Efficient β-galactosidase immobilized on glycidyl methacrylate polyHIPE

Abstract

Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monoliths (PolyGMA) were synthesized by high internal phase emulsion (HIPE) templating and polymerisation. The porous monoliths exhibited a hierarchical porous structure with primary pores (cavities, average diameter 35 μm) interconnected by secondary pores (average diameter 5 μm). FTIR spectroscopy confirmed the chemical composition and identified characteristic functional groups of both GMA and EGDMA. The polyGMA materials were ground and sieved to obtain particles between 710 μm and 1000 μm in diameter, which were subsequently used to immobilize the enzyme β-galactosidase. Immobilization was performed using two methods, namely direct binding via epoxide groups and binding after the activation with glutaraldehyde. The glutaraldehyde method resulted in higher enzyme loading (0.43 mg of enzyme per 100 mg of polyGMA) and significantly improved catalytic activity compared to direct binding. The immobilized β-galactosidase was used for lactose hydrolysis under various conditions using both batch and flow-through reactors. Optimal activity was observed at pH 6.5 and 35 °C, with kinetic parameters v_max = 0.64 mmol L⁻¹∙min⁻¹ and K_M = 38.8 mmol mol⁻¹. Reuse tests showed stable performance over five cycles. Comparatively, non-porous polyGMA exhibited negligible enzymatic activity compared to polyHIPE supported enzyme. In addition, lactose hydrolysis was investigated in a flow-through system at different flow rates (0.5–2.5 mL min⁻¹). The highest conversion (100 %) was observed at a flow rate of 0.5 mL∙min-¹, while a higher flow rate of 2.5 mL∙min-¹ resulted in a lower conversion (approx. 35 %), both at the lactose concentration of 4 g L⁻¹.