Optimization of fermentation conditions for whole cell catalytic synthesis of D-allulose by engineering Escherichia coli.

D-allulose/D-psicose is a significant rare sugar with broad applications in the pharmaceutical, food, and other industries. In this study, we cloned the D-allulose 3-epimerase (DPEase) gene from Arthrobacter globiformis M30, using pET22b as the vector. The recombinant E. coli strain pET22b(+) was successfully constructed and expressed, providing an efficient whole-cell catalyst for converting inexpensive D-fructose into D-allulose. Subsequently, we optimized the induction and incubation conditions step by step using the single-factor method and used Lactobacillus plantarum(LAB) 217-8 to enhance the purity of D-allulose in the system. Ultimately, the BL21/pET22b(+)-E. coli strain achieved a conversion rate of up to 33.91% under optimal conditions, converting D-fructose to D-allulose. After purification, the purity of D-allulose reached 64.73%. Efficient production of D-allulose is a significant achievement, paving the way for future probiotic applications in its conversion.