Milk Oligosaccharides - Advanced Dairy Chemistry - page 334

platypus (monotremes) are fucosyllactose and difucosyllactose, respectively
(Messer and Urashima, 2002). Furthermore, the higher milk oligosaccharides
of the platypus contain lacto-N-neotetraose or lacto-N-neohexaose as core
units (Amano et al., 1985), which is a feature that is shared by many eutherian
milk oligosaccharides. In these respects, also, eutherian milk oligosaccharides
are more similar to those of monotremes than to those of marsupials.
The milk of all three infraclasses of mammals (eutherians, marsupials and
monotremes) contains acidic (sialyl) in addition to neutral oligosaccharides
(Urashima et al., 2001). Milk of the echidna, a monotreme, uniquely contains,
as its major oligosaccharide, a sialyllactose in which the sialic acid residue has a
4-O-acetyl substituent (Kamerling et al., 1982).
It is worth noting that oligosaccharides dominate over free lactose in the
milk of monotremes, marsupials and a few species of eutherians such as the
Canoidea (other than the dog, Canis familiaris); the biological significance of
this phenomenon, which appears to be found mainly in species whose neo-
nates are altricial, is open to speculation (Messer and Urashima, 2002).

8.11. Future Aspects of Milk Oligosaccharides

In the above discussion, the main focus has been on the chemical structures
and biological significance of oligosaccharides of human milk and colostrum,
rather than of other species. Among more than 100 human milk oligosac-
charides, each oligosaccharide may have its own specific role as a prebiotic
and/or receptor analogue for different pathogenic microorganisms. Based on
these functions, the possible utilization of artificial human milk oligosacchar-
ide-like components on an industrial scale will be discussed below.
2 0 -FL is significant in the prevention of diarrhea caused by C. jejuni
(Ruiz-Palacios et al., 2003; Morrow et al., 2004). As bovine milk does not
contain this saccharide, there is a need for the development of techniques for
its preparation and also incorporation into infant formulae produced from this
milk. Murata et al. (1999a) prepared Fuc( 1-2)Gal( 1-4)GlcNAc, a saccharide
that is similar to 2 0 -FL, using p-nitrophenyl- - L -fucopyranoside as a donor and
N-acetyllactosamine as an acceptor, by reverse hydrolysis with fucosidase from
porcine liver. However, the yields were low and Fuc( 1-3) Gal( 1-4)GlcNAc
and Fuc( 1-6)Gal( 1-4)GlcNAc were formed as undesirable by-products. It
may be that one could use a different, more suitable, fucosidase that would give
a higher yield of 2 0 -FL, and one could develop a method that uses fucose instead
of p-nitrophenyl- - L -fucopyranoside as a donor and lactose as an acceptor.
As shown by Kitaoka et al. (2005), LNT has the most potential as a
candidate for prebiotics. As this saccharide has not been detected in bovine
milk, there is a need for development of a method for its preparation, so that it