Application of residual cooking oil to improve the production of a low-toxic biosurfactants extract

Residual cooking oil (RCO) bioconversion into value-added products is one of the best options to manage this waste. Thus, the feasibility of producing lipopeptides by Pseudomonas syringae pv tabaci using this residue is reported for the first time. Surface activity, stability, and cytotoxicity of biosurfactants were explored by surface tension, emulsification indexes (EI24), and mammalian cell viability assays. It was demonstrated that a mixture of RCO and glycerol (1:1) as carbon source increased the production titer from 1.47 to 2.70 g/L, syringopeptin being the main component. The produced lipopeptides were able to reduce the water surface tension down to38 mN/m and emulsify effectively (EI up to 67 %) a wide variety of hydrophobic compounds at 0.10 g/L. Moreover, these lipopeptides at 1.0 g/L resulted to be highly compatible with mammalian cells (viability superior to 70 %), demonstrating that at the working concentrations are non-toxic and thus, adequate for food and pharmaceutical applications. [Display omitted] •Residual frying oil improves biosurfactant production by P. syringae pv tabaci.•The biosurfactant extract mostly consists of a lipopeptides mixture.•Biosurfactants showed an emulsifying activity of up to 67 % against waste motor oil.•The lipopeptides exhibited a critical micelle concentration of 0.86 g/L.•Biosurfactants at 1.0 g/L resulted to be non-toxic against mammalian cells.