Prebiotic effects of agal-oligosaccharides on bifidobacteria and its application in fermented milk

The abilities of six bifidobacteria isolates, which are B. adolescentis BCRC 14606, B. breve BCRC 11846, B. bifidum BCRC 14615, B. infantis BCRC 14602, B. lactis Bb-12 and B. longum BCRC 14634, to utilize five different agal oligosaccharides of Monostroma nitidum, Geledium, Gracilaria, Ulva and Porphyra were studied, with regard to production of bacterial cell mass. Porphyra oligosaccharides supported best growth of B. lactis Bb-12. Then, the prebiotic effect of Porphyra oligosaccharides cultured with B. lactis Bb-12 was compared to commercial prebiotics such as fructo-oligosaccharides, isomalto-oligosaccharides, and galacto-oligosaccharides. The total counts of B. lactis Bb-12 in the treatment of Porphyra oligosaccharides was increased from 7.3 log CFU/mL to 8.1 log CFU/mL, but in the treatments of fructo-oligosaccharides, isomalto-oligosaccharides, and galacto-oligosaccharides the total counts were increased to 1.2, 1.8 and 1.6 log CFU/mL, respectively. The growth of Clostridium perfringens BCRC 10913 cultured alone in the treatment of Porphyra oligosaccharides was lower than in another treatment of oligosaccharides (p < 0.05). In vitro experiment showed the changes of total counts on C. perfringens co-cultured with B. lactis Bb12. The total counts of Clostridium perfringens were decreased significantly in co-cultured experiment with different oligosaccharides. The highest colony counts of B. lactis Bb12 were obtained in fermented milk with 1% Porphyra oligosaccharides. The activity of α- galactosidase was increased from 0 nM/ml whey/hr to 23.55 nM/ml whey /hr but it was decreased to 10.19 nM/ml whey/hr after 36 hours. However, the antioxidant activities were increased with fermentation time. The ferrous ion chelating activity of fermented milk with 1% Porphyra oligosaccharides was increased from 0.6% to 30% with the fermentation time. The DPPH radical-scavenging activity of fermented milk with 1% Porphyra oligosaccharides was increased from 3.2% to 59.2% with the fermentation time. The hydrogen peroxide radical-scavenging activity of fermented milk with 1% Porphyra oligosaccharides was increased from 1.0% to 49.0% with the fermentation time.