The culture of coccolithophorid algae is an attractive option for sequestration or recycling of CO2 as they can fix carbon by photosynthesis as well as in calcium carbonate scales known as coccoliths. They also produce high amounts of lipids which have a potential application as a renewable fuel. Five species of coccolithophorids (Pleurochrysis carterae, CCMP647, Pleurochrysis sp. CCMP1211, Gephyrocapsa oceanica CS-335/2, Emiliania huxleyi CCMP371, and Emiliania huxleyi CS-369) were screened for their ability to grow at high temperature. All species grew up to 28oC except E. huxleyi CS-369. However, Pleurochrysis sp. CCMP 1211 which was found to clump and can therefore not be recommended for large-scale cultivation. The salinity tolerance of these species was also examined. Growth of P. carterae, G. oceanica, and E. huxleyi in laboratory scale closed photobioreactors (plate, carboy, airlift, and tubular photobioreactors) showed the plate photobioreactor to be the best closed cultivation system. The highest productivities were achieved by P. carterae in the plate photobioreactor and were 0.54 g.L-1.d-1, 0.12 g.L-1.d-1, 0.06 g.L-1.d-1 for total dry weight, lipid and CaCO3 respectively. The growth of P. carterae and E. huxleyi was also examined in an outdoor raceway pond. The E. huxleyi culture was easily contaminated resulting in the loss of the culture in less than three weeks, but P. carterae grew well over a period of 13 months. The overall total dry weight productivity of P. carterae was 0.19 g.L-1.d-1 with lipid and CaCO3 contents of up to 33% and 10% of dry weight respectively. There was little protozoan and bacterial contamination. Medium pH increased to pH 11 during the day and was found to be a reliable variable for maintaining the health of the culture. A maximum pH achieved during the day of less than pH 8.5 indicated the imminent collapse of the culture. Heavy rain and low temperature were the main reasons for culture loss in mid winter, whereas high temperature during summer favoured P. carterae growth. A comparison of the growth of P. carterae and Dunaliella salina MUR8 in the raceway ponds showed no significant differences between these two species with regard to areal total dry weight productivity and lipid content. The effects of several limiting factors were also examined. A reduction in medium pH resulting from CO2 addition inhibited the growth of E. huxleyi in the plate photobioreactor, whereas P. carterae growth and productivities increased in the pH range of pH 7.7 to 8.0 in the plate photobioreactor and pH 9.1 to 9.6 in the outdoor raceway pond. The best operational pond depth for outdoor raceway culture of P. carterae was between 16 cm and 21 cm. Early morning temperatures, especially during the winter, highly affected the growth of P. carterae in the raceway pond, whereas artificially increasing the medium temperature improved the health of the culture but resulted in little increase in productivity. Photosynthesis of P. carterae was found to be highly inhibited by high oxygen concentration in the medium irrespective of temperature or irradiance. An economic model of P. carterae in a 63 ha raceway plant resulted in a cost for the biomass of between 7.35 Aus$.Kg-1 and 14.17 Aus$.Kg-1 depending on the harvesting method used.

This study investigated In situ biodiesel production with supercritical methanol. A micro-algae based feedstock was used and obtained from a local water treatment plant situated just outside of Bethal, South Africa (S 26° 29’ 19.362” E 29° 27’ 11.552”). The wet feedstock was used as harvested with only the excess moisture being removed. Characterisation of the feedstock showed that a wide variety of macro-algae, micro-algae, cyanobacteria and bacterial species were present in the feedstock. The main algal species isolated from the feedstock were Nostoc sp. and Chlamydomonas. The feedstock was found to have a higher heating value (HHV) of 22 MJ.kg-1 and a lower heating value (LHV) of 16.03 MJ.kg-1 with an inherent moisture content of 270g.kg-1 feedstock. The protein and fat content of the feedstock was determined by the Agricultural Research Council (ARC) and found to be 370.1 g.kg-1 and 61.6 g.kg-1 on a moisture free basis respectively. The high protein and fat content gives a theoretical bio-yield of 430 wt%. The low lignin content and high cellulose and hemi-cellulose content indicated that the feedstock would be suitable for energy production. Three experimental sets were performed to determine the effect certain reaction parameters will have on the bio-char, bio-oil and biodiesel yields. The first set entailed hydrothermal liquefaction without the addition of methanol. The second set involved in situ biodiesel production with supercritical methanol, while both supercritical methanol and an acid catalyst were used during in situ biodiesel in the third set. For the first set of experiments the effect of temperature (240°C to 340°C in intervals of 20°C) on the crude bio-oil and bio-char yields were investigated. The highest bio-char yield was found to be 336g g char.kg-1 biomass at 280°C, while the highest crude bio-oil yield was 470.7 g crude bio-oil per kg biomass at 340°C. In the second set of experiments the dry biomass loading was kept constant at 500 g.kg-1 and the temperature varied (240°C to 300°C in intervals of 20°C) along with methanol to dry biomass ratio (1:1, 3:1 and 6:1). The optimum bio-oil yield of 597.1 g bio-oil per kg biomass for this set was found at 500 g.kg-1 biomass loading, 300°C and 3:1 methanol to dry biomass ratio. The highest bio-char yield was found to be 382.6 g bio-char.kg-1 biomass for a 1:1 methanol to dry biomass weight ratio set with 500 g.kg-1 biomass loading at 280°C. An increase in methanol ratio also led to an increase in crude bio-oil yields however the 3:1 methanol to dry biomass mass ratio was found to give the highest bio-oil yield and the purest biodiesel, with less unsaturated FAME. The 6:1 methanol to dry biomass mass ratio did however increase the FAME yield, which tends to show completion of the in situ production of biodiesel. This was also seen in the amount fatty acid methyl esters (FAME) present in the crude bio-oil as the degree of transesterification starts to increase with an increase in methanol. The FAME content was determined using gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). During the last set of experiments the temperature (260°C to 300°C in intervals of 20°C) and methanol to dry biomass ratio (1:1, 3:1 and 6:1) was varied at a constant catalyst loading of 1 wt% of the dry biomass. The optimum yields achieved were 627 g crude bio-oil per kg biomass and 376 g bio-char per kg biomass at 300°C and 280°C, respectively. These yields were achieved at 500 g.kg-1 biomass loading and 6:1 methanol ratio. Compared to the experiments where no catalyst was used, a slight increase in the yield was observed with the addition of an acid catalyst. This might be due to the base metals present in the feedstock that can lead to saponification during transesterification without the addition of an acid catalyst. An overall improvement in the extraction of crude bio-oil was observed with in situ production compared to hydrothermal liquefaction. During in situ liquefaction, the bio-oil yield increased by 150 g crude bio-oil per kg biomass higher, while the bio-char yields did not significantly vary at the optimum point of 280°C this finding has a significant value for green coal research. The highest HHV for the bio-char of 27 MJ.kg-1 +/- 0.17 MJ.kg-1 was found at 280°C and a 3:1 methanol ratio. The HHV of the bio-char decreases with an increase in temperature as more of the hydrocarbons are dissolved and form part of the bio-crude make-up. The highest HHV recorded for the crude bio-oil was 42 MJ.kg-1 at a 6:1 methanol ratio, a temperature of 300°C and an acid catalyst. The crude bio-oil HHV, which increased with an increase in temperature, is well within the specifications of the biodiesel standard (SANS, 1935). The highest FAME yield of 39.0 g.kg-1 was obtained using a 6:1 methanol ratio and a temperature of 300°C in the presence of an acid catalyst. The crude oil contained 49.0 g.kg-1 triglycerides with alkenes (C13, C15 and C17) making up the balance. The purest biodiesel yield was achieved at 3:1 methanol to dry biomass mass ratio, as it had the lowest yield unsaturated methyl esters. The overall FAME yield increased with an increase in methanol ratio. The derivatised FAME yields were the highest during hydrothermal liquefaction (55.0 g.kg-1 biomass). The in situ production of biodiesel from waste water clarifier effluent stream was found to be possible. Further investigation is needed into sufficient harvesting methods, including the optimum harvesting location, as this will result in fewer impurities in the stream and subsequent higher yields. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

This study investigated In situ biodiesel production with supercritical methanol. A micro-algae based feedstock was used and obtained from a local water treatment plant situated just outside of Bethal, South Africa (S 26° 29’ 19.362” E 29° 27’ 11.552”). The wet feedstock was used as harvested with only the excess moisture being removed. Characterisation of the feedstock showed that a wide variety of macro-algae, micro-algae, cyanobacteria and bacterial species were present in the feedstock. The main algal species isolated from the feedstock were Nostoc sp. and Chlamydomonas. The feedstock was found to have a higher heating value (HHV) of 22 MJ.kg-1 and a lower heating value (LHV) of 16.03 MJ.kg-1 with an inherent moisture content of 270g.kg-1 feedstock. The protein and fat content of the feedstock was determined by the Agricultural Research Council (ARC) and found to be 370.1 g.kg-1 and 61.6 g.kg-1 on a moisture free basis respectively. The high protein and fat content gives a theoretical bio-yield of 430 wt%. The low lignin content and high cellulose and hemi-cellulose content indicated that the feedstock would be suitable for energy production. Three experimental sets were performed to determine the effect certain reaction parameters will have on the bio-char, bio-oil and biodiesel yields. The first set entailed hydrothermal liquefaction without the addition of methanol. The second set involved in situ biodiesel production with supercritical methanol, while both supercritical methanol and an acid catalyst were used during in situ biodiesel in the third set. For the first set of experiments the effect of temperature (240°C to 340°C in intervals of 20°C) on the crude bio-oil and bio-char yields were investigated. The highest bio-char yield was found to be 336g g char.kg-1 biomass at 280°C, while the highest crude bio-oil yield was 470.7 g crude bio-oil per kg biomass at 340°C. In the second set of experiments the dry biomass loading was kept constant at 500 g.kg-1 and the temperature varied (240°C to 300°C in intervals of 20°C) along with methanol to dry biomass ratio (1:1, 3:1 and 6:1). The optimum bio-oil yield of 597.1 g bio-oil per kg biomass for this set was found at 500 g.kg-1 biomass loading, 300°C and 3:1 methanol to dry biomass ratio. The highest bio-char yield was found to be 382.6 g bio-char.kg-1 biomass for a 1:1 methanol to dry biomass weight ratio set with 500 g.kg-1 biomass loading at 280°C. An increase in methanol ratio also led to an increase in crude bio-oil yields however the 3:1 methanol to dry biomass mass ratio was found to give the highest bio-oil yield and the purest biodiesel, with less unsaturated FAME. The 6:1 methanol to dry biomass mass ratio did however increase the FAME yield, which tends to show completion of the in situ production of biodiesel. This was also seen in the amount fatty acid methyl esters (FAME) present in the crude bio-oil as the degree of transesterification starts to increase with an increase in methanol. The FAME content was determined using gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). During the last set of experiments the temperature (260°C to 300°C in intervals of 20°C) and methanol to dry biomass ratio (1:1, 3:1 and 6:1) was varied at a constant catalyst loading of 1 wt% of the dry biomass. The optimum yields achieved were 627 g crude bio-oil per kg biomass and 376 g bio-char per kg biomass at 300°C and 280°C, respectively. These yields were achieved at 500 g.kg-1 biomass loading and 6:1 methanol ratio. Compared to the experiments where no catalyst was used, a slight increase in the yield was observed with the addition of an acid catalyst. This might be due to the base metals present in the feedstock that can lead to saponification during transesterification without the addition of an acid catalyst. An overall improvement in the extraction of crude bio-oil was observed with in situ production compared to hydrothermal liquefaction. During in situ liquefaction, the bio-oil yield increased by 150 g crude bio-oil per kg biomass higher, while the bio-char yields did not significantly vary at the optimum point of 280°C this finding has a significant value for green coal research. The highest HHV for the bio-char of 27 MJ.kg-1 +/- 0.17 MJ.kg-1 was found at 280°C and a 3:1 methanol ratio. The HHV of the bio-char decreases with an increase in temperature as more of the hydrocarbons are dissolved and form part of the bio-crude make-up. The highest HHV recorded for the crude bio-oil was 42 MJ.kg-1 at a 6:1 methanol ratio, a temperature of 300°C and an acid catalyst. The crude bio-oil HHV, which increased with an increase in temperature, is well within the specifications of the biodiesel standard (SANS, 1935). The highest FAME yield of 39.0 g.kg-1 was obtained using a 6:1 methanol ratio and a temperature of 300°C in the presence of an acid catalyst. The crude oil contained 49.0 g.kg-1 triglycerides with alkenes (C13, C15 and C17) making up the balance. The purest biodiesel yield was achieved at 3:1 methanol to dry biomass mass ratio, as it had the lowest yield unsaturated methyl esters. The overall FAME yield increased with an increase in methanol ratio. The derivatised FAME yields were the highest during hydrothermal liquefaction (55.0 g.kg-1 biomass). The in situ production of biodiesel from waste water clarifier effluent stream was found to be possible. Further investigation is needed into sufficient harvesting methods, including the optimum harvesting location, as this will result in fewer impurities in the stream and subsequent higher yields. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Microalgae surpass the lipid productivity of terrestrial plants by several folds. However, due to the high moisture content and rigidity of algal cell walls, extraction of lipids from algae is still a significant technological challenge. In this research, an attempt was made to develop an algal lipid separation process which is energy efficient and effective. Algal related research requires a unique set of knowledge in areas of algae culturing, measuring cell concentration, harvesting, cell rupturing and lipid quantification. The first section of this thesis focuses on the state of the art as well as knowledge gained during preliminary studies. The second section of this thesis focuses on selecting a suitable measurement technique for quantification of algal cell disruption induced by homogenization. The selected method, hemocytometry was used to measure the degree of algal cell disruption induced by homogenization. In the third section, various homogenization treatments were evaluated for determining the fraction of cells disrupted during the homogenization. Finally, lipid extraction efficiency of homogenized algae was evaluated using different extraction solvents under different homogenization conditions. Preliminary research concluded that using cell counting is the most suitable technique to measure the effect of high pressure homogenization on concentrated microalgae. It was observed that higher pressure and increased number of passes increase the degree of cell disruption. Concentrated, non stressed samples show best response to homogenization. Out of the three solvents used for solvent extraction, chloroform gave a higher extraction yield at low intensity homogenizations. However at harsher homogenization levels the advantage of chloroform was not significant. Lipid extraction efficiency increases with increased levels of homogenization. However, a significant increase in lipid yields was not detected beyond 20 000 psi and 2 passes of homogenization treatment.

<p>Algae is regarded as a good potential substrate for biogas production, due to high cells productivity, low cellulose and zero lignin content. Two parts were included in this study: first, cultivations of micro-algae (<em>Chlorella sorokiniana</em> and <em>Tetraselmis suecica</em>) at two different nitrate concentrations, also the effect of addition of CO₂ on algae grow was investigated in this first part. Second, batch fermentations of the cultivated micro-algae as well as a powder <em>Chlorella</em> (obtained from Raw Food Shop) and a dry mix filamentous algae (collected in the pounds in the park at the back of the Tema-building and then dried) were performed. In this part also effects of thermo-lime pretreatment (room temperature, 80^oC, 105^oC and 120^oC) on the algae biogas potentials was investigated.</p><p> </p><p>Both strains of micro-algae cultured at low nitrate gave more CH₄ yield: 319 (±26) mL and 258 (±12) mL CH₄per added gVS was obtained during the degradation of <em>Chlorella sorokiniana </em>grown at 0.4mM-N and 2mM-N level, respectively. For<em> Tetraselmis suecica</em> 337 (±37) mL and 236 (±20) mL CH₄ per added gVS was obtained at 2.4mM-N and 12mM-N level, respectively. Powder <em>Chlorella</em> gave the highest biogas production (719 ±53 mL/added gVS) and CH₄ yields (392 ±14 mL/added gVS), followed by the dry filamentou<em>s</em> algae (661 ±20 mL biogas and 295 ±9 mL CH₄ per added gVS) and <em>Tetraselmis suecica</em> (12 mM-N; 584 ±7 mL biogas and 295 ±9 mL CH₄ per added gVS).</p><p> </p><p>A negative effect of lime treatment at room temperature on CH₄ yield of algal biomass was obtained. Lime treatment at 120^oC showed the fastest degradation rate for <em>Tetraselmis</em> <em>suecica </em>and powder <em>Chlorella</em> during the initial 5 days of incubation.  </p><p> </p><p><em>Chlorella sorokiniana</em> and <em>Tetraselmis suecica</em> cultures flushed with biogas containing 70% and also CO₂ enriched air (5% CO₂) did not increase cells growth (measured as OD₆₀₀) if compared to references grown under air. On the contrary, a clearly inhibition effect on the algal cells growth was observed in some cultures.</p>

Les efflorescences phytoplanctoniques nuisibles et/ou toxiques impactent depuis très longtemps les écosystèmes marins du monde entier. Ces développements massifs ont un effet néfaste sur les écosystèmes et leur exploitation. Les lagunes du Languedoc-Roussillon sont touchées depuis plusieurs décennies. En plus des risques sanitaires récurrents dus aux genres Dinophysis (toxines DSP) et Alexandrium (toxines PSP), Vulcanodinium rugosum a été identifiée en 2011 dans la lagune d’Ingril. Cette nouvelle espèce est productrice de pinnatoxines (neurotoxines). A travers ces travaux de thèse, la biologie de cette nouvelle espèce (cycle de vie, condition de croissance, production de toxines), ses capacités de contamination des mollusques et sa distribution géographique dans les lagunes limitrophes ont été étudiées sur des cultures au laboratoire et via des suivis environnementaux.Les résultats de cette étude ont mis en évidence le caractère thermophile et euryhalin de cette microalgue (croissance optimale à 25°C et à une salinité de 40 ) avec des plages de croissance comprises entre 20 et 30°C. Sa capacité à croître sur une source azotée organique (urée) a été observée in vitro. Son expansion à des lagunes du Languedoc-Roussillon autre que l’étang d’Ingril, a été confirmée par la mise en évidence de la contamination des moules par la pinnatoxine G. La survie de ce dinoflagellé dans le tractus digestif des moules et des huîtres prouve que le transfert de coquillages est une source de contamination potentielle des écosystèmes non impactés par cette espèce toxique.Le cycle de vie de V. rugosum n’a pu être élucidé que partiellement, le kyste de résistance n’ayant pas été identifié formellement. Les kystes temporaires apparaissent comme des stades très importants à prendre en considération en raison de leur capacité à se diviser et de leur forte présence sur les macrophytes. Ces formes temporaires de résistance peuvent constituer une source de contamination non négligeable des mollusques dans la lagune de l’Ingril même lorsque les cellules végétatives de V. rugosum sont peu présentes dans la colonne d’eau. En raison des faibles densités de V. rugosum in situ et la difficulté de son identification sur des critères morphologique, sa surveillance dans le cadre du REPHY demeure difficile. Ainsi l’utilisation de systèmes d’échantillonnage passifs (SPATT) constitués de résines qui adsorbent les toxines dissoutes dans l’eau permettrait la détection précoce des toxines associées à ces espèces benthiques émergentes. Cette étude met en évidence la prolifération d’une espèce émergente thermophile qui pourrait avec d’autres et à la faveur de changements climatiques constituer des problèmes sanitaires et économiques importants dans les écosystèmes lagunaires vulnérables de la Méditerranée. / Harmful and / or toxic phytoplankton blooms impact for a long time marine ecosystems worldwide. These massive developments have an adverse effect on ecosystems and their exploitation. The lagoons of the region Languedoc-Roussillon are affected for decades. In addition to recurring health risks from Dinophysis (DSP toxins) and Alexandrium (PSP toxins), Vulcanodinium rugosum was identified in 2011 in the lagoon Ingril. This new species product pinnatoxins (neurotoxins). Through this thesis work, the biology of this new species (life cycle, growth condition, toxin production), its shellfish contamination capacity and geographic distribution in neighboring lagoons were studied on cultures in the laboratory and via environmental monitoring.The results of this study have demonstrated its thermophilic and euryhaline features (optimum salinity and temperature of 25°C and 40 respectively) and its growth ranges between 20 and 30°C. Its ability to grow on an organic nitrogen source (urea) has been showed in vitro. Its expansion in other lagoons of Languedoc-Roussillon, was confirmed by the contamination of the mussels by the pinnatoxin G. The survival of this organism in the digestive tract of mussels and oysters proves that the transfer of shellfish is potentially a source of contamination of new ecosystems not yet affected by this toxic species.The life cycle of V. rugosum has not been fully described because the resistance cyst has not been formally identified. Temporary cysts appear as very important stages to be considered because of their ability to divide and their strong presence on macrophytes. These temporary forms of resistance may be a significant source of contamination of shellfish in the lagoon of the Ingril even when the vegetative cells of V. rugosum are weakly present in the water column. Because of the low densities of V. rugosum in situ and the difficulty of its identification on morphological criteria, the monitoring within the REPHY protocol remains difficult. Thus the use of passive sampling systems (Spatt) made with resins which adsorb toxins dissolved in water would make possible the early detection of toxins associated with these emerging benthic species. This study highlights the growth of an emerging thermophilic species that might with others and thanks to climate change provide important health and economic problems in vulnerable lagoon ecosystems of the Mediterranean.

As the global population rises to an estimated 9.4bn by 2050, the pressure for food, fuel and freshwater will continue to increase. Current renewable energy technologies are not widely applicable to the transport sector, which requires energy dense liquid fuels that drop into our existing infrastructure. Algal biofuels promise significantly higher yields than plants, without the displacement of valuable agricultural resources and have the potential to meet the global demand for transport fuel. Fossil fuel energy is largely ‘a legacy of algal photosynthesis’, with algae accounting for ~50% of global CO2 fixation today. In addition, these curious organisms show remarkable diversity in form, behaviour and composition. Recently there has been a global resurgence of interest in microalgae as a resource of biomass and novel products. With the present level of technology, knowledge and experience in commercial scale aquaculture, the capital cost and energy investment for algal biomass production is high. Culturing, harvesting and disrupting microalgal cells account for the largest energy inputs with more positive energy balances requiring low energy designs for culture, dewatering and extraction, efficient water and nutrient recycling with minimal waste. Little is known about the variable cell wall of microalgae, which presents a formidable barrier to the extraction of microalgal products. Staining, transmission electron microscopy (TEM) and enzymatic digestion were all utilised in an attempt to visualise, digest and characterise the cell wall of stock strains of Chlorella spp. and Pseudochoricystis ellipsoidea. The presence of algaenan, a highly resistant biopolymer, rendered staining and enzymatic digestion techniques ineffective. TEM revealed that algaenan is present in the outer walls of microalgae in a variety of conformations which appeared to impart strength to cells. A preliminary investigation utilising Fusarium oxysporum f.sp. elaeidis as a novel source of enzymes for the digestion of algaenan has also been described. Methods were developed for the mutagenesis of Chlorella emersonii and P. ellipsoidea using EMS and UV with the intent of generating cell-wall mutants. Although no viable cell wall mutants were produced, a viable pale mutant of C. emersonii was recovered 5 from UV mutagenesis. Growth rates of the pale mutant were significantly slower than the wild type, yet FAME profile was largely unaffected. Fluorescence activated cell sorting (FACS) was also investigated as a means for the rapid screening of mutagenized cells for cell wall mutants. In an attempt to reduce cooling costs of closed-culture systems, temperature tolerant species of microalgae were sought by bioprospecting the thermal waters of the Roman Baths. Numerous methods for isolation and purification of microalgae from the Baths were employed, ultimately yielding seven diverse isolates including cyanobacterial, eukaryotic, filamentous and single celled species. Despite some species possessing an increased tolerance to higher temperatures, none showed marked temperature tolerance coupled with high productivity. Further improvements to the culture conditions may have improved the productivity at higher temperatures. All seven isolates were deposited to the Culture Collection of Algae and Protozoa (CCAP). A variety of extraction methods including soxhlet, beadbeating, sonication and microwaving was investigated for efficacy of extracting fatty acid methyl esters (FAMEs) from C. emersonii. Beadbeating proved most effective in the extraction of FAMEs from C. emersonii. Microwaving showed potential as a rapid method of extraction yet was coupled with degradation of FAMEs, requiring further method development to resolve this issue. Method development has been a significant component of the work described in this thesis.

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2017-08-18T21:04:45Z No. of bitstreams: 1 Jonas F Recalcatti 2016.pdf: 1372488 bytes, checksum: dc974cf30808e2ac26e1121f83b9cf4a (MD5) / Made available in DSpace on 2017-08-18T21:04:45Z (GMT). No. of bitstreams: 1 Jonas F Recalcatti 2016.pdf: 1372488 bytes, checksum: dc974cf30808e2ac26e1121f83b9cf4a (MD5) Previous issue date: 2016-09-08 / The necessity of alternative energy sources is an example of action that may contribute to diminish environment related issues. Thus, biofuels rise as an option that fit to sustainable development, because they are produced from renewable sources of energy in order to reduce harmful gas emissions to the environment. Studies approach the potential of micro-algae to produce biodiesel, a biofuel obtained from the oil of oilseeds and micro-algae. The micro-algae consist of a variety of autotrophic, prokaryotic or eukaryotic organisms. Their simple structure allows them to easily convert solar energy into chemical energy. The products of this conversion are been used to obtain biomass from micro-algae and, consequently, products of commercial applications. Some micro-algae contain high levels of lipid, showing the potential of these microorganisms to produce biofuels. In this way, the objective of this paper was to study the micro-algae Chlamydomonas reinhardtii cultivation, growing with and without nitrogen, for the extraction and quantification of oil from this biomass in different temperatures and the analysis of the composition of the fatty acids produced. From the results obtained with the extraction, it has been seen that the deletion of nitrogen influence lipids productivity, rising the levels of the lipids on the micro-algae biomass when compared to lipids levels of the biomass cultivated with nitrogen, showing better outcomes when extracted at the temperature of 45º C (7% with nitrogen and 11% without nitrogen), independently of cultivation conditions. The deletion of nitrogen on the cultivation does not interfere significantly with the composition of the fatty acids in the oil of the biomass from the micro-algae. What predominates in its composition are saturated fatty acids (C 16:0) and mono-unsaturated (C 14:1, C 16:1 and C 20:1), propitious to biodiesel production. The results obtained show that the biomass Chlamydomonas reinhardtii micro-algae has the potential to produce biodiesel, when cultivated on the conditions tested on this paper. / A necessidade de fontes alternativas de energia são exemplos de ações que podem contribuir para amenizar os problemas relacionados ao meio ambiente. Assim, os biocombustíveis surgem como uma opção que se ajusta ao desenvolvimento sustentável, pois estes são produzidos a partir de fontes de energia renováveis de forma a diminuir a emissão de gases nocivos ao ambiente. Estudos abordam as potencialidades de microalgas para a produção de biodiesel, um biocombustível obtido a partir do óleo de diversas oleaginosas e microalgas. As microalgas consistem em uma variedade de organismos autotróficos, procarióticos ou eucarióticos, a estrutura simples das microalgas permite que elas convertam facilmente a energia solar em energia química. Desta forma, o trabalho teve como objetivo estudar o cultivo da microalga Chlamydomonas reinhardtii, em meios de cultivo com e sem nitrogênio, para extração e quantificação do óleo desta biomassa em diferentes temperaturas e análise da composição dos ácidos graxos produzidos. A microalga Chlamydomonas reinhardtii foi cultivada em meio com e sem nitrogênio. Após a recuperação da biomassa, esta foi analisada quanto à matéria orgânica e inorgânica, teor de clorofila a e b e por fim, foi obtido e quantificado o teor lipídico presente na biomassa, analisando-se o perfil de ácidos graxos presentes por cromatografia gasosa. A partir dos resultados obtidos com a extração, observou-se que, a supressão de nitrogênio influencia na produtividade de lipídeos, aumentando os teores destes na biomassa da microalga, quando comparado ao teor lipídico da biomassa cultivada com nitrogênio, apresentando maiores rendimentos quando extraído na temperatura de 45º C (7% CN e 11% SN), independente da condição de cultivo. A supressão de nitrogênio no meio de cultivo não interfere significativamente na composição dos ácidos graxos no óleo da biomassa algácea, predominando em sua composição ácidos graxos saturados (C 16:0) e mono-insaturados (C 14:1, C 16:1 e C 20:1), propícios para a produção de biodiesel. Os resultados obtidos demonstram que a biomassa microalga Chlamydomonas reinhardtii apresenta potencial para produção de biodiesel, quando cultivada nas condições testadas neste estudo.

Algae is regarded as a good potential substrate for biogas production, due to high cells productivity, low cellulose and zero lignin content. Two parts were included in this study: first, cultivations of micro-algae (Chlorella sorokiniana and Tetraselmis suecica) at two different nitrate concentrations, also the effect of addition of CO2 on algae grow was investigated in this first part. Second, batch fermentations of the cultivated micro-algae as well as a powder Chlorella (obtained from Raw Food Shop) and a dry mix filamentous algae (collected in the pounds in the park at the back of the Tema-building and then dried) were performed. In this part also effects of thermo-lime pretreatment (room temperature, 80oC, 105oC and 120oC) on the algae biogas potentials was investigated. Both strains of micro-algae cultured at low nitrate gave more CH4 yield: 319 (±26) mL and 258 (±12) mL CH4 per added gVS was obtained during the degradation of Chlorella sorokiniana grown at 0.4mM-N and 2mM-N level, respectively. For Tetraselmis suecica 337 (±37) mL and 236 (±20) mL CH4 per added gVS was obtained at 2.4mM-N and 12mM-N level, respectively. Powder Chlorella gave the highest biogas production (719 ±53 mL/added gVS) and CH4 yields (392 ±14 mL/added gVS), followed by the dry filamentous algae (661 ±20 mL biogas and 295 ±9 mL CH4 per added gVS) and Tetraselmis suecica (12 mM-N; 584 ±7 mL biogas and 295 ±9 mL CH4 per added gVS). A negative effect of lime treatment at room temperature on CH4 yield of algal biomass was obtained. Lime treatment at 120oC showed the fastest degradation rate for Tetraselmis suecica and powder Chlorella during the initial 5 days of incubation. Chlorella sorokiniana and Tetraselmis suecica cultures flushed with biogas containing 70% and also CO2 enriched air (5% CO2) did not increase cells growth (measured as OD600) if compared to references grown under air. On the contrary, a clearly inhibition effect on the algal cells growth was observed in some cultures.

Les objectifs de ce travail étaient d’approfondir les connaissances sur les capacités d’adaptation des diatomées à différentes concentrations de CO2 et plus précisément sur l’implication des CCM dans l’assimilation du carbone minéral dissous. Des études sur la physiologie, les enzymes de différentes voies métaboliques et des analyses de transcriptomique et de protéomique ont été réalisées. Nous avons observé que les espèces de diatomées étudiées étaient capables de réguler leurs systèmes de concentration du carbone minéral suivant les conditions environnementales. Certaines semblent utiliser préférentiellement le CO2 ou le bicarbonate tandis que d’autres espèces utilisent les deux. L’activité des anhydrases carbonique est fortement induite en faible concentration de CO2. Nos travaux montrent cependant, que l’activité de cette enzyme est variable d’une espèce à l’autre. Nous avons aussi observé que dans la majorité des diatomées que nous avons étudiées, la photosynthèse de type C3 et non de type C4 est présente, apportant ainsi un éclairage à une véritable controverse sur le métabolisme du carbone chez les diatomées. Nos travaux soulignent de plus, une grande diversité de stratégies de CCM chez les diatomées. Chez T. pseudonana, une nouvelle protéine, LCIP63, a été observée en conditions de faible concentration de CO2. Son rôle physiologique est actuellement inconnu ouvrant de nouvelles perspectives de recherche. / The objectives of this work were to improve the knowledge on ability of diatoms to scope with different CO2 concentrations and to study their carbon concentrating mechanisms (CCM). Studies of their physiology, their metabolic enzymes, and analyses at transcriptomic and proteomic levels were performed. In all studied diatoms, the CCMs can be regulated according to CO2 availability in the environment. Some diatoms seem to use preferentially CO2, others, bicarbonate and some can use both. The carbonic anhydrase (CA) activity is strongly induced when cells were grown at low vs high CO2. However, our work shows that CA activity is highly variable among the different diatoms. Most of the studied diatoms perform a C3 photosynthesis and not C4 photosynthesis. In diatoms, there is a huge diversity in the CCM strategy. A new protein, LCIP63, was observed when T. pseudonana was grown under low CO2. The physiological role of this protein is yet unknown and this finding opens new research perspectives.