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 bioca talyst 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 ex clude viability and cell reproduction: prolonged contacts between immo bilized system and substrate favour discharge of bud cells in solution , The phenomenon is suppressed by coating the SiO2-sol layer with a fi lm composed of triethoxysilane and diethoxymethylsilane. This fact is attributed to the mechanical features of this film, which displays a t ensile strength sufficient to contrast the tensile stress exerted by c ell 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.