| Ovomucin(Ovomucin,OVM)is a high molecular weight glycoprotein derived from egg whites of poultry eggs and is a promising new food ingredient with numerous biological activities such as regulation of intestinal flora and inhibition of cholesterol absorption.Isoelectric point precipitation is the conventional method for the preparation of OVM on a large scale.However,the OVM prepared by this method is highly insoluble in aqueous solutions,which limits its further exploitation as a food ingredient.Ultrasonic modification is an effective method to improve the solubility of proteins,but its ability to improve the functional properties of proteins may also cause changes in their structure and biological functions.Little information is available on the effects of ultrasonic modification on the structure and properties of OVM.Therefore,in this study,based on the evaluation of ultrasonic modification on the structure,solubility properties and bioactivity of OVM,the potential promotive effects of ultrasonically modified OVM on intestinal health were investigated around the interaction between ultrasonically modified OVM and intestinal flora to provide a reference for its further development and application in food materials.The main studies and results are as follows:(1)Spectrophotometry,Fourier transform infrared spectroscopy and in vitro functional simulation assays were used to investigate the effects of different ultrasound modification times at 400 W power on the secondary structure,physicochemical properties and biological activity of OVM.The results showed that the sonication modification induced the conversion of β-fold and β-turn to irregularly curled structures by promoting the depolymerization of insoluble OVM aggregates.The solubility increased to 90.0% at 45 min of sonication at 400 W power,and the flowability and thermal stability were significantly improved.In addition,sonication modification significantly improved the cholesterol adsorption capacity,α-amylase inhibition and α-glucosidase inhibition of OVM and its mock digestion products.These results suggest that ultrasonic modification is a simple and effective method to improve the physicochemical and functional properties of OVM.(2)In vitro simulated digestion and anaerobic fermentation models were established,and the degree of utilization of ultrasonically modified OVM,the intestinal flora composition and short-chain fatty acid content of the fermentation broth were determined by spectrophotometry,16 S rRNA analysis and gas chromatography.The results showed that after in vitro simulated gastrointestinal digestion,the molecular mass of ultrasonically modified OVM decreased and the concentrations of soluble total sugars,reducing sugars,peptides,free amino acids and sialic acid in the digestate increased,indicating that the simulated gastrointestinal fluid had a certain degradation effect on ultrasonically modified OVM and the active factor sialic acid at its sugar base terminus was able to be shed by the action of gastrointestinal digestive enzymes.However,after 1 h of digestion,the decrease in molecular weight was not significant as the digestion time increased,indicating that the ultrasonically modified OVM was able to tolerate the enzymatic degradation of gastrointestinal digestive enzymes to a certain extent.The concentration of soluble total sugars,reducing sugars,peptides,total protein and sialic acid in the fermentation broth decreased significantly under the action of intestinal flora,and the content of short-chain fatty acids in the fermentation broth increased significantly to 606.72±10.27 μL/L,indicating that the ultrasonically modified OVM could be continuously utilized by intestinal bacteria.The results of 16 S rRNA analysis of the intestinal flora showed that undigested ultrasonically modified OVM increased total short-chain fatty acid,acetic and propionic acid production and decreased the p H of the fermentation broth by increasing the abundance of short-chain fatty acids producing bacteria such as Bacteroides and Bifidobacterium and decreasing the content of harmful bacteria such as Dorea and Escherichia-Shigella.The p H of the fermentation broth was reduced.(3)The faecal flora of four healthy donors were selected(where sample A was an enterotype dominated by Faecalibacterium and Bifidobacterium,sample B was an enterotype dominated by Faecalibacterium and Bacteroides,and sample C was an enterotype dominated by Faecalibacterium,Bacteroides,Agathobacter and Bifidobacterium as the dominant enterotype,and sample D was Faecalibacterium,Bacteroides and Bifidobacterium as the dominant enterotype),using spectrophotometric methods,16 S rRNA analysis and gas chromatography to study the effects of ultrasound-modified OVM on the regulation of different donor faecal flora were investigated using spectrophotometry,16 S rRNA analysis and gas chromatography.The results showed that there were significant differences in the degree of fermentation utilization of ultrasonically modified OVM by different donor faecal flora,with the B donor faecal flora showing the highest protein utilization of ultrasonically modified OVM at 41.45% and the C donor faecal flora showing the highest carbohydrate utilization of ultrasonically modified OVM at 83.73%.The degree of utilisation of ultrasonically modified OVM by different donor faecal flora was confirmed by HPGPC chromatogram.After 48 h of fermentation with ultrasonically modified OVM,the different donor faecal flora were able to promote intestinal health by decreasing Escherichia-Shigella abundance,increasing Bacteroides abundance and increasing acetate,propionic acid,isobutyric acid,isovaleric acid and total short-chain fatty acids content by decreasing flora F/B values.However,it was only able to significantly increase the abundance of Bifidobacterium in intestinal phenotypes dominated by Faecalibacterium(15.3%),Bacteroides(17.0%)and Bifidobacterium(18.0%).In addition,Bacteroides enrichment varied between donor faecal fermentations,with Bacteroides caccae predominating in B donor faecal fermentations and Bacteroides vulgatus in C donor faecal fermentations. |
PDF Full Text Request