Study On The Growth And Its Metabolism Of Lactobacillus Casei Zhang Under Glucose-restricted Environment Using Comparative Proteomics And Metabolomics

Increased public awareness of the health-promoting properties of lactic acid bacteria(LAB)has resulted in a number of opportunities for their commercialization.During production,LAB are subjected to a various stresses,for example,it is affected by the glucose-restricted environment during the fermentation of soymilk.,and this stress which not only deteriorate the physiological condition of the LAB but also hamper their subsequent application.Therefore,the mechanism(s)by which LAB adapt to stressful environments needs to be studied.In this study Lactobacillus casei Zhang generation 0,as well as generations 1,000,2,000,3,000,4,000,5,000,6,000,7,000,and 8,000,which have been subcultured for almost 4 years under glucose-restricted conditions was used as a proteomics research.We applied tandem mass spectrometry to identify,quantify and bioinformatics of these L.casei Zhang generations.The results are listed below:(1)Proteins whose abundance was increased by glucose restriction were related to fructose and mannose metabolism,amino acid synthesis,carbon metabolism,the pentose phosphate pathway,glycolysis/gluconeogenesis,and the phosphotransferase system.(2)In a Gene Ontology analysis,the differentially abundant proteins were mainly enriched in the metabolism and cells and membranes categories;the major molecular function was catalytic activity.(3)Key differentially abundant proteins protect L.casei Zhang against glucose stress by modulating carbohydrate,energy,nucleic acid,and amino acid metabolism and membrane transport.The results of a metabolomic analysis of L.casei Zhang generations 0,2,000,4,000,6,000,and 8,000 are summarized below.(1)The differentially abundant metabolites were enriched in glycolysis/gluconeogenesis,aspartate metabolism,fructose and mannose degradation,lactose synthesis,and cysteine and tryptophan metabolism.(2)After depletion of glucose,L casei Zhang switches from sugar to other substances(e.g.,amino acids)as its source of carbon and energy.Also,sugar substitutes are produced to protect cells.(3)The differentially abundant metabolites were related to carbohydrate metabolism(?-D-fructose 1,6-bisphosphate,and glyceraldehyde-3-phosphate),amino acid metabolism(L-proline,L-serine,and L-asparagine),and nucleotide metabolism(thymine,uridine,and adenosine).The results of our proteomic and metabolomic analyses of the effect of glucose restriction on L.casei Zhang will facilitate screening for LAB with enhanced stress resistance,as well as optimization of their industrial-scale production.