The cecal bacteria and short-chain fatty acid concentrations were determined in ICR mice that were fed a purified diet with 2.5% galactosyllactose (GL) or 2.5% lactose and that were given drinking water containing GL (0%, 2%, or 4%) and a standard purified diet. In mice fed a 2.5% GL diet, staphylococci significantly decreased in number (p< 0.001) compared to animals fed a 2.5% lactose diet. Although the numbers of other bacterial groups showed no significant changes by GL feeding, the rate of bifidobacteria to the total bacterial counts was two times larger in the GL-fed mice than the lactose-fed animals. Propionate and butyrate concentrations significantly increased in the GL-fed animals (p< 0.01-0.001) compared to those in the lactose group. Animals given GL in drinking water showed increased concentrations of acetic, propionic and n-butyric acids (p< 0.05-0.01) in proportion to the GL concentrations. In contrast, iso-butyrate and iso-valerate decreased in concentration in the GL groups (p< 0.05-0.01). The possible functions, other than a bifidobacterial growth factor, of GL are discussed.

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(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.

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Abstract The effect of lactitol on intestinal bacteria was compared with that of lactulose in vitro and in vivo. The utilization of lactitol and lactulose by human intestinal bacteria (11 genera, 35 species, 48 strains) in vitro was tested by measuring the pH of the medium after a 48-hr incubation. Lactitol was utilized by 15 strains, and lactulose by 37 strains. That is, lactitol was utilized by fewer species of Bifidobacterium, Lactobacillus, Bacteroides and Clostridium than lactulose was. The cecal microbial flora was examined in rats treated orally with lactitol or lactulose for 7.5 days. The changes in the cecal flora caused by lactitol were almost the same as those caused by lactulose at the medium and high doses. The increases in the numbers of bifidobacteria were particularly noticeable Enterobacteriaceae, Streptococcus and bacteroidaceae also increased at the high dose of both drugs.

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