(A) suspension of Kluyveromyces marxianus cells (256 mg ml(-1)) with inulinase activity were immobilized in barium alginate treated with glutaraldehyde. After five runs of inulin hydrolysis, the immobilized cells system had up to 85% residual activity. When beads were heat treated at 65 degreesC for 5 min, the hydrolysis rate of inulin was improved without affecting the stability of the system in five hydrolysis batches. Immobilized enzyme was thermostable at temperatures between 45 and 65 degreesC. The system efficiency (eta) was highly dependent on bead diameter, reaching values up to 0.79 with a bead diameter of 1.43 mm. Inulin diffused into alginate matrix with a diffusion coefficient (D-E) of 2.5 x 10(-6) cm(2) s(-1), resulting in apparent kinetic values of the immobilized enzyme of K-m' = 0.522 mM and V-max' = 113.7 mu mol min(-1); while values for free enzyme were 0.15 mM and 250 mu mol min(-1). Thiele module values (Phi) were close to 1, indicating that the limitations of the system were due to diffusional resistance of substrate.