Characterization of Structure and Cellular Immunity Bioactivity of Milk-Derived Galactooligosacchrides Prepared by Lactobacillus delbrueckii subsp. bulgaricus Fermentation

Abstract

In this study, the milk-derived Galactooligosacchar ides (GOS) were produced by Lactobacillus delbrueckii subsp. bulgaricus and refined by an ultrafiltration-nanofiltration continuous membrane. By further investigation, we f ound that the GOS product purified by gel permeation chromatography mainly contained l ow molecular weight disaccharide and trisaccharide, that is, 4- β -galactobiose and tri-galacto-oligosaccharides. The cellular immune activity of the purified GOS was evaluated b y using Intestinal Epithelial Cells (IECs). Results showed that GOS could significantly (P< 0.05) promote IECs proliferation in a dose and time dependent manner, and the relati ve proliferation rate after 24 hours culture was high up to 158% at the concentration of 100 μ g mL -1 , which was three time the value after 4 hours culture without GOS. Moreov er, the production of IL-6 was observably increased and up to 133.54 ng L -1 with addition of 100 μ g mL -1 GOS. These data implied that the purified GOS might have a rol e in promoting the immune adjustment, which could be utilized as a novel and natural immunoregulatory agent in the field of medicine and functional food. This work al so revealed that the employment of transgalactosylation activity of β -galactosidase derived from the fermentation of probiotics such as Lactobacillus delbrueckii subsp. bulgaricus would enhance the value of the milk product due to the form of GOS. Keywords : Fermentation, Galacto-oligasacchrides, Immunoregu latory activity, Probiotics.