Metabolomics Study Of Different Base Materials Fermented By Streptococcus Thermophilus S10

The strain Streptococcus thermophilus S10 was isolated from a naturally fermented milk product collected in Qinghai,China.Streptococcus thermophilus S10 as a fermentation agent has the characteristics of producing aroma and stickiness,and making the fermented milk have a small change in lactic acid.Even though the significance of Streptococcus thermophilus species in dairy product fermentation industry,scarce studies have systematically tracked metabolites changes in the fermentation process of different base materials.This work applied the ultra high performance liquid chromatography couple to quadrupole time-of-flight mass spectrum method in combination with multivariate analysis Principal component analysis and Orthogonal Partial Least Squares Discriminant Analysis to identify differential biomarkers in the milk,brown milk and whey fermentation.The specific experimental results were as follows.1)A total of thirty-nine significant differential metabolites were identified between milk and fermented milk,including peptides,amino acids,fatty acids and related metabolites,vitamins.The content of L-Leu-Gly-L-Ser-L-Glu-Gly,tyrosine,cysteine,α-stearic acid,lauric acid and vitamin B2 in fermented milk were significantly higher than milk.These enriched differential metabolites contribute to the unique flavor,taste,and aroma of fermented milk.The formation of S-methyl thioesters from short chain fatty acids providing a unique flavor to fermented milk.Whereas,peptides containing Gly-,Ala-,and Asp-residues also give fermented milk the sourness flavor,while other peptides give fermented milk beneficial functions like biological activity2)A total of forty-three significant differential metabolites were identified between brown milk and brown fermented milk,including peptides,amino acids,fatty acids and related metabolites,carbohydrate metabolites,vitamins and nucleosides.The content of Gly-Gly,Gly-Gly-Pro,leucine,lysine,stearic acid,oleic acid,hypoxanthine,riboflavin and other metabolites in brown fermented milk were significantly higher than brown milk.These enriched differential metabolites changed the sensory quality of brown fermented milk.The bitterness and astringency of brown fermented milk are likely to be due to some of these amino acids,whereas the sweetness and sourness could be a result of changes in peptides and carbohydrate levels.3)A total of thirty-six significant differential metabolites were identified between whey and fermented whey beverage,including peptides,amino acids,and organic acids.The content of Pro-Glu-Gly-Ile-Ala-Gly-Glu-Arg,Gln-Lys-His-Ser,glutamine,succinic acid,and fumaric acid in fermented whey beverage were much higher than in whey.The peptides changed not only have nutritional functions which are easy to digest and absorb,but also have many physiological functions such as antibacterial activity,immune activity,and anti-inflammatory effects.The increase of glutamine can improve the body’s antioxidant capacity,and the changed organic acids make up the unique flavor of fermented whey beverage.This study indicates that Streptococcus thermophilus S10 shows good metabolic characteristics during the fermentation of milk,brown milk,and whey.These data provide a theoretical basis for the future development and improvement of fermented dairy products of Streptococcus thermophilus.