The immunomodulatory effect of GMP and its derivates on the cell proliferative response of human macrophagelike cell, U937, and its effect on phagocytic activities via incorporation of fluorescence beads were studied. GMP was found to be a potent immunoenhancer at low concentrations, significantly enhancing the proliferation and phagocytic activities of U937. The modulatory function could be radically altered by enzymatic treatments. Pepsin digestion significantly enhanced the degree of cell proliferation and phagocytic activities, whereas trypsin had no significant effect. The immunoenhancing effects decreased significantly after sialidase treatment; however, more than 70% of activity was retained after treatment. GMP with different carbohydrate chains was shown to possess different modulatory capabilities. Sialic acid-rich GMP fractions showed an enhanced response. These findings indicate that both the carbohydrate chains compositions, including the terminal sialic acids and the polypeptide portions of GMP, are essential for the stimulatory effects of GMP on cell proliferation and phagocytic activities of U937.

Glycomacropeptide (GMP) has heterogeneous carbohydrates, and this attributes to its various biological activities. In this study, we compared the chromatographic profiles of GMP isolated by three methods (trichloracetic acid fractionation, ethanol precipitation, and ultrafiltration) from whey protein isolate (WPI). Seven sharp heterogeneous GMP peaks were eluted from GMP prepared by ethanol precipitation and ultrafiltration using Mono Q anionic chromatography, while only 5 peaks were seen in TCA treated sample. The TCA pretreatment recovered only sialo-GMP (glycosylated) and eliminated all contaminated proteins; however, the recovery rate was the lowest (6.7% of the initial WPI). Ethanol precipitation recovered 20.4% of GMP from WPI and 75.7% was glycosylated, but the heating process might lead to degradation of glycosidic residues. Ultrafiltration was found to be the most effective in recovering GMP. The recovery rate was 33.9% with 81.6% sialo-GMP. We concluded that carbohydrate profile of GMP varied widely and depended on the isolation method. Based on the high recovery of sialo-GMP, the combination of ultrafiltration and anionic chromatography might be a suitable and practical approach on an industrial scale.

The presence of antiadhesive component(s) in the hen egg yolk against foodborne pathogens was anticipated from results of a previous animal study conducted by the authors. The previous work showed egg yolk powder without specific antibodies is effective in controlling Salmonella enteritidis,Salmonella typhimurium, and Escherichia coli O157:H7 colonization in laying hens. Therefore, this study was necessary to locate the activity and identify the effective component(s). In vitro experiments were conducted using confluent Caco-2 cell monolayers. S. enteritidis, S. typhimurium, and E. coli O157:H7 were investigated against the various extracted granule and plasma fractions in three different assays: adhesion elimination, adhesion prevention, and antimicrobial. This study revealed original findings and identified the protective yolk fraction against the foodborne pathogens as the granule component, high-density lipoproteins (HDL). The protective activity conveyed by HDL was confirmed to remain intact despite peptic and tryptic enzymatic digestion and to have antiadhesive but not antimicrobial effect.