ABSTRACT Photobioreactor Design for Improved Energy Efficiency of Microalgae Production Alexander Burns The objective of this research was to investigate a new photobioreactor (PBR) design for microalgae production that retains the typical advantages of existing tubular PBRs while reducing power consumption by providing simultaneous culture circulation and gas exchange with airlift alone and no centrifugal recirculating pump. Traditional tubular PBR designs feature a compressed air supply and a centrifugal pump for culture circulation and gas exchange. Circulation and gas exchange in a closed-system PBR is necessary to keep the algae suspended and to provide sufficient mass transfer (mainly for the exchange of oxygen and carbon dioxide). In a traditional tubular PBR sparged air keeps the culture well mixed and strips out excess dissolved oxygen in an airlift-column unit, while the centrifugal pump circulates the culture in the tubular stage and decreases the amount of air bubbles traveling into this stage; where most of the photosynthesis occurs. The PBR design proposed herein does away with the usual centrifugal pump. The air blower performs both gas exchange in the airlift columns and system-wide circulation. This builds on a previous tubular PBR design that provides circulation and gas exchange by airlift alone, which was patented by Cathcart in 2011. However, the Cathcart patent does not provide data on mixing, gas exchange, energy consumption, flow regime or biomass productivity. The new design described here builds on the Cathcart design, but includes several unique design features, such as larger diffuser columns which provide airlift-induced flow for a series of vertical PBR tubes. To perform a power consumption v analysis, a pilot-scale prototype of the new PBR design was built and operated. The prototype PBR consisted of two airlift columns attached to 9 m of vertical serpentine tubing connected to the top and bottom by standard 90-degree PVC elbows in a U-bend fashion to each column to make a total working volume of 235 L. The airlift columns were about 1.5 m tall and 30.5 cm ID, while the serpentine tubes were about 0.9 m tall and 7.6 cm ID to make a total of five vertical tubes for every airlift column. Data collected for this prototype design suggest an average overall areal productivity (OAP) of 111 g m-2 d-1 (g biomass m-2 total land area with empty space day-1), an average illuminated surface productivity (ISP) of 14.3 g m-2 d-1 (g biomass m-2 reactor photo-stage day-1), an average volumetric productivity (VP) of 0.55 g L-1 d-1 (g biomass L-1 reactor working volume day-1), a specific power input in the range of 330 to 360 W m-3 (W power needed for culture circulation and gas exchange m-3 reactor working volume) and a specific biomass productivity (SBP) in the range of 17.6 to 19.1 mg kJ-1 (mg biomass kJ-1 energy needed for culture circulation and gas exchange) with Chlorella vulgaris as the model algae. The biomass productivity per energy input (SBP) of the new PBR design appears to be higher than that of similar designs currently described in the literature. Elimination of the centrifugal pump in a tubular PBR design is a concept worth further study for potential energy savings.

The push for alternatives to petroleum fuels has forced researchers to look for highly productive, renewable, non-food resources. The advantages of using microalgae instead of traditional oil crops for biofuel production include high oil yields, rapid reproductive rates, and versatile growing requirements. In order to reduce the cost of producing microalgae based biofuels, wastewater has been used as a nutrient source instead of specialized plant nutrients. The purpose of this study was to compare the relative effectiveness of different combinations of microalgae strain and dairy wastewater for increasing biomass. The methods for monitoring growth included optical density, cell counting, biomass estimation by chlorophyll-a, and volatile suspended solids. The analyses compared four concentrations of wastewater media as well as four strain treatments: Chlorella vulgaris, Tetraselmis sp., mixed freshwater culture and mixed saltwater culture. Optimum wastewater concentrations for microalgae growth were approximately 0% and 25% for most strain treatments. The results of the wastewater treatments concluded that dairy wastewater could serve as an effective nutrient substitute for plant food at concentrations approximately 25%. Chlorella vulgaris and Tetraselmis sp. prevailed over the mixed cultures for biomass production. Nitrate was the most limiting nutrient and exhibited the greatest reductions, sometimes in excess of 90%. The regression equations derived from the volatile suspended solids data achieved high R2 values and determined that total nitrogen, ammonium, and nitrate were significant in the model. In those equations, increasing either ammonium or nitrate yielded an increase in volatile suspended solids. With regards to comparing biomass quantification methods, the two most useful and reliable biomass quantification methods were optical density and volatile suspended solids.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22849号 / 農博第2432号 / 新制||農||1082(附属図書館) / 学位論文||R2||N5309(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 佐藤 健司, 教授 澤山 茂樹, 教授 菅原 達也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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In this research a test system was developed that is designed as a tool to evaluate the potential hazard of chemicals to aquatic ecosystems. The system developed is a linear three-trophic level food chain consisting of an alga (Ch/ore/la vulgaris), rotifer (Brachionus calyciflorus), and fish (Pimephales promelas). The chemostat design used for the lower two trophic levels was crucial in being able to supply the top trophic level with sufficient food on a continuous basis. The system was initially evaluated using copper (Cu) and selenium (Se) as toxicants. In the copper experiments, results of a 7 day three-trophic level toxicity test were compared with a series of single species tests. The LOEC was 31.5 µg/L based on a temporary impairment of the algal population growth, with a corresponding NOEC of 16.2 µg/L. The algal population at all initially impaired treatment levels demonstrated recovery to control levels by the end of the test. Single species tests with the same species showed impairment at treatment concentrations lower than the corresponding value from the three-trophic level test. The difference in sensitivity is attributable to the fact that most of the Cu in the single species tests was in the dissolved form (approximately 80 %), whereas in the trophic level test most of the Cu was not ( < 15 % dissolved Cu). The three-trophic level Se experiment lasted for 25 days, with both short-term and long-term impacts evident. At the algal trophic level, growth was not impaired on a daily basis at any of the exposure levels (110.3, 207.7, and 396.1 µg/L Se). However, algal densities were slightly reduced at the 207. 7 and 396.1 µg Sell treatments, although not significantly different when the data was pooled across days. Rotifer populations were impaired at these same levels by day 4, and succumbed to the Se by day 7. Fathead minnow growth was also impaired at these two concentrations by day 7. In addition, sub lethal impairment of rotifer and fish growth was evident at the 110.3 pg/L level after day 20 indicating a more subtle trophic impact. Bioconcentration factors ranged between 100 and 1000 µg/L and were found to be dependent on the species, treatment, and day. / Ph. D.

A new five-step purification procedure was developed which could be completed in five days with an 80 to 85 percent yield of electrophoretically pure nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase from Chlorella sorokiniana. A monospecific, highly purified antibody against the enzyme was prepared from the antisera of immunized rabbits. The antibody was purified on a stable antigen affinity column which was prepared by covalent-coupling of the holoenzyme to CNBr activated Sepharose 4B followed by cross-linking of the enzyme subunits together with dimethylsuberimidate. With ³H-leucine and ³⁵S-sulfate, as labeling agents of whole cells, the reproducibility and efficiency of both direct- and indirect-immunoprecipitation procedures were tested with pure labeled-enzyme as an internal standard. For these studies, a partially purified sheep anti-rabbit immunoglobulin G fraction was employed as a secondary antibody. A modified indirect immunoprecipitation procedure was tested in a cell cycle experiment to determine whether it would be feasible to use as a tool for further cell cycle experiments on enzyme turnover. Although the method was somewhat lengthy, it appeared to be reliable and was used to reveal that during the first one-third of the cell cycle of fully-induced cells, the NADPGDH has a maximum half-life of 1.6 h. Rocket immunoelectrophoresis was used to show that enzyme catalytic activity and antigen increased in a parallel fashion during the cell cycle of fully-induced cells. These data suggest that the cell cycle catalytic activity pattern reflects de novo synthesis of new molecules of enzyme. Since the enzyme in fully-induced cells undergoes rapid in vivo degradation, changes in the rate of enzyme synthesis probably determine the rate of enzyme accumulation during the Chlorella cell cycle in the continuous presence of ammonium. / Ph. D.

L'électrocoagulation (EC) est une méthode électrochimique non spécifique couramment utilisée pour le traitement de l'eau et des eaux usées. Dans ce travail, l’EC est d'abord étudiée comme une technique classique de traitement des eaux usées dédiée à l'élimination des protéines de lactosérum de l'eau pour laquelle les mécanismes d'élimination sont expliqués et un modèle est développé. Ensuite, l'utilisation de l’EC est étendue à la séparation et à la purification d’acides gras volatils issus de la fermentation acidogénique. Dans cette deuxième étude, les effets des paramètres opératoires sur l'efficacité et le coût de l’EC sont discutés. En outre, l’EC est utilisée pour la récolte de deux espèces de microalgues de leur milieu de culture. En ce qui concerne la récolte de Chlamydomonas reinhardtii, la méthodologie de la surface de réponse est utilisée et deux modèles permettant de prédire respectivement l'efficacité de la récupération et le coût opératoire sont développés. La récolte d’une autre espèce de microalgues, Chlorella vulgaris, est étudiée en utilisant l’EC respectivement en mode discontinu et continu. En mode discontinu, les effets des principaux paramètres de fonctionnement sur l'efficacité du processus sont expliqués et les mécanismes de récupération sont discutés. Dans l'étude en mode continu, la méthodologie de la surface de réponse est utilisée et un modèle permettant de prédire l’efficacité de récupération des microalgues est développé. Enfin, la comparaison des performances de l'EC en mode continu avec et sans échange de polarité aux performances de l'EC en mode discontinu est effectuée. / Electrocoagulation (EC) is a non-specific electrochemical method usually used for water and wastewater treatment. In this work, EC is firstly investigated as a conventional wastewater treatment technique for the removal of whey proteins from water, where the mechanisms of removal are explained and a model on whey proteins elimination is developed. Then, EC use is extended for the separation and purification of volatile fatty acids issued from acidogenic fermentation. In this second study, the effects of operating parameters on EC efficiency and cost are discussed. Moreover, EC is used for the harvesting of two microalgae species from their culture medium. In the study that concerns recovering Chlamydomonas reinhardtii, response surface methodology (RSM) is employed and two models for predicting recovery efficiency and operating cost are developed. The harvesting of the other microalgae species Chlorella vulgaris is studied using EC in the batch and continuous modes. In the batch mode, the effects of the main operating parameters on the process effectiveness are explained along with discussing the mechanisms of recovery. In the continuous mode study, response surface methodology (RSM) is applied and a model for predicting microalgae recovery is developed. Finally, comparison of EC performance in continuous mode with and without polarity exchange (PE) to EC performance in batch mode is carried out.

In our pervious study, the ethanol extracts from Eupatorium fortunei Turcz at concentrations of 200 ÷ 500 mg L-1 significantly inhibited the growth of Microcystis aeruginosa, which is the most common species, responsible for toxic cyanobacteria blooming in fresh water. o-Coumaric acid (or 2-hydroxy-cinnamic acid) isolated from E. fortunei was tested its growth-inhibitory effect on M. aeruginosa and Chlorella vulgaris at the concentrations of 1.0, 10.0 and 100.0 mg L-1 in the 96- hour experiment by the optical density and the analytical method of chlorophyll a concentration. Results indicated that the compound strongly affected towards M. aeruginosa at the concentration of 100.0 mg L-1 with the inhibition efficiency (IE) values of 76.76 % and 84.66 %, respectively while those for C. vulgaris were lower just of 60.59%, and 74.53 %, respectively. The obtained data demonstrated that two methods were highly consistent and o- coumaric acid was more toxic to M. aeruginosa than C. vulgaris at all tested concentrations (p<0.05). The images of M. aeruginosa and C. vulgaris cells under the light microscope clearly showed the damage of these cells under the attck of o-coumaric acid. Although o-coumaric compound was widely demonstrated antibacterial properties in previous reports, to the best of our knowledge, our study was the first report about effect of o- coumaric acid on the growth of M. aeruginosa and C. vulgaris. / Những nghiên cứu trước đây đã chỉ ra rằng cao chiết etanol từ cây Mần tưới Eupatorium fortune Turcz tại dải nồng độ 200 ÷ 500 μg mL-1 ức chế mạnh sinh trưởng của Microcystis aeruginosa, - loài phổ biến nhất gây nên sự bùng nổ tảo độc trong hệ sinh thái nước ngọt. o-Coumaric axit (hay 2-hydroxy-cinnamic axit) phân lập từ E. fortune được tiến hành đánh giá ảnh hưởng lên sinh trưởng của hai loài M. aeruginosa và Chlorella vulgaris tại ba nồng độ là 1.0, 10.0 and 100.0 mg L-1 trong thời gian 96 giờ thực nghiệm theo phương pháp đo mật độ quang và phân tích hàm lượng chlorophyll a. Kết quả nghiên cứu cho thấy sau 96 giờ phơi nhiễm tại nồng độ 100 mg L-1 hoạt chất ức chế mạnh tới M. aeruginosa với giá trị ức chế sinh trưởng (IE) tương ứng là 76.76 và 84.66%. Giá trị IE đối với C.vulgaris ghi nhận thấp hơn chỉ là 60.65 và 74.53%, tương ứng. Hai phương pháp phân tích trên có tính nhất quán cao và o-coumaric ức chế sinh trưởng lên loài M.aeruginosa mạnh hơn so với loài C.vulgaris tại tất cả các nồng độ nghiên cứu (p<0.05). Ảnh chụp các tế bào M.aeruginosa và C.vulgaris dưới kính hiển vi điện tử đã chứng minh những tổn thương của tế bào dưới tác động của o-coumaric axit. Mặc dù o- coumaric cho thấy đặc tính chống khuẩn cao trong các công bố trước đây, nhưng theo hiểu biết của chúng tôi đây là nghiên cứu đầu tiên công bố về ảnh hưởng của hoạt chất o-coumaric axit lên sinh trưởng của M. aeruginosa và C. vulgaris.

The use of microalgae culture to convert CO2 from power plant flue gases into biomass that are readily converted into biofuels offers a new frame of opportunities to enhance, compliment or replace fossil-fuel-use. Apart from being renewable, microalgae also have the capacity to utilise materials from a variety of wastewater and the ability to yield both liquid and gaseous biofuels. However, the processes of cultivation, incorporation of a production system for power plant waste flue gas use, algae harvesting, and oil extraction from the biomass have many challenges. Using SimaPro software, Life cycle Assessment (LCA) of the challenges limiting the microalgae (Chlorella vulgaris) biofuel production process was performed to study algae-based pathway for producing biofuels. Attention was paid to material use, energy consumed and the environmental burdens associated with the production processes. The goal was to determine the weak spots within the production system and identify changes in particular data-set that can lead to and lower material use, energy consumption and lower environmental impacts than the baseline microalgae biofuel production system. The analysis considered a hypothetical transesterification and Anaerobic Digestion (AD) transformation of algae-to- biofuel process. Life cycle Inventory (LCI) characterisation results of the baseline biodiesel (BD) transesterification scenario indicates that heating to get the biomass to 90% DWB accounts for 64% of the total input energy, while electrical energy and fertilizer obligations represents 19% and 16% respectively. Also, Life Cycle Impact Assessment (LCIA) results of the baseline BD production scenario show high proportional contribution of electricity and heat energy obligations for most impact categories considered relative to other resources. This is attributed to the concentration/drying requirement of algae biomass in order to ease downstream processes of lipid extraction and subsequent transesterification of extracted lipids into BD. Thus, four prospective alternative production scenarios were successfully characterised to evaluate the extent of their impact scenarios on the production system with regards to lowering material use, lower energy consumption and lower environmental burdens than the standard algae biofuel production system. A 55.3% reduction in mineral use obligation was evaluated as the most significant impact reduction due to the integration of 100% recycling of production harvest water for the AD production system. Recycling also saw water demand reduced from 3726 kg (freshwater).kgBD- 1 to 591kg (freshwater).kgBD- 1 after accounting for evaporative losses/biomass drying for the BD transesterification production process. Also, the use of wastewater/sea water as alternative growth media for the BD production system, indicated potential savings of: 4.2 MJ (11.8%) in electricity/heat obligation, 10.7% reductions for climate change impact, and 87% offset in mineral use requirement relative to the baseline production system. Likewise, LCIA characterisation comparison results comparing the baseline production scenarios with that of a set-up with co-product economic allocation consideration show very interesting outcomes. Indicating -12 MJ surplus (-33%) reductions for fossil fuels resource use impact category, 52.7% impact reductions for mineral use impact and 56.6% reductions for land use impact categories relative to the baseline BD production process model. These results show the importance of allocation consideration to LCA as a decision support tool. Overall, process improvements that are needed to optimise economic viability also improve the life cycle environmental impacts or sustainability of the production systems. Results obtained have been observed to agree reasonably with Monte Carlo sensitivity analysis, with the production scenario proposing the exploitation of wastewater/sea water to culture algae biomass offering the best result outcome. This study may have implications for additional resources such as production facility and its construction process, feedstock processing logistics and transport infrastructure which are excluded. Future LCA study will require extensive consideration of these additional resources such as: facility size and its construction, better engineering data for water transfer, combined heat and power plant efficiency estimates and the fate of long-term emissions such as organic nitrogen in the AD digestate. Conclusions were drawn and suggestions proffered for further study.