Display of a sucrose isomerase on the cell surface of for synthesis of isomaltulose from sugar cane by-products.

Isomaltulose (α-d-glucopyranosyl-1,6-d-fructofuranose) is an important industrial and raw food material, which can be synthesised from the by-products of sugar cane processing through sucrose isomerization conversion. In this study, we constructed a surface display vector of sucrose isomerase from (SIase) by a glycosylphosphatidylinositol (GPI)-cell wall protein (CWP) anchor signal sequence and successfully displayed SIase on the cell surface of thereby increasing the conversion efficiency of isomaltulose. The highest activity of the displayed SIase reached 2910.3 U/g of cell dry weight. Compared with the free SIase, the displayed enzyme showed good stability at a broad range of temperatures (20-45 °C). The half-life at 40 °C increased from 62 to 141 min and the deactivation constants ( ) reached 4.91 × 10 min. Using low-cost cane molasses as the substrate, the isomaltulose conversion rate remained at 85% even after 9 batches were processed, which is a highly desired outcome for industrial use.