Hybrid organic- inorganic matrices for bacteria immobilization: effect of storage relative humidity.

MARÍA L. FOGLIA; GISELA S. ALVAREZ; MARTÍN F. DESIMONE; LUIS E. DIAZ

Villa Carlos Paz, Córdoba, Argentina

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en; 2008

Hybrid materials used for bacteria immobilization can be defined as nanocomposites with organic and inorganic components. The aim of this work was to combine them in order to obtain materials that could find a compromise between different properties  such as mechanical strength, permeability, moisture and immobilized bacteria viability.  In this respect, we used sodium silicate as the inorganic component and sodium alginate, polyvinylalcohol (PVA), polyethyleneglycol (PEG), polyoxyethylene 20 cetyl ether (Brij 58)  or carboxymethylcellulose (CMC) as the organic part. We also exposed every type of hybrid material to different storage relative humidities ranging from 15 % to 58 %. Viability of entrapped Escherichia coli was evaluated as well as the percentage of residual water and physical integrity of materials. When nutrients were added together with bacteria, no significant differences were found among the five hybrid and the inorganic silicate matrices. High bacteria counts (107/108) were observed for humidities above 15 % but for bacteria stored at 15% of relative humidity there was a decreased in the viability of approximately four orders of magnitude (104). When no nutrients were added, bacteria count was around 104 for every humidity condition evaluated and some differences were found among matrices. Hybrid materials used for bacteria immobilization can be defined as nanocomposites with organic and inorganic components. The aim of this work was to combine them in order to obtain materials that could find a compromise between different properties  such as mechanical strength, permeability, moisture and immobilized bacteria viability.  In this respect, we used sodium silicate as the inorganic component and sodium alginate, polyvinylalcohol (PVA), polyethyleneglycol (PEG), polyoxyethylene 20 cetyl ether (Brij 58)  or carboxymethylcellulose (CMC) as the organic part. We also exposed every type of hybrid material to different storage relative humidities ranging from 15 % to 58 %. Viability of entrapped Escherichia coli was evaluated as well as the percentage of residual water and physical integrity of materials. When nutrients were added together with bacteria, no significant differences were found among the five hybrid and the inorganic silicate matrices. High bacteria counts (107/108) were observed for humidities above 15 % but for bacteria stored at 15% of relative humidity there was a decreased in the viability of approximately four orders of magnitude (104). When no nutrients were added, bacteria count was around 104 for every humidity condition evaluated and some differences were found among matrices.