Research Progress on Efficient Biocatalytic Synthesis of D-Allulose

D-allulose is a novel low-calorie rare sugar with special physiological functions, including blood sugar regulation and antioxidant effects. In present, the biological synthesis of D-allulose mainly utilized D-allulose 3-epimerase to catalyze the conversion of D-fructose into D-allulose. The large-scale biosynthesis of D-allulose using biological enzymes has primarily focused on improving the catalytic activity, thermal stability, and acid tolerance of D-allulose 3-epimerase to meet industrial production requirements. The research progress on the current status of D-allulose production and the latest advances in its biosynthesis, including molecular-directed modification of isomerases, ultra-high-throughput screening assisted by directed evolution, and novel enzyme immobilization strategies to enhance the industrial properties of D-allulose 3-epimerase were summarized. Furthermore, the application of whole-cell catalytic systems in D-allulose production was also discussed. The aim of this review was to provide a reference for the efficient and green biosynthesis of D-allulose and to propose challenges and possible solutions in industrial production.