Dual-enzyme co-immobilization for the one-pot production of glucose 6-phosphate from maltodextrin

D-tagatose (D-tag) is a natural yet rare hexose that can be used as a functional sweetener owing to its hypoglycemic and anticaries properties. A four-step enzymatic cascade reaction was performed to synthesize d-tagatose from maltodextrin. In this study, we constructed a catalytic cascade system by co-immobilizing α-glucan phosphorylase (αGP) and phosphoglucomutase (PGM) on Duolite A568 exchange resin to produce glucose 6-phosphate (G6P), a precursor of d-tagatose. Our results showed that the thermal stability of co-immobilized αGP&PGM was enhanced comparing to free enzymes. Co-immobilized αGP&PGM retained 63.4% activity after incubating at 75 °C for 36 h, whereas free enzymes retained only 12% activity. Moreover, the relative activity of co-immobilized αGP&PGM was consistently maintained above 78.5% after eight cycles of reuse, and its storage stability was approximately eleven times higher than that of the free enzymes after storage at 4 °C for 60 days. Notably, we successfully co-immobilized dual enzymes on the resin using poly (ethylene glycol) diglycidyl ether, which was found to be more effective than glutaraldehyde. The results suggested that co-immobilized αGP&PGM could act as a promising catalyst for the one-pot production of G6P and be used in the starting pathway for the further production of d-tagatose.