Rhamnolipid production using BS18 and evaluation of its efficiency along with phytoremediation and bioaugmentation for bioremediation of hydrocarbon contaminated soils.

This study reports the combined use of a rhamnolipid type biosurfactant (BS) along with phytoremediation and bioaugmentation (BA) for bioremediation of hydrocarbon-contaminated soils. Bacterial isolates obtained from hydrocarbon contaminated soil were screened for rhamnolipid production and isolate BS18, identified as , was selected for bioremediation experiments. Growth of BS18 in mineral salt medium (MSM) with diesel oil as the carbon source showed a maximum biomass of 8.2 g L, rhamnolipid production of 2.2 mg g cell dry weight, surface tension reduction of 28.6 mN/m and emulsification potential (EI%) of 65.6. Characterization of rhamnolipid based on Fourier transmittance infrared (FTIR) analysis confirmed the presence of OH, CH/CH, C=O, and COO stretching vibrations, respectively, which are distinctive features of rhamnolipid type BSs. In bioremediation experiments, the lowest hydrocarbon concentration of 2.1 mg g of soil for non-sterilized soil and 4.3 mg g of soil for sterilized soil was recorded in the combined application of rhamnolipid, phytoremediation, and BA. This treatment also yielded the highest hydrocarbon degrading bacterial population (6.4 Log Cfu g of soil), highest plant biomass (8.3 g dry weight plant), and the highest hydrocarbon uptake (512.3 mg Kg of plant).