Abstract
(1) We prepared transgalactosylated disaccharides containing a mixture of β 1-4 linked galactooligosaccharides (4'-GOS) that were prepared from lactose by the transgalactosylating reaction of β-galactosidase, and investigated the effects of 4'-GOS on the growth of established enterobacterial strains, on the production of hydrogen gas in exhalation and on the human fecal microflora and their metabolism.(2) To investigate in vitro utilization of 4'-GOS by bacteria, each oligosaccharide purified from the mixture was used. All lactose-available bacteria were able to utilize the transgalactosylated disaccharides. All of the bifidobacteria tested, Lactobacillus acidophilus, L. reuteri, L. salivarius, Mitsuokella multiacidus, Enterococcus faecium and Streptococcus intermedius could use the trisaccharides for their growth. The tetra-saccharides were utilized by B. adolescentis, B. breve, B. infantis and E.faecium. The utilization pattern of reconstituted mixtures of transgalactosylated oligosaccharides like 4'-GOS was shown as an intermediate pattern be-tween the disaccharides and the trisaccharides.(3) To test the digestibility of 4'-GOS in the intestine, hydrogen gas in the exhalation of subjects given 4'-GOS was analyzed. Seventeen of 20 men apparently produced hydrogen gas. This fact shows that 4'-GOS was a mixture of non-digestible saccharides.(4) In daily feeding of 4'-GOS (2.5 g and 10 g/day) to the subject groups (lower and higher numbers of indigenous bifidobacteria, respectively) during 3 weeks, both groups showed significant increases in the number of fecal bifidobacteria. Especially in the lower group, the population of these bacteria was maintained after feeding. The deoxycholic acid content in the feces was tending downward in the feeding period in both groups. By 4'-GOS-feeding, the content of fecal non-primary bile acids (deoxycholic acid, lithocholic acid and ursodeoxycholic acid) were reduced in 78% of the lower group (7 of 9men) and in 88% of the higher group (7 of 8 men). The contents of acetic acid, propionic acid and butyric acid in feces were significantly decreased in the higher group by feeding, but the ratio of each acid to all of the short-chain fatty acids was kept constant in spite of the feeding.(5) These results show that 4'-GOS was a mixture of non-digestible oligosaccharides, that it stimulated bifidobacteria growth, and that it may influence bile acid metabolism.
