Sucrose isomerase (Slase) has been used to produce palatinose, a structural isomer of sucrose, which has many beneficial health properties, such as low-glycemic and low-insulinemic indices. A gene corresponding to Slase from Enterobacter sp. FMB-1 was expressed in Lactococcus lactis MG1363 using the P170 expression system. The autoinducible promoter (P170) and an optimized signal peptide (SP310mut2) were used to induce and secrete Slase in L lactis. One-step Ni-NTA affinity chromatography and Western blot analysis demonstrated that Slase was successfully secreted to the culture supernatant, although 60% of the recombinant enzymes were retained inside the cells. The production of the recombinant Slase was highly correlated with pH (pH 6) and glucose concentration (30 g/L) of the medium. The extracellularly produced recombinant Slase was functionally active, effectively transforming 50 g/L sucrose to 36 g/L palatinose, with a conversion rate of 72% in the culture supernatant. (C) 2010 Elsevier Ltd. All rights reserved.