Engineering a Synthesis Platform of Galactosylglycerol Based on Whole Cells with Surface-Displayed β-Galactosidase via Transglycosylation Catalysis and Glucose Consumption

Galactosylglycerol (GG) is a valuable glycoside formed by linking galactose to the hydroxyl group of glycerol via a glycosidic bond, serving as the key synthetic precursor of galactosylglycerides. Herein, we report an efficient synthetic route for GG via the transglycosylation activity of β-galactosidase BgaD-D. Four surface display systems of Escherichia coli were evaluated, and AIDA-I-BgaD-D demonstrated the highest enzyme activity (12.84 U/mL) and display ratio. Under optimized reaction conditions, the highest GG conversion rate of 86.03% was obtained after 12 h, overmatching the catalytic performance of reverse hydrolysis in previous studies. Subsequently, a glucose consumption system based on cell metabolism was established, achieving an outstanding GG purity (in total sugar) of 93.28% and a recovery rate of 91.31%, guaranteeing the effective preparation of GG by a dextran gel chromatography column. This work demonstrates a sustainable and efficient route for GG synthesis, providing a novel and feasible pathway for biomanufacturing of related derivatives.