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

In this study, the milk-derived GalactoOligoSaccharides (GOS) were produced by Lactobacillus delbrueckii subsp. bulgaricus and refined by an ultrafiltration-nanofiltration continuous membrane. By further investigation, we found that the GOS product purified by gel permeation chromatography mainly contained low molecular weight disaccharide and trisaccharide, that is, 4-β-galactobiose and tri-galacto-oligosaccharides. The cellular immune activity of the purified GOS was evaluated by 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 relative proliferation rate after 24 hours culture was high up to 158% at the concentration of 100 μg mL-1, which was three time the value after 4 hours culture without GOS. Moreover, the production of IL-6 was observably increased and up to 133.54 ng L-1 with addition of 100 μg mL-1 GOS. These data implied that the purified GOS might have a role 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 also 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.