Screening and Functional Characterization of Fermentation Bacteria Isolated from Jeotgal, a Traditional Korean Fermented Seafood Product

다국어 초록 (Multilingual Abstract)

In this study, the diversity and functional potential of halophilic bacteria isolated from 15 jeotgal samples representing seven raw materials and four regions in Korea were evaluated. Bacteria were isolated from jeotgal to screen those with high hydrolase activity, including amylase, protease, esterase, and lipase, resulting in the selection of five strains exhibiting strong enzymatic activities. All strains showed stable growth at 5–10% NaCl and pH 6–7, and the strains JAMA1, JAMA4, and JAMA11 were also able to grow at pH 5, indicating their potential applicability in jeotgal fermentation. Five strains exhibiting strong hydrolytic activity were selected and identified as Halobacillus (KGMA1, KGMA2) and Bacillus (JAMA1, JAMA4, JAMA11) based on 16S rRNA gene analysis. Safety evaluations showed that all selected strains exhibited γ-hemolysis, lacked gelatinase and biogenic amine production, and were susceptible to most tested antibiotics. Functional analyses demonstrated strong antioxidant activity in ABTS and superoxide dismutase (SOD)-like assays, as well as variable antimicrobial activity against foodborne pathogens Staphylococcus aureus, Bacillus cereus, and Vibrio parahaemolyticus. JAMA4 exhibited the strongest growth inhibitory effects against all three tested foodborne pathogens, including V. parahaemolyticus. Immune-related assays using THP-1–derived macrophages revealed that the fermentation supernatants modulated the expression of IL-6, TNF-α, and IL-1β, and JAMA4 induced immune-related gene expression across multiple markers, exhibiting the most desirable overall functional profile. Taken together, Bacillus tequilensis JAMA4 demonstrated the most favorable combination of enzymatic, antioxidant, antimicrobial, and immunomodulatory properties. These findings suggest that JAMA4 may be a promising functional starter culture candidate capable of enhancing the quality, safety, and health-promoting attributes of fermented seafood products.

목차 (Table of Contents)

• 1. INRODUCTION 10
• 2. MATERIALS AND METHODS 12
• 2.1 Collection of Jeotgal Samples 12
• 2.2 Characterization of Jeotgal Samples 12
• 2.3 Bacterial Isolation from Jeotgal Samples 13
• 2.4 Evaluation of Hydrolytic Enzyme Activities 14
• 2.5 Evaluation of Acid and Salt Tolerance 15
• 2.6 Phylogenetic Analysis Based on 16S rRNA Gene Sequences 16
• 2.7 Safety Assessment 17
• 2.7.1 Hemolytic Activity 17
• 2.7.2 Gelatinase Activity 17
• 2.7.3 Antibiotic Susceptibility 17
• 2.7.4 Biogenic Amine (BA) Production 18
• 2.8 Evaluation of Radical Scavenging Activities 19
• 2.8.1 Preparation of cell-free supernatants 19
• 2.8.2 DPPH Assay 19
• 2.8.3 ABTS Assay 19
• 2.8.4 SOD-like Activity Assay 20
• 2.9 Evaluation of Anti-Pathogenic Activities 21
• 2.10 Assessment of Cell-Based Immune Activities Using RT-qPCR 22
• 2.11 Statistical Analysis 23
• 3. RESULTS 24
• 3.1 Collection and Characterization of Jeotgal Samples 24
• 3.2 Isolation and Screening of Microorganisms from Jeotgal 26
• 3.3 Selection and Identification of Strains with High Fermentation Potential 30
• 3.4 Safety Evaluation of Selected Strains 35
• 3.5 Functional Evaluation of Selected Strains 38
• 3.6 Immune-Related Activities of Fermentation Supernatants 43
• 4. DISCUSSSION 45
• 5. CONCLUSION 52
• 6. 국문 요약 53
• 7. REFERENCES 55