LEAD BIOSORPTION BY LACTIC ACID BACTERIA ISOLATED FROM KEFIR

GERBINO, O. E.; TYMCZYSZYN E,; MOBILI, P; A. GOMEZ ZAVAGLIA

Villa Carlos Paz. Cordoba. Argentina.

Congreso; VI Congreso de la Sociedad Argentina de Microbiología General; 2009

SAMIGE

Lead biosorption by lactic acid bacteria isolated from kefir E. Gerbino, E.E. Tymczyszyn, P. Mobili, A. Gómez-Zavaglia Centro de Investigación y Desarrollo en Criotecnología de Alimentos -CIDCA-(UNLP-CIC-CONICET) E-mail: egerbino@cidca.org.ar Lead is a toxic heavy metal, that unlike many other toxic compounds is not degradable and tends to accumulate in the exposed organisms (WHO, 1995). Food and water are the primary sources of lead exposure. In spite of the fact that natural concentrations of lead in water rarely exceed the guideline value (10 ug/l) (WHO 2006), different anthropogenic sources, such as fertilizers used in agriculture, metal mines and smelters, can increase the concentration of this metal. For this reason, removal of lead from food and water represents a challenge. Available conventional methods (precipitation, flocculation, ion exchange, and membrane filtration) for removal metals from water at low concentrations are claimed to be expensive and inefficient (Atkinson et. al 1998). In this work, two strains of Lactobacillus kefir (Lactobacillus kefir JCM 5818 and Lactobacillus kefir CIDCA 8348) isolated from kefir grains were assessed for their adsorption properties to remove lead from water. Microorganisms were grown in 10 ml LAPTg (Raibaud, P. et al 1973) broth at 30 ºC for 48 h, harvested and washed twice with milli Q water. The pellets obtained were suspended in 1 ml of different concentrations of lead (0-50 mg/l) and further incubated for 24 hs at 30 ºC. After that, the suspensions were centrifuged and the lead concentration in the supernatant was measured by atomic absorption spectrometry. Lead removal ability of the studied strains was evaluated using a Langmuir isotherm according to Davis et al., 2003. After that, the maximum binding capacity (q max) and the coefficient related to affinity of binding (b) were determined for each strain. These parameters (q max and b) were calculated as 26.9 mg/g and 0.32 mg/l for L. kefir 8348 and 44.6 mg/g and 0.36 mg/l for L. kefir 5818, respectively. The binding of lead increased with the metal concentration until a saturation point was reached. The maximum lead percentage removal was higher for L. kefir 5818 than for L. kefir 8348, and this could be assigned to differences in the chemical composition of the bacterial surfaces. Taking into account the high efficiency of both strains in lead removal, they could be considered as an interesting alternative in decontamination processes.