Effect of acid and alkali stress on extracellular metabolite profile of Lactobacillus plantarum ATCC 14917.

Abstract

As a multifunctional lactic acid bacterium, Lactobacillus plantarum has been proved to survive in the human gastrointestinal tract, and it can also colonize this tract. In this study, the effects of L. plantarum ATCC 14917 metabolic profile caused by initial acid-base (pH 5.5 and 8.5) stress were investigated using 1 H nuclear magnetic resonance spectroscopy and multivariate data analysis. The results showed that the metabolome mainly consisted of 14 metabolites, including the components like amino acids, sugars, organic acids, and alkaloids. According to the nontargeted principal component analysis, there was a decrease in most of the metabolites in the alkali-treated group (mainly change in PC1) except acetate, whereas the production of lactate and glycine was increased in the acid-treated group (mainly change in PC2). Furthermore, the initial alkali stress inhibits the secretion of lactic acid, as a decrease was observed in the activity of lactate dehydrogenase and acetic dehydrogenase of L. plantarum ATCC 14917 in the alkali group. All these findings revealed that alkali stress could limit the acid environment formation of L. plantarum 14917 in the fermentation process; however, low acid pH is more suitable for the growth of L. plantarum.