A lipase [triacylglycerol ester hydrolase (EC 3.1.1.3)] was encapsulated in sodium alginate (AlgNa)/poly(vinyl alcohol) (PVA) microspheres. Spherical AlgNa/PVA beads were prepared by the ionotropic gelation of an AlgNa/PVA blend in the presence of calcium tetraborate (CaB4O7). The particles were spherical and had an average diameter of 400 mu m. The microspheres were studied with differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, and water transport by the equilibrium degree of swelling. The elevation of the glass-transition temperature of the microspheres indicated specific crosslinking reactions of the component polymers (AlgNa/PVA). FTIR spectra showed no evidence of a strong chemical interaction changing the nature of the functional groups of both AlgNa and PVA in the AlgNa/PVA blends. The water diffusion coefficients increased with increasing PVA content in the microspheres, indicating a decrease in the resistance to mass transfer through the AlgNa/PVA microsphere wall. The AIgNa/PVA microspheres were characterized by the Michaelis constant (Km) and the maximum reaction velocity (V-max), which were determined for both free and immobilized lipases. The enzyme affinity for the substrate (K-M/V-max) remained quite good after immobilization. (c) 2006 Wiley Periodicals, Inc.