Research On The Enhanced Amelioration Of Ulcerative Colitis By The Single Bacteria Encapsulation System Of Nissle 1917 Based On Oxidized Starch

Ulcerative colitis is an incurable and recurrent disease.Probiotics have the potential to significantly enhance intestinal health;however,oral probiotic delivery is limited by the harsh environment of the digestive tract,and conventional large-size encapsulated carriers transit too quickly in the colon of colitis patients.Rice starch is a kind of natural polysaccharide.Its polyhydroxy structure makes it easy to obtain ideal functional properties through modification.The modified starch prepared by oxidation can overcome the problems of poor water solubility of natural starch,which possesses good biocompatibility and the ability of film formation.It is a promising encapsulation polymer.In this study,natural rice starch was used as raw material,and its ideal functional properties were given by debranching-oxidation modification.Subsequently,it was used to form single-cell probiotic nanocoatings to enhance the oral delivery of probiotics.This study provides a novel idea for the development of probiotic special medical food for the prevention and control of chronic diseases.(1)A water-soluble oxidized starch was prepared from natural rice starch by debranching-oxidation modification,and its structural properties and physicochemical properties were determined.Debranching-oxidation modification effectively prevents starch molecules from aggregating in water to form large particles,deprives of starch crystallization ability,and enables higher water solubility of starch.These changes were positively correlated with the oxidation degree of starch.Among them,OS30 not only possesses a higher proportion of A chain,a smaller average chain length and less aggregation behavior,but also has excellent water solubility and delicate uniform film formation.It promises to be a healthy and safe carrer material.(2)We used E.coli strain Nissle 1917(EcN)as a demonstration probiotic and then encapsulated it via electrostatic and hydrogen bonding interactions between polyethyleneimine(PEI)and OS30 to produce EcN@P/O.After the basic characterization of EcN@P/O,its resistance to the digestive tract environment was further evaluated.When incubated in a reaction system containing PEI(Mw 10000,20 μg/mL)and OS30(2 mg/mL)for 30 min,the surface of EcN can form a dense and uniform shell.The formation of the shell was achieved by interweaving OS30 and the PEI as polymers on the surface of EcN or by depositing them as nanoparticles on the surface of individual bacteria.This singlecell encapsulation strategy has shown no significant impact on morphology and growth of bacteria,and has conferred additional properties on EcN to resist damage from the harsh environment of the digestive tract.When they were simultaneously exposed to simulated gastric fluid for 30 min,the survival rate of EcN@P/O was 11.29 times higher than that of unencapsulated bacteria.After exposure to simulated intestinal fluid and bile salts for 2 h,the survival rates of EcN@P/O were 26.68%and 11.65%higher than those of unencapsulated bacteria,respectively.Additionally,in a complex in vivo environment,the number of living bacteria in the stomach and small intestine of EcN@P/O was 40 times and 74 times higher than that of unencapsulated bacteria after 4 h of intragastric administration.(3)The typical colitis mice model was induced by dextra sulfate sodium.The ameliorative effect of EcN@P/O on colitis mice was assessed in terms of signs,histopathological damage,inflammatory factor expression and intestinal microecology.EcN@P/O provide enhanced health benefits for colitic mice compared to EcN.For example,it significantly improved colonic pathological shortening,weight loss,colonic histopathological damage,and decreased appetite in colitis mice,as well as reduced the disease activity index scores,splenic index.In addition,the expression of myeloperoxidase and the secretion of TNF-α and IL-6 were similarly depressed in colitis mice that received EcN@P/O.Notably,it effectively reversed the dextra sulfate sodium-induced dysbiosis.Therefore,the structure and function of the intestinal flora of colitic mice that received EcN@P/O were similar to those of normal mice.It was attributed to the fact that EcN@P/O treatment increased the number of OTUs,α-diversity,β-diversity,relative abundance of beneficial bacteria(Lachnospiraceae NK4A136,Lachnoclostridium,Desulfovibrio,Intestinimonas,and Odoribacter)and metabolic function of intestinal flora in colitic mice.