Promoting Effects Of Peptides From Chinese Yam On The Growth Of Bifidobacteria In Vitro

Dioscareaopposita,also known as Chinese yam,is the rhizome of perennial winding herbs of Dioscorea zingiberensis.It is a traditional food homologous to medicine and food in China,and it also belongs to the dual-use resources of medicine and food announced by the Ministry of Health of China.Bioactive peptides is a kind of peptides that are beneficial to life.Because of their rich structural types and various physiological activities,bioactive peptides are the most popular research objects and promising functional factors in the international food industry.In this study,using Chinese yam as raw material,the optimized technology of ultrasound-assisted preparation of Chinese yam peptide was obtained through a single factor and response surface test.The in vitro model was used to explore the probiotic activity of Chinese yam peptide in promoting intestinal probiotics.The fermentation products of intestinal probiotics were analyzed to provide a reference for developing and utilizing Chinese yam peptides.The main results are as follows:1.Establishment of the preparation technology of Chinese yam peptides:using the crude protein of Chinese yam extracted by alkali dissolution and acid precipitation as raw material,taking the degree of hydrolysis as the index,and based on determining the type of protease,through single factor test and response surface optimization,the technological conditions for the preparation of peptide of Chinese yam protein by ultrasonic pretreatment were as follows:after pretreatment of 25 min with ultrasonic power of 375 W and ultrasonic temperature of 45℃,the enzymatic hydrolysis process of the pepsin addition amount of 3000 U/g and enzymatic hydrolysis time of 1 h was adopted.The degree of hydrolysis under the optimal conditions was 24.96±0.14%,which was consistent with the predicted value of 24.94%and was 12.38%higher than that of the preparation process without ultrasonic under the same conditions.2.Study on the effect of Chinese yam peptides on the proliferation of probiotics:ultrasound-assisted peptides were used in the culture of lactic acid and bifidobacteria bacteria to study the effects of these peptides on the in vitro proliferation of these bacteria.The results showed that Chinese yam peptides could significantly promote the proliferation of Lactobacillus casei,Lactobacillus plantarum,Bifidobacterium bifidum,Lactobacillus acidophilus,Lactobacillus rhamnosus,Lactobacillus fermentans and Bifidobacterium breve in vitro.Still,no significant effect was shown on Lactobacillus bulgaricus proliferation.At the end of culture,OD₆₀₀values of the 7 kinds of lactic acid bacteria were increased by111%,108%,107%,109%,125%,113%and 106%respectively;the viable counts increased by 221%,135%,150%,139%,141%,117%and 120%respectively.In addition,Chinese yam peptide could advance the logarithmic phase and prolong the stable phase of Lactobacillus rhamnosus,thus increasing its growth rate.3.Analysis of simulated intestinal fermentation products of Chinese yam peptides:the contents of acetic acid,propionic acid,and butyric acid produced by Lactobacillus casei,Lactobacillus plantarum,Lactobacillus bulgaricus,Bifidobacterium bifidum,Lactobacillus acidophilus,Lactobacillus fermentans,and Bifidobacterium breve were analyzed by simulating the intestinal environment in vitro.The results showed that the main products of Chinese yam peptides fermented by lactic acid bacteria and Bifidobacterium in vitro were acetic acid,a small amount of propionic acid,and butyric acid.The acetic acid content of Lactobacillus casei,Lactobacillus plantarum,Lactobacillus bulgaricus,Lactobacillus rhamnosus,and Lactobacillus acidophilus reached the maximum at24 h,which was 6.150 mg/m L,6.254 mg/m L,5.376 mg/m L,5.034 mg/m L and 6.280mg/m L,respectively.The maximum acetic acid concentration of Lactobacillus fermentum and Bifidobacterium brevis was recorded as 5.169 mg/m L and 4.940mg/m L,respectively,at 48 h.At the same time,the acetic acid content of Bifidobacterium bifidum reached the maximum value of 5.003 mg/m L at 12 h.4.Study on the effects of Chinese yam peptides with different molecular weights on the proliferation of probiotics:the effects of Chinese yam peptides with molecular weights less than 3 ku,3～10 ku,and greater than 10 ku on the growth of four kinds of infant available probiotics in vitro were investigated,and the effect of Chinese yam peptide on the proliferation of probiotics in vitro was further discussed.The results showed that the proliferation-promoting effect of peptides with a molecular weight greater than 10 ku on four probiotics was significantly lower than that of peptides with a molecular weight lesser than 10 ku.The peptide with a molecular weight less than 3 ku had the best effect on the proliferation of Lactobacillus fermentans and Bifidobacterium brevis,the viable counts were 1.11times and 1.13times of that of 10 ku,respectively,and the molecular weight of p H was significantly lower than that of 10 ku.The molecular weight of 3～10 ku was the best in promoting the proliferation of Lactobacillus rhamnoides and Lactobacillus acidophilus,the viable counts were 1.78 and 1.12times higher than that of 10 ku,and the molecular weight of p H was significantly lower than that of 10 ku.5.Chinese yam peptides amino acid composition analysis and the growth of probiotics:the influence of molecular weight less than 3 ku,3～10 ku,more than 10 ku Chinese yam peptides contain glutamic acid,aspartic acid,threonine,serine and other 17 kinds of amino acids,with the decrease of the Chinese yam peptides molecular weight components,such as glutamic acid,aspartic acid and phenylalanine amino acid content increased.The probiotics growth promoting effect of Chinese yam peptides with molecular weight less than10 ku was better than that of Chinese yam peptides with molecular weight more than 10 ku,which was related to the higher content of glutamic acid,aspartic acid and phenylalanine.