Immobilization of maltogenase onto polyurethane microparticles from poly(vinyl alcohol) and hexamethylene diisocyanate

A series of porous polyurethane (PU) microparticles from poly(vinyl alcohol) (PVA) and hexamethylene diisocyanate (HMDI) using different ratios of components were obtained by one step method. Molar compositions of PU microparticles were estimated by determination of nitrogen, isocyanate and hydroxyl groups. PU carriers which were synthesized using optimal initial molar ratios of PVA and HMDI were applied for immobilization of maltogenase (MG) from Bacillus stearothermophilus. Immobilized enzyme exhibited higher catalytic activity and enhanced temperature stability in comparison with the native MG. Maximal loading 7.78 mg/g wet carrier was reached when PU microparticles with initial molar ratio of PVA and HMDI = 1:3 was used as a carrier for immobilization. The high efficiency of immobilization (EI) was obtained using PU microparticles when initial molar ratio of HMDI and PVA was 1:1–1:10. High stability of MG immobilized onto PU microparticles during storage was demonstrated. Immobilized starch hydrolyzing enzyme was successfully tested in batch and column type reactors for hydrolysis of potato starch. MG immobilized onto PU enables easy separation from the reaction medium and reuse of the immobilized preparation over seven reaction cycles in bath operation and at least three cycles in column type reactor.