Synthesis of novel galactose containing chemicals by β-galactosidase from Enterobacter cloacae B5

The β-galactosidase from Enterobacter cloacae B5 was employed to synthesize novel galactose containing chemicals (GCCs) using mannitol, sorbose, and salicin as acceptors in the presence of o-nitrophenyl-β-d-galactopyranoside (oNPGal) as donor. The influences of the process parameters on GCC synthesis using mannitol as an acceptor, including effects of variations in initial substrate concentration, reaction time, and temperature, were studied in detail. The mannitol derivative reached a yield of 14.6% when the enzyme was used in the presence of 30 mM oNPGal and 60 mM mannitol at 50 °C for 10 min. The sorbose and salicin derivatives reached yields of 19.4% and 25.2%, respectively, under the same conditions except for acceptor concentrations. Through analysis of ESI-MS and NMR spectroscopy, the three derivatives were identified to be β-d-galactopyranosyl-(1 → 1′)-d-mannitol, β-d-galactopyranosyl-(1 → 1′)-l-sorbose, and 2-(hydroxymethyl) phenyl β-d-galactopyranosyl-(1 → 6′)-β-d-glucopyranoside.