In recent decades, the production of palatinose has aroused great interest since this structural isomer of sucrose has an interesting potential. Using immobilized in chitosan Serratia plymuthica cells, a complete conversion of concentrated sucrose solutions into palatinose was achieved in a "batch"-type enzyme reactor. Under typical process conditions, the specific productivity was in the range of 0.76-1.15 h(-1) (kg sucrose converted, kg(-1) catalyst). The effect of the inlet sucrose concentration (30-70%), the reaction temperature of 30-60 degrees C and the residence time (Rt) of the substrate solution on the specific volumetric productivity of the biocatalyst in a tubular fixed-bed reactor during continuous sucrose conversion into palatinose was studied. Residence time of 1.7-3.0 h was necessary for the achievement of 98-100% conversion of sucrose at substrate concentration of 30-50%. Considerably longer residence time (4-5 h) was needed for reaching the same conversion rate of concentrated sucrose solutions (60-70%). The composition of the outlet sugar solutions was investigated. The highest palatinose content was achieved (similar to 94%), when 40% inlet sucrose solution was used. It decreased in the case of more concentrated inlet sucrose solutions, but not below 78%. Operational stability of 155 days was achieved. The final value of the cumulative productivity of the reactor during continuous process of conversion was 1488 kg of palatinose produced per dm(3) of biocatalyst. (c) 2006 Elsevier Inc. All rights reserved.