Abstract
Recently, oligosaccharides have been acknowledged to have physiological activity and many of them have been used for food. These oligosaccharides are generally produced from various food materials using bioreactors are separation systems. We studied the separation properties of nanofiltration membranes for model oligosaccharide solutions, and applied them to purify oligosaccharides extracted from Jerusalem artichoke (Helianthus tuberosus L.) to develop an oligosaccharide purification system with nanofiltration processes. The observed rejections (Robs) and the permeate fluxes (Jv) of four membranes, G 5, G 10, G 20 and G 50, for oligosaccharides having smaller pore sizes in the order in G 5<G 10<G 20<G 50, were evaluated by the batch filtration at various pressures. In all of the membranes, Jv increased linearly with pressure. The Robs increased with the molecular weight of oligosaccharide. The Robs for each oligosaccharide became low in sequence from G 5, G 10, G 20 and G 50. It appeared that G 5, G 10 and G 20 had effective pore sizes to separate the oligosaccharides, and G 50 could remove high molecular weight molecules over 10, 000 Daltons. The extract of Jerusalem artichoke contained fructo-oligosaccharides linking from 2 to 10 sugar units. In the extract filtrations, membranes rejected oligosaccharides almost in the same level as the model filtration, however, the fluxes decreased with increase in the concentration of saccharide and/or high molecules in the extract.
