The Oligosaccharides Utilization Properties Of Lactic Acid Bacteria And Their Effects In Mice Gut

Functional oligosaccharides can’t be digested and absorbed in human small intestine, but can selectively increase the proliferation and short chain fatty acids(SCFA) production of intestinal symbiotic microorganisms. The utilization of functional oligosaccharides is recognized as a novel and important property of probiotics. However, it still remains unknown whether the colonization of probiotics in gut is related to their utilization properties of oligosaccharides.This research studied the utilization properties of lactic acid bacteria(LAB) to use fructooligosaccharide(FOS) and xylooligosaccharide(XOS) in vitro and detected the influences of oligosaccharides on the colonization of LAB in mice gut. The SCFA concentration in mice feces and the changes of mice physiology and intestinal microbiota were also studied. The main contents and conclusions are as follows.We investigated the preferences of LAB from different species to FOS and XOS on MRS-oligosaccharides agar mediums added with bromcresol purple. Then the generation time and the rate of acid production of LAB were also detected when they used FOS or XOS as the sole carbon source. It was demonstrated that the utilization of oligosaccharides by LAB had its strain specificity and regularity. FOS and XOS could not be utilized by all the strains of Lactobacillus rhamnosus and Streptococcus thermophilus, while they could be utilized by all the strains of Lactobacillus plantarum. Growth rate of the strains was positively correlated with the rate of acid production and the acidification rate of Lactobacillus was generally higher than that of Bifidobacteria.11 strains of LAB of different species were selected due to the results in vitro and combined with FOS-XOS mixture in different ways for animal experiment. Mice feces were collected at different time points. The method of PCR-DGGE was established to build an identification ladder as a standard and to detect the colonization of LAB in mice gut. Results showed that when the dose of oligosaccharides was 4 g/day for adult(Projected equally to mice dose in this research), strains with no preference of FOS and XOS could not colonize in mice gut, while the colonization time of the strains with oligosaccharides preference in mice gut was not positively correlated with the oligosaccharides utilization ability in vitro. The short-term administration of oligosaccharides had no significant promotion to LAB colonization and the long-term administration of oligosaccharides prolonged the colonization time of some strains.The concentration of SCFA in mice feces was detected by GC-MS. It showed that mice fecal SCFA was mainly acetic acid. Feeding mice with LAB, oligosaccharides and LAB-oligosaccharides mixture significantly increased the fecal SCFA concentration. The effects of LAB and LAB-oligosaccharides mixture were more pronounced. As a consequence, the SCFA concentration reached above 30 μmol/g.The body weight of mice was monitored during the experiment. Mice blood was collected for serum biochemical detection before sacrificing. The viscera index, cecum total weight and empty weight of mice were calculated once the mice were sacrificed. It was found that LAB or oligosaccharides did not influence the body weight of mice whereas the combination of LAB and oligosaccharides slightly decreased the body weight. The viscera index, cecum total weight and empty weight along with TC, Ig G, Ig M in serum didn’t change obviously during the experiment. The LAB-oligosaccharides mixture significantly reduced TG in mice serum. In addition, ingestion of LAB, oligosaccharides or LAB-oligosaccharides mixture led to an increase of HDL-C and a decreace of LDL-C in mice serum.We took mice feces as samples to study the changes of intestinal microbiota by Illumina Miseq, a high-throughput sequencing platform. It indicated that LAB, oligosaccharides and their mixture could increase the Alpha diversity and shortly influence the Beta diversity of mice intestinal microbiota. The Alpha and Beta diversity would restore to original level when stop gavaging. LAB, oligosaccharides and their mixture had no obvious impacts on categories of intestinal microbiota at phylum level, but could influence the relative abundances of Bacteroidetes, Firmicutes, Actinobacteria and Proteobacteria. These microbiota restored to original level when the gavage was stopped. On the genus level, LAB, oligosaccharides and their mixture brought an increase of generic number of intestinal microbiota. Exogenous Bifidobacterium bifidum and Streptococcus thermophilus led to a relative abundance increase of Bifidobacterium and Streptococcus rapidly in fecal microbiota. After stopping the gavage, the relative abundance would also return to the original level while the continuing gavage of oligosaccharides could slow down this return. The oligosaccharide dose of this research slightly increased the relative abundance of Bifidobacterium in mice feces, but it was not so effective as LAB. The relative abundance of Lactobacillus was not significantly affected in all animal groups.