Isolation and Characterization of Lactobacillus Strains from Korean Traditional Fermented Foods

다국어 초록 (Multilingual Abstract)

Isolation and Characterization of Lactobacillus Strains from Korean Traditional Fermented Foods Kwang Rak Hong Department of Bio-Resources Science Graduate School of Dankook University Advisor: Professor Dae-Kyung Kang This study aimed to evaluate the probiotic characteristics of 11 lactic acid bacteria strains isolated from kimchi, a representative Korean traditional fermented food, including acid resistance, bile tolerance, mucosal adhesion ability, and antimicrobial activity. Through 16S rRNA gene sequencing analysis, nine strains were identified as L. plantarum, while the remaining two were identified as L. fermentum and L. brevis. The 11 strains were designated as MD152 to MD160, MD165, and MD167. Lactobacillus rhamnosus GG, known for its well-studied efficacy, was used as a control group. Half of the isolated strains exhibited acid resistance similar to LGG, with MD159 showing the highest stability under acidic conditions. Furthermore, 10 of the strains, except for MD158, demonstrated clear bile acid resistance. All strains showed a mucin adherence capacity that was up to 15% lower than that of LGG. Antimicrobial activity measurements against pathogenic microorganisms revealed that strains MD159 and MD165 showed overall strong antimicrobial effects. To further investigate the potential of MD159 as a functional probiotic, whole genome sequencing (WGS) analysis was performed, followed by assessments of antibiotic resistance genes and virulence factor genes to confirm its safety. In conclusion, among the 11 isolated strains, L. plantarum MD159 exhibited comprehensive probiotic activity and has the potential for use as a promising probiotic strain. Keywords: Korean traditional fermented food, Probiotics, L. plantarum, LGG

목차 (Table of Contents)

• I. INTRODUCTION 1
• II. LITERATURE REVIEW 3
• 2.1. Lactic acid bacteria (LAB) 4
• 2.2. Probiotics 5
• III. MATERIALS AND METHODS 7
• 3.1. Isolation and screening of LAB 8
• 3.2. Resistance to gastric acid and bile acid measurement 10
• 3.3. Mucin adhesion measurement 11
• 3.4. Antimicrobial activity 12
• 3.5. Phylogenetic tree analysis 13
• 3.6. Whole genome sequence analysis 14
• 3.7. Statistical analysis 15
• IV. RESULTS AND DISCUSSION 16
• 4.1. Isolation and screening of LAB 17
• 4.2. Gram staining and catalase test 18
• 4.3. Carbohydrate fermentation patterns 19
• 4.4. Acid and bile salts tolerance 21
• 4.5. Adherence to mucin 24
• 4.6. Antimicrobial activity 26
• 4.7. 16S rRNA gene sequencing analysis for isolated LAB 28
• 4.8. Phylogenetic analysis 31
• 4.9. Whole genome sequencing for L. plantarum MD159 33
• 4.9.1. General characteristics of MD159 genome 33
• 4.9.2. Antimicrobial resistance gene analysis 36
• 4.9.3. Virulence factor gene analysis 38
• V. CONCLUSION 40
• VI. REFERENCES 42