| 摘要 | 第7-10页 |
| ABSTRACT | 第10-13页 |
| ABBREVIATIONS | 第14-17页 |
| CHAPTER 1 INTRODUCTION AND REVIEW OF LITERATURE | 第17-51页 |
| 1.1 The historyof yogurt | 第17-19页 |
| 1.2 Yogurt in commonly nomadic people of Qinghai province | 第19-23页 |
| 1.3 Importance of yogurt for human health | 第23-24页 |
| 1.4 The history of lactic acid bacteria | 第24-27页 |
| 1.5 Classification of lactic acid bacteria | 第27-29页 |
| 1.5.1 Cell morphology of Lactic Acid Bacteria | 第28-29页 |
| 1.6 Characteristics of lactic acid bacteria | 第29-34页 |
| 1.6.1 Acid tolerance of lacticacid bacteria | 第30-31页 |
| 1.6.2 Bile salt tolerance of lacticacid bacteria | 第31页 |
| 1.6.3 Antibiotic resistance of lacticacid bacteria | 第31-32页 |
| 1.6.4 Adherence to intestinal epithelial cells of lacticacid bacteria | 第32-34页 |
| 1.7 Lactic acid bacteria and its function | 第34-42页 |
| 1.7.1 Cholesterol assimilation of lacticacid bacteria | 第36-38页 |
| 1.7.2 Antioxidant capacity of lacticacid bacteria | 第38页 |
| 1.7.3 Antimicrobial effects of Lacticacid bacteria | 第38-42页 |
| 1.8 Application of lactic acid bacteria | 第42-43页 |
| 1.9 Ready to Eat Food (RTE) and its microbial contamination | 第43-46页 |
| 1.10 Potential of LAB application in control of microbial contamination in food and RTE food | 第46-49页 |
| 1.11 Aims of the Study | 第49-50页 |
| 1.12 Schematic Diagram of the Project | 第50-51页 |
| CHAPTER 2 MATERIALSANDMETHODS | 第51-64页 |
| 2.1 Samplingofyogurts | 第51页 |
| 2.2 Isolation of lactic acid bacteria | 第51-52页 |
| 2.3 Molecular identification of lactic acid bacteria `DNAextraction | 第52-54页 |
| 2.3.1 DNA extraction | 第52-53页 |
| 2.3.2 Amplification of 16Sr RNAsequence | 第53页 |
| 2.3.3 Sequencing of amplified 16Sr RNAproduct | 第53-54页 |
| 2.4 Antimicrobial activity analysis | 第54-55页 |
| 2.5 Antimicrobial susceptibility tests | 第55-56页 |
| 2.6 Acid and bile salts tolerance tests | 第56-57页 |
| 2.7 Adhesion to Caco-2 cells | 第57-58页 |
| 2.8 Antioxidative assays | 第58-59页 |
| 2.8.1 DPPH (2, 2-Diphenyl-1-picryl hydrazyl) Radical scavenging capacity assay | 第58-59页 |
| 2.9 Isolation and characterization of E. coli isolated from RTEfood | 第59-60页 |
| 2.10 Antimicrobial activity of LAB against E. coli from RTEfood | 第60-62页 |
| 2.11 Statistical Analysis | 第62-64页 |
| CHAPTER 3 RESULTS | 第64-93页 |
| 3.1 Isolation of lacticacidbacteria | 第64-66页 |
| 3.2 Molecular identification of LAB 16S r RNA gene sequencing | 第66-71页 |
| 3.2.1 Polymerase chain reaction (PCR) and 16S r RNAgene sequencing | 第68-71页 |
| 3.2.2 Phylogenetic tree based on the 16S r RNAgene sequences | 第71页 |
| 3.3 Antimicrobial activity of lactic acid bacteria isolates against different bacterial pathogens | 第71-78页 |
| 3.3.1 Antimicrobial activity cell free supernatant of lactic acid bacteriaagainstpathogens | 第73-74页 |
| 3.3.2 Inhibitory activity of neutralized cell free supernatant of lactic acid bacteriaagainstpathogens | 第74-76页 |
| 3.3.3 Inhibitory activity of neutralized cell free supernatant treated with catalase | 第76-78页 |
| 3.4 Antimicrobial susceptibility test of lactic acid bacteria strains | 第78-81页 |
| 3.5 Acid and bile tolerance of lactic acid bacteria isolates | 第81-83页 |
| 3.6 Adhesion to Caco-2 cells by lactic acid bacteria | 第83-86页 |
| 3.7 Antioxidant Capacity of lactic acid bacteria isolates | 第86-87页 |
| 3.8 Prevalence and characterization of E. coli from RTE Food | 第87-90页 |
| 3.8.1 Antimicrobial resistance among 267 E. coli isolated fromready-to-eatfoods | 第88-90页 |
| 3.9 Antimicrobial effect of lactic acid bacteria against E. coli strains isolated from (RTE) foods | 第90-93页 |
| CHAPTER 4 DISCUSSION | 第93-112页 |
| REFERENCES | 第112-132页 |
| APPENDIX | 第132-139页 |
| ACKNOWLEDGEMENTS | 第139-140页 |
| Resume | 第140-141页 |
