of crude oil-contaminated soils

Oil pollution is a great threat to all forms of aquatic and terrestrial life. Vetiver (Vetiveria zizanioides L.) is a C4 perennial grass which can grow on diverse environments and may have the potential to be used for remediation of contaminated areas. Therefore, a controlled greenhouse experiment was conducted to study growth performance, petroleum tolerance and total petroleum hydrocarbons (TPHs) removal potency of vetiver and hydrocarbon-degrading bacteria over a period of 120 days in contaminated soils with various oil concentrations (0, 2, 4, 6, 8, 10, and 12% w/w). The results showed that chlorophyll (Chl) a and Chl b content decreased in contaminated soils, although carotenoid content increased. Vetiver grass showed no sign of toxicity and thrived well in contaminated soils by applying survival approaches. Total antioxidant activity, malondialdehyde, and proline contents in root and shoot of vetiver increased in the presence of crude oil. The results revealed that decreasing of TPHs was in the range of 47e77% by vetiver, 53.3e87.4% by bacteria, and 57.5e84.6% by plant-bacteria treatments. Therefore, this plant could be used effectively for cleansing crude oil-contaminated soil, particularly in the presence of degrading bacteria. However, it needs more studies in field conditions where the physicochemical and biological characteristics of natural polluted soils may affect plant and bacteria remediation efficiency.