Studies on Biological Production of Isomaltulose Using Sucrose Isomerase: Current Status and Future Perspectives

Isomaltulose, as a safe sucrose substitute, is widely used as a functional sweetener due to its promising properties, such as slower digestion, prolonged energy release, and less cariogenicity. The transformation of sucrose to isomaltulose by free sucrose isomerase (SIase) or microbial cells harboring the SIase gene has received considerable attention in the industry. Heterologous expression of SIase in food-safe grade strains has become a hot topic due to its broad applicability in the food industry. Thanks to rapid developments in genetic engineering technology, SIases from different sources have been heterogeneously expressed in Escherichia coli, which significantly increased the enzyme's titer. This review presents a systematic and detailed summary of the contemporary biotechnological approaches employed for isomaltulose production, including the source, structural determination, catalysis mechanism, heterologous expression, catalytic reaction condition optimization of SIase, and immobilization of cells. In addition, protein engineering, heterologous expression in food-grade safety strains, fermentation optimization strategies, and immobilization techniques of SIase are introduced in detail. Towards the end, the review is wrapped up with the concluding remarks, and future strategies are outlined for improving the biological production of isomaltulose.Graphical Abstract Summary of biological isomaltulose production from sucrose catalyzed by sucrose isomerase.