Characterisation and Application Studies of Sophorolipid Biosurfactant by Candida tropicalis RA1

Abstract

The present study reports isolation of Candida tropicalis RA1 from oil contaminated refinery soil. The study depicted production of 31 g sophorolipid (SLs) l-1 by Candida tropicalis RA1 until 240 h, using soya oil. Semi-purified SLs had critical micelle concentration of 0.5%, minimum surface tension of 30 mN m-1, oil spreading activity of 32.2 mm2, and emulsification index of 85% against crude oil. The major SLs forms observed were non-acetylated lactonic and di-acetylated acidic type, with 35.5% and 32.2% relative abundance. Semi–purified SLs inhibited human pathogens; Escherichia coli, Listeria monocytogenes and Staphylococcus aureus at 1000, 500, and 250 µg ml-1 minimum inhibitory concentrations (MIC) respectively. In addition, C. tropicalis RA1 represented 74% mercury biosorption at 0.5 mg l-1 concentration, by day 15. The present study reports establishment of equilibrium phase of lead, cadmium, and mercury at concentrations higher than maximum contaminant levels (MCL) standards. The observations reveal the future potential applications of C. tropicalis RA1 in the industrial, biomedical, and bioremediation fields respectively.