The demand of rare earth elements (REE) has grown over the past decades due to their importance in high technology devices such as wind turbines, superconductors, rechargeable batteries, autocatalytic converters, magnets, or LED lighting. The development of clean mining processes is gaining interest and the biomining of REE is mainly focused on monazite using phosphate solubilizing microorganisms. The members of the genus Burkholderia can dissolve phosphorous from inorganic rocks. Furthermore, several species of Burkholderia are able to produce biosurfactants named rhamnolipids. Nevertheless, rhamnolipid interactions with REE have been poorly investigated. The aim of the present work is the study of the solubilization of monazite and the recovery of REE using the bacterium Burkholderia thailandensis, and the influence of the rhamnolipids produced by the bacteria in the REE mobilization. B. thailandensis grown in nutrient broth with 1% monazite (w/v) reached 8.3 mg·l−1 REE after 15 days. To produce rhamnolipids, B. thailandensis was grown in medium supplemented with 10% glycerol and the biosurfactants were extracted. The critical micelle concentration (CMC) was determined: 94.45 mg·l−1 for commercial rhamnolipids and 60.41 mg·l−1 for purified rhamnolipids. The maximum REE solubilization was obtained at CMC reaching 9.36 mg·l−1 with commercial rhamnolipids and 5.13 mg·l−1 with rhamnolipids produced by B. thailandensis E264.

The authors are grateful for the financial support given by the Spanish Ministry of Science and Innovation to fund this work (project PID2021-125797OB-I00).

Peer reviewed

11 p.-8 fig.