Study On Fermentation Of Dendrobium Candidum By Lactobacillus Plantarum And Its Fermentation Activity

Dendrobium candidum(D.candidum)which is mainly distributed in tropical areas,contains polysaccharides,polyphenols and other bioactive substances.At present,the main research has focused on D.candidum and its polysaccharides,while the components and biological activities of fermented D.candidum have received limited attention,especially the effect on intestinal microbiota.It is well known fermentation of Lactobacillus plantarum can improve the biological activity of food.Therefore,in this study,D.candidum was used as the main fermentation substrate with Lactobacillus plantarum as the fermentation strain.Through the Box-Behnken design-response surface method,the free-radical clearance rate was taken as the objective to optimize the fermentation conditions of D.candidum.The components of fermented D.candidum were ananlysed by Untargeted metabolomics and HPLC.The antioxidant capacity of D.candidum before and after fermentation was researched by used with four kinds of antioxidant tests.Metagenomic and metabolomic techniques were applied,and immune factors,biomarkers of oxidative stress,mucosal barrier-related proteins and short-chain fatty acids(SCFAs)were determined to reveal the effects of fermented D.candidum(FDC)on intestinal inflammation induced by oxazolone in zebrafish.The results are as follows:(1)The best conditions for fermentation of D.candidum were as follows: the concentration of D.candidum was 5%,the concentration of fructose syrup was 5%,fermentation time was 31 h.Under these conditions,the free radical scavenging rate of D.candidum fermented by Lactobacillus plantarum was 93%.The chemical composition of D.candidum was significantly changed during fermentation,which the contents of phydroxycinnamic acid,p-hydroxybenzoic acid and syringic acid were significantly increased.(2)FDC significantly increased antioxidant capacity,repaired intestinal barrier and improved intestinal immune index.In zebrafish,after the 21 st day of FDC intervention,the abundance of Lactobacillus,Faecalibacterium and Rummeliibacillus increased,but the abundance of the genera Shewanella,Geodermatophilus,Peptostreptococcaceae and Mycobacterium decreased.Meanwhile,FDC significantly increased the contents of SCFAs,MUC2,ZO-1,occludin,GSH-Px,SOD,IL-4 and IL-10.In addition,network analysis based on multi-omics indicated that FDC intake leads to changes in intestinal microbiota and intestinal metabolites,resulting in enhanced host immune function.These results indicate that FDC can improve intestinal health by regulating intestinal microbiota and its metabolites to treat intestinal inflammation and regulate the host immune system.The present research extended our understanding of the utilization of D.candidum and provides a basis for the development of new healthy products of D.candidum.