The Study On The Adhesion Mechanism Of Yeast-derived Mannan Oligosaccharides To Bacteria

Manno-oligosaccharide is a common functional oligosaccharide with promoting proliferation of beneficial bacteria,inhibiting adhesion of pathogens and increasing the immune response of intestinal mucosa.But fewer studies were focused on its structure-function relationship,and mechanism of action of manno-oligosaccharides.In this study,structure-function relationship were studied by simulating the gastrointestinal environment and feed processing technique.The effect of manno-oligosaccharides on bacterial agglutination was investigated by co-cultivation with Lactobacillus acidophilus and Escherichia coli,repectively.The effects of oligosaccharide on intestinal bacteria were studied with IPEC-1 cells.（1）Yeast Manno-oligosaccharides PW120 and PW220 were treated with 6 mol/L HCl,0.1 mol/L HCl,120°C&0.15 MPa,and 120°C.The results showed that the functional group structure of manno-oligosaccharides were not modified by 0.1 mol/L HCl,6 mol/L HCl,high temperature with high pressure,and high temperature gelatinization.The surface with pores of manno-oligosaccharide was made by 0.1mol/L HCl,and gelatinization with pores were appeared by 6 mol/L HCl,high temperature with high pressure treatments.The biggest weight loss rate of manno-oligosaccharides PW120 and PW220 were 270.94°C and267.76°C,respectively,and the mass loss rate were 76.472%and 74.156%,respectively.The thermal stability of PW120 was higher than PW220.The crystal structure of the two oligosaccharides were not changed by high temperature and high pressure and gelatinization,but the unit cell structure were modified by hydrochloric acid.（2）Lactobacillus acidophilus and Escherichia coli were cultured in medium with manno-oligosaccharides PW120 and PW220 for 24 hours at 37°C,then the cells were observed,and OD₆₀₀ was measured.The results showed that Lactobacillus acidophilus and Escherichia coli were agglutinated with 1%manno-oligosaccharide in medium.E.coli was agglutinated by 0.2%of two kinds of manno-oligosaccharides at 6-9 h（P<0.05）,and0.5%PW120 had a significant agglutination effect on E.coli at 12-24 h（P<0.05）.Between0.2%to 2.0%manno-oligosaccharide medium,both two manno-oligosaccharides had significant agglutination effect on Lactobacillus acidophilus at 3-24 h（P<0.05）.Lactobacillus acidophilus was agglutinated significantly in 0.5%PW220 and 0.2%PW120medium at 0-12 h（P<0.05）,and agglutinated significantly in 1%PW220 and PW120medium at 12-24 h.（3）Porcine intestinal epithelial cells（IPEC-1）were used as models to investigate the effects of different concentrations of mannobiose and mannotriose on the adhesion,invasion and damage of IPEC-1 cells.The results showed that mannobiose and mannotriose could significantly inhibit the adhesion and invasion of E.coli to IPEC-1 cells,but had no significant effect on Lactobacillus acidophilus.Lactobacillus acidophilus has a certain adhesion to IPEC-1,but does not have the ability to infect IPEC-1 cells.The adhesion inhibition of mannobiose and mannotriose at 40μg/mL to E.coli was the strongest;mannobiose and mannotriose could reduce the damage of E.coli and Lactobacillus acidophilus on IPEC-1 cells.