Lactic acid bacteria (LAB) and probiotics promise specific health benefits to their host. However, good storage stability is a prerequisite for their functioning and industrial use. This study aimed to evaluate glutathione (GSH) as a potential protective agent for improving microbial stability deteriorated by freeze-drying, freeze-thawing, and cold treatments. In this study, the optimal concentration of glutathione (50% w/w) was 1%, showing effective protection on the viability and stability of various LAB strains (Lactiplantibacillus plantarum MG4229 and MG4296, Lactococcus lactis MG5125, Limosilactobacillus fermentum MG4295, Lacticaseibacillus paracasei MG5012, and Bifidobacterium animalis ssp. lactis MG741). Glutathione-containing protectants considerably improved the viability of all of these strains after freeze-drying compared with non-coated probiotics. Survivability in the gastrointestinal (GI) tract, accelerated stability tests, and adhesion assays on intestinal epithelial cells were performed to determine whether glutathione enhances bacterial stability. Based on morphological observations, protectants containing GSH were coated onto the cell surface, resulting in effective protection against multiple external stress stimuli. The applicability of GSH as a new and effective protective agent can improve the stability and viability of various probiotics with anti-freezing and anti-thawing effects.

In this study, lactic acid bacteria (LAB) with antioxidative and probiotic activities were isolated from the vaginas of Korean women and from fermented food. Among 34 isolated LAB strains, four strains (MG4221, MG4231, MG4261, and MG4270) exhibited inhibitory activity against nitric oxide production. The MG4221 and MG4270 strains were identified as Lactobacillus plantarum, and MG4231 and MG4261 were identified as Lactobacillus fermentum. These strains were able to tolerate pepsin and pancreatin, which is required for probiotic potential. The antioxidant effects of culture filtrates obtained from selected strains included 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging capacity. Most of the culture filtrates had effective DPPH scavenging activity.In conclusion, the selected strains have significant activities and are potentially applicable to the development of functional foods. These strains might also contribute to the prevention and control of several diseases associated with oxidative stress, when used as functional probiotics.

Lactic acid bacteria have become popular because of their γ-aminobutyric acid (GABA)-producing ability. In the present study, we selected four Levilactobacillus brevis strains (MG5552, MG5405, MG5261, and MG5522) with GABA-producing ability from the 33 strains isolated from various fermented foods in South Korea. We evaluated their GABA-producing ability using thin-layer chromatography and determined the GABA levels produced by each strain using an amino acid analyzer. Moreover, we investigated the anti-inflammatory activity of the selected strains, and the results revealed that the cell-free supernatant of the strains decreased nitric oxide (NO), inducible nitric oxide synthase (iNOS) expression, and nuclear factor kappa B (NF-κB) activity in RAW264.7 macrophages. Therefore, these GABA-producing LAB strains can regulate nerve excitement and act as probiotics with anti-inflammatory activity.