| Dietary nutrients can effectively regulate the composition proportion and function of digestive tract microorganisms,and protein is an important nutrient in human daily diet.Probiotics in the gut microbiota contribute to the metabolic health of the host,improve the intestinal microenvironment,maintain intestinal homeostasis,and prevent and treat disease.The ability of probiotics to proliferate and their ability to adhere to the intestinal tract are important factors that determine their ability to colonize the intestinal tract.Substances called prebiotics often have probiotic activities such as improving colonization resistance and regulating intestinal microenvironment.Currently,studies on the intestinal probiotics activity of polysaccharides have been relatively mature,but there are few studies on the intestinal probiotics activity of proteins.Based on this,this study was conducted to investigate the proliferation rate and total number of colonies of probiotic bacteria by adding food-derived protein(Ilisha elongata protein,Soy protein,Whey protein),and to establish a new probiotic adhesion model based on mouse intestinal tissues to investigate the effect of food-derived protein on the number of probiotic bacteria adhering to the intestine and the intestinal microenvironment,and to investigate the effect of different food-derived proteins on proliferation and intestinal adhesion of probiotic bacteria.We also analyzed the structure and amino acid composition of food-derived proteins to investigate the relationship between the effect of food-derived proteins on the growth and adhesion characteristics of Lactobacillus plantarum and the structure and composition of the proteins.The main studies and results are as follows.(1)Eight aquatic crude proteins were extracted by aqueous extraction method,and the probiotic proliferation ability of each aquatic crude protein was evaluated by culturing Bifidobacterium lactis M8,Lactobacillus plantarum LP45,and Bifidobacterium bifidum BBi32 in nitrogen source deficient medium and measuring the growth generation time and total colony number of probiotic bacteria.The results showed that the protein hydrolysis system of LP45 was more active and more capable of utilizing the protein,and the IeP had the most significant effect on the proliferation rate and proliferation total colony number of LP45.(2)The protein molecular weight distribution,microstructure,secondary structure content and amino acid composition of IeP,SP and WP were investigated by using SDS-PAGE,scanning electron microscopy,infrared spectroscopy analysis,circular dichroism and amino acid analysis.The results showed that the molecular weight of IeP was mainly distributed between 14.3 and 97.2 kDa,the molecular weight of SP was mainly distributed between 29.0 and 97.2 kDa,and the molecular weight of WP was smaller mainly distributed between 20.1 and 29.0 kDa,and the microscopic morphology of IeP was more complex and the structure was more dense.the irregularly curled structure of IeP was significantly lower than that of SP and WP,and the ?-helical component of IeP was also significantly higher than that of WP.The?-helical component of IeP was also significantly higher than that of SP and WP,which suggests that IeP is more stable than the other two food-derived proteins.The amino acid composition of IeP,SP and WP revealed that the food-derived proteins were rich in amino acids,with high EAA content and high levels of glutamic acid,aspartic acid and lysine,presumably with strong free radical scavenging activity and providing rich nutritional prerequisites for enteric probiotic fermentation.Comparison of the effects of three foodderived proteins,IeP,SP and WP,on the growth characteristics of LP45 showed that the growth time of LP45 in the control group was 2.27 ± 0.03 and the total number of colonies was 1.95×109 CFU/mL,while the addition of 1 mg/mL of IeP significantly accelerated the growth rate of Lactobacillus plantarum and significantly increased the total number of colonies proliferated,with the growth time The growth time was shortened to 1.49 ± 0.01 and the total number of colonies increased to 2.385×1010 CFU/mL,which was an order of magnitude increase;the addition of 1 mg/mL SP significantly accelerated the growth rate of LP45 and significantly increased the total number of proliferating colonies,the growth time was shortened to 1.56 ± 0.01 and the total number of colonies increased to 6.5×109 CFU/mL;the addition of 1 mg/mL WP significantly accelerated the growth rate of LP45 and significantly increased the total number of proliferating colonies;the addition of 1 mg/mL WP significantly accelerated the growth rate of LP45 and significantly increased the total number of colonies.The addition of 1 mg/mL WP significantly accelerated the growth rate of LP45 and reduced the total number of colonies,with a shortened growth generation of 1.55 ± 0.16 and a total number of colonies of 1.6×109 CFU/mL.In a comprehensive comparison,IeP was more effective than SP and WP in increasing the total colony number of LP45,while the addition of food-derived protein had less effect on the acid production capacity of LP45.(3)The effect of food-derived protein on the adhesion capacity of LP45 was evaluated indirectly by using the addition of food-derived protein to culture LP45 and measuring the changes of hydrophobic capacity,self-aggregation capacity and copolymerization capacity of probiotic bacteria.The results showed that IeP had a small effect on the hydrophobicity,selfaggregation and copolymerization ability of LP45,while SP significantly decreased the hydrophobicity,significantly elevated the self-aggregation ability and decreased the copolymerization ability of LP45.WP had less effect on hydrophobicity and self-aggregation ability of LP45,but decreased copolymerization ability.A novel probiotic adhesion model based on mouse intestinal tissues was constructed,and the number of adherent colonies and scanning electron micrographs were measured to visually evaluate the adhesion ability.The changes of intestinal polysaccharide content,protein content and biofilm were also measured to investigate the changes of intestinal microenvironment caused by food-derived protein on probiotic adhesion.The results showed that Ilisha elongata fish protein significantly increased the number of adherent live bacteria of LP45 on duodenum,SP significantly increased the number of adherent live bacteria of LP45 on jejunum,and WP had less effect on the number of adherent live bacteria of LP45 on each intestinal segment,and all three food-derived proteins may promote probiotic bacteria in the intestine by stimulating LP45 to secrete extracellular polysaccharides,epithelial proteins and other adhesins as well as stimulating intestinal secretion of adhesion.The microenvironment of adhesion in each intestinal segment was improved by stimulating the colonization of the intestinal tract. |
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