Valorization of agro-industrial wastes towards the production of rhamnolipids

•Oil mill wastewater (OMW) was evaluated as an inductor of rhamnolipid production.•A culture medium containing corn steep liquor, molasses and OMW was designed.•Pseudomonas aeruginosa #112 produced 5.1g rhamnolipid/l using that medium.•The critical micelle concentration of the purified rhamnolipids was 13mg/l.•This medium represents a sustainable alternative for rhamnolipid production. In this work, oil mill wastewater (OMW), a residue generated during olive oil extraction, was evaluated as an inducer of rhamnolipid production. Using a medium containing as sole ingredients corn steep liquor (10%, v/v), sugarcane molasses (10%, w/v) and OMW (25%, v/v), Pseudomonas aeruginosa #112 produced 4.5 and 5.1g of rhamnolipid per liter in flasks and reactor, respectively, with critical micelle concentrations as low as 13mg/l. Furthermore, in the medium supplemented with OMW, a higher proportion of more hydrophobic rhamnolipid congeners was observed comparing with the same medium without OMW. OMW is a hazardous waste which disposal represents a serious environmental problem; therefore, its valorization as a substrate for the production of added-value compounds such as rhamnolipids is of great interest. This is the first report of rhamnolipid production using a mixture of these three agro-industrial by-products, which can be useful for the sustainable production of rhamnolipids.