Abstract

The removal of heavy metal contaminants from the environment is one of the potential areas in which the usefulness of biosurfactants has not been thoroughly explored. The molecular nature of biosurfactants offers the possibility of interaction with the metals in solution, aiding in their subsequent removal and/or recovery. In the present research work, a systematic isolation and screening program was undertaken for obtaining biosurfactant-producing bacteria. A total of 129 isolates were screened and three bacterial isolates were selected for high surface tension reducing ability. Pseudomonas aeruginosa, Stenotrophomonas koreensis (Strain DX1 16S ribosomal RNA gene, partial sequence NCBI Acc. No. GQ 493998 BankIt 1255714) and Rhodococcus spp isolates were identified by routine microbiological tests, API-32 and 16s rRNA profiling. The surface tension reduction of MS medium for the three isolates was: P. aeruginosa, 62.3 to 31.6 dynes/cm; S. koreensis, 62.4 to 27.8 dynes/cm; in 24 to 30 h for both organisms andRhodococcus spp, 64.4 to 43.7 dynes/cm in a period of 48 h. The emulsification index for all three isolates was 100% in diesel, petrol, toluene and sunflower oil. The ability of S. koreensis to remove heavy metal ions from solutions was explored. More than 30% of lead and cadmium ions were removed from 200 ppm metal solutions.

Key words: Biosurfactant, Stenotrophomonas koreensis, surface tension, heavy metals, lead, cadmium.