MICROALGAE BIOPHOTONIC OPTIMIZATION OF PHOTOSYNTHESIS BY WEAKLY ABSORBED ... PDF
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MICROALGAE BIOPHOTONIC OPTIMIZATION OF PHOTOSYNTHESIS BY WEAKLY ABSORBED WAVELENGTHS by ERICO ROLIM DE MATTOS (Under the Direction of Keshav Das and Miguel Cabrera) ABSTRACT Adjusting the light supply to microalgae cultures at high cell density can enhance photosynthetic efficiency at latter stages of cultivation providing extra biomass growth and production. First we investigate inoculum cultivation based on physical and developmental characteristics. Chlorella sorokiniana cultures inoculated with inoculum at three different physiological stages (lag, exponential and stationary) were cultivated under three different CO 2 concentrations (0.038%, 5% or 10% CO v/v). Samples inoculated with lag phase inoculum 2 supplied with 5% CO achieved the maximum biomass production whereas samples supplied 2 with 0.038% CO never reached exponential growth. The better growth of samples inoculated 2 with lag phase inoculum was attributed to its increased number of cells compared to the other two inocula. In another set of experiments, we investigate changes in the light supply to optimize biomass growth at high culture cell densities. First, using chlorophyll fluorescence measurements we evaluated the effects of 6 wavelengths (λ , λ , λ , λ , λ , λ ) and a full 627nm 617nm 590nm 530nm 505nm 470nm spectrum neutral white LED at three different light intensities on the quantum yield of photosystem II (Φ ) and non-photochemical quenching (NPQ) in the microalgae Chlorella PSII sorokiniana at three different cell densities (OD 0.5, 1.0 and 1.5). An inverted correlation between Φ and light intensity was found across the whole experiment. PSII As C. sorokiniana cell density increased a decrease in Φ values measured under the PSII green light was observed. NPQ had a noticeable decrease under all light sources as the culture density increased from OD 0.5 to 1.0. To confirm the indications found in the previous experiment, in a second experiment photosynthetic activity and biomass production induced by 4 different LEDs (λ , λ , 470nm 530nm λ , and white-3000K) were analyzed on high-density cultures of Scenedesmus bijuga. As 655nm culture density increased, the weakly absorbed green light became more photosynthetically efficient than the red light, thereby inducing significantly higher oxygen evolution at culture concentration of 1.45 g/L. High-density culture (2.19 g/L) cultivated under the green light showed higher biomass production rate (30 mg/L/d) with a 8.43% dry biomass growth in a 6-day period compared to the red light that induced 4.35% dry biomass growth during the same period. INDEX WORDS: microalgae, photosynthesis, biomass, production ii MICROALGAE BIOPHOTONIC OPTIMIZATION OF PHOTOSYNTHESIS BY WEAKLY ABSORBED WAVELENGTHS by ERICO ROLIM DE MATTOS BS, Universidade de Sao Paulo, Brazil, 2008 A Dissertation Submitted to the Graduate Faculty of the University of Georgia in Partial Fulfillment of the Requirement for the Degree DOCTOR OF PHYLOSOPHY ATHENS, GEORGIA 2013 © 2013 Erico Rolim de Mattos All Rights Reserved MICROALGAE BIOPHOTONIC OPTIMIZATION OF PHOTOSYNTHESIS BY WEAKLY ABSORBED WAVELENGTHS by ERICO ROLIM DE MATTOS Major Professor: Miguel Cabrera Committee: Keshav Das Marc van Iersel Mark Haidekker Gregory Schmidt Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia August 2013 DEDICATION I dedicate this dissertation to my parents Alda and Jose Paulo and my brother Gustavo, who always supported and encouraged me. iv ACKNOWLEDGEMENTS I would like to express my sincerest and profound gratitude to Dr. Keshav Das for such innate and extraordinary mentorship and guidance in my studies and in my life, allowing me to grow up as a person and as a researcher. I will be forever grateful. I would like to thank Dr. Miguel Cabrera for all the academic guiding and support along my PhD. I would like to thank Dr. Marisa d’Arce for the constant support and encouragement. This step in my life started because of you. I would also like to thank Ryan Adolphson for his initiative and trust which gave me the opportunity to get here. To my fellow lab mates, especially Eric, Ronnie, Rekha and Ana I would like to acknowledge the constant entertainment, help, knowledge and friendship. And last but not the least, I’d like to thank the faculty of my committee, especially Dr. van Iersel, Dr. Haidekker, and Dr. Schmidt. I have learned so much with all of you. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .............................................................................................................v CHAPTER 1 INTRODUCTION ..........................................................................................................1 2 LITERATURE REVIEW ...............................................................................................4 Microalgae ................................................................................................................4 Applications .............................................................................................................5 Cultivation in Photobioreactors ...............................................................................8 Photosynthetic Active Radiation............................................................................12 Photosynthesis........................................................................................................13 Efficiency of Photosynthesis..................................................................................16 Green Light ............................................................................................................18 References ..............................................................................................................21 3 EFFECTS OF INOCULUM PHYSIOLOGICAL STAGE ON THE GROWTH CHARACTERISTICS OF CHLORELLA SOROKINIANA CULTIVATED UNDER DIFFERENT CO2 CENCENTRATIONS ....................................................................28 Abstract ..................................................................................................................29 Introduction ............................................................................................................30 Materials & Methods ..............................................................................................32 Results & Discussion .............................................................................................35 Conclusion..............................................................................................................42 vi References ..............................................................................................................43 Tables and Figures .................................................................................................45 Addendum ..............................................................................................................54 References ..............................................................................................................56 4 CHANGES IN CHLOROPHYL FLUORESCENCE PARAMETERS IN DIFFERENT CHLORELLA SOROKINIANA CELL DENSITIES ............................57 Abstract ..................................................................................................................58 Introduction ............................................................................................................59 Materials & Methods .............................................................................................62 Results ....................................................................................................................65 Discussion ..............................................................................................................67 Conclusion .............................................................................................................72 References ..............................................................................................................73 Tables and Figures .................................................................................................76 5 ENHANCEMENT OF BIOMASS PRODUCTION IN SCENEDESMUS BIJUGA HIGH DENSITY CULTURE USING WEAKLY ABSORBED GREEN LIGHT ......80 Abstract ..................................................................................................................81 Introduction ............................................................................................................82 Materials & Methods .............................................................................................84 Results & Discussion .............................................................................................89 Conclusion .............................................................................................................95 References ..............................................................................................................96 Tables and Figures .................................................................................................98 vii 6 GENERAL OVERVIEW ............................................................................................107 viii
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