Isolation, characterization, and genomic analysis of Pediococcus pentosaceus M1 and Staphylococcus capitis D3 nitrate-reducing bacteria from fermented Korean food

Nitric oxide plays a crucial role in maintaining homeostasis in the human body via various functions, such as vasodilation and neurotransmitter activity. However, after 40 years of age, its production decreases by 50%, and after 70 years, almost no nitric oxide is produced. Nitrate-reducing microorganisms could be a promising approach to increase the production of NO. In this study, we isolated nitrate-reducing microorganisms from traditionally fermented foods. Of the 2628 isolated bacteria, 367 reduced nitrates. Two strains that exhibited high nitrite production were Pediococcus pentosaceus M1 and Staphylococcus capitis D3. The D3 strain was confirmed to be coagulase negative. Whole-genome sequencing analysis of the M1 and D3 strains was conducted using the Illumina and Nanopore hybrid methods. P. pentosaceus and S. capitis had 1216 and 1846 core genes, respectively. Furthermore, virulence factor analysis revealed the absence of enterotoxin genes in S. capitis. A search for genes associated with nitrate metabolism revealed the presence of genes, such as narZ and glnR. Evaluation of the nitrate reduction based on carbon source revealed that the M1 strain efficiently utilized glucose, whereas the D3 strain did not efficiently use the carbon source. Finally, acid and bile resistances were measured for the strains. The survival rate of M1 was found to be 96.59% (acid) and 93.92% (bile), whereas that of D3 was 17.46% (acid) and 65.1% (bile). Further research is recommended to explore the potential applications in commercial food products and to evaluate their long-term safety and efficacy.