Synthesis and evaluation of biosurfactant produced by Candida lipolytica using animal fat and corn steep liquor

• Low-cost media were evaluated for biosurfactants production by Candida lipolytica.
• The biosurfactant is an anionic glycolipid.
• The biosurfactant recovered 70% of the residual oil from oil-saturated sand.
• The cheaply produced glycolipid has potential of application in the oil industry.

In the present study, low-cost media based on animal fat and corn steep liquor combined with glucose, yeast extract, urea and other inorganic nitrogen sources were evaluated for the production of biosurfactants by the yeast Candida lipolytica UCP0988 in batch shake flasks. At the end of the 6-day fermentation period, the medium containing only animal fat (5%) and corn steep liquor (2.5%) yielded the maximal reduction in surface tension (from 50 to 28 mN/m). The properties of the biosurfactant separated by different organic solvent extractions were investigated and the critical micelle concentration was determined. Preliminary chemical characterisation revealed the anionic nature of the biosurfactant. Compositional analysis of the biosurfactant was carried out using thin layer chromatography. The biosurfactant produced by the isolate was characterised as a glycolipid. Emulsification activity and surface tension stability of the biosurfactant produced using different hydrocarbons and vegetable oils and the effect of pH, temperature and the addition of salt were also studied. The cell-free broth (crude biosurfactant) was effective at recovering up to 70% of the residual oil from oil-saturated sand samples and also effective at oil displacement (54%). The crude biosurfactant from C. lipolytica and aqueous solutions of the isolated biosurfactant at 0.04%, 0.08% and 0.16% were effective in recovering up to 100% of the motor oil from the walls of the beakers. These properties indicate the potential of a cheaply produced glycolipid for application in the oil industry.