Title Page
Contents
Abstract 8
Introduction 10
Materials and Methods 15
2.1. Bacterial strains 15
2.2. Nisin purification 15
2.3. NaCl solutions 16
2.4. Fish sample preparation 16
2.5. pH measurement 16
2.6. Fish sample treatment preparation 17
2.7. Enumeration of bacteria 17
2.8. Antimicrobial assay: Agar disk-diffusion method 18
2.9. Time-kill test (time-kill curve) 18
2.10. Statistical analysis 19
Results 20
3.1. Purification of nisin Z 20
3.2. Antimicrobial activity of nisin Z and NaCl 22
3.3. Analysis of pH value 34
Discussion 38
Conclusion 43
References 46
Table 1. Effects on combination of nisin Z (1000 IU) and NaCl (3, 5 & 7%) on L. monocytogenes at 4 ℃ for 12 hrs 29
Table 2. Effects on combination of nisin Z (1000 IU) and NaCl (3, 5 & 7%) on S. aureus at 4℃ for 12 hrs 30
Fig.1. Chemical structure of nisin 12
Fig.2. Schematic diagram of nisin Z production and purification 22
Fig.3. Agar disk diffusion method: Clear zone of nisin Z, NaCl (3, 5, and 7%) and their... 23
Fig.4. Agar disk diffusion method: Clear zone of nisin Z, NaCl (3, 5, and 7%) and their... 24
Fig.5. Clear zone of nisin Z, NaCl (3, 5, and 7%) and their combination effect on L.... 25
Fig.6. Clear zone of nisin Z, NaCl (3, 5, and 7%) and their combination effect on S.... 26
Fig.7. Effects of nisin Z, NaCl and their combination on L. monocytogenes in minced olive... 31
Fig.8. Effects of nisin Z, NaCl and their combination on S. aureus in minced olive flounder... 33
Fig.9. Changes in pH value of minced olive flounder against L. monocytogenes during... 35
Fig.10. Changes in pH value of minced olive flounder against S. aureus during storage at... 37