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. Process performance is compared for all systems and transport limitations discussed as functions of porosity and specific surface area of the trapping supports studied here. © 1993.