Isomaltulose production via yeast surface display of sucrose isomerase from Enterobacter sp. FMB-1 on Saccharomyces cerevisiae

The gene encoding sucrose isomerase from Enterobacter sp. FMB-1 species (ESI) was displayed on the cell surface of Saccharomyces cerevisiae EBY100 using a glycosylphosphatidylinositol (GPI) anchor attachment signal sequence. Fluorescence activated cell sorting (FACS) analysis and immunofluorescence microscopy confirmed the localization of ESI on the yeast cell surface. The displayed ESI (dESI) was stable at a broad range of temperatures (35–55 °C) and pHs (pH 5–7) with optimal temperature and pH at 45 °C and pH 7.0, respectively. In addition, the thermostability of the dESI was significantly enhanced compared with the recombinant ESI expressed in Escherichia coli. Biotransformation of sucrose to isomaltulose was observed in various ranges of substrate concentrations (50–250 mM) with a 6.4–7.4% conversion yield. It suggested that the bioconversion of sucrose to isomaltulose can be successfully performed by the dESI on the surface of host S. cerevisiae.