Advances in the Production of D-Tagatose Using L-Arabinose Isomerase.

D-tagatose is a rare sugar that occurs naturally and combines high sweetness with a low caloric value. It has several beneficial effects, including anticariogenic activity, modulation of the intestinal microbiota, and potential benefits for diabetes management. It is used as a novel sweetener and pharmaceutical excipient in the food and pharmaceutical industries. Currently, D-tagatose is produced mainly through chemical synthesis and biocatalysis. The chemical preparation of D-tagatose requires complex product purification and entails high waste-treatment costs, while biological preparation of D-tagatose offers high catalytic efficiency, mild reaction conditions, and fewer by-products. Therefore, in recent years, the biocatalytic conversion of D-galactose into D-tagatose using L-arabinose isomerase (L-AI) has attracted considerable attention, prompting extensive efforts to develop more economical and environmentally friendly production methods. To date, L-AI from various microbial sources has been identified and characterized, and researchers have engineered L-AI into a more effective biocatalyst through mutagenesis to improve process feasibility. This paper comprehensively reviews the current status and the latest advancements in the synthesis of D-tagatose from the perspective of biocatalysis.