Immobilization of yeast cells in hydroxyethylmethacrylate gels

Whole cells of Saccharomyces cerevisiae were entrapped in polymers of 2-hydroxyethylmethacrylate and sucrose hydrolysis catalysed by its invertase was investigated. Analysis of the experimental results confirmed that diffusional resistance to mass transfer of reactant and product was not induced by immobilization. For the yeast cells in the hydrogel, invertase activity obeyed Michaelis-Menten kinetic and the value of Km (40 mM) was the same as that for yeast cells in bulk phase. The recovery of biocatalyst activity ranged between 17% and 23%, depending on immobilization temperature; the optimum pH range was found to be slightly wider. Storage stability at refrigerator temperature was quite satisfactory; invertase half-life was 267 days. Operational stability of immobilized cells at 45°C (half-life 110 days) was almost twice that of free cells. Finally, cell distribution in the polymer, observed with a scanning electron microscope, was found to be uniform.