Biosurfactant Mediated Degradation of Phenanthrene

Abstract

Biosurfactant (BS) produced from a marine bacterium Pseudomonas aeruginosa JP-11 and a terrestrial bacterium Bacillus subtilis SJ301 was utilized for phenanthrene degradation in culture medium and soil consortium. Functional and structural characterization by ATR-FTIR spectroscopy and XRD analysis revealed the structure of crude BS from JP-11 and SJ301 as glycolipid and lipopeptide respectively. BS of both the isolates JP-11 and SJ301 could reduce the surface tension of medium to 33.446 ± 0.029 mN/m and 37.15 mN/m respectively, with BS JP-11 having the maximum emulsification index of 52.94%. BS of JP-11 supplemented in the culture medium of JP-11 degraded 54.62% of phenanthrene with respect to BS of SJ301 supplemented in culture medium of SJ301 which degraded 43.29% of phenanthrene. Maximum degradation of phenanthrene was carried out by B. subtilis SJ301 and consortium of P. aeruginosa JP-11 and B. subtilis SJ301 in the soil consortium with 85.73 and 86.15 % of phenanthrene degradation respectively. The major functional groups involed in BS-phenanthrene interaction was -OH and - NH stretch, S-H stretch and P=O stretch. Fluorescence spectroscopy study showed the presence of one and three binding sites in the fluorophore of JP-11 and SJ301 with binding constant (Kb) of 3.32 M-1 and 4.08 M-1 respectively. With an increase in phenanthrene concentration (20-100 mg/l), fluorescence quenching reaction occurred which was spontaneous at 298 K with the ∆G value of - 2.89 and -3.40 kJ/K/mol for JP-11and SJ301 respectively. Zeta potential analysis showed an increase in negative charge with increasing phenanthrene concentration from 20 to 100 mg/l indicating stable BS-phenanthrene interaction. Microbial consortium present in sample 1, 9, 10 had similar microbial communities arising from a single node, whereas microbial consortium present in sample 2, 7, 5 belonged to a different node from the sample of 8, 6, 3 representing the community structure change in the soil consortium in presence of phenanthrene.