Regulation Of Probiotics Growth And Intestinal Flora Of Pregnant Women By Dietary Sialic Acid

The human intestine contains a large number of microorganisms,which form an important microecosystem in the body.The composition of intestinal microorganisms is influenced by the host and the environment,and their growth and metabolism also affect the host’s metabolism and health.There are indigestible sugars in the human diet that are degraded and utilized by intestinal microorganisms,which in turn regulate the composition of intestinal microorganisms and produce various small-molecule metabolites.Some animal-derived diets contain sialic acid,an important component of glycoproteins,oligosaccharides,and glycolipids,which have multiple physiological functions.There are microorganisms in the human intestine that can utilize sialic acid.Therefore,dietary sialic acid may affect the intestinal flora,especially the combined sialoglycan rich in animal mucin,which can inhibit the growth of pathogenic bacteria and promote the growth of beneficial bacteria.This study focuses on edible bird’s nest(EBN),a mucin-rich food containing sialic acid,as the main research object,with defatted milk powder and egg yolk peptide,which are also rich in sialic acid,as controls.This study compares the differences in the antioxidant activity of natural diets rich in sialic acid,EBN before and after acid treatment,and sialic acid monomers,as well as their effects on the fermentation of different probiotics and fecal bacteria from pregnant women in vitro.The study also explores whether dietary sialic acid improves the probiotic activity of soybean proteins.The main research contents are:(1)The in vitro antioxidant activity of sialic acid from different dietary sources was investigated.The DPPH radical scavenging ability,hydroxyl radical scavenging ability,superoxide anion radical scavenging ability and reducing power of skim milk powder,yolk peptide,skim EBN,skim EBN and sialic acid monomer were determined.The results showed that natural dietary sialic acid has good antioxidant activity,while the antioxidant activity of defatted EBN was lower compared to intact EBN with complete sugar chains.(2)The effect of sialic acid from different dietary sources on the growth and metabolism of probiotics was studied.The growth of four probiotics and mucin-loving Akkermansia muciniphila was compared during anaerobic fermentation in vitro.The results showed that the overall production of propionic acid by two Lactobacillus strains was higher than that of Bifidobacterium.The concentration of butyric acid produced by Bifidobacterium brevis,Bifidobacterium animalis and Lactobacillus rhamnosus during EBN fermentation was significantly higher than that of other groups.EBN can promote the growth of mucin-loving A.muciniphila.Intact EBN with complete sugar chains can significantly promote the growth of probiotics that can utilize sialic acid,such as B.brevis,and increase the production of organic acids by probiotics to improve the intestinal environment.(3)The effects of different dietary sialic acids on the gut microbiota of healthy women and pregnant women of different ages through in vitro anaerobic fermentation was compared.The results showed that dietary sialic acid can increase the accumulation of short-chain fatty acids in the gut microbiota,improve the richness and diversity of the gut microbiota,and promote the enrichment of probiotics while inhibiting the growth of pathogenic bacteria.EBN can reduce the relative abundance of potential pathogenic bacteria such as Escherichia-Shigella,Enterobacter,and Klebsiella,and increase the relative abundance of potential probiotics such as Bacteroides,Faecalibacterium,and Ruminococcus.The effect of EBN on promoting the growth of beneficial bacteria and inhibiting pathogenic bacteria is better than that of desialylated EBN in pregnant women,verifying the importance of the integrity of the terminal sialic acid glycans of EBN for its biological activity.(4)The effect of dietary sialic acid on the probiotic activity of soybean protein was investigated.Soybean protein was compared with commercial pancreatic digest broth.Addition of soy protein to the culture medium caused slight growth delay in bacteria,but the addition of EBN to the culture medium still promoted the growth of probiotics.Therefore,the addition of dietary sialic acid can improve the probiotic activity of soy protein with N-glycans of highly mannose.