Rapid, quantitative analysis of 3′- and 6′-sialyllactose in milk by flow-injection analysis–mass spectrometry: Screening of milks for naturally elevated sialyllactose concentration

Abstract

Non-protein-bound oligosaccharides are important bioactive components of cow milk, with potential human-health benefits such as stimulation of the growth of beneficial gut bacteria and defense against pathogens. In bovine milk, the majority of oligosaccharides are sialylated; 3'-sialyllactose (3'-N-acetylneuraminyl-D-lactose; 3'-SL) is the predominant sialylated oligosaccharide, followed by 6'-sialyllactose (6'-N-acetylneuraminyl-D-lactose; 6'-SL). Both 3'-SL and 6'-SL have antimicrobial activity. As bovine milk products such as infant formula can be an important component of the human diet, and the concentrations of 3'-SL and 6'-SL are lower in bovine milk compared with human milk, we aimed to identify cows that naturally produce higher concentrations of sialyllactose in their milk. Milk from such cows could be used to produce foods with an increased sialyllactose content, potentially providing increased health benefits. We speculated that cows overexpressing 3'-SL and 6'-SL would exist at low frequency in the population and, to allow their efficient identification, we developed a novel assay for 3'-SL and 6'-SL utilizing flow-injection analysis-mass spectrometry, which could be used for high-throughput analysis of milk samples. We then determined 3'-SL and 6'-SL concentrations in milk samples from 15,507 cows from Friesian, Jersey, and Friesian-Jersey crossbred animals. We found 329 cows with concentrations of 3'-SL or 6'-SL >2-fold higher than the mean, 26 cows with concentrations of 3'-SL or 6'-SL >3-fold higher than the mean, and 1 cow with concentrations of 3'-SL >4-fold higher than the mean. Although these outliers were observed across the 3 groups of cows, breed had a strong effect on mean 3'-SL and 6'-SL concentrations.

Changes in the Milk Metabolome of the Giant Panda (Ailuropoda melanoleuca) with Time after Birth – Three Phases in Early Lactation and Progressive Individual Differences

“…Their MS/MS spectra displayed common fragments but in different ratios (Fig D.1 in S1 File ). By comparing the fragmentation patterns with published data [ 42 ], these two compounds were confirmed as 3’-sialyllactose (N262, high in the first week of lactation) and 6’-sialyllactose (N351, low in the first week of lactation). Differences in these two disaccharide isomers with time after birth have been noted in the milk of other species, though with different relative kinetics from that which we observed for giant pandas [ 43 ], or with different relative concentrations between individuals [ 44 ].…”

Cell-Free Spent Media Obtained from Bifidobacterium bifidum and Bifidobacterium crudilactis Grown in Media Supplemented with 3′-Sialyllactose Modulate Virulence Gene Expression in Escherichia coli O157:H7 and Salmonella Typhimurium

“…Furthermore, Lactobacillus acidophilus La-5 grown in medium supplemented with dairy ingredients such as whey, presented a protective effect in EHEC-infected mice (Zeinhom et al, 2012 ). However, BMO concentration in bovine milk is lower than HMO concentration in human milk (Barile et al, 2009 ; Tao et al, 2009 ; Kelly et al, 2013 ). Also, fucosylation occurs at very low frequency compared to sialylation, which is contrary to human milk (Tao et al, 2008 ).…”

Genome of Bifidobacteria and Carbohydrate Metabolism

“…More than 60 kinds of BMO have already been identified ( Pacheco et al ., 2014 ). The composition of sialylated BMO compounds reaches 70%, whereas it is 20% for HMOs ( Kelly et al , 2013 ). They are constructed from a lactose heart, but can also be constructed from a lactosamine heart that human milk does not contain.…”