Comparison of the efficiency of different NF membranes for the enrichment of milk oligosaccharides from bovine milk

Oligosaccharides in milk (MOS) have been reported in the literature to exert various bioactivities and to modulate the immune system. However, processes to obtain milk oligosaccharides on industrial scale as food ingredients are currently not available. Therefore, the aim of the study on hand was the evaluation of different nanofiltration (NF) membranes for the enrichment of MOS from bovine milk. Moreover, a transfer of the NF process from laboratory to pilot plant and industrial scale was performed. The immunostimulatory effect of the MOS concentrates was studied by the activity of NF kappa B in human embryotic kidney cells (HEKnf kappa bRE-cells). NF was carried out with lactose hydrolyzed skimmed and ultrafiltered milk permeate by application of different membranes. The quantification of MOS was determined by high-pH anion-exchange chromatography with pulsed amperometric detection and parallel online electrospray ion trap mass spectrometry. The enrichment of MOS (3-sialyl-lactose, 6-sialyl-lactose, N-acetylgalactosaminyl-lactose) on laboratory, pilot plant and industrial scale was achieved by the retention of these oligosaccharides of at least 50 % in NF retentate. The content of MOS in relation to total sugar content in the retentate from NF on industrial scale was 100-fold higher than in the initial sample. The MOS retentates and the standards (3-sialyl-lactose, 6-sialyl-lactose) exhibited increased NF kappa B activity in HEKnf kappa bRE-cells. Although there exist a few studies about the enrichment of MOS by NF, this is the first report about a screening of the efficiency of different NF membranes for the enrichment of MOS on different technological scales of production.