EPS production by A. ferrooxidans through stimulation with exogenous galactose in the bioleaching of pyrite

PAVEZ B., SAAVEDRA A., DIAZ M., GENTINA JC

Antofagasta

Simposio; International Biohydrometallurgy Symposium; 2013

GECAMIN

Extracellular polymeric substances (EPS) play an important role in the adhesion of bacteria to metal sulphides, biofilm formation and efficiency of the bioleaching process. Previous studies suggested a potential connection between galactose and EPS formation. In this context this research focuses on the influence to the presence of exogenous galactose in the bioleaching to pyrite. For this were performed 5 sub cultures to A. ferrooxidans strain in shake flasks with 200 ml of fermentation medium at 30°C,  200 rpm, 40 g.L-1 pyrite and an pH initial of 1.8, to which was determined the kinetic of bioleaching to pyrite during 15 days. Assays were performed in a medium supplemented with exogenous galactose (0.25% w/v) and without exogenous galactose (control) both with an initial concentration of ferric sulphate in the first three sub cultures of 5 g.L-1, decreasing in the last two sub cultures to 2.5 g.L-1. Visualized by confocal laser scanning microscopy (CLSM), samples to days 1 and 15 of each sub cultures in both conditions, the cells were labelled with propidium iodide and carbohydrates of EPS with Wheat Germ Agglutinin (WGA), obtained on the 15th day of the fifth sub culture EPS volume for the control of 3.06 μm3/μm2 on the mineral surface and in the presence of exogenous galactose 7.16 μm3/μm2 on the mineral surface. Was also observed that in the fifth sub culture the volumetric productivity in the control was 0.0065 gr.L-1.hrs-1 and in the presence of exogenous galactose was 0.0076 gr.L-1.hrs-1. The results reveal that galactose in bioleaching to pyrite stimulates EPS´s production and  may favour the bioleaching process.