Abstract
In the present work, the production of biosurfactant was studied from the bacterial strains isolated from the marine sponge Clathria sp. sample collected from oil-contaminated coastal region of V.O. Chidambaranar Harbour, Thoothukudi, Tamil Nadu, India. Six morphologically distinct biosurfactant-producing bacterial strains (SJ1-SJ6) isolated on oil agar plates were further screened for biosurfactant production (BP). Based on the screening results, the isolate SJ2 showed a surface tension reduction value of 31.6 mN m(-1), oil displacement zone of 26 mm and positive results of drop collapse test with the emulsification index percentage (EI24%) of 68.14%, and the bacterial adherence to hydrocarbon percentage of 79.2% was selected as the most potential BP strain, and it was identified as Enterobacter cloacae using 16S rRNA gene sequencing. Growth and BP optimization revealed 36 h of incubation period, 150 rpm agitation, pH 7.5, 37 degrees C temperature, 1% salinity, 2% glucose as carbon source and 1% yeast extract as nitrogen source were the ideal conditions with the biosurfactant yield of 2.61 g L-1. FTIR and MALDI-TOF-MS analysis of the biosurfactant showed the presence of functional groups, and it was a rhamnolipid. This rhamnolipid biosurfactant showed antibacterial activity against tested bacterial pathogens.