Characterization of an aerated submerged hollow fiber ultrafiltration device for efficient microalgae harvesting

The present work characterizes a submerged aerated hollow fiber polyvinylidene fluorid (PVDF) membrane (0.03 μm) device (Harvester) designed for the ultrafiltration (UF) of microalgae suspensions. Commercial baker\u27s yeast served as model suspension to investigate the influence of the aeration rate of the hollow fibers on the critical flux (CF, J$_{c}$) for different cell concentrations. An optimal aeration rate of 1.25 vvm was determined. Moreover, the CF was evaluated using two different Chlorella cultures (axenic and non-axenic) of various biomass densities (0.8–17.5 g DW/L). Comparably high CFs of 15.57 and 10.08 L/m/$^{2}$/h were measured for microalgae concentrations of 4.8 and 10.0 g DW/L, respectively, applying very strict CF criteria. Furthermore, the J$_{c}$-values correlated (negative) linearly with the biomass concentration (0.8–10.0 g DW/L). Concentration factors between 2.8 and 12.4 and volumetric reduction factors varying from 3.5 to 11.5 could be achieved in short-term filtration, whereat a stable filtration handling biomass concentrations up to 40.0 g DW/L was feasible. Measures for fouling control (aeration of membrane fibers, periodic backflushing) have thus been proven to be successful. Estimations on energy consumption revealed very low energy demand of 17.97 kJ/m$^{3}$ treated microalgae feed suspension (4.99 × 10$^{-3}$ kWh/m$^{3}$) and 37.83 kJ/kg treated biomass (1.05 × 10$^{-2}$ kWh/kg), respectively, for an up-concentration from 2 to 40 g DW/L of a microalgae suspension

Cold-adapted culturing of the microalga Monoraphidium sp. in thin-layer raceway pond for biomass production

Three cultivation regimes were tested in cold-adapted cultures of the green microalga Monoraphidium in an outdoor thin-layer raceway pond: cultivation under sunlight; its combination with continuous supplementary illumination; and nitrogen depletion using both light sources. The highest volumetric and areal productivity, 0.16 g L−1 d−1 and 3.22 g m−2 d−1, respectively corresponding to the specific growth rate μ of 0.191 d−1 were achieved when sunlight was combined with supplementary illumination. The maximum total fatty acid content, 20.29 % of DW, rich in oleic acid, 54 % of total fatty acid content, was achieved under nitrogen depletion stress. An outstanding amount of lutein, 26.39 mg lutein g−1 DW, was detected grown under sunlight in the first trial. From the harvested and fermented biomass in the second trial 236 mLN g−1oTS of methane was generated

Psycho-social stigmatization of people with epilepsy from the perspective of public

This bachelor thesis is about epilepsy and about attitudes towards people with epilepsy and stigmatization from perspective of public. The theoretical part is divided to four chapters. The first one focuses on general clarification of terms which are related to epilepsy. In the chapter two there is analyzed psycho-social impact of epilepsy. The two following chapters deal with public attitudes towards the people who suffer from epilepsy and the connection between stigma and epilepsy. The practical part includes a research. This research was externalized using quantitative method in form of questionnaires and its aim was to find out the degree of stigmatization of people with epilepsy from the perspective of public and also to detect the public attitudes towards the people suffering from epilepsy

Advertising literacy. Teoretical koncept and didactic application.

This diploma thesis which is called Advertising literacy, theoretical concept and didactic application deals not only with the concepts of advertising and advertising literacy as such, but also focuses on advertising literacy more specifically for children and the possibility of developing this, very important, literacy. One part of this work deals with the function of advertising, the effects of advertising, the history of advertising and the psychology of advertising. An important part is also a section on advertising literacy and its components and possibilities for its development. In the practical part, this work presents proposals of activities, which can be used at schools´ education that will lead to the development of advertising literacy of students

Sulfur compounds of "sweet garlic" (\kur{Tulbaghia violacea} Harv.)

The theoretical part of the Bachelor thesis summarizes the formation pathways of sulfur compounds in plants of the genus Allium and shows the similarity between "regular" garlic (Allium sativum L.) and "sweet" garlic (Tulbaghia violacea Harv.). In the experimental part, marasmicin was extracted from the rhizomes of T. violacea and allicin was synthesized from diallyl disulfide. Antimicrobial properties of both compounds were tested in two ways - by the disk diffusion method against several strains of bacteria and yeasts (Clavibacter michiganensis, Erwinia amylovora, Xanthomonas axonopodis, Bacillus cereus, Escherichia coli, Micrococcus luteus and Saccharomyces cerevisiae) and by dilution method against three strains of bacteria (Bacillus cereus, Escherichia coli and Micrococcus luteus)

Cultivation, Monitoring and Application of Migroalgae Cultures.

This thesis deals with microalgae mass cultures grown in laboratory as well as outdoor cultivation systems and a potential use of their biomass. Case studies illustrate the correlation of changes in growth rate with photosynthetic activity, physiological features and biomass composition under various conditions (high irradiance intensity, optimal/suboptimal temperature and the presence of some metalloids). The special attention was also paid to evaluation of the bioavailability of Se-enriched Chlorella biomass which is commonly used as a food supplement. As concerns methodology, photosynthesis monitoring techniques, namely chlorophyll fluorescence were employed as an important tool to estimate microalgae activity

Digestate as sustainable nutrient source for microalgae - challenges and prospects

The interest in microalgae products has been increasing, and therefore the cultivation industry is growing steadily. To reduce the environmental impact and production costs arising from nutrients, research needs to find alternatives to the currently used artificial nutrients. Microalgae cultivation in anaerobic effluents (more specifically, digestate) represents a promising strategy for increasing sustainability and obtaining valuable products. However, digestate must be processed prior to its use as nutrient source. Depending on its composition, different methods are suitable for removing solids (e.g., centrifugation) and adjusting nutrient concentrations and ratios (e.g., dilution, ammonia stripping). Moreover, the resulting cultivation medium must be light-permeable. Various studies show that growth rates comparable to those in artificial media can be achieved when proper digestate treatment is used. The necessary steps for obtaining a suitable cultivation medium also depend on the microalgae species to be cultivated. Concerning the application of the biomass, legal aspects and impurities originating from digestate must be considered. Furthermore, microalgae species and their application fields are essential criteria when selecting downstream processing methods (harvest, disintegration, dehydration, product purification). Microalgae grown on digestate can be used to produce various products (e.g., bioenergy, animal feed, bioplastics, and biofertilizers). This review gives insight into the origin and composition of digestate, processing options to meet requirements for microalgae cultivation and challenges regarding downstream processing and products

Digestate as Sustainable Nutrient Source for Microalgae—Challenges and Prospects

The interest in microalgae products has been increasing, and therefore the cultivation industry is growing steadily. To reduce the environmental impact and production costs arising from nutrients, research needs to find alternatives to the currently used artificial nutrients. Microalgae cultivation in anaerobic effluents (more specifically, digestate) represents a promising strategy for increasing sustainability and obtaining valuable products. However, digestate must be processed prior to its use as nutrient source. Depending on its composition, different methods are suitable for removing solids (e.g., centrifugation) and adjusting nutrient concentrations and ratios (e.g., dilution, ammonia stripping). Moreover, the resulting cultivation medium must be light-permeable. Various studies show that growth rates comparable to those in artificial media can be achieved when proper digestate treatment is used. The necessary steps for obtaining a suitable cultivation medium also depend on the microalgae species to be cultivated. Concerning the application of the biomass, legal aspects and impurities originating from digestate must be considered. Furthermore, microalgae species and their application fields are essential criteria when selecting downstream processing methods (harvest, disintegration, dehydration, product purification). Microalgae grown on digestate can be used to produce various products (e.g., bioenergy, animal feed, bioplastics, and biofertilizers). This review gives insight into the origin and composition of digestate, processing options to meet requirements for microalgae cultivation and challenges regarding downstream processing and products

Diurnal changes of photosynthesis and growth of Arthrospira platensis cultured in a thin-layer cascade and an open pond

Diel changes in photosynthetic performance and biomass productivity were thoroughly examined in Arthrospira platensis cultures grown outdoors in an open circular pond (OCP) and a thin-layer cascade (TLC). The two cultures were grown at the same areal biomass density, but temperature maxima were adjusted to optimal (33 °C) and suboptimal (25 °C). At the optimal temperature, the cultures grown in TLC showed about 20% higher photosynthetic activity than those in OCP, while at the suboptimal one photosynthetic activity dropped by 20% and 35% in the TLC and OCP, respectively. Accordingly, the highest biomass productivity over 20 g m− 2 d− 1 was attained in the TLC at the optimal temperature, while at the suboptimal temperature the productivity decreased by 20%. In the OCP, the biomass productivity at both temperatures was about one third lower compared to those in the TLC. The better culture performance in the TLC was mainly ascribed to the shorter light path that promoted much faster light/dark cycles favourable for photosynthesis, as well as the faster warming of the cultures in the morning as compared to the OCP cultures. Monitoring photosynthesis performance of a culture can indicate design improvements, which may capitalize this photochemical advantage, increasing biomass productivity further.Consiglio Nazionale delle Ricerche/[N.0012463]/CNR/ItaliaCzech Academy of Sciences/[CNR-16-29]/CAS/República ChecaALGATECH – The Centre of Algal Biotechnology/[LO1416]/ALGATECH/República ChecaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de BiologíaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR

Variables Governing Photosynthesis and Growth in Microalgae Mass Cultures

Since the 1950s, microalgae have been grown commercially in man-made cultivation units and used for biomass production as a source of food and feed supplements, pharmaceuticals, cosmetics and lately biofuels, as well as a means for wastewater treatment and mitigation of atmospheric CO2 build-up. In this work, photosynthesis and growth affecting variables—light intensity, pH, CO2/O2 exchange, nutrient supply, culture turbulence, light/dark cell cycling, biomass density and culture depth (light path)—are reviewed as concerns in microalgae mass cultures. Various photosynthesis monitoring techniques were employed to study photosynthetic performance to optimize the growth of microalgae strains in outdoor cultivation units. The most operative and reliable techniques appeared to be fast-response ones based on chlorophyll fluorescence and oxygen production monitoring, which provide analogous results