Metabolism of fructooligosaccharides by lactic acid bacteria and bifidobacteria.

摘要

Fermentation of fructooligosaccharides (FOS) and other oligosaccharides has been suggested to be an important property for selection of bacterial strains used as probiotics. Despite the considerable commercial and research interests in oligosaccharides and probiotic bacteria, relatively little is known about which strains actually metabolize and how lactobacilli and bifidobacteria utilize FOS. The objective of this research was to identify lactic acid bacteria and bifidobacteria capable of fermenting FOS, to study FOS metabolism by these organisms and to determine how they accumulate and use FOS.; To investigate which strains metabolize FOS, lactic acid bacteria and bifidobacteria were screened for their ability to ferment fructooligosaccharides (FOS) on MRS agar. Of 28 strains of lactic acid bacteria and bifidobacteria examined, 12 of 16 Lactobacillus strains and 7 of 8 Bifidobacterium strains fermented FOS. Only strains that gave a positive reaction by the agar method reached high cell densities in broth containing FOS.; To identify and characterize the FOS transport system of Lactobacillus paracasei 1195, radiolabeled FOS was synthesized enzymatically from [3H]-sucrose using fructosyltransferase. FOS hydrolysis activity was detected only in cell extracts prepared from FOS- or sucrose-grown cells and was absent in cell-free supernatants. Competition experiments showed that glucose, fructose, and sucrose reduced FOS uptake, but other mono-, di-, and trisaccharides were less inhibitory. When cells were treated with sodium fluoride, iodoacetic acid, and other metabolic inhibitors, FOS transport rates were reduced by up to 60%. Ionophores that abolished the proton-motive force only slightly decreased FOS transport. In contrast, uptake was inhibited by ortho-vanadate, an inhibitor of ATP-binding cassette (ABC) transport systems. These results suggest that FOS transport in L. paracasei 1195 is mediated by a high-affinity ABC transporter. In contrast, we discovered that sucrose was transported and phosphorylated by a phosphoenolpyruvate-dependent phosphotransferase system.