Abstract
Probiotics play crucial roles in promoting gut health, enhancing immunity, and combating pathogenic microorganisms, with increasing interest in their applications in the food and therapeutic industries. Lactococcus lactis, a well-known lactic acid bacterium, has emerged as a promising candidate owing to its probiotic traits and safety profile. In this study, we investigated the probiotic potential and genomic profile of Lactococcus lactis SK2-659, a strain isolated from Thai fermented green mustard (Pak-kad-dong). Genomic analysis revealed numerous genes associated with probiotic traits, including stress tolerance, adhesion, and antimicrobial activity, with a particular focus on bacteriocin SK2-659, which was effective against pathogenic bacteria such as Helicobacter pylori. The bacteriocin produced by L. lactis SK2-659, identified as nisin Z, disrupts bacterial membranes via pore formation, leading to cell lysis. Metabolomic profiling further highlighted its ability to increase carbohydrate and amino acid metabolism, supporting cell growth and survival in acidic environments. Also, amino acid metabolism (elevated tryptophan, tyrosine, histidine) supports acid tolerance and immune modulation. Tryptophan metabolism produces indole derivatives, which are known to benefit gut health and immunity. Additionally, strain SK2-659 demonstrated strong tolerance to gastrointestinal conditions, high adhesion capacity to intestinal cells, and immunomodulatory effects, contributing to gut health. Safety assessments confirmed the absence of virulence factors, pathogenic traits, and antibiotic resistance genes, along with a lack of biogenic amine production, underscoring its suitability for food and health applications. These findings establish L. lactis SK2-659 as a promising probiotic candidate with potential industrial applications in functional foods, food preservation, and therapeutic products. Given its probiotic properties, antimicrobial activity, and safety profile, this strain is particularly suited for the food industry as a functional food ingredient and natural bio-preservative, as well as the healthcare and pharmaceutical industries for use in therapeutic probiotics and gut health formulations.
