Effect of various parameters on viability and growth of bacteria immobilized in sol–gel-derived silica matrices |
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Authors: | Gisela S Alvarez María L Foglia Guillermo J Copello Martín F Desimone Luis E Diaz |
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Institution: | (1) Cátedra de Química Analítica Instrumental, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956 Piso 3, (1113) Buenos Aires, Argentina;(2) National Research Council (CONICET), Buenos Aires, Argentina |
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Abstract: | Immobilized bacteria are being extensively used for metabolite production, biocatalysts, and biosensor construction. However,
long-term viability and metabolic activity of entrapped bacteria is affected by several conditions such as their physiological
state, the presence of high-osmolarity environments, porous structure and shrinkage of the matrix. The aim of this work was
to evaluate the effect of various parameters on bacteria immobilized in sol–gel-derived silica matrices. With this purpose,
we evaluated the stress of immobilization over bacteria cultures obtained from different growing states, the effect of cell
density and bacteria capability to proliferate inside matrices. Best results to attain longer preservation times were obtained
when we immobilized suspensions with an optimized bacterial number of 1 × 107 cfu/gel in the presence of LB medium using aqueous silica precursors. Furthermore, the impact of osmotic stress with the
subsequent intracellular trehalose accumulation and the addition of osmolites were investigated. Shorter preservation times
were found for bacteria immobilized in the presence of osmolites while trehalose accumulation in stressed cells did not produce
changes on entrapped bacteria viability. Finally, nutrient addition in silica matrices was studied indicating that the presence
of a carbon source without the simultaneous addition of nitrogen was detrimental for immobilized E. coli. However, when both carbon and nitrogen sources were present, bacteria were able to survive longer periods of time. |
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Keywords: | Additives Bacteria Escherichia coli Immobilization Living cells Sol– gel |
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