Search Results (5)

Kimchi is a fermented Korean food typically made with napa cabbage, garlic, radish, ginger, and chili pepper. It is becoming increasingly popular due to its flavor, high fiber content, and purported probiotic benefits. The microbial ecology of the fermentation community has been extensively studied, though what’s less understood is how its microbial community changes when nutrients or pathogens are introduced. To study this, we used gnotobiotic cabbage media inoculated with a kimchi starter culture as a model system. These inoculated samples were exposed to E. coli or Bacillus cereus, with or without added nutrients in the form of tryptic soy broth (TSB). We tracked pH, colony-forming units (CFUs), and community composition over time. We also used Oxford Nanopore sequencing to analyze the 16S rRNA gene (V4–V9), followed by use of the Emu algorithm for taxonomic assignments. As expected, LABs suppressed pathogens, but this effect was weaker early on in the nutrient-rich condition. Pathogen exposure changed the overall community—Lactobacillus species became more common, and Leuconostoc mesenteroides less so. Interestingly, adding nutrients alone caused similar microbial shifts to those seen with pathogen exposure. This could suggest that nutrient levels have a larger impact on the final microbiome structure than direct microbial competition. Together, these findings suggest that monitoring total microbial composition, and not just the presence of pathogens, may be important for ensuring kimchi fermentation reproducibility. Full article

A plant-based beverage enhanced with GABA was developed through serial co-fermentation using Leuconostoc citreum S5 and Lactiplantibacillus plantarum KS2020. The first lactic acid fermentation was performed by Leu. citreum S5 with a vegetable mixture consisting of sliced radish, ginger, garlic, red pepper, bell pepper, and sucrose. The viable cell count of Leu. citreum S5 increased to 9.11–9.42 log CFU/mL with higher sucrose contents, indicating the highest value of 9.42 log CFU/mL at 5% sucrose on day 1. Mannitol and dextran production levels in the first fermented vegetable mixture were 6.66–14.54 mg/mL and 0.44–2.26%, respectively. A higher sucrose content produced more dextran, resulting in a concomitant increase in viscosity of 49.4 mPa·s. The second co-fermentation for the kimchi beverage base was performed by Lb. plantarum KS2020 for 5 days, resulting in 8.22–9.60 log CFU/mL. The pH of the co-fermented kimchi beverage base increased to 6.19–9.57 with an increasing monosodium glutamate (MSG) content (3–7%), while titratable acidity significantly decreased to 0.0–0.8%. The final co-fermented kimchi beverage base was enriched with 2.6% GABA. Consequently, a GABA kimchi beverage base with probiotics, a red pigment, and a pleasant flavor was developed using only vegetable ingredients by serial co-fermentation using lactic acid bacteria. Full article

Kimchi made from small-type (Altari) radishes grown in late spring is more pungent than that made from autumn-grown Altari radishes, which poses a major challenge in the kimchi industry. The mechanism through which the pungency of Altari radish changes seasonally has not been intensively investigated. In this study, three small-type radish cultivars with different pungency levels were cultivated in spring and autumn to identify the factors affecting the seasonal-dependent pungency of small-type radishes. The contents of pungency-related metabolite glucoraphasatin and other polar metabolites were analyzed. Although a previous study reported that the glucoraphasatin concentration affects the pungency of radish, in the current study, the concentration of neither glucoraphasatin nor its hydrolysis product (raphasatin) could fully explain the change in the pungency associated with radish cultivars grown in the two seasons. The change in the pungency of radish by season may be explained by the ratio of raphasatin content to total sweetness of sugars. In addition, the polar metabolites that differ with season were analyzed to identify seasonal biomarkers and understand the seasonal changed physio-biochemistry. Full article

The purpose of this study was to investigate the probiotic properties of lactic acid bacteria isolated from Korean radish water kimchi (dongchimi). A total of 800 isolates of lactic acid bacteria were isolated from kimchi, and the strain having reduction and tolerance capability for nitrate and nitrite was selected and identified as Lactiplantibacillus plantarum LB5 (LPLB5) by 16S rRNA sequencing. LPLB5 showed higher tolerance to acidic pH values (pH 2.5), 0.3% bile salts, and heat treatment (40, 50, and 60 °C). Antibacterial activity showed strong inhibition against four food-borne pathogenic bacteria (E. coli O157:H7 ATCC 35150, Pseudomonas aeruginosa KCCM 12539, Listeria monocytogenes KCCM 40307, and Staphylococcus aureus ATCC 25923). The strain did not show any antibiotic resistance, β-hemolytic activity, or ability to produce β-glucuronidase. LPLB5 also exhibited a 30% auto-aggregation ability and 33–60% co-aggregation ability with four pathogenic bacteria (E. coli O157: H7 ATCC 35150, E. coli KCTC 2571, L. monocytogenes ATCC 51776, and S. aureus ATCC 25923). Moreover, the strain showed approximately 40% 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical- and 10% 2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical-scavenging activity. In cell culture studies, human colon epithelial cells (Caco-2) were treated with LPLB5 (10⁶ and 10⁷ CFU/mL); the bacteria showed more than 70% adherence onto and a 32% invasion rate into the Caco-2 cells. LPLB5 significantly decreased the mRNA expression levels of pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-α)) and increased the mRNA expression levels of anti-inflammatory cytokines (interleukin-4 (IL-4), interleukin-10 (IL-10), and interferon-gamma (IFN-γ)) in lipopolysaccharide-stimulated Caco-2 cells. Our data suggest that LPLB5 is safe and possesses probiotic, antioxidant, and anti-inflammatory activities. Full article

In this study, biogenic amine content in two types of fermented radish kimchi (Kkakdugi and Chonggak kimchi) was determined by high performance liquid chromatography (HPLC). While most samples had low levels of biogenic amines, some samples contained histamine content over the toxicity limit. Additionally, significant amounts of total biogenic amines were detected in certain samples due to high levels of putrefactive amines. As one of the significant factors influencing biogenic amine content in both radish kimchi, Myeolchi-aekjoet appeared to be important source of histamine. Besides, tyramine-producing strains of lactic acid bacteria existed in both radish kimchi. Through 16s rRNA sequencing analysis, the dominant species of tyramine-producing strains was identified as Lactobacillus brevis, which suggests that the species is responsible for tyramine formation in both radish kimchi. During fermentation, a higher tyramine accumulation was observed in both radish kimchi when L. brevis strains were used as inocula. The addition of Myeolchi-aekjeot affected the initial concentrations of histamine and cadaverine in both radish kimchi. Therefore, this study suggests that reducing the ratio of Myeolchi-aekjeot to other ingredients (and/or using Myeolchi-aekjeot with low biogenic amine content) and using starter cultures with ability to degrade and/or inability to produce biogenic amines would be effective in reducing biogenic amine content in Kkakdugi and Chonggak kimchi. Full article