Title Page
Contents
ABSTRACT 9
Chapter 1. Bacterial community of galchi-baechu-kimchi using culture-independent and culture-dependent approaches 11
1. Introduction 11
2. Material and methods 13
2.1. Kimchi and bacterial strain isolation 13
2.2. Viable bacteria counts 13
2.3. Determination of pH and NaCl concentration 14
2.4. Pyrosequencing 14
2.5. Identification of bacteria from media 15
3. Results 17
3.1. Viable bacteria counts of galchi-baechu-kimchi 17
3.2. pH and NaCl concentration of galchi-baechu-kimchi 17
3.3. Bacterial community based on culture-independent analysis 20
3.4. Bacterial community based on culture-dependent analysis 20
4. Discussion 27
Chapter 2. Selection of starter candidates among Bacillus species originated from kimchi through safety and technological assessments 31
1. Introduction 31
2. Material and methods 34
2.1. Antibiotic susceptibility 34
2.2. Presence of enterotoxin genes 35
2.3. Hemolysis 35
2.4. Technological assessments 37
3. Results 38
3.1. Antibiotic susceptibility of Bacillus species 38
3.2. Enterotoxin genes from Bacillus species 39
3.3. Identification of hemolysis of Bacillus species 43
3.4. Technological properties of Bacillus species 43
4. Discussion 47
References 49
국문요약 56
Table 1. Viable bacterial counts on different media 18
Table 2. pH values and NaCl concentration of galchi-baechu-kimchi 19
Table 3. Microbial diversity indices of galchi-baechu-kimchi 22
Table 4. Numbers of bacterial species isolated from galchi-baechu-kimchi using different media 24
Table 5. Primer sets for the detection of toxin factors in Bacillus species 36
Table 6. Minimum inhibitory concentration distributions for eight antibiotics and Bacillus strains 41
Table 7. Technological properties of the Bacillus isolates 46
Table 8. Selected starter candidates among the Bacillus strains 48
Fig. 1. Bacterial community of galchi-baechu-kimchi based on culture-independent analysis 23
Fig. 2. Bacterial community of galchi-baechu-kimchi based on culture-dependent analysis using three different media 25
Fig. 3. Principal component analysis based on the relative abundances of bacterial communities using media 26
Fig. 4. Bacterial venn diagram of culture-independent and culture-dependent detected species 29
Fig. 5. Heat map of the Culture-independent (NGS) and Culture-dependent using three different media 30
Fig. 6. Minimum inhibitory concentration distributions for eight antibiotics and Bacillus strains 40
Fig. 7. α-Hemolytic (A) and β-hemolytic (B) activities of Bacillus strains 45