In Vitro Simulated Digestion Of Goat Milk Protein And The Effect Of Goat Milk On Gut Microbes

Goat milk is an important special milk with important nutritional and functional properties,and the main products processed and utilized are goat mature milk and colostrum.Based on the analysis of the basic components of goat mature milk and colostrum,this study applied in vitro simulated gastrointestinal digestion and high-throughput sequencing technology to study the digestive characteristics of goat milk protein and the influence of goat milk on gut microbiota,to provide the basis for the development of goat milk.1.The components of goat mature milk and colostrum.The contents of protein,fat,mineral,lactose and dry matter in goat mature milk were 3.59%,4.02%,0.72%,4.51%and 12.57%,while the contents in goat colostrum were 8.78%,6.61%,0.94%,2.14%and 19.14%.In terms of protein composition,the high content of casein in goat mature milk was 2.23 g/100g,which was mainly composed of ?s2-casein,?s1-casein and?-casein,and whey protein was mainly composed of ?-lactalbumin and ?-lactoglobulin;the high content of whey protein in goat colostrum was 3.91 g/100g,which was mainly composed of lactoferrin,serum albumin and immunoglobulin,and casein was mainly composed of ?s2-casein,?s1-casein and ?-casein.The essential amino acid content in goat mature milk and colostrum were 1.68 g/100g and 1.89 g/100g,while the non-essential amino acid content in goat mature milk and colostrum were 1.69 g/100g and 3.06 g/100g respectively.Goat mature milk and goat colostrum were mainly composed of medium and long-chain fatty acids,and goat colostrum contained more abundant butyric acid and caproic acid.The contents of EGF(epidermal growth-promoting factor),IGF-1(insulin-like factor),LTF(lactoferrin)and IgG(immunoglobulin G)in goat colostrum were as high as 53.67 ng/ml,422.27 ng/ml,and 1534.33 ?g/ml and 8123.33 ?g/ml respectively,while the content of cAMP(cyclic adenosine monophosphate)in goat mature milk was as high as 1878.67 ng/ml.2.The digestive characteristics of protein in goat milk.The digestion characteristics of protein in goat milk were studied by simulating adult and infant gastrointestinal digestion.The results showed that the digestibility of casein and whey protein in the fasting state was significantly higher than that in the normal state and fullness state in the simulated adult gastrointestinal digestion conditions.When simulating the digestion of adult and infant gastrointestinal digestion conditions,the digestibility of casein and whey protein separated was higher than that in goat milk;the digestibility of casein was significantly higher than ?-lactoglobulin and a-lactalbumin,and protein digestion mainly occurred in the intestine.3.The influence of goat mature milk and colostrum on gut microbiota.The effect of goat mature milk and colostrum on gut microbiota was studied by high-throughput sequencing technology.The results showed that the abundance of microbial communities of mice fed with goat colostrum and goat mature milk decreased but the diversity increased.Goat mature milk could promote the growth of intestinal probiotics Lactobacillus,Muribaculum,Roseburia,Enterorhabdus,Butyricimonas and Streptococcus.Goat colostrum could promote the growth of intestinal probiotics Alistipes,Blautia and Lachnospira,while also cause the growth of intestinal pathogen Helicobacter.The correlation between milk components and gut microbiota indicated that lactose was beneficial to the growth of Lactobacillus and Roseburia,while milk fat could promote the growth of the pathogen Helicobacter.4.The influence of goat milk components on gut microbiota.The components of goat milk were separated,and the effects of different components(milk fat,casein,whey protein,milk whey and whey supernatant)on gut microbiota were studied using high-throughput sequencing technology.The results showed that different milk components had different impacts on the composition of gut microbiota.Goat milk could significantly promote the growth of intestinal probiotic Lactobacillus.Milk fat caused the the abundance and diversity of microbial communities decreased,and the pathogen Bacteroides and Anaerotruncus increased significantly(P<0.05).Casein could promote the growth of intestinal probiotic Blautia.Whey protein was able to significantly increase the abundance of Blautia,Alloprevotella and Bilophila,and decrease the abundance of pathogen Helicobacter(P<0.05).Milk whey significantly increased the abundance of Streptococcus,Blautia,Intestinimonas and Butyricimonas,and promoted the butyrate metabolism.Whey supernatant significantly increased the abundance of Streptococcus,and promoted the carbohydrate metabolism,energy metabolism,polysaccharide biosynthesis metabolism,cofactor metabolism and vitamin metabolism(P<0.05).