Selective diffusion of glucose, maltose, and raffinose through calcium alginate membranes characterized by a mass fraction of guluronate

Abstract

Glucose was selectively separated from an aqueous solution of mixed sugars (glucose 180Da, maltose 342Da, and raffinose 504Da) by static diffusion, and not ultrafiltration, without the driving force of pressure. The calcium alginate membrane described in this study provides a simple technical medium for sugar separation. Excellent selectivity based on the molecular size of sugar was realized. The mass fraction of homopolymeric blocks of guluronate in alginate polymer chains (FGG) was defined as a gravimetric ratio of homopolymeric blocks of α-l-guluronate in sodium alginate to the total mass of the sodium alginate polymer. FGG was a key factor for regulating the mass transfer characteristics of the calcium alginate membrane. Two different FGG membranes were employed to assess the selective separation of glucose. The effective diffusion coefficient in the membrane (Deff) was determined from the mass transfer flux through the calcium alginate membrane. The effective diffusion coefficient in the FGG 0.56 membrane exhibited a 38-fold decrease in the mixed system of the three sugars, even when the molecular weight showed only a 2.8-fold increase from glucose to raffinose. In the FGG 0.18 membrane, the effective diffusion coefficient exhibited a 14-fold decrease. The mass fraction of guluronate blocks was a dominant factor that regulated the selective diffusion of the sugars. The design of a calcium alginate membrane based on the mass fraction of guluronate blocks is promising for desirable selective sugar separation in industrial applications.