Study On The Metabolomics Of Fermented Milk Of Lactobacillus Helveticus H9 Based On LC-MS

Lactobacillus helveticus H9 is a probiotic,which was isolated from kurut in Tibet area.It showed good tolerance to stomach intestinal juice and has ACE-inhibitory activity,suggesting that it was an ideal strain for probiotic research.Lactobacillus helveticus strain has a wide range of applications in fermented dairy products,however post-acidification is a dificiency in the industrial application for Lactobacillus helveticus.Meanwhile,post-acidification has certain damage to the taste and flavor for fermented dairy products.In order to elucidate the fermentation characteristics and provide the therotical thesis for weaking the post-acidification of L.helveticus H9,this study used UPLC Q-Tof to analyze the metabolites of it.Based on PCA and OPLS-DA,this study analyzed the metabolites of L.helveticus H9 and YF-L904.The results showed that there is a significant difference in amino acids,vitamins and nucleic acids during fermermented phases.Metabolites,such as phenylalanine,threonine,leucine,tyrosine,vitamin H,nicotinic acid,thymidine and cytidine were significantly decreased,whereas carnitine,adenine,tryptophan were increased in L.helveticus H9 group during fermentation prophase.Lysine,nicotinic acid,and adenine were significantly decreased,whereas homoserine and serine were significantly increased during fermentation metaphase.Besides,tyrosine and glutamine were significantly reduced,and metabolites such as phosphorylcholine and thymine increased during fermentation endphase.Moreover,these metabolites are mainly manifested in the levels of glycolysis,pentose phosphorylation,fatty acid metabolism,carnitine metabolism,methionine metabolism,aspartic acid metabolism,pyrimidine metabolism,vitamin metabolism,cysteine metabolism,and betaine metabolism.Among these metabolites,the aspartic acid metabolism and carnitine metabolism play a key role in the fermentation process of L.helveticus H9.The threonine is significantly increased in the middle fermentation stage,which is an important determinant factor for the rapid growth of L.helveticus H9 from fermentation metaphase to endphase.Carnitine metabolism in lipid metabolism is mainly involved in the transport of fatty acids,which has a certain degree of influence on the post-acidification of L.helveticus H9.The IPI,ALPM,and VAGTWY in protein metabolism have blood pressure lowering effects,and uric acid with antioxidant activity has also been found which provide basis for its probiotic characteristics.