Nghiên cứu hoạt tính và cơ chế kháng khuẩn của tinh dầu màng tang (litsea cubeba) đối với vi khuẩn gây bệnh và khả năng ứng dụng trong nuôi trồng thuỷ sản

DECLARATION I hereby declare that this thesis is an original work and that it has not been previously presented at my university or any other university for any degree I also declare that, to the best of my knowledge and belief, this thesis contains no material previously published by any other person except where due acknowledgement has been made Date 06th July 2018 On behalf of the supervisors CHU Ky Son NGUYEN Hai Van i ACKNOWLEDGEMENTS I would like thank my co-supervisor Dr Samira SARTER and Assoc Prof CHU-KY Son who have supported and guided me from the initial to the final level to develop an understanding of the subject I have been extremely lucky to have advisors who cared so much about my work, and who responded to my questions and queries so promptly This thesis would not have been possible without their encouragement and support Thank you for all you have taught me and the support you gave me during the preparation of my thesis I am deeply grateful to all members of the jury for agreeing to read the manuscript and to participate in the defense of this thesis I wish to express my gratitude to Dr Jean-Christophe MEILE who kindly taught me knowledge and laboratory techniques in antibacterial mechanisms I am also very grateful to Dr Marc LEBRUN who helped me to learn techniques to analyze composition in his laboratory I also like to thank all the members of staff at CIRAD, UMR Qualisud who helped me in my supervisor’s absence I would like to thank Dr Domenico CARUSO from URM ISEM (IRD), Dr NGUYEN Ngoc Tuan and Ms TRINH Thi Trang from Vietnam National Uinverist of Agriculture for their helps and teaching me about providing for the research, especially in aquaculture sector In particular, I wish to thanks Dr Domenico CARUSO for helping me in the implementation of immunological protocols I thank Dr NGUYEN Thi Hong Van from Vietnam Academy of Science and Technology who taught me the extraction technique of essential oils I extend my sincere thanks to all members of the Center for Research and Development in Biotechnology, the Department of Food Technology and the School of Biotechnology and Food Technology, and all those who contributed directly or indirectly to my thesis I could not have achieved this goal without the help and support of so many people Many thanks to Dr NGUYEN Hoang Nam Kha, NGUYEN Huu Cuong and Marc LARTAUD for their kind help with my research I am grateful to Hien, Hai, Hoa, Nhi, Nam, Chanh and Nhan for all their help and assistance with my experiments I have been blessed with a ii friendly and cheerful group of fellow students I would like to thank all my friends, Phuong Anh, Phuong, Lan, Nghia, Van, Tam… for their encouragement Thank is not enough for Amandine for her support in my first time in France I would especially like to thank all members of my family for the love, support and constant encouragement I have gotten over the years You are the salt of the earth, and I undoubtedly could not have done this without you To anyone that may I have forgotten I apologize Thank you as well This project was made possible thanks to the grant provided by the CIRAD – France, as well as the French Ministry of Foreign Office for providing part of funds to the project ESTAFS (Ethnobotany for Sustainable and Therapy in Aquaculture and Food Safety) project in the frame of the Bio-Asia program iii ABSTRACT The threat of bacterial resistance to antibiotics has created an urgent need to develop new antimicrobials In this context, a growing interest has arisen towards herbal therapy For the screening test, the antibacterial activities and chemical compositions of nine commercial essential oils obtained from Aromasia company (clove basil Ocimum gratissimum, cajeput Meulaleuca leucadendron, cinnamon Cinnamomum cassia, Indian prickly ash Zanthoxylum rhesta, sweet wormwood Artemisia annua, basil Ocimum basilicum, Mexican tea Chenepodium ambrosioides, corn mint Mentha arvensis, may chang Litsea cubeba) were tested Due of high antibacterial acitivities, widely distributed and limit of studies in Vietnam, May chang L cubeba was selected for further research L cubeba leaf EOs collected from North Vietnam were characterized by their high content in either 1,8-cineole or linalool Linalool-type EOs were more effective than 1,8-cineoletype EO leaf samples, LC19 (1,8-cineole-type) and BV27 (linalool-type), showed strong bactericidal effect against Escherichia coli EOs caused changes in cell morphology, loss of integrity and permeability of the cell membrane, as well as DNA loss However, LC19 showed antimicrobial effects against E coli differed with BV27 LC19 mostly affected to the cell membrane, leding to a significant cell filamentation rate and altered cell width, whereas BV27 damaged cell membrane integrity leading to cell permeabilization and altered the nucleoid morphology L cubeba fruit EO, as similar with oxytetracycline, exhibited higher survival rates and lower bacterial concentrations of the whiteleg shrimp than the control (EO and antibioticfree) However, the application of L cubeba EO in aquaculture has been limited The common carp was fed with (control), 2, and 8% (w/w) L cubeba leaf powder supplementation diets Weight gain, specific growth rate and feed conversion ratio were improved together with the increasing of L cubeba leaf powder in a doserelated manner L cubeba leaf powder increased nonspecific immunity (lysozyme, haemolytic and bactericidal activities of plasma) of carps After infection with A hydrophila, the survival percent of fish fed with L cubeba leaf powder were significantly higher than that of control Therefore, our results could be of great potential for the discovery of plant candidates for the sustainable therapy in aquaculture including fish and shrimp to improve food quality and safety Keywords: Litsea cubeba, essential oils, antibacterial mechanism, chemical diversity, pathogenic bacteria, aquaculture, sustainable therapy, Vietnam iv TABLE OF CONTENTS Page LIST OF ABBREVIATIONS ………………………………………………………… viii LIST OF TABLES ……………………………………………………………………… x LIST OF FIGURES ………………………………………………………………………xi INTRODUCTION ……………………………………………………………………… CHAPTER LITERATURE REVIEW 1.1 Essential oils: plant-based alternatives to antibiotics 1.1.1 Definitions and biological activities of essential oils 1.1.2 Chemical composition of essential oils 1.1.2.1 Terpenes 1.1.2.2 Phenylpropanoids 1.1.2.3 Sulfur and nitrogen compounds of essential oils 1.1.3 Antibacterial activity of essential oils 1.1.3.1 In vitro tests of antibacterial activity of essential oils 1.1.3.2 Litsea cubeba 12 1.1.4 Synergistic effects of essential oils on the antibacterial activity 14 1.1.5 Antibacterial mechanism of essential oils 15 1.2 Aquaculture in Vietnam 20 1.2.1 Overview of aquaculture in Vietnam 20 1.2.2 Cultured species 22 1.2.2.1 Common carp (Cyprinus carpio) 22 1.2.2.2 Whiteleg shrimp (Litopenaeus vannamei) 23 1.2.3 Bacterial diseases in aquaculture 23 1.2.3.1 Aeromonas hydrophila 24 1.2.3.2 Vibrio parahaemolyticus 25 1.2.4 Utilization of antibiotic in aquaculture 26 1.2.4.1 Situation of antibiotic utilization in aquaculture 26 1.2.4.2 Consequences of antibiotic overuse in aquaculture 28 1.3 Potential of plant-based products in aquaculture 29 1.3.1 Plants as a growth promoter 29 1.3.2 Plants as a immunostimulants of fish 31 1.3.3 Plants as a antibacterial agents 34 v 1.4 Aims of the thesis 35 CHAPTER MATERIALS AND METHODS 37 2.1 Materials 37 2.1.1 Essential oils and other antibacterial agents 37 2.1.1.1 Commercial EOs 37 2.1.1.2 Extracted L cubeba leaf EOs 38 2.1.1.3 Antibiotics 38 2.1.2 Bacterial strains 38 2.2 Methods 39 2.2.1 Extraction and yield of L cubeba leaf EOs 39 2.2.2 Chemical analysis of EOs 40 2.2.3 Disc diffusion method 41 2.2.4 Microdilution method 42 2.2.5 Synergy studies of L cubeba fruit EO and other antibacterial agents by checkerboard method 43 2.2.6 Effect of L cubeba leaf EOs (LC19 and BV27) on cell viability of E coli 45 2.2.7 Effects of L cubeba leaf EOs (LC19 and BV27) on membrane integrity and membrane permeabilization of E coli 45 2.2.8 Effects of L cubeba leaf EOs (LC19 and BV27) on cell size of E coli 47 2.2.9 Effects of L cubeba leaf EOs (LC19 and BV27) on DNA of E coli 47 2.2.10 Toxicity of bacterial pathogens in aquaculture 47 2.2.11 Effects of L cubeba fruit EO and OTC in shrimp assays 48 2.2.12 Experimental design in carp 49 2.2.12.1 Preparation of fish 49 2.2.12.2 Preparation of L cubeba leaf powder 49 2.2.12.3 Preparation of carp feed by enriching L cubeba leaf powder 50 2.2.12.4 Feeding experiments and growth promoters 50 2.2.13 Humoral immune responses induced of carp by plant materials 50 2.2.13.1 Lysozyme activity 51 2.2.13.2 Bactericidal activity 51 2.2.13.3 Alternative complement activity 51 2.2.14 Experimental infection of carp 52 2.2.15 Statistical analysis 52 CHAPTER RESULTS AND DISCUSSION 53 vi 3.1 Screening of commercial EOs for antimicrobial activity 53 3.1.1 Chemical composition of commercial EOs 53 3.1.2 Antibacterial activity (inhibition zones) of commercial EOs 54 3.1.3 Antibacterial activity (MIC and MBC values) of nine commercial EOs 59 3.2 Chemical compositions and antibacterial activities of L cubeba EO 65 3.2.1 Synergy study of L cubeba fruit EO and other antibacterial agents 65 3.2.2 Chemical composition diversity of L cubeba leaf EOs 71 3.2.3 Antibacterial activity of L cubeba leaf EOs 78 3.3 Antibacterial mechanism of L cubeba leaf EOs 82 3.3.1 Effect of L cubeba leaf EOs LC19 and BV27 on viability of E coli 82 3.3.2 Integrity of E coli cell membranes after exposure to L cubeba leaf EOs LC19 and BV27 86 3.3.3 Variation of E coli cell length treated with L cubeba leaf EOs LC19 and BV27……………… 90 3.3.4 Effect of L cubeba leaf EOs LC19 and BV27 on DNA of E coli 92 3.4 Application of L cubeba plant extract in aquaculture 97 3.4.1 Effect of L cubeba fruit EO on whiteleg shrimp L vannamei 97 3.4.2 Effect of L cubeba plant powder on common carp C carpio 101 3.4.2.1 Enhancement of common carp growth promotion 101 3.4.2.2 Improvement of common carp immunostimulation 102 3.4.2.3 Effect on common carp survival 105 CONCLUSION AND PROSPECTS ………………………………………………… 112 REFERENCES ………………………………………………………………………….114 PUBLICATIONS……………… …………………………………………………… 135 APPENDIX …….……………………………………………………………………… 136 vii LIST OF ABBREVIATION ACP: Alternative Complement Pathway AHPND: Acute Hepatopancreas Necrosis Disease AHPNS: Acute Hepatopancreas Necrosis Syndrome ANOVA: Analysis of variance ATCC: American Type Culture Collection CCP: Classical Complement Pathway DAPI: 4′,6-dia-mino-2-phenylindole EO: Essential oil FAO: Food and Agriculture Organization FCE: Food Conversion Efficiency FCR: Feed Conversion Ratio FIC: Fractional Inhibitory Concentration GC: Gas Chromatography GC/MS: Gas Chromatography – Mass Spectrometry g/t: Gram per metric ton h: hour HP: Hepatopancreas i.p: intraperitoneally KI: Kovats Index LCP: Lectin Complement Pathway LD50: Lethal Dose 50 LPS: Lipopolysaccharides MBC: Minimum Bactericidal Concentration MHA: Mueller Hinton Agar MHB: Mueller Hinton Broth MIC: Minimum Inhibitory Concentration NA: Nutrient Agar OD: Optical Density OM: Outer Membrane OTC: Oxytetracycline PI: Propidium Iodide viii RBC: Red Blood Cell SEM: Scanning Electron Microscopy SGR: Specific Growth Rate TEM: Transmission Electron Microscopy VASEP: Vietnam Association of Seafood Exporters and Processors WBC: White Blood Cell WG: Weight Gain WHO: World Health Organization ix LIST OF TABLES Table 1.1: Classification terpenes by the number of isoprene units ([35]) Table 1.2: Classification monoterpenes by functional groups ([35]) Table 1.3: Lists of the essential oils used in this study Table 1.4: MICs of essential oils tested in vitro against pathogenic bacteria 11 Table 1.5: Essential oils/components and their identified target sites and modes of action 21 Table 1.6: Main causes of outbreaks diseases in shrimps and fish farming 23 Table 1.7: Effect of plant extract on growth promotion of fish 30 Table 1.8: Effect of plant extract on immunostimulant and antibacterial activities of fish ([12, 117, 165]) 33 Table 2.1: Interaction between two antibacterial agents ([74, 182]) 44 Table 3.1: Chemical composition of the nine commercial EOs used in this study 53 Table 3.2: Antibacterial activity of nine commercial EOs (inhibition zones in mm) against 10 bacterial strain 56 Table 3.3: Antibacterial activity (MIC and MBC in mg/mL, MBC/MIC) of nine commerical EOs against bacterial strains 57 Table 3.4: FIC values and the combinations effects of L cubeba fruit EO and other EOs against pathogenic bacterial 66 Table 3.5: FIC values and combinations effects of L cubeba fruit EO and antibiotics against pathogenic bacteria 66 Table 3.6: List of L cubeba leaf EOs samples collected 71 Table 3.7: Chemical composition of L cubeba leaf EOs samples from different provinces of North Vietnam 76 Table 3.8: Antibacterial activity of L cubeba leaf EOs, 1,8-cineole and linalool against pathogenic bacterial strains 80 Table 3.9: Effects of two L cubeba leaf EOs (LC19 and BV27) on viability, size, membrane and DNA integrity of E coli cells 89 Table 3.10: In-vivo antimicrobial activity of L cubeba fruit EO and oxytetracycline on whiteleg shrimp 99 Table 3.11: Growth parameters of C carpio after 21 days of feeding with different doses of L cubeba leaf powder 102 Table 3.12: Mortality and Relative Percent Survival of C carpio fed with different doses of L cubeba leaf powder 106 x PUBLICATIONS Nguyen Hai Van, Caruso Doménico, Lebrun Marc, Nguyen Ngoc Tuan, Trinh Thi Trang, Meile Jean-Christophe, Chu-Ky Son, Sarter Samira (2016) Antibacterial activity of Litsea cubeba (Lauraceae) and its effects on the biological response of common carp Cyprinus carpio challenged with Aeromonas hydrophila Journal of Applied Microbiology, 121(2), pp 341-351 Hai Van Nguyen, Thu Trang Vu, Son Chu-Ky, Samira Sarter (2017) Interaction effect of essential oil and antibiotic on antibacterial against pathogenic bacteria in aquaculture Journal of Science and Technology, 55(5A), pp 66-73 Nguyen Hai Van, Meile Jean-Christophe, Lebrun Marc, Caruso Doménico, Chu-Ky Son, Sarter Samira (2017) Litsea cubeba leaf essential oil from Vietnam: chemical diversity and its impacts on antibacterial activity Letters in Applied Microbiology, 66, pp 207-214 135 APPENDIX TABLE Table 1: Retention time and Kovats index of series alkane Retention time 2.25 3.041 4.502 6.828 9.943 13.535 17.313 21.05 24.712 28.217 31.585 34.824 Kovats index 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 Table 2: Final concentration of two component in checkerboard method MIC B MIC B 1/2 MIC B 1/4 MIC B 1/8 MIC B 1/16 MIC B MIC A MIC A 1/2 MIC A 1/4 MIC A 1/8 MIC A 1/16 MIC A 2:2 1:2 1/2:2 1/4:2 1/8:2 1/16:2 2:1 1:1 1/2:1 1/4:1 1/8:1 1/16:1 2:1/2 1:1/2 1/2:1/2 1/4:1/2 1/8:1/2 1/16:1/2 2:1/4 1:1/4 1/2:1/4 1/4:1/4 1/8:1/4 1/16:1/4 2:1/8 1:1/8 1/2:1/8 1/4:1/8 1/8:1/8 1/16:1/8 2:1/16 1:1/16 1/2:1/16 1/4:1/16 1/8:1/16 1/16:1/16 Table 3: pH water of aquarium Treatment A1 A2 A3 Mean SD B1 B2 B3 Mean SD C1 C2 C3 Mean SD D1 D2 D3 Mean SD D1 7.75 7.50 7.75 7.67 0.14 7.75 7.75 7.75 7.75 0.00 7.25 8.00 7.75 7.67 0.38 8.00 8.00 7.75 7.92 0.14 D2 7.50 7.50 7.50 7.50 0.00 7.75 7.50 7.50 7.58 0.14 7.50 8.25 7.50 7.75 0.43 7.50 7.75 8.00 7.75 0.25 D3 7.50 7.50 7.50 7.50 0.00 7.50 8.00 7.50 7.67 0.29 7.50 8.00 7.75 7.75 0.25 7.75 7.75 7.75 7.75 0.00 D4 7.50 7.50 7.00 7.33 0.29 7.50 7.75 7.25 7.50 0.25 7.50 7.50 7.25 7.42 0.14 7.25 7.75 7.75 7.58 0.29 D5 7.25 7.75 7.00 7.33 0.38 7.50 7.50 7.25 7.42 0.14 7.25 7.25 7.25 7.25 0.00 7.00 7.50 7.25 7.25 0.25 D6 7.75 8.50 7.50 7.92 0.52 7.75 7.75 7.75 7.75 0.00 8.00 8.00 7.75 7.92 0.14 8.00 8.25 7.75 8.00 0.25 D7 7.75 8.00 7.25 7.67 0.38 8.25 8.00 7.50 7.92 0.38 7.75 8.00 7.50 7.75 0.25 7.50 8.00 7.75 7.75 0.25 D8 7.50 7.75 7.00 7.42 0.38 7.25 7.50 7.00 7.25 0.25 7.50 7.50 7.50 7.50 0.00 7.00 7.75 7.75 7.50 0.43 D9 7.50 7.50 7.25 7.42 0.14 7.50 7.50 7.00 7.33 0.29 7.50 7.50 7.50 7.50 0.00 7.00 7.50 7.75 7.42 0.38 Day D10 7.25 7.25 7.75 7.42 0.29 7.25 7.50 7.50 7.42 0.14 7.50 7.50 7.75 7.58 0.14 7.25 7.50 7.25 7.33 0.14 D11 7.25 8.00 7.50 7.58 0.38 7.50 7.50 7.50 7.50 0.00 7.75 7.50 7.25 7.50 0.25 8.00 7.75 7.50 7.75 0.25 D12 7.50 8.00 7.50 7.67 0.29 7.50 7.50 7.25 7.42 0.14 7.50 7.50 7.50 7.50 0.00 7.75 7.50 8.00 7.75 0.25 D13 7.75 7.50 7.25 7.50 0.25 7.75 7.75 7.50 7.67 0.14 7.25 7.75 7.25 7.42 0.29 7.50 7.25 7.75 7.50 0.25 D14 7.25 7.50 7.50 7.42 0.14 7.50 7.50 7.50 7.50 0.00 7.50 7.75 7.50 7.58 0.14 7.25 7.50 7.75 7.50 0.25 D15 7.25 7.50 7.25 7.33 0.14 7.25 7.50 7.00 7.25 0.25 7.25 7.75 7.75 7.58 0.29 7.50 7.25 7.75 7.50 0.25 D16 7.25 7.50 7.50 7.42 0.14 7.50 7.50 7.25 7.42 0.14 7.50 7.75 7.25 7.50 0.25 7.50 7.50 7.75 7.58 0.14 D17 7.75 8.00 7.75 7.83 0.14 7.25 7.75 7.50 7.50 0.25 7.50 7.50 7.50 7.50 0.00 7.75 7.00 7.75 7.50 0.43 D18 7.75 7.75 7.25 7.58 0.29 7.25 7.50 7.75 7.50 0.25 7.50 7.50 7.00 7.33 0.29 7.75 7.25 8.00 7.67 0.38 D19 7.75 7.25 7.50 7.50 0.25 7.75 7.75 7.50 7.67 0.14 7.50 7.50 7.50 7.50 0.00 7.75 7.75 8.00 7.83 0.14 D20 7.50 8.00 7.00 7.50 0.50 7.25 7.50 7.50 7.42 0.14 7.25 7.75 7.25 7.42 0.29 7.75 7.50 8.00 7.75 0.25 A: control (0% of L cubeba plant powder enriched-diets), B: 2% w/w of L cubeba plant powder enriched-diets; C: 4% w/w of L cubeba plant powder enriched-diets, D: 8% w/w of L cubeba plant powder enriched-diets SD: Standard Deviation D21 7.50 7.50 7.75 7.58 0.14 8.00 7.00 7.50 7.50 0.50 7.25 7.75 7.25 7.42 0.29 8.00 7.75 7.50 7.75 0.25 Table 4: Water temperature during feeding experiment Day Treatment D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 D19 D20 D21 A1 A2 A3 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 28.0 28.0 28.0 28.0 28.0 28.0 26.5 26.5 26.5 25.5 25.5 25.5 25.5 26.0 25.0 28.5 28.5 28.5 27.5 27.5 27.5 28.5 28.5 28.5 28.0 27.5 28.0 26.0 26.0 26.0 27.5 27.5 27.5 28.5 28.5 28.5 26.5 26.5 26.5 26.0 26.0 26.0 24.5 24.5 24.5 25.5 25.5 25.5 26.5 26.5 26.5 26.5 26.5 26.5 Mean SD 27.5 0.0 27.5 0.0 27.5 0.0 28.0 0.0 28.0 0.0 26.5 0.0 25.5 0.0 25.5 0.5 28.5 0.0 27.5 0.0 28.5 0.0 27.8 0.3 26.0 0.0 27.5 0.0 28.5 0.0 26.5 0.0 26.0 0.0 24.5 0.0 25.5 0.0 26.5 0.0 26.5 0.0 B1 B2 B3 Mean SD 27.5 27.5 27.5 27.5 0.0 27.5 27.5 27.5 27.5 0.0 27.5 27.5 27.5 27.5 0.0 28.0 28.0 28.0 28.0 0.0 28.0 28.0 28.0 28.0 0.0 26.5 26.5 26.5 26.5 0.0 25.5 25.5 25.5 25.5 0.0 25.5 25.5 25.5 25.5 0.0 28.5 28.5 28.5 28.5 0.0 27.5 27.5 27.5 27.5 0.0 28.5 28.5 28.5 28.5 0.0 28.0 27.5 27.5 27.7 0.3 26.0 26.0 26.0 26.0 0.0 27.5 27.5 27.5 27.5 0.0 28.5 28.5 28.5 28.5 0.0 26.5 26.5 26.5 26.5 0.0 26.0 26.0 26.0 26.0 0.0 24.5 24.5 24.5 24.5 0.0 25.5 25.5 25.5 25.5 0.0 26.5 26.5 26.5 26.5 0.0 26.5 26.5 26.5 26.5 0.0 C1 C2 C3 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 28.0 28.0 28.0 28.0 28.0 28.0 26.5 26.5 26.5 25.5 25.5 25.5 26.0 25.5 25.0 28.5 28.5 28.5 27.5 27.5 27.5 28.5 28.5 28.5 27.5 27.5 27.5 26.0 26.0 26.0 27.5 27.5 27.5 28.5 28.5 28.5 26.5 26.5 26.5 26.0 26.0 26.0 24.5 24.5 24.5 25.5 25.5 25.5 26.5 26.5 26.5 26.5 26.5 26.5 Mean SD 27.5 0.0 27.5 0.0 27.5 0.0 28.0 0.0 28.0 0.0 26.5 0.0 25.5 0.0 25.5 0.5 28.5 0.0 27.5 0.0 28.5 0.0 27.5 0.0 26.0 0.0 27.5 0.0 28.5 0.0 26.5 0.0 26.0 0.0 24.5 0.0 25.5 0.0 26.5 0.0 26.5 0.0 D1 D2 D3 Mean SD 27.5 27.5 27.5 27.5 0.0 27.5 27.5 27.5 27.5 0.0 27.5 27.5 27.5 27.5 0.0 28.0 28.0 28.0 28.0 0.0 28.0 28.0 28.0 28.0 0.0 26.5 26.5 26.5 26.5 0.0 25.5 25.5 25.5 25.5 0.0 25.5 26.0 25.0 25.5 0.5 28.5 28.5 28.5 28.5 0.0 27.5 27.5 27.5 27.5 0.0 28.5 28.5 28.5 28.5 0.0 27.5 27.5 28.0 27.7 0.3 26.0 26.0 26.0 26.0 0.0 27.5 27.5 27.5 27.5 0.0 28.5 28.5 28.5 28.5 0.0 26.5 26.5 26.5 26.5 0.0 26.0 26.0 26.0 26.0 0.0 24.5 24.5 24.5 24.5 0.0 25.5 25.5 25.5 25.5 0.0 26.5 26.5 26.5 26.5 0.0 26.5 26.5 26.5 26.5 0.0 A: control (0% of L cubeba plant powder enriched-diets), B: 2% w/w of L cubeba plant powder enriched-diets; C: 4% w/w of L cubeba plant powder enriched-diets, D: 8% w/w of L cubeba plant powder enriched-diets SD: Standard Deviation Table 5: NH3, NH4 of water aquarium during feeding experiment D1 D4 D7 D10 D13 D17 D19 D22 NH4 pH NH3 NH4 pH NH3 NH4 pH NH3 NH4 pH NH3 NH4 pH NH3 NH4 pH NH3 NH4 pH NH3 NH4 pH NH3 A1 0.5 8.5 0.08 0.5 7.5 0.009 0.5 0.03 0.006 0.5 0.03 0.5 0.003 0.05 0.5 7.5 0.009 A2 0.5 8.5 0.08 0.5 7.5 0.009 0.5 8.5 0.08 0.006 0.5 0.03 0.5 0.03 0.006 0.5 0.003 A3 0.5 0.03 0.5 0.003 0.5 0.003 0.5 7.5 0.009 0.5 7.5 0.009 7.5 0.02 0.5 7.5 0.009 0.5 7.5 0.009 Mean 0.063 0.007 0.038 0.007 0.023 0.018 0.022 0.007 SD 0.029 0.003 0.039 0.002 0.012 0.014 0.025 0.003 B1 0.5 0.03 7.5 0.02 0.5 8.5 0.08 0.5 0.003 0.5 7.5 0.009 0.5 0.003 0.05 0.5 7.5 0.009 B2 0.5 8.5 0.08 7.5 0.02 0.5 0.03 0.5 7.5 0.009 0.5 7.5 0.009 0.5 0.003 0.5 7.5 0.009 0.5 7.5 0.009 B3 0.05 0.5 7.5 0.009 0.5 7.5 0.009 0.5 7.5 0.009 0.5 7.5 0.009 7.5 0.02 0.5 7.5 0.009 0.5 0.03 Mean 0.053 0.016 0.040 0.007 0.009 0.009 0.023 0.016 SD 0.025 0.006 0.036 0.003 0.010 0.024 0.012 C1 C2 0.5 C3 0.5 8.5 0.15 7.5 0.02 0.5 0.03 0.5 7.5 0.009 0.5 7.5 0.009 0.5 7.5 0.009 0.5 0.03 7.5 0.02 0.5 0.003 0.03 0.5 7.5 0.009 0.5 7.5 0.009 0.5 7.5 0.009 0.5 7.5 0.009 0.006 0.5 7.5 0.006 0.5 7.5 0.009 0.5 7.5 0.009 0.03 0.009 0.5 7.5 0.02 0.5 7.5 0.009 7.5 0.009 0.5 7.5 0.009 Mean 0.063 0.013 0.023 0.013 0.006 0.015 0.013 0.009 SD 0.076 0.006 0.012 0.006 0.003 0.013 0.006 D1 0.5 8.5 0.08 0.006 0.5 7.5 0.009 0.5 0.003 0.5 0.03 0.5 0.003 0.5 0.03 0.5 0.03 D2 0.5 0.03 7.5 0.02 0.5 0.03 0.5 7.5 0.009 0.5 7.5 0.009 0.05 0.5 0.03 7.5 0.02 D3 0.5 0.03 7.5 0.02 0.5 0.03 0.5 0.003 0.5 0.03 0.05 0.5 0.03 0.5 0.03 Mean SD 0.047 0.015 0.023 0.005 0.023 0.034 0.03 0.027 0.029 0.008 0.012 0.003 0.012 0.027 0.006 A: control (0% of L cubeba plant powder enriched-diets), B: 2% w/w of L cubeba plant powder enriched-diets; C: 4% w/w of L cubeba plant powder enriched-diets, D: 8% w/w of L cubeba plant powder enriched-diets SD: Standard Deviation Figure Figure 1: Litsea cubeba leaf and fruit samples Figure 2: Extraction essential oils by Clevenger-type apparatus Essential oil Figure 3: Principe of diffusion method Incubation on MHA at 37/30oC, 24h MBC Figure 4: Principe of MIC and MBC method Ocimum gratissimum Melaleuca leucadendron Cinnamomum cassia Zanthoxylum rhesta Artemisia annua Litsea cubeba Ocimum basilicum Chenopodium ambrosioides Mentha arvensis Figure 5: Chromatogram of essential oils used in this study Litsea cubeba HG01 Litsea cubeba YB03 Litsea cubeba YB04 Litsea cubeba YB05 Litsea cubeba BV06 Litsea cubeba YB07 Litsea cubeba TN08 Litsea cubeba YB09 Litsea cubeba YB10 Litsea cubeba HG11 Litsea cubeba YB12 Litsea cubeba PT13 Litsea cubeba PT15 Litsea cubeba YB16 Litsea cubeba LC17 Litsea cubeba TD18 Litsea cubeba LC19 10 Litsea cubeba PT20 Litsea cubeba YB21 Litsea cubeba PT22 Litsea cubeba PT23 Litsea cubeba LC24 Litsea cubeba BV25 Litsea cubeba TD26 Litsea cubeba BV27 Figure 6: Chromatogram of 25 Litsea cubeba leaf essential oils Control negative Control positive 11 Zone inhibition of cinnamon C loureiri, Indian prickly ash Z rhesta, Sweet wormwood A annua against V parahaemolyticus Zone inhibition of May chang L cubeba against V.algenolyticus Zone inhibition of basil O basilicum, Mexican tea C ambrosioides, corn mint M arvensis and cefoxitine against S aureus Zone inhibition of clove basil O.gratissimum, cajeput M leucadendron and amikacine against S aureus Figure 7: Zone inhibition of essential oil and antibiotic against pathogenic strains 12 Figure 8: Microscopy LEICA DM6000B Lysozyme activity (U/mL) Figure 9: Water quality test kit 3500 y = 323,89x - 171,56 R² = 0,9867 3000 2500 2000 1500 1000 500 0 Concentration hen egg white (µg/mL) Figure 10: Lysozyme hen egg white standard 13 10 Figure 11: Preparation of carp feed 14 ... investigation on this field in Vietnam is still limited in Vietnam Therefore, we conducted the thesis entitled “Antibacterial activity and mechanism of May Chang (Litsea cubeba) essential oil against... antibacterial activities of one EO having the best antibacterial activity (among tested EOs content 1) in Vietnam • Investigation the mechanism of action of the EO in term of cell viability, membrane... on the antibacterial activity 14 1.1.5 Antibacterial mechanism of essential oils 15 1.2 Aquaculture in Vietnam 20 1.2.1 Overview of aquaculture in Vietnam 20 1.2.2