Chemistry Reference
In-Depth Information
lactobacilli, Kobayashi et al. (1990) patented a method for producing a
processed milk containing galacto-oligosaccharide. In their patent, milk
was treated with a
-galactosidase derived from S. thermophilus or Lb.
delbrueckii subsp. bulgaricus so as to change at least 15% of the lactose in the
milk into galacto-oligosaccharide. The Lactobacillus enzyme was found to be
useful as it performed transgalactosylation reactions even when the lactose
concentration was quite low. Other enzyme sources, such as that from the well-
established A. oryzae, act largely hydrolytically when the lactose is in low
concentrations as found in milk.
Bifidobacterium Species
Tzortzis et al. (2005a) have used whole cells of B. bifidum NCIMB 41171 to
produce galacto-oligosaccharides from lactose. Optimum enzyme activity
occurred at pH 6.8-7.0 and 408C. A 50% (w/w) solution of lactose gave a
20% mixture of oligosaccharides. The mixture comprised 25% disaccharides
(other than lactose), 35% trisaccharides, 25% tetrasaccharides and 15% pen-
tasaccharides. These proportions seemed to be produced consistently by this
organism. Current interest in bifidobacteria as a source of
-galactosidase
may be generated by the ability of at least some strains of Bifidobacterium to
produce higher proportions of longer chain oligosaccharides than most other
lactases studied to date.
Van Laere et al. (2000) studied the ability of several strains of Bifido-
bacterium to metabolize a GOS mixture, which had been purified so that it
contained 6% tri-, 17% tetra-, 37% penta-, 27% hexa- and 8.5% hepta-
oligosaccharide. These proportions were different from most commercial
GOS products which contain predominantly trisaccharide and only low
concentrations of the higher oligosaccharides. This study found that
Bifidobacterium adolescentis DSM 20083 could utilize the higher oligosac-
charides better than other species. Thus, it may be that longer chain oligo-
saccharides are of value for the manufacture of particular symbiotic
mixtures of prebiotic and probiotic, aimed to stimulate the growth of
particular strains of bifidobacteria.
Rabiu et al. (2001) have shown, in a study of five strains of Bifidobac-
terium, that their
-galactosidases predominantly produced (1
!
6) GalP
linkages as opposed to the (1
!
4) linkages generated by the
-galactosidases
of many microbial species (see Table 5.4). These authors also noted the
production of unusual higher chain oligosaccharides by these bifidobacter-
ialenzymes.Tzortziset al. (2005b) also recorded mostly Gal
(1
!
6)
Gal linkages in their oligosaccharide mixture produced by B. bifidum
NCIMB 41171.
