Untargeted metabolomics based on LC-MS to elucidate the mechanism underlying nitrite degradation by Limosilactobacillus fermentum RC4

Nitrite is a common additive that is used in processed meat products as a flavor enhancer, color fixative, and preservative; however, its excessive intake is harmful. Lactic acid bacteria are known to degrade nitrite, but the underlying mechanism remains unclear. Herein we cultured Limosilactobacillus fermentum RC4, which shows effective nitrite degradation ability, in modified de Man, Rogosa and Sharpe broth containing different sodium nitrite (NaNO2) concentrations [0 (control), 100, and 300 mg/L]. Fermentation broth samples were analyzed using liquid chromatography-tandem mass spectrometry, followed by multivariate statistical analyses. In comparison with the control group, 39 (6 upand 33 downregulated) and 68 (17 upand 51 downregulated) significantly differential metabolites were identified in the 100 and 300 mg/L experimental groups, respectively. These metabolites mainly were amino acids, glucides, and purines and principally associated with amino acid, carbohydrate, and purine metabolism. In the process of NaNO2 degradation by L. fermentum RC4, energy supply and tolerance to osmotic stress were enhanced, antioxidant capacity was reduced, and cell growth was inhibited. This is the first systematic study to report the potential mechanism via which L. fermentum RC4 degrades nitrite.

Automated summary

In this study, Limosilactobacillus fermentum RC4 was cultured and found to have effective nitrite degradation ability. During the process of nitrite degradation, significant metabolic changes occurred, mainly involving amino acid and purine metabolism. Additionally, energy supply was enhanced, antioxidant capacity was reduced, and cell growth was inhibited.