Fifty-three plant-associated microorganisms were investigated for their ability to convert sucrose to its isomers. These microorganisms included one Dickeya zeae isolate and 7 Enterobacter, 3 Pantoea, and 43 Pectobacterium species. Eleven out of the 53 strains (21%) showed the ability to transform sucrose to isomaltulose and trehalulose. Among those, Pectobacterium carotovorum KKH 3-1 showed the highest bioconversion yield (97.4%) from sucrose to its isomers. In this strain, the addition of up to 14% sucrose in the medium enhanced sucrose isomerase (Slase) production. The Slase activity at 14% sucrose (47.6 U/mg dcw) was about 3.6-fold higher than that of the negative control (13.3 U/mg dcw at 0% sucrose). The gene encoding Slase; which is comprised a 1776 bp open reading frame (ORF) encoding 591 amino acids, was cloned from P. carotovorum KKH 3-1 and expressed in Escherichia coil. The recombinant Slase (PCSI) was shown to have optimum activity at pH 6.0 and 40 degrees C. The reaction temperature significantly affected the ratio of sucrose isomers produced by PCSI. The amount of trehalulose increased from 47.5% to 79.1% as temperature was lowered from 50 degrees C to 30 degrees C, implying that Slase activity can be controlled by reaction temperature. (C) 2013 Elsevier Inc. All rights reserved.