Effects Of Growth Temperature On Metabolic Characteristics Of Lactobacillus Paracasei PC-01

Lactobacillus paracasei PC-01 is a probiotic strain with good gastrointestinal digestion tolerance and fermentation characteristics.It has important application value in probiotic starters and fermented dairy products.Preliminary studies have found that temperature causes changes in the growth characteristics of strains and has a significant impact on the fermentation quality.This study analyzed the metabolites the growth process at typical fermentation temperatures(30°C and 37°C),revealing the Lactobacillus paracasei PC-01 correlation between metabolites differences and growth characteristics at different temperatures :(1)Comparison of growth characteristics found that the acid production rate of Lactobacillus paracasei PC-01 grown at 37°C decreased significantly quicker than 30°C(p<0.05),and the p H gradually became constent with the extension of the fermentation time.The biomass and the number of viable bacteria grown at 30°C were significantly higher than those at 37°C(p<0.05).(2)SPME-GC-MS analysis of samples from three different culture periods(prefermentation,mid-fermentation and late-fermentation)found that there were 9 kinds of fatty acids including 5 kinds of saturated fatty acids at 30°C and 37°C in Lactobacillus paracasei PC-01(methyl myristate,methyl myristate,methyl palmitoleate,methyl stearate and heptadecanoic acid),4 kinds of unsaturated fatty acids(methyl palmitoleate,methyl linoleate,methyl oleate and methyl cis-11,14-eicosadienoate).Their saturated fatty acid content and the relative content of unsaturated fatty acid were significantly different(p<0.05).(3)UPLC Q-TOF-MS non-targeted metabolomics analysis of samples from 24 different culture periods(lag phase,log phase,stable phase and decay phase)found that the amino acid,there were significant differences in fatty acids,peptides and other metabolites(p<0.05).There are 5 different metabolites in the lag phase(?-amino acids,amphetamine and ribonucleotides,etc.),5 different metabolites in the log phase(linoleic acid,palmitic acid,etc.),19 different metabolites in the stable phase(acetyl amino acids,?-linolenic acid and phenylalanine,etc.),20 kinds of metabolites in the decay periods(glutamine,?-dicarboxylic acid and ?-phenylacrylic acid etc.).The metabolic pathways of Lactobacillus paracasei PC-01 at 30°C and 37°C mainly involve the biosynthesis of unsaturated fatty acids,saturated fatty acids,phenylalanine,tyrosine and tryptophan.This study reveals the growth and metabolism of Lactobacillus paracasei PC-01 at different temperatures and its mechanism from the metabolic level,which provides a useful reference for the improvement of the later fermentation characteristics of this strain and the optimization of the culture process.