β-galactosidase-catalyzed synthesis of 3-O-β-D-galactopyranosyl-sn-glycerol: Optimization by response surface methodology

Abstract

In this study, the synthesis of 3-O-β-D-galactopyranosyl-sn-glycerol (GG) was performed by the reverse hydrolysis of D-galactose and glycerol using β-galactosidase from Kluyveromyces lactis. Four process variables, reaction temperature (30.0–45.0 °C), reaction time (24–48 h), enzyme concentration (150.00–350.00 U/mL), and substrate molar ratio (glycerol:D-galactose, 7.5:12.5 mmol/mmol) were investigated and optimized via response surface methodology (RSM) for optimal GG synthesis. Both quadratic equations and the optimal reaction conditions were established. Results showed that the four variables, i.e., reaction temperature, reaction time, enzyme concentration, and substrate molar ratio had significant (p < 0.0001) effects on the synthesis of GG. The optimal reaction conditions were identified as 350.00 U/mL of β-galactosidase concentration and 8.65:1.00 of substrate molar concentration ratio (glycerol: D-galactose) at 39.8 °C and 48 h of reaction. Under these conditions, the GG concentration was 140.03 g/L and GG yield was 55.71%, which both were close to the predicted values (143.26 g/L and 56.73%). This finding proves the RSM to be a useful tool in optimizing process conditions for GG synthesis.