Metabolome Analysis Of Milk Fermented By The Probiotic Lactobacillus Plantarum P-8

Metabonomics is an important branch of systems biology,which focuses on the study of small molecules in biological samples.As a new research technology,it has been widely used in various fields such as food quality,nutrition analysis,and tracking of origin.In recent years,researchers have developed a keen interest in applying meta-bonomics research techniques in the scientific evaluation of probiotics-fermented dairy products.The probiotic strain,Lactobacillus plantarum P-8 was isolated from naturally fermented yoghurt collected in Bayannaoer City of Inner Mongolia,and it has excellent properties,such as regulation of blood lipid and anti-oxidation.In this work,firstly,the milk production was fermented with commercial starter YC-X11 in adjunct with L.plantarum P-8.And the fermented milk was analyzed with ultra-high-performance liquid chromatography coupled with tandem quadrupole time-of-flight-mass spectrometry(UPLC/Q-TOF-MS)and multivariate statistical methods to identi-fy the small molecule metabolites during fermentation.The main results follow:(1)When the single strain of L.plantarum P-8 was used in the fermentation,the time to reach the end point was 13 hours.The fermentation time required 5 hours with both L.plantarum P-8 and commercial starter YC-X11.During the fermentation process,the bacterial viable counts in different fermentated milk significantly increas ed(P<0.05),and the titratableacidity significantly increased(P<0.05).Compared with the commercial fermented milk and the fermented milk with L.plantarum P-8,the different metabolites in the fermented milk with the single strain of L.plantarum P-8 were organic acid(13),polypeptide(7),free amino acid(8),nucleic acid metabolites(5)and aromatic substance(5).The different metabolites with the commercial fermented milk were organic acid(11),polypeptide(4),free amino acid(10),nucleic acid metabolites(4)and aromatic substance(2)in femented milk with L.plantarum P-8.3-Phenyllactate,phenylacetaldehyde,methionine,serine and Lys-Val etc.levels in fermented milk with L.plantarum P-8 were significantly higher than that of commercial fermented milk(P<0.05),which involves the tricar boxylic acid cycle,amino acid metabolism,active polypeptide hydrolysis and synthe-sis of flavor substances.(2)The different metabolites between the mixed fermented milk and the fermented milk with L.plantarum P-8 were organic acid(7),polypeptide(4),free amino acid(4),nucleic acid metabolites(4)and aromatic substance(3).The content of Ala-Ile,Asn-Ser,Pro-Asn,Val-Asn,Lauric acid,Myristic acid,and Dopamine in the mixed fermentation milk was significantly higher than that in the fermented milk with L.plantarum P-8.The different metabolites between the mixed fermented milk and commercial fermented milk were organic acid(3),polypeptide(4),free amino acid(3),nucleic acid metabolites(1)and aromatic substance(4).The human body essential amino acids threonine,galactose,four kinds of polypeptide Lys-Val,Val-Val and Met-Gln,flavor substances amyl lemon acid ethyl ester,salicylic acid,acetic acid ester and benzoic acid ester,and the neural regulation substances serotonin levels in the mixed fermented milk were significantly higher than that of commercial fermented milk.It proved that the flavor and nutrition of the mixed fermented milk were better than commercial fermented milk.(3)Based on the results of L.plantarum P-8 metabonomics difference,combin-ed with the complete genome sequence of L.plantarum P-8,this study analyzed glucose metabolism,hydrolysis of protein metabolism,fatty acid metabolism and gamma aminobutyric acid metabolism system characteristics of L.plantarum P-8,further explained the metabolic pathways changes and metabolites of L.plantarum P-8 in the fermentation process.The above results showed that L.plantarum P-8 could use its own metabolism to generate specific amino acids and peptides during the fermentation process,which add special nutritional value to the fermented dairy products.The implementation and completion of this work can lay a solid theoretical foundation for the optimization of industrial production of L.plantarum P-8 fermented milk.