Valorization of agro-industrial wastes towards the production of rhamnolipids

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 5.1 g of rhamnolipid per liter in flasks and reactor, respectively, with critical micelle concentrations as low as 13 mg/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.

This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI- 01-0145-FEDER-006684). The authors also thank the FCT for the financial support under the scope of the Project RECI/BBBEBI/ 0179/2012 (FCOMP-01-0124-FEDER-027462). E.J. Gudiña was supported by the Post-Doctoral fellowship CEB-BPD/01/2015/07 from the project UID/BIO/04469/2013, financed by FCT. A.I. Rodrigues was supported by the doctoral Grant SFRH/BD/111600/2015 provided by FCT.