EVALUATION OF THE OPTIMAL CONDITIONS FOR LITHIUM REMOVAL IN AQUEOUS SOLUTIONS USING BACTERIA ISOLATED FROM THE SALAR DEL HOMBRE MUERTO

DIEDRICH, EMILIA; IRAZUSTA, VERÓNICA

Congreso; XVIII Congreso Argentino de Microbiología General, SAMIGE 2022; 2022

Sociedad Argentina de Microbiología General

Mining is one of the oldest activities of humanity and allows the extraction of a wide variety of elements present in the environment. Currently, one of the metals of great interest due to its wide range of applications is lithium (Li), being natural brines the most important reserves in the world. There are microorganisms naturally adapted to conditions of extreme salinity such as of those of the Argentine Puna. Recent studies have confirmed the interaction of halotolerant bacteria isolated from the Salar del Hombre Muerto with Li dissolved in aqueous solutions.In this work, the ability of three bacterial strains previously isolated from the Salar del Hombre Muerto, Bacillus sp. HX11, Bacillus sp. HA120A and Brevibacterium sp. SX139, to: i) grow at different LiCl concentrations; ii) produce biofilms; and iii) remove Li from solutions, was investigated.Growth was estimated as biomass production and evaluated using 96-well plates with nutrient broth and increasing concentrations of LiCl (0, 10, 20, 30, 40, 50, 60 and 70 g/l) by measuring for 48 h the optical density (OD) at 600 nm wavelength. The biofilm-forming capacity was evaluated at six days under the same conditions used for growth evaluation using crystal violet. The removal of Li from aqueous solutions was studied at different concentrations of Li (0.4; 0.45; 0.5; 1 and 1.5 mg/l) with 0.2 and 0.4 mg of cells, respectively, taking samples at time 0 (immediately after inoculating the cells), at 2 h and at 22 h. The quantification of Li remaining in the cell-free supernatant was carried out by quinizarin reagent, measuring the OD at 601 nm. The percentage of Li remaining in solution and the Specific Lithium Removal (SLR) were calculated.The three strains studied were able to grow in the lowest concentrations of LiCl (0, 10, 20 and 30 g/l), while tolerated the highest concentrations tested (40, 50, 60 and 70 g/l LiCl). Although all the strains were capable of producing biofilms at all the concentrations evaluated, Bacillus sp. HX11 and HA120A showed the highest production at the lowest concentrations of LiCl, and this biofilm production decreased as the LiCl concentration increased. Brevibacterium sp. SX139 showed the highest tolerance to LiCl however, it produced biofilms in significantly lower amounts than the other two strains. Bacillus sp. HX11 achieved the highest Li removal values, removing almost 100% of the Li in the 0.45 mg/l Li solution at 22 h of incubation, with an SLR of 2.24 mg Li/g cells. At the shortest incubation time, Bacillus sp. HX11 showed an SLR value of 1.88 mg Li/g cells in the presence of 1 mg/l Li. The three strains showed SLR values around 2 mg Li/g cells at the shortest incubation time in the presence of 1 mg/l Li, decreasing to zero value at 22 h. These bacterial strains have a great potential for metal removal and therefore can be considered as a promising alternative in soluble Li recovery processes.