Maria Bielecka

Effect of non-digestible oligosaccharides on gut microecosystem in rats

Abstract Effect of commercial or new-developed preparations of non-digestible oligosaccharides: fructo-oligosaccharides, lactulose, corn dextrins and corn resistant starch, on microecology of Wistar rats was investigated. A control group was fed a casein diet with 10% cellulose. The experimental groups were administered diets in which cellulose was replaced by the examined preparations. After 4-week feeding experiments, a high increase in live bifidobacteria number by 1.2 and 1.4 log cfu/g of faeces was found in groups fed resistant starch and lactulose. An increase in coliform number by 0.6–0.8 log cfu/g was found in all the groups. No or only negligible changes in numbers of the total mesophilic aerobic and facultatively anaerobic bacteria count, and the spores of anaerobic and aerobic bacteria, were observed. Fructo-oligosaccharides and lactulose lowered pH and gave the best trophic effect in caecum (significantly increased weights of: caecum with contents, cecal walls and cecal contents as well as dry weight of contents), whereas resistant starch increased markers of unhealthy cecal changes (N-NH3 content and β-glucuronidase activity). The activity of bacterial saccharolytic enzymes changed in a substrate-specific manner in relation to the examined non-digestible oligosaccharide preparations.

Interaction of Bifidobacterium and Salmonella during associated growth

Interaction of 15 Bifidobacterium (belonging to species B. animalis, B. globosum and B. breve) and six Salmonella (belonging to species S. enteritidis and S. typhimurium) strains was examined during associated growth at optimum conditions for the two genera. All strains of Bifidobacterium investigated were antagonistic to Salmonella. Three strains of Bifidobacterium bactericidal to Salmonella were identified. The kinetics of Salmonella inhibition was as follows: growth of Salmonella was inhibited before the end of the exponential phase, then succeeded by a rapid decrease of live-cell numbers at the beginning of the stationary phase, after which the cell death rate was lower. Growth of Bifidobacterium in the associated cultures was similar to that in monocultures.