Entrapment of viable microorganisms by SiO2 sol-gel layers on glass surfaces: trapping, catalytic performance and immobilization durability of Saccharomyces cerevisiae.

Yeast cells are immobilized into SiO2-sol layers coating glass sheets, starting from a SiO2-sol dispersion of viable cells and using the dip-coating method for deposition on the glass surface. The trapped biocatalyst survives experimental working-up and displays kinetic behavior excluding mass transport interference during sucrose degradation. The morphological and other physical features of SiO2-sol layers do not exclude viability and cell reproduction: prolonged contacts between immobilized system and substrate favour discharge of bud cells in solution. The phenomenon is suppressed by coating the SiO2-sol layer with a film composed of triethoxysilane and diethoxymethylsilane. This fact is attributed to the mechanical features of this film, which displays a tensile strength sufficient to contrast the tensile stress exerted by cell reproduction.