SURFACTANT-AIDED DISPERSED AIR FLOTATION AS A HARVESTING AND PRE-EXTRACTION TREATMENT FOR CHLORELLA SACCHAROPHILA by Mariam Alhattab Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Dalhousie University Halifax, Nova Scotia August 2018 © Copyright by Mariam Alhattab, 2018 DEDICATION I dedicate this thesis to my parents, Tayser and Manal Alhattab, my brothers (Mohammed, Ahmed, and Mahmoud), my husband (Ismail Alghalayini), my niece (Minu), and my friends (Farah Hamodat and Halah Shahin). Without their support, patience and love, the completion of this work would not have been possible. ii TABLE OF CONTENTS List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... xi Abstract ...................................................................................................................... xiii List of Abbreviations Used .............................................................................................. xiv Acknowledgements .......................................................................................................... xvi Chapter 1 Introduction ......................................................................................................1 Chapter 2 Literature Review .............................................................................................6 2.1 Introduction ................................................................................................................6 2.2 Microalgae Harvesting ...............................................................................................6 2.2.1 Sedimentation .................................................................................................... 7 2.2.2 Filtration ........................................................................................................... 10 2.2.3 Centrifugation .................................................................................................. 16 2.2.4 Flocculation ...................................................................................................... 19 2.2.5 Electrophoresis ................................................................................................. 33 2.2.6 Flotation ........................................................................................................... 37 2.2.7 Combination of Techniques ............................................................................. 61 2.3 Microalgae Pre-Treatment .......................................................................................63 2.3.1 Bead Milling .................................................................................................... 63 2.3.2 Ultrasonication ................................................................................................. 69 2.3.3 High Pressure Homogenization ....................................................................... 75 2.3.4 Steam Explosion .............................................................................................. 77 2.3.5 Autoclaving ...................................................................................................... 80 2.3.6 Freeze Drying ................................................................................................... 82 2.3.7 Sun Drying ....................................................................................................... 83 iii 2.3.8 Solar Drying ..................................................................................................... 84 2.3.9 Oven Drying ..................................................................................................... 85 2.3.10 Spray Drying .................................................................................................. 86 2.3.11 Drum Drying .................................................................................................. 87 2.3.12 Microwave ..................................................................................................... 88 2.3.13 Enzyme Hydrolysis ........................................................................................ 93 2.3.14 Surfactant Disruption ................................................................................... 100 2.4 Microalgae Oil Extraction......................................................................................105 2.4.1 Solvent Extraction .......................................................................................... 106 2.4.2 Soxhlet Solvent Extraction............................................................................. 117 2.4.3 Accelerated Solvent Extraction (ASE) .......................................................... 121 2.4.4 Supercritical CO2 ........................................................................................... 124 2.4.5 Expeller Press ................................................................................................. 129 2.4.6 OriginOil Single-Step Extraction ................................................................... 130 Foreword to Chapter 3 .....................................................................................................132 Chapter 3 Comparative Analysis of Microalgae Harvesting Techniques .....................133 3.1 Abstract ..................................................................................................................133 3.2 Introduction ............................................................................................................134 3.3 Methodology ..........................................................................................................134 3.3.1 Selection of Criteria ....................................................................................... 134 3.3.2 Assigning Score to Each Criterion ................................................................. 134 3.4 Results and Discussion ..........................................................................................136 3.5 Conclusions ............................................................................................................147 Foreword to Chapter 4 .....................................................................................................149 Chapter 4 Overview of Microalgae Disruption Techniques for Product Recovery- Infuluence of Cell Wall Composition...........................................................150 iv 4.1 Abstract ..................................................................................................................150 4.2 Introduction ............................................................................................................151 4.3 Overview of Microalgae Cell Wall Composition and Structure ............................153 4.4 Effect of Cell Wall Disruption on Product Recovery for Various Microalgae Species .........................................................................................................................157 4.4.1 Scenedesmus/ Tetradesmus ............................................................................ 157 4.4.2 Botryococcus .................................................................................................. 168 4.4.3 Chlorella/ Chloroidium .................................................................................. 170 4.4.4 Tetraselmis ..................................................................................................... 175 4.4.5 Nannochloropsis ............................................................................................ 177 4.4.6 Other Microalgae ........................................................................................... 179 4.5 Effect of Cell Wall Disruption on Product Recovery from Microalgae with Similar Characteristics ..............................................................................................................181 4.6 Limitations and Future Challenges ........................................................................189 4.7 Conclusions ............................................................................................................191 Foreword to Chapter 5 .....................................................................................................192 Chapter 5 Comparative Analysis of Microalgae Oil Extraction Techniques ................193 5.1 Abstract ..................................................................................................................193 5.2 Introduction ............................................................................................................193 5.3 Methodology ..........................................................................................................194 5.3.1 Selection of Criteria ....................................................................................... 194 5.3.2 Assigning a Score to Each Criterion .............................................................. 194 5.4 Results and Discussion ..........................................................................................196 5.5 Conclusions ............................................................................................................201 Foreword to Chapter 6 .....................................................................................................202