This study investigated the extraction of lipids and β-carotene from microalgae using microemulsions as an alternative to current solvents. Type I and type IV microemulsions composed of 4% lecithin, sorbitan monooleate, PEG-6-caprylic glycerides, and ethyl caprate were able extract lipids from lyophilized microalgae better than hexane and ethyl caprate. HPLC quantified the extracted β-carotene, with type IV microemulsions extracting the most β-carotene at 0.137±0.074% (w/w) of the total microalgae biomass after an hour. The growth recovery of the microalgae after extraction was observed over 2 weeks. Variability in the data prevented definite conclusions about the ability of algae to grow after extraction. The type IV extractions consistently showed some signs of survival. After two weeks, a pale-green colour was observed in the 15min and 1h extractions. This study showed that microemulsions can successfully extract lipids from microalgae; future work would apply microemulsion formulations to live algal cells for in-situ extraction.

The extraction of oil from microalgae was investigated. The study focused on the hydrothermal liquefaction of the microalgae Microcystis aeruginosa, Cyclotella meneghinia and Nitzschia pusilla. M. aeruginosa was collected from the Hartebeespoort dam, while C. meneghinia and N. pusilla were cultured in the laboratory. The experiments were conducted in a high pressure autoclave with an inert atmosphere. Sodium carbonate was studied as a potential catalyst. The hydrothermal liquefaction of M. aeruginosa, C. meneghinia and N. pusilla was carried out at various reaction temperatures and catalyst loads. For the liquefaction of M. aeruginosa the residence times were also varied. The reaction temperatures ranged from 260 to 340 °C, while the catalyst loads varied between 0 and 10 wt% Na2CO3. The residence time was varied between 15 and 45 minutes. The study showed that hydrothermal liquefaction of M. aeruginosa produced a maximum oil yield of 15.60 wt% at 300 °C, whereas the thermochemical liquefaction of C. meneghinia and N. pusilla produced maximum yields of 16.03 wt% and 15.33 wt%, respectively, at 340 °C. The residence time did not influence thermochemical liquefaction of the algae, while an increase in the catalyst load reduced the oil yield. The reaction conditions had no effect on the elemental composition or the calorific value of the thermochemical liquefaction oil. The calorific value of the hydrothermal liquefaction oils ranged from 28.57 to 35.90 MJ.kg -1 . Hydrothermal liquefaction of microalgae produced oil that can be used as substitute for coal in simple gasification processes. The study showed that microalgal blooms, such as the M. aeruginosa blooms of the Hartebeespoort dam, can be used for the extraction of oil through hydrothermal liquefaction. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2010.

The extraction of oil from microalgae was investigated. The study focused on the hydrothermal liquefaction of the microalgae Microcystis aeruginosa, Cyclotella meneghinia and Nitzschia pusilla. M. aeruginosa was collected from the Hartebeespoort dam, while C. meneghinia and N. pusilla were cultured in the laboratory. The experiments were conducted in a high pressure autoclave with an inert atmosphere. Sodium carbonate was studied as a potential catalyst. The hydrothermal liquefaction of M. aeruginosa, C. meneghinia and N. pusilla was carried out at various reaction temperatures and catalyst loads. For the liquefaction of M. aeruginosa the residence times were also varied. The reaction temperatures ranged from 260 to 340 °C, while the catalyst loads varied between 0 and 10 wt% Na2CO3. The residence time was varied between 15 and 45 minutes. The study showed that hydrothermal liquefaction of M. aeruginosa produced a maximum oil yield of 15.60 wt% at 300 °C, whereas the thermochemical liquefaction of C. meneghinia and N. pusilla produced maximum yields of 16.03 wt% and 15.33 wt%, respectively, at 340 °C. The residence time did not influence thermochemical liquefaction of the algae, while an increase in the catalyst load reduced the oil yield. The reaction conditions had no effect on the elemental composition or the calorific value of the thermochemical liquefaction oil. The calorific value of the hydrothermal liquefaction oils ranged from 28.57 to 35.90 MJ.kg -1 . Hydrothermal liquefaction of microalgae produced oil that can be used as substitute for coal in simple gasification processes. The study showed that microalgal blooms, such as the M. aeruginosa blooms of the Hartebeespoort dam, can be used for the extraction of oil through hydrothermal liquefaction. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2010.

Differences in biofilm formation between Scenedesmus obliquus and Chlorella vulgaris were examined, as well as the effects of substrate properties. Species selection and species control had significant effects. In non-sterile conditions, C. vulgaris shifted from planktonic (23.7% attachment) to sessile (79.8% attachment) growth, and formed films of higher average thickness (52 ± 19 µm) than in sterile conditions (7 ± 6 µm). By contrast, S. obliquus attained similar thicknesses (54 ± 31 µm and 53 ± 38 µm) in both sterile and non-sterile conditions. The effect of substrate properties was minimal. Both species grew films of similar thickness (~ 30 µm for S. obliquus, <10 µm for C. vulgaris) on materials ranging from hydrophilic (glass) to hydrophobic (polytetrafluoroethylene). Micropatterning the surface also had little effect on film formation. The results indicate that species selection and species control are more important that substrate properties in the development of microalgal biofilms.

Differences in biofilm formation between Scenedesmus obliquus and Chlorella vulgaris were examined, as well as the effects of substrate properties. Species selection and species control had significant effects. In non-sterile conditions, C. vulgaris shifted from planktonic (23.7% attachment) to sessile (79.8% attachment) growth, and formed films of higher average thickness (52 ± 19 µm) than in sterile conditions (7 ± 6 µm). By contrast, S. obliquus attained similar thicknesses (54 ± 31 µm and 53 ± 38 µm) in both sterile and non-sterile conditions. The effect of substrate properties was minimal. Both species grew films of similar thickness (~ 30 µm for S. obliquus, <10 µm for C. vulgaris) on materials ranging from hydrophilic (glass) to hydrophobic (polytetrafluoroethylene). Micropatterning the surface also had little effect on film formation. The results indicate that species selection and species control are more important that substrate properties in the development of microalgal biofilms.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 147-165).

Thesis (Ph.D.) - University of St Andrews, April 2008. / Restricted until 11th April 2010.

Microalgae reactors, commonly known as photobioreactors, have become increasingly popular as an alternative for wastewater treatment. These systems reduce pollutants and remove nutrients such as nitrogen and phosphorous compounds from wastewater utilizing microalgae and bacteria. The biomass produced in the reactors can potentially be used to produce biofuels and decrease some of the energy demands of the process. Wastewater treating photobioreactors are a relatively new technology and many aspects of their microbiology need further study. This thesis presents a broad overview of the algal and bacterial communities present in these systems by looking at the most important species, metabolic pathways and growth dynamics of both algae and bacteria. The experiments presented in this thesis were conducted using municipal wastewater from the Västerås wastewater treatment plant. The wastewater was inoculated with algae from Lake Mälaren and compared to non-inoculated reactors. Overall, the inoculated reactors demonstrated better algal growth than those that were not inoculated. The tested systems also removed much of the ammonium and phosphorous present in the wastewater. The dominant algae in the tested systems belonged to the genera Scenedesmus, Desmodesmus and Chlorella. In addition to algae, the systems contained a large number of bacteria, mostly from the phyla Proteobacteria and Bacteroidetes. The algal photobioreactors contained a lower abundance of genes related to nitrogen metabolism, virulence and antibiotic resistance compared to the initial wastewater, showing that a shift in the bacterial community had occurred. The bacteria found in the systems were shown to be involved in synthesis of vitamins essential for algae growth such as vitamin B12, suggesting cooperation between the bacteria and algae. / I takt med att världens befolkning ökar, så produceras dagligen allt mer avfall. Detta kan orsaka stora problem för miljön. När det byggs nya system för vattenrening behöver vi även ta hänsyn till kravet att minska energiåtgången. Dagens vattenreningssystem har vissa tillkortakommanden när det gäller reningsnivåer och energianvändning. Ett alternativ till dagens system, kan vara fotobioreaktorer, dvs. vattenrening med hjälp av mikroalger. Dessa system använder mikroalger och bakterier för att rena vattnet från föroreningar, kväve och fosfor. Vattenrening med fotobioreaktorer är en relativt ny teknik. Flera aspekter gällande biologin i dessa system har ännu inte studerats i detalj. Den här avhandlingen presenterar en översikt av de alger och bakterier som är aktiva i fotobioreaktorer. Andra viktiga aspekter som tillväxt, arter samt vattenreningsförmåga har också studerats. Ett antal försök genomfördes där alger från Mälaren tillsattes i vatten från Västerås kommunala vattenreningsanläggning. Storleken på försöken varierade mellan 250 ml och 20 liter. Det visade sig att algerna hade en bra tillväxt samt att mängden ammonium och fosfor minskade i vattnet under försöksperioden. De alger som tillväxte mest i studien tillhörde Scenedesmus, Desmodesmus och Chlorella. Förutom alger tillväxte även ett stort antal bakterier från grupperna Proteobacteria and Bacteroidetes. Dessa bakterier visade sig syntetisera viktiga vitaminer, t.ex. vitamin B12, som algerna normalt inte kan syntetisera själva. Sammanfattningsvis, så presenterar denna avhandling viktig information gällande alger och bakterier i en fotobioreaktor. Informationen kan vara ett viktigt bidrag till framtida utveckling av storskaliga fotobioreaktorer för vattenrening.

Silicone rubber is a promising candidate for the next generation of electrical insulators on account of the prolonged hydrophobicity of the polymers. However, microalgae biofouling is always a concern for high voltage insulators installed in coastal regions. To understand how microalgae species interact with polymer surfaces that are used in electrical insulator applications, a study has been conducted to determine the interactions of a benthic and a pelagic algal species with polydimethylsiloxane surfaces. The adhesion strength of algal species were quantified with two different types of flow cells employed for our studies. These two types of flow cells are microfluidic chips and a laser-cut flow cell chamber, which provide a high and low wall shear stress, respectively. A video analysis software was designed to automate all aspects of the flow rate profile, data acquisition, and image analysis. Pristine poly(dimethyl siloxane) (PDMS), deionized water-exposed PDMS, and salt solution-exposed PDMS samples were used as substrates in adhesion experiments. The results indicate that surface hydrophobicity played a critical role in adhesion strength. At low shear stress, both B. braunii and T. rotula cells demonstrate a strongest adhesion strength onto the pristine PDMS surface, while show the weakest adhesion strength onto the salt solution exposed PDMS surface. At high shear stress, all PDMS surfaces provide an equal adhesion environment to the both species. / Graduate / 2021-12-11

Traditional terrestrial crops are currently being utilized as a feedstock for biofuels but resource requirements and low yields limit the sustainability and scalability. Comparatively, next generation feedstocks, such as microalgae, have inherent advantages such as higher solar energy efficiencies, larger lipid fractions, utilization of waste carbon dioxide, and cultivation on poor quality land. The assessment of microalgae-based biofuel production systems through lifecycle, technoeconomic, and scalability assessments has been forced to extrapolate laboratory-scale data due to the immaturity of the technology. This type of scaling leads to large uncertainty in the current near-term productivity potential and ultimately the results from modeling work that rely on this type of modeling. This study integrated a large-scale validated outdoor microalgae growth model that utilizes 21 species and reactor-specific inputs that accurately account for biological effects such as nutrient uptake, respiration, and temperature with hourly historical meteorological data from around the world to determine the current global productivity potential. A global map of the microalgae lipid and biomass productivity has been generated based on the results of annual simulations at 4,388 global locations spread over the seven continents. Maximum annual average yields between 24-27 m3·ha-1·yr-1 are found in Australia, Brazil, Colombia, Egypt, Ethiopia, India, Kenya, and Saudi Arabia with the monthly variability (minimum and maximum) yields of these locations ranging between 14 and 33 m3·ha-1·yr-1. A scalability assessment that leverages geographic information systems data to evaluate geographically realized microalgae productivity, energy consumption, and land availability has been performed highlighting the promising potential of microalgae-based biofuels compared to traditional terrestrial feedstocks. Results show many regions can meet their energy requirements through microalgae production without land resource restriction. Discussion focuses on sensitivity of monthly variability in lipid production compared to annual average yields, biomass productivity potential, effects of temperature on lipid production, and a comparison of results to previous published modeling assumptions.