키토산의 식품관련 박테리아 및 효모에 대한 항균작용
antimicrobial activity of chitosan against food-related bacteria and yeast
- 주제(키워드) chitosan , food , antimicrobial activity
- 발행기관 아주대학교
- 지도교수 박연희
- 발행년도 2009
- 학위수여년월 2009. 2
- 학위명 박사
- 학과 및 전공 일반대학원 분자과학기술학과
- 실제URI http://www.dcollection.net/handler/ajou/000000009470
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Abstract Chitosan is obtained by deacetylating chitin, which is naturally abundant, nontoxic，and biodegradable. Chitosan has several useful physicochemical and bioactive properties such as antimicrobial activity. The objective of this study is to investigate the practical application of the antimicrobial activity of chitosan for food preservation. The inhibitory mode of action and the effects of food components on the antibacterial activity of chitosan were investigated. In addition, the selective control of yeast using chitosan was studied in a mixed culture with lactic acid bacteria. The antimicrobial activity of chitosan was investigated against bacteria and yeast. Chitosan of MW 3 kDa showed higher inhibitory effect than chitosan of MW 10 kDa, 50 kDa and glucosamine. Transmission electron microscopic observation showed chitosan disrupted cell envelopes, released cellular components, resulting in loss of cell viability. The binding of chitosan on the cell surface was investigated using FITC-chitosan with non-growing cells. The binding was accomplished within 5 min and the maximum amount of bound FITC-chitosan was proportional to the concentration up to 200 ppm. The pretreatment of Ca2+, Mg2+ to the cells decreased the inhibitory activity of chitosan and binding of FITC-chitosan. Bound FITC-chitosan was decreased about 20-50% by chitosanase. To investigate the application of chitosan as natural food preservative, the effects of several food components on the inhibitory activity of chitosan was determined. The addition of NaCl and sucrose decreased the inhibitory effect of chitosan while ethanol and the organic acids enhanced the antibacterial activity. The results obtained using the non-growing cells, showed NaCl repressed the inhibitory activity of chitoasn by acting directly on the cells. In contrast, sucrose added to the cell prior to chitosan treatment showed no effect on the viability or FITC-chitosan binding of the cells, which suggested the interaction of sucrose with chitosan affected its activity. To control yeast by chitosan in a mixed culture with lactic acid bacteria, the addition of 100 ppm of chitosan inhibited S. cerevisiae and K. lactis more than Lactobacilli spp. or P. pentosaceus. The addition of chitosan in the period of mixed fermentation reduced the population of yeast and lactic acid bacteria depending on the concentration of chitosan. This suggests the possible use of chitosan to inhibit selectively yeast in a mixed fermentation process with lactic acid bacteria and to adjust the population of yeast and lactic strains at an adequate level. In conclusion, this study showed the practical use of chitosan in food products as biopreservative against a broad spectrum of bacteria and yeast associated with food. The possibility of chitosan to control some species among the large variety of microorganisms involved in the mixed fermentation was also demonstrated.
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CONTENTS
LIST OF TABLES i
LIST OF FIGURES ii
ABSTRACT vi
I. Introduction 1
II. Antimicrobial activity of chitosan 21
1. Introduction 21
2. Materials and methods 22
2.1 Chitosan preparation 22
2.2 Microorganisms and cultivation 22
2.3 Evaluation of antimicrobial activity 23
2.4 Transmission electron microscopy 23
3. Results and discussion 24
3.1 Antimicrobial activity of chitosan against food-borne pathogens 24
3.2 Antimicrobial activity of chitosan against lactic acid bacteria 32
3.3 Antimicrobial activity of chitosan against yeast 38
3.4 Transmission electron microscopy 44
4. Conclusions 46
III. Inhibitory action mode of chitosan 47
1. Introduction 47
2. Materials and methods 48
2.1 Strains and cultivation 48
2.2 Preparation of FITC-labeled chitosan 48
2.3 FITC-labeled chitosan binding to cells 49
2.4 Effect of Ca2+ on the growth 49
2.5 Effect of Ca2+, Mg2+ on the binding of FITC-chitosan 49
2.6 Removal of bound FITC-chitosan by chitosanase 50
3. Results and discussion 50
3.1 FITC-chitosan binding to cells 50
3.2 Effect of cations 53
3.3 Removal of bound FITC-chitosan by chitosanase 56
4. Conclusions 58
IV. Effects of food components on the antibacterial activity of chitosan 59
1. Introduction 59
2. Materials and methods 60
2.1 Inhibition by chitosan 60
2.2 Inhibition test for non-growing cells 60
2.3 Determination of FITC-chitosan binding to cells 60
3. Results and discussion 61
3.1 Effects of food components on the antibacterial activity of chitosan during growth 61
3.2 Effects of food components on the sensitivity of non-growing cells to chitosan 66
3.3 Effects of food components on the binding of FITC-chitosan to the cells 71
4. Conclusions 75
V. Control of yeast by chitosan in a mixed culture with lactic acid bacteria 76
1. Introduction 76
2. Materials and Methods 77
2.1 Microorganisms and cultivation 77
2.2 Inhibition test 77
3. Results and discussion 77
3.1 Growth of yeast and lactic acid bacteria in the presence of chitosa 77
3.2 Effect of chitosan addition during mixed culture 86
4. Conclusions 92
VI. Summary and future research 93
References 97
국문요약 107
