Conjugation of oligosaccharides with casein

Abstract

In this study, sialyl oligosaccharides (SOs) were isolated from bovine colostrum using an ion exchange method. The method was modified by using ammonium bicarbonate as the eluent which can be readily removed by cation exchange resin. SOs were characterized using high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS), and the present study found that the ESI mass spectral patterns of α-2-3 and α-2-6 sialyl linkages were different. The lactonisation of disialyl lactose (DSL) was investigated. The 1H and 13C NMR spectra of DSL dilactone are reported for the first time Non-enzymatic browning between lactose and sodium caseinate was studied at different relative humidities (RHs) using a variety of analytical methods such as furosine, loss of lysine UV absorbance, fluorescence, and loss of lactose. All the analytical methods showed that the maximal conjugation rate occurred at intermediate RH. However, some discrepancies existed between the results of different methods. The results also showed that the degradation of Amadori product increased with RH. It is the first time that the conjugation of sialyl lactose with casein through Maillard reaction has been studied. An HPLC-UV-MS method was established to monitor the α-dicarbonyls generated during the lactose-casein conjugation. Bioassay results showed that both lactose-casein and sialyl lactose-casein conjugates have specific inhibition effects on S. typhimurium binding to cells derived from human colonic adenocarcinoma. Based on the sialic acid content, sialyl lactose-casein conjugate exerts the effect at much lower concentration than free sialyl lactose. This could be attributed to a polyvalent effect.