Palatinose is a non-cariogenic disaccharide obtained from the enzymatic conversion of sucrose, used in food industries as a sugar substitute. Free and Ca-alginate immobilized cells of Erwinia sp. D12 were used to produce palatinose from sucrose. Palatinose production was studied in a repeated-batch process using different immobilized biocatalysts: whole cells, disrupted cells and glucosyltransferase. Successive batches were treated with the immobilized biocatalyst, but a decrease in palatinose production was observed. A continuous process using a packed-bed reactor was investigated, and found to produce 55-66% of palatinose during 17 days using immobilized cells treated with glutaraldehyde and a substrate flow speed of 0.56 ml min(-1). However, immobilized cells in a packed-bed reactor failed to maintain the palatinose production for a prolonged period. The free cells showed a high conversion rate using batch fermentation, obtaining a palatinose yield of 77%. The cells remained viable for 16 cycles with high palatinose yields (65-77%). Free Erwinia sp. D 12 cells supported high production levels in repeated-batch operations, and the results showed the potential for repeated reuse. (C) 2007 Elsevier B.V. All rights reserved.363202208