Metal Biosorption by Surface layer from Bacillus species

ALLIEVI MARIANA C; SABBIONE FLORENCIA; PRADO ACOSTA MARIANO; PALOMINO MARÍA MERCEDES; RUZAL SANDRA M.; SANCHEZ RIVAS CARMEN

JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY

KOREAN SOC MICROBIOLOGY & BIOTECHNOLOGY

Año: 2011 vol. 21 p. 147 - 153

1017-7825

Abstract Cultures and spores from Gram positive bacteria were analyzed for their capacity of copper biosorption. Only Bacillus species endowed of Surface layer proteins (S-layers) like Bacillus sphaericus and B. thuringiensis, showed a significant absorption capacity. This capacity (nearly 50%) was retained after heating of cultures, thus supporting that structural elements of the envelopes, such as S-layers, are responsible for such activity. Purified S-layers from two Bacillus sphaericus strains had the ability to biosorb copper. Copper biosorption parameters were determined for strain B. sphaericus 2362 and after analyses by means of the Langmuir model, the affinity and capacity were shown to be comparable to other bacterial biosorbents. A competitive effect of Ca2+ and Zn2+, but not of Cd2+, was also observed, thus indicating that other cations may be biosorbed by this protein. Spores which have been shown to be proficient for copper biosorption were further analyzed for the presence of S-layer content. The retention of S-layers by these spores was clearly observed, and after extensive treatment to eliminate the S-layers, the biosorption capacity of these spores was importantly reduced. This is the first report for a direct correlation between S-layer content and metal biosorption.