The purpose of this study was the production of maltobionic acid, in the form of sodium maltobionate, by Z. mobilis cells immobilized in polyurethane. The in situ immobilized system (0.125-0.35mm) was composed of 7g polyol, 3.5g isocyanate, 0.02g silicone, and 7g Z. mobilis cell, at the concentration of 210g/L. The bioconversion of maltose to sodium maltobionate was performed with different cell concentrations (7.0-9.0 gimobilized/Lreaction_medium), temperature (30.54-47.46°C), pH (5.55-7.25), and substrate concentration (0.7-1.3mol/L). The stability of the immobilized system was evaluated for 24h bioconversion cycles and storage of 6months. The maximum concentration of sodium maltobionate was 648.61mmol/L in 34.34h process (8.5 gdry_cell/Lreaction_medium) at 39°C and pH 6.30. The immobilized system showed stability for 19 successive operational cycles of 24h bioconversion and 6months of storage, at 4°C or 22°C.