Rhizodegradation of petroleum hydrocarbons by Sesbania cannabina in bioaugmented soil with free and immobilized consortium

The present study reports the effect of bioaugmentation by free and immobilized bacterial culture on the rhizodegradation of petroleum-polluted soil using Sesbania cannabina plant. Total petroleum hydrocarbon (TPH), hydrocarbon-degrading bacterial counts, microbial activity and root morphology were assessed during 120 days of plant growth. TPH concentration analyzed by GC-MS showed that bioaugmentation did not improve the TPH degradation. TPH concentration decreased from 2541 mg kg(-1) to 673 mg kg(-1) and 867 mg kg(-1) in the rhizosphere of free (FR) and immobilized bacterial inoculated (IR) soil, respectively at the 120th day while in the rhizosphere of uninoculated soil (CR) concentration decreased to 679 mg kg(-1) only at the 90th day, showing higher and rapid rhizodegradation with indigenous bacteria than bioaugmented bacterial cultures. Various predominant bacterial groups responsible for higher TPH degradation in the rhizosphere of S. cannabina were identified by PCR-DGGE analysis. It is concluded that natural plant-microbe interaction in the rhizosphere of S. cannabina was efficient enough to degrade TPH and plant rhizosphere keeps bacterial community in its surrounding therefore immobilized culture had no obvious effect on petroleum degradation. (C) 2012 Elsevier B.V. All rights reserved.