Prebiotic potential of a refined product containing pectic oligosaccharides

Apple pomace samples were subjected to Simultaneous Saccharification and Fermentation (SSF) to yield a medium containing mainly lactic acid and oligosaccharides. After lactic acid removal by ion exchange, the SSF medium was refined by a two-step (diafiltration-concentration) membrane treatment. Limited losses of glucooligosaccharides, galactooligosaccharides, xylooligosaccharides and arabinooligosaccharides were noticed in permeates, whereas the concentrate from the second stage showed low concentrations of lactic acid, arabinose and NaCl, which were extensively removed in the refining process. About 60% other the non-saccharide compounds present in the solution fed to membranes were removed in permeates, whereas oligogalacturonides were quantitatively recovered in the final concentrate. The refined product was assayed for its prebiotic potential by means of in vitro fermentability assays performed with individual microbial strains or human fecal inocula. In this latter case, the dynamics of microbial populations was assessed by Fluorescent In Situ Hybridization (FISH). The experimental results proved the prebiotic effects caused by the refined product obtained in this work, which included the promotion of beneficial bacterial growth and the increase of short chain fatty acids (SCFA) concentrations.