2-O-α-D-glucosyl glycerol production by whole-cell biocatalyst of lactobacilli encapsulating sucrose phosphorylase with improved glycerol affinity and conversion rate.

BACKGROUND: 2-O-α-D-glucosyl glycerol (2-αGG) is a valuable ingredient in cosmetics, health-care and food fields. Sucrose phosphorylase (SPase) is a favorable choice for biosynthesis of 2-αGG, while its glucosyl-acceptor affinity and thermodynamic feature remain largely unknown, limiting 2-αGG manufacturing.

RESULTS: Here, three SPases were obtained from lactobacilli and bifidobacteria, and the one encoded by Lb. reuteri SDMCC050455 (LrSP) had the best transglucosylation ability, with 2-αGG accounting for 86.01% in the total product. However, the LrSP exhibited an initial forward reaction rate of 11.83/s and reached equilibrium of 56.90% at 110 h, indicating low glycerol affinity and conversion rate. To improve catalytic efficiency, the LrSP was overexpressed in Lb. paracasei BL-SP, of which the intracellular SPase activity increased by 6.67-fold compared with Lb. reuteri SDMCC050455. After chemically permeabilized with Triton X-100, the whole-cell biocatalysis of Lb. paracasei BL-SP was prepared and showed the highest activity, with the initial forward reaction rate improved to 50.17/s and conversion rate risen to 80.79% within 17 h. Using the whole-cell biocatalyst, the final yield of 2-αGG was 203.21 g/L from 1 M sucrose and 1 M glycerol.

CONCLUSION: The food grade strain Lb. paracasei was used for the first time as cell factory to recombinantly express the LrSP and construct a whole-cell biocatalyst for the production of 2-αGG. After condition optimization and cell permeabilization, the whole-cell biocatalyst exhibited 23.89% higher equilibrium conversion and 9.10-fold of productivity compared with the pure enzyme catalytic system. This work would provide a reference for large-scale bioprocess of 2-αGG.