Bioaccumulation of lithium by Bacillus pumilus isolated from High Altitude Andean Lakes

CURIA, VICTORIA; BELFIORE, C; KURTH, D; FARIAS, ME

Córdoba

Congreso; XI Congreso Argentino de Microbiologia General SAMIGE; 2015

SAMIGE

p { margin-bottom: 0.1in; direction: ltr; line-height: 120%; text-align: left; widows: 2; orphans: 2; }Lithium(Li) is a metal that has several industrial applications and due itslarge storage capacity, low weight and long life, Li ion rechargeable batteries are preferred for electronic devices. In recent years therewas an exponential increase in demand for this mineral. It is widely distributed in nature, the largest reserves of Li (over 85%) are inthe so-called "triangle of lithium" the Salar de Atacama in Chile, Salar de Uyuni in Bolivia and Salar del Hombre Muerto in Argentina, being Argentina the third world producer of Li.The recovery of Li from salar brines involves solar evaporation of the brine in several stages until its content reaches 6%, evaporating large quantities of water. The extremophile bacteria are an important asset to use in bioremediation and bioleaching, however at the moment there are few reports of the bacterial ability to biosorb Li.In this regard, the aim of the present work was to evaluate the ability of bacteria isolated from Andean lakes (HAAL), to grow in presence of Li and the faculty to recover this metal by biosorption, as that could be used in non-metalliferous mining.B.pumilus Act108 is a Gram-positive bacterial strain, isolated from Laguna Negra (Catamarca, Argentina). The first assays for determination of Li tolerance were carried out in plates containing LB agar medium supplemented with LiCl 0.7 and 1.1 M. Plates without metals were included as control. After incubation at 30° C for 48hours, the strain showed good growth in either case. Cell growth onliquid cultures was monitored by optical density at 600 nm using a spectrophotometer Ultrospec 10. Cells were resuspended at an initialOD600: 0.05 in fresh LB and LB + 0.7M Li. The strain was incubated at160 rpm and 30° C for 24 hours, samples were taken periodically and OD was determined. The growth curve shows the ability to adaptation of the cells to grow in presence of Li, since they showed a behavior similar to control cells.The accumulation of Li by B. pumilus was examined in several conditions of pH, time, volume and molarity of the Li solution. Based on the results of all the tested conditions, the highest accumulation was obtained with the following method: 70 mg dry wt of microorganisms were resuspended in 45 ml of solution (pH 7.5) containing 0.1 M Li and the suspension was shaken for 3 h at room temperature. The supernatant was recovered by centrifugation. The amount of metal ions accumulated by the cells was determined by measuring the metal content in the supernatant using an inductively coupled plasma optical emission spectrometry (ICP-OES), the assay was performed in duplicate. The amount of Li accumulated on average was 39 mg/g dry wet cells (5619 µM/ g dry wet cells), representing 8,6 % of Li available. The results show that a high Li accumulating ability was exhibited by B. pumilus. Compared with results obtained by other authors our strain shows an increased capacity to bind Li.