Production of recombinant proteins by sol–gel immobilized Escherichia coli

The aim of this work was to study the functionality and quantitative level of recombinant protein produced from bacteria immobilized and preserved in sol–gel matrices. Matrices prepared from two precursors, silicon dioxide and tetraethoxysilane, were studied. In previous works we analyzed the number of viable cells and level of recombinant protein production from cultures started with immobilized Escherichia coli, stored in sealed tubes at 4 and 20 °C. We observed that the amount of bacteria in silicon dioxide derived matrix conserved in the same order of magnitude as before immobilization, during 2 months, but those in an alkoxide derived matrix decrease until no viable cells were detected at both 4 and 20 °C after 42 days. In this work, immobilized bacteria were used as culture starter to produce recombinant proteins with a yield comparable with glycerol stocks. T-cell proliferation and gel filtration assays suggest that SAgs produced from cultures started with sol–gel immobilized bacteria retain their biological activity. Affinity assays using a resonant biosensor showed that Streptococcal Superantigen (SSA) has affinity for human Vβ5.2 produced from sol–gel immobilized bacteria with KD = 7.5 μM. These results contribute to the development of methods for microbial cells preservation under field conditions.