Nanofiltration potential for the purification of highly concentrated enzymatically produced oligosaccharides

tThe performance of five commercial nanofiltration (NF) membranes was evaluated in thefractionation of enzymatically produced galacto-oligosaccharides (GOS). Filtration experi-ments were performed by modifying the solute concentration (10.5-40oBrix) and effectivetransmembrane pressure (TMPe) from 5 to 40 bar.In terms of flux and apparent rejection (Rap), thin film composite membranes (ATF andNFA) resulted inadequate. Polyamide membrane (GE) showed a better performance in termsof low Rapfor mono and disaccharides, as well as a negligible fouling; however, a strongreduction of flux was observed when increasing the solute concentration.Polyethersulphone (PES) membranes (NP030 and NP010) showed a very good performancein terms of low Rapvalues for monosaccharides and disaccharides at TMPevalues lowerthan 25 bar. Membrane NP010 showed the highest flux at all the operating conditions inves-tigated, producing total rejection of GOS at 40 bar with high potential for their concentration;however, selectivity could not be controlled because of the high Rapin lactose. At an oper-ating TMPeof 20 bar, GOS were fractionated with sustainable fluxes (28 kg/m2/h) and a goodselectivity, even when highly concentrated solutions (40oBrix) were treated, demystifyingthe limitation of nanofiltration as a downstream operation for treating highly concentratedsolutions.