Presently, two Chlorella sorokiniana strains sampled during summer (CS-S) and winter (CS-W) from ... more Presently, two Chlorella sorokiniana strains sampled during summer (CS-S) and winter (CS-W) from a maturation pond and isolated by dominance were studied on their behavior on temperature and light extremes in batch experiments. Although both strains showed no differences in their tolerance of temperatures up to 45°C, the growth rates, pigment contents and fatty acid compositions in response to PAR at 700 and 1,500 µmol m-2 sec-1 differed. CS-W was less affected by photoinhibition and maintained constantly high growth rates. High radiation resulted in both strains in an equivalent decrease of chlorophyll a and accessory pigments indicating that the latter did not function as a light filter. PUFAS (18:3 and 16:3) increased in CS-W at high radiation by > 60% and decreased in CS-S by 8 %. Results indicate that CS-W is highly favorable for mass cultivation particularly in outdoors, in which diurnal variations of solar radiation occur.
Im Rahmen der Internationalen Bauaustellung wurde 2013 in Hamburg eine Bioenergiefassade an einem... more Im Rahmen der Internationalen Bauaustellung wurde 2013 in Hamburg eine Bioenergiefassade an einem Wohnhaus installiert und seitdem erfolgreich betrieben. Anhand dieses Projektes wurde erstmals der Nachweis erbracht, dass in speziellen plattenförmigen Fassadenelementen, sogenannten Photobioreaktoren, über die einfallende Solarstrahlung Wärme und Algen Biomasse erzeugt werden kann. Das Forschungsteam FABIG-ein Verbundprojekt mit der Technischen Universität Dresden, ADCO Technik GmbH, Arup Deutschland GmbH und SSC GmbH-entwickelte diese zu geschosshohen, plattenförmigen Fassadenelementen aus Glas so weiter, dass sie nunmehr in die Primär-und Sekundarfassade integriert werden können. Das Team erarbeitete zunächst Konstruktionskonzepte für einen geklebten plattenförmigen Photobioreaktor und untersuchte die Klebkonstruktion, die haustechnische Anbindung sowie die Fassadenintegration näher. Der Beitrag beschreibt den Entwurf eines plattenförmigen Photobioreaktors mit besonderem Hinblick auf die innenliegenden Verklebungen zum Abtrag ständiger und dynamischer Beanspruchungen. Vorausgehende Material-und Klebstoffuntersuchungen werden erläutert. Aufbauend auf den Erkenntnissen der experimentellen Untersuchungen realisierte das Forschungsteam einen Prototyp der Größe 3,00 x 1,35 m² für einen Freiland-Teststand zur Untersuchung der Langzeitstabilität. Der Beitrag schließt mit einem Ausblick auf die zukünftige Fassadenintegration. Facade Elements for Bioenergy Building Skin-Development of a Prototype. The German FABIG team, consisting of Technischen Universität Dresden, ADCO Technik GmbH, Arup Deutschland GmbH und SSC GmbH, develops flat panel bioreactors of glass for building skins. This paper introduces the construction of the facade module focusing on inner load-bearing adhesives. The stages of development are presented starting from the constructional design via experimental studies to the assembly of the first prototype concluding with a concept for future facade integration.
European Biomass Conference and Exhibition Proceedings, 2013
Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supe... more Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supercritical water gasification at 650°C, 28 MPa and a residence time of 3 minutes. The long term aim is to gain a higher process efficiency through recycling of byproducts of supercritical water gasification and waste water during the cultivation of microalgae. The first step of the project, the general feasibility of conversion of microalgae via supercritical water gasification to a hydrogen-rich combustible gas is presented. The product gas consisted of hydrogen, methane, carbon dioxide, and ethane. A product gas with a higher heating value of 36 to 38 MJ/kg TOC could be reached, the carbon gasification yield was 64% respectively 69,5% in the two first experiments.
Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supe... more Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supercritical water gasification. The long term aim is to gain higher process efficiency through recycling of byproducts of supercritical water gasification and waste water during the cultivation of microalgae. The first step of the project, the general feasibility of conversion of microalgae Scenedesmus obliquus via supercritical water gasification to a hydrogen‐rich combustible gas is presented. The product gas had a higher heating value and consisted of hydrogen, methane, carbon dioxide, and ethane.
Green microalgae are gaining increased interest due to their ability to accumulate high-value com... more Green microalgae are gaining increased interest due to their ability to accumulate high-value compounds such as pigments, oils, antioxidants, and aromatics. These hydrophobic compounds can be extracted from the culture by the means of the biocompatible surfactantbased in situ cloud point extraction. In this study, we developed a continuous cloud point extraction using the nonionic surfactant Triton X-114, in order to extract the lipophilic substances from a green microalgae culture and accumulate these in the surfactant-rich phase. Cinnamic acid was applied as tracer in order to determine the optimal operating conditions for the extraction in a stirred extraction column. This model substance shows satisfying partitioning in the micellar phase (= 1.2 ± 0.2) and the maximal yield of 79.1 ± 0.2 % in a corresponding batch experiment. The process window for the continuous extraction was developed based on three parameter ranges: feed-to-solvent ratio of 6-10, a total column capacity of 1-2 l•h-1 , and a stirring speed of 20-60 rpm. Statistical experimental design utilizing a response surface method was applied to investigate the influence of the three process parameters mentioned above on the yield and productivity of cinnamic acid. The optimal conditions for the in situ extraction of the microalgae were validated with an Acutodesmus obliquus culture (cell dry weight = 1 g•l-1). A total amount of 0.2 ± 0.1 gAlgae product/kgCulture (0.2 ± 0.1 gAlgae product/gcell dry weight) accumulated in the extract phase. A good biocompatibility of the surfactant with the microalgae cells in raffinate was demonstrated by measuring the photosynthetic activity with a pulse amplitude measurement. This study demonstrated for the first time a successful application of a surfactant-based cloud point extraction of microalgae in a continuous mode. The presented results proved the potential of the in situ surfactant-based extraction of microalgae products as an alternative to conventional extraction techniques. Highlights Cloud point extraction as an in situ method for separation of algae products Optimization of the continuous Triton X-114 extraction for enhanced productivity Biocompatible continuous cloud point extraction with Acutodesmus obliquus Accumulation of algae products in the micellar phase of Triton X-114 Influence of the cloud point extraction with Triton X-114 on the cell morphology
Separation and Purification Technology, Oct 1, 2014
ABSTRACT In this work micelle-mediated extraction was investigated in order to develop an alterna... more ABSTRACT In this work micelle-mediated extraction was investigated in order to develop an alternative process for the in situ extraction of hydrophobic substances from microalgae cultures. The main requirements for an in situ extraction process such as biocompatibility, phase separation behavior and partitioning of the hydrophobic target substance between micellar- and aqueous phases were studied for a number of surfactants. The cloud point temperatures (CPT) as well as the biocompatibility of seven nonionic surfactants with the microalgae Scenedesmusobliquus were determined as a function of time. For the most biocompatible surfactant, Triton X-114 with a biocompatibility of 98%, the kinetics of phase separation in the temperature range between 30 and 40 °C have been investigated. The fastest phase separation (12 min) took place at a Triton X-114 concentration of 3 wt% at 40 °C, in contrast to the slowest (55 min) at a Triton X-114 concentration of 5 wt% at 30 °C. The partitioning of representative hydrophobic substances between the both phases was predicted using the model COSMO-RS, the results were compared to experimental data with satisfying accordance (LogPcalc. palmitic acid: 0.82; LogPexp. palmitic acid: 0.75). Based on these results the extraction of valuable compounds from the microalgae S.obliquus was realized on a pilot plant and compared to the lab scale experiments.
In the present study a control system was developed and tested which allowed to maintain an optim... more In the present study a control system was developed and tested which allowed to maintain an optimum of both heat and microalgae production in a bioenergy façade and use of the heat to supply a residential building with hot water and heating. The control was developed for and implemented in the residential building BIQ Das Algenhaus , Hamburg, Germany. It automatically operates all system components of the 170 m ² bioenergy façade as well as the management utilities which supply the building with heat. During a one-year monitoring in 2017/18, it was shown that the temperature in the culture medium of the bioenergy façade could be kept at the optimal cultivation temperature range between 20 and 35 °C. In addition to the biomass production, the façade produced heat as a result of the solar radiation. This heat has been extracted from the façade and utilized as a heat source for the building's supply system. The ratio between the solar radiation on the façade's surface and the heat produced-called energy conversion coefficient-was 0,38 across the year. The system supplied 59 % of the building's annual total heat consumption of 63 MWh/a for hot water and heating. In the months May to August, the bioenergy façade served as the sole primary heat source for the building and the 50% surplus heat were stored in the soil below the building. The heat stored in the soil resulted in a regeneration of the soil temperature and allowed to cover the heat demand during winter. 80% of the heat extracted from the façade were used instantaneously and without intermediate storage. This indicates that the control optimally regulates the heat flows for direct use and thus minimizes storage losses. The results show that bioenergy façades can be perfectly integrated into cities to help transfer them from being places of abundant resource consumption to places of production of resources by producing heat and biomass concomitantly.
ABSTRACT The micellar in situ extraction of hydrophobic compounds from microalgae cultures (Chlam... more ABSTRACT The micellar in situ extraction of hydrophobic compounds from microalgae cultures (Chlamydomonas reinhardtii, Chlorella vulgaris, Scenedesmus obliquus) using nonionic surfactants (Triton X-114, Tergitol TMN 6, Tergitol 15-s-7) was studied in lab- and pilot scale. Therefore, phase separation behavior of the cloud point systems as well as the biocompatibility of the surfactants was investigated. It was shown that algae cells are concentrated in the aqueous phase, whereas the hydrophobic compounds (fatty acids) are enriched in the micellar phase. The thermodynamic model COSMO-RS was used to calculate partitioning coefficients of fatty acids between the phases. The biocompatibility of the surfactants applied was studied by monitoring the photosynthetic activity of algae upon contact with surfactants using puls amplitude modulation. Significant differences in growth and the photosynthetic activity of different algae strains after exposure to surfactants were determined. Whereas the photosynthetic activity of C. reinhardtii decreased rapidly upon contact with surfactants, the photosynthetic activity of S. obliquus, was 90% in comparison to a control after exposure for 240 min to all tested surfactants. C. vulgaris showed an intermediate decrease. Thus, besides extraction, surfactants might be applied to control the growth of certain algae enabling the monoalgal culturing in outdoor cultivation of microalgae since the growth of the less surfactant-tolerant microalgae could be suppressed. Overall, the results indicate that a micellar extraction with nonionic surfactants offers the opportunity for an in situ extraction of hydrophobic substances directly from the culture medium and might be a promising alternative to a classic solvent extraction of dried algal biomass.
Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supe... more Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supercritical water gasification at 650°C, 28 MPa and a residence time of 3 minutes. The long term aim is to gain a higher process efficiency through recycling of byproducts of supercritical water gasification and waste water during the cultivation of microalgae. The first step of the project, the general feasibility of conversion of microalgae via supercritical water gasification to a hydrogen-rich combustible gas is presented. The product gas consisted of hydrogen, methane, carbon dioxide, and ethane. A product gas with a higher heating value of 36 to 38 MJ/kg TOC could be reached, the carbon gasification yield was 64% respectively 69,5% in the two first experiments.
Environmental pollutants might significantly affect the ecological integrity of coastal waters. B... more Environmental pollutants might significantly affect the ecological integrity of coastal waters. Biological indicators like seaweeds have been used globally to assess water pollution. In the present work, the seaweed Ellisolandia elongata was used to evaluate the pollution status in coastal waters around Essaouira city. Three sites were chosen: One as reference station (S1) and two polluted ones (S2 and S3). Seaweed biodiversity, physiologic parameters of E. elongata, as well as, abiotic parameters were studied. Results showed that at the polluted stations, seaweed biodiversity was significantly lower than in S1. However, the concentrations of Total Suspended Solids, Electrical Conductivity, Biological Oxygen Demand, Chemical Oxygen Demand, Ammonium, and Orthophosphates at S2 were significantly higher than at S1. Metal content of E. elongata remained below detection limit at all stations except for Zn and Cu at S2 considered the most polluted station. With respect to the physiologic parameters, Proline, Glycine Betaine and Polyphenol contents at S2 were above, whereas, Chlorophyll a content and axis length were below those determined at the reference station. From the results it can be concluded that seaweed E. elongata could be a good indicator to determine organic pollution in marine ecosystems.
Early microbial degradation processes and accumulation of carbonyl compounds and carboxylic acids... more Early microbial degradation processes and accumulation of carbonyl compounds and carboxylic acids in seston aggregates under oxic and suboxic environmental conditions were studied. In laboratory experiments, aerobic decomposition of seston material increased after aggregation and maximum rates were reached after about 70 h. Seston material that became refractory to aerobic degradation was mineralized anaerobically with nitrate as the terminal electron acceptor at a rate amounting to about 50% of the maximum rate during the previous aerobic incubation. During both early aerobic and anaerobic degradation of seston, a decrease in particulate organic carbon (POC) and the C:N ratio was observed. A net production of glyoxylate and glycolaldehyde occurred under anaerobic heterotrophic conditions and concentrations up to 4 and 30 pg 1-', respectively, were detected in the field when dissolved oxygen concentrations were below 3 mg I-'. Glycolaldehyde was identified as an indicator of anaerob~c degradation processes which occurred in the open water of the Elbe estuary for suspended seston aggregates 5 2 mm in diameter. Results indicate a strong coupling between aerobic and anaerobic processes in the aggregates whereby anaerobic net production of DOC could significantly enhance O2 consun~ption.
This study investigates the feasibility of microalgae cultivation with the effluent (permeate) of... more This study investigates the feasibility of microalgae cultivation with the effluent (permeate) of a decentralized anaerobic membrane bioreactor (AnMBR) treating high strength domestic wastewater. Two experiments, consisting of three and two successive batch experiments with incubation times varying between 5 and 9 days, were conducted. Nutrient removal and growth of the microalgae species Acutodesmus obliquus were studied for the following culture media: (A) permeate, (B) permeate enriched with iron (Fe), magnesium (Mg), manganese (Mn), sulfur (S) and the chelating agent EDTA, (C) commercial fertilizer as control culture. Initial nutrient concentrations in the culture media ranged from 9.3 to 16.6 mg•L À1 total phosphorus (TP) and from 85.1 to 126.2 mg•L À1 total nitrogen (TN). TP reached an average removal of 97%, 98% and 99% in (A), (B) and (C) respectively. An average TN removal of 94% and 96% was achieved in (B) and (C). Starting from the third batch of the first experiment and the second batch of the second experiment, the culture with permeate (A) showed a decrease in TN removal. Further batch experiments showed the need to add iron to ensure an optimal TN removal from the permeate.
Flat panel photobioreactors consisting of different layers of glass panes, designed to allow heat... more Flat panel photobioreactors consisting of different layers of glass panes, designed to allow heat and microalgae biomass production in a water layer by solar radiation at the facade of buildings (i.e. bioenergy facade), were acoustically examined and further developed for increased sound insulation against external noise exposure. The sound insulation was first examined by simulations on double-, triple-and four-skin bioreactor variants. Parameters such as the distance between panes, the number and types of layers, as well as the material and thickness of the glass panes, were varied. Especially the influence of decoupling layers and an airlift on the sound reduction index was evaluated. Based on the simulation results, a modular prototype was developed which could be converted into a double-, triple-or four-skin structure as required. The sound reduction of these was studied in an acoustic window laboratory experimentally. The highest measured weighted sound reduction index of 51 dB was obtained with a four-skin photobioreactor variant with four glass pane layers and a water layer. The weighted sound reduction indexes for alternative four-skin opaque prototype variants with a plasterboard layer were 2-3 dB lower. The double-and triple-skin variants achieved 43-47 dB. The use of XPS as insulation material in the outer air layers of the triple-and four-skin variants reduced the weighted sound reduction index by 2 dB. The airlift needed for turbulent mixing of the microalgae had no effect on the sound insulation but increased the average ambient noise level by up to 10 dB. With 51 dB, the four-shell photobioreactor prototype achieves sound insulation class 5 according to the german regulation VDI 2719 for windows and thus fulfills the function of a sound insulation element in the facade of buildings or in a soundproof wall. Highlights • Sound insulation of flat panel photobioreactors can be increased to 51 dB by two additional glass panes to a four skin type. • A four skin type is also favourable with respect to thermal insulation and allows higher solar heat gains. • The sound propagation speed in the water interlayer and therefore the dynamic stiffness changes with the filling stage of the intermediate water layer and the amount of bubbles of the airlift. • The influence of dynamic stiffness of the intermediate layer on the weighted sound reduction index decreases as the thickness of the prototype and the number of layers increases. • An increase in the thickness of the air layer between the panes from 5 to 40 mm increases the sound reduction index for all frequencies.
Blue-green light is known to maximize the degree of fatty acid (FA) unsaturation in microalgae. H... more Blue-green light is known to maximize the degree of fatty acid (FA) unsaturation in microalgae. However, knowledge on the particular waveband responsible for this stimulation of FA desaturation and its impact on the pigment composition in microalgae remains limited. In this study, Acutodesmus obliquus was cultivated for 96 h at 15°C with different light spectra (380-700 nm, 470-700 nm, 520-700 nm, 600-700 nm, and dark controls). Growth was monitored daily, and qualitative characterization of the microalgal FA composition was achieved via gas chromatography coupled with electron impact ionization mass spectrometry (GC-EI/MS). Additionally, a quantitative analysis of microalgal pigments was performed using high-performance liquid chromatography with diode array detection (HPLC-DAD). Spectra that included wavelengths between 470 and 520 nm led to a significantly higher percentage of the polyunsaturated fatty acids (PUFA) 18:3 and 16:4, compared to all other light conditions. However, no significant differences between the red light cultivations and the heterotrophic dark controls were observed for the FA 18:3 and 16:4. These results indicate, that exclusively the blue-green light waveband between 470 and 520 nm is responsible for a maximized FA unsaturation in A. obliquus. Furthermore, the growth and production of pigments were impaired if blue-green light (380-520 nm) was absent in the light spectrum. This knowledge can contribute to achieving a suitable microalgal pigment and FA composition for industrial purposes and must be considered in spectrally selective microalgae cultivation systems.
Microalgae have been considered as a potential feedstock for biomaterial compounds production. In... more Microalgae have been considered as a potential feedstock for biomaterial compounds production. In the southern Mediterranean region, which suffers from water scarcity, using wastewaters as culture media for microalgae cultivation is recommended. Hence, an algal strain is needed, which exhibits high growth under the prevailing temperature and light conditions. To obtain such strains, natural samples were collected from a maturation pond in the Peri-Urban Area of Marrakech (Morocco) and cultivated in different types of wastewaters at light intensity of 1,500 µmol m-2 s-1 and temperature up to 45°C in a batch system. Three types of wastewaters were used: raw, treated, not sterilized treated domestic wastewater from muti-soil layering system and tap water, started with the same concentrations of nitrogen and phosphorus. Results showed Chlorella was the only strain able to grow under the cultivation conditions established. This microalgae was identified by partial rbcL-gene as Chlorella sorokiniana with a genetic similarity of 98.8%, and registered under UCAM 001 (GenBank number MT999855). This finding indicates that the strain can be used for biomass production and phycoremediation process in semi-arid area. In addition, microalgae isolation by dominance could be a fast approach to obtain adapted strains for outdoor mass cultivation.
Presently, two Chlorella sorokiniana strains sampled during summer (CS-S) and winter (CS-W) from ... more Presently, two Chlorella sorokiniana strains sampled during summer (CS-S) and winter (CS-W) from a maturation pond and isolated by dominance were studied on their behavior on temperature and light extremes in batch experiments. Although both strains showed no differences in their tolerance of temperatures up to 45°C, the growth rates, pigment contents and fatty acid compositions in response to PAR at 700 and 1,500 µmol m-2 sec-1 differed. CS-W was less affected by photoinhibition and maintained constantly high growth rates. High radiation resulted in both strains in an equivalent decrease of chlorophyll a and accessory pigments indicating that the latter did not function as a light filter. PUFAS (18:3 and 16:3) increased in CS-W at high radiation by > 60% and decreased in CS-S by 8 %. Results indicate that CS-W is highly favorable for mass cultivation particularly in outdoors, in which diurnal variations of solar radiation occur.
Im Rahmen der Internationalen Bauaustellung wurde 2013 in Hamburg eine Bioenergiefassade an einem... more Im Rahmen der Internationalen Bauaustellung wurde 2013 in Hamburg eine Bioenergiefassade an einem Wohnhaus installiert und seitdem erfolgreich betrieben. Anhand dieses Projektes wurde erstmals der Nachweis erbracht, dass in speziellen plattenförmigen Fassadenelementen, sogenannten Photobioreaktoren, über die einfallende Solarstrahlung Wärme und Algen Biomasse erzeugt werden kann. Das Forschungsteam FABIG-ein Verbundprojekt mit der Technischen Universität Dresden, ADCO Technik GmbH, Arup Deutschland GmbH und SSC GmbH-entwickelte diese zu geschosshohen, plattenförmigen Fassadenelementen aus Glas so weiter, dass sie nunmehr in die Primär-und Sekundarfassade integriert werden können. Das Team erarbeitete zunächst Konstruktionskonzepte für einen geklebten plattenförmigen Photobioreaktor und untersuchte die Klebkonstruktion, die haustechnische Anbindung sowie die Fassadenintegration näher. Der Beitrag beschreibt den Entwurf eines plattenförmigen Photobioreaktors mit besonderem Hinblick auf die innenliegenden Verklebungen zum Abtrag ständiger und dynamischer Beanspruchungen. Vorausgehende Material-und Klebstoffuntersuchungen werden erläutert. Aufbauend auf den Erkenntnissen der experimentellen Untersuchungen realisierte das Forschungsteam einen Prototyp der Größe 3,00 x 1,35 m² für einen Freiland-Teststand zur Untersuchung der Langzeitstabilität. Der Beitrag schließt mit einem Ausblick auf die zukünftige Fassadenintegration. Facade Elements for Bioenergy Building Skin-Development of a Prototype. The German FABIG team, consisting of Technischen Universität Dresden, ADCO Technik GmbH, Arup Deutschland GmbH und SSC GmbH, develops flat panel bioreactors of glass for building skins. This paper introduces the construction of the facade module focusing on inner load-bearing adhesives. The stages of development are presented starting from the constructional design via experimental studies to the assembly of the first prototype concluding with a concept for future facade integration.
European Biomass Conference and Exhibition Proceedings, 2013
Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supe... more Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supercritical water gasification at 650°C, 28 MPa and a residence time of 3 minutes. The long term aim is to gain a higher process efficiency through recycling of byproducts of supercritical water gasification and waste water during the cultivation of microalgae. The first step of the project, the general feasibility of conversion of microalgae via supercritical water gasification to a hydrogen-rich combustible gas is presented. The product gas consisted of hydrogen, methane, carbon dioxide, and ethane. A product gas with a higher heating value of 36 to 38 MJ/kg TOC could be reached, the carbon gasification yield was 64% respectively 69,5% in the two first experiments.
Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supe... more Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supercritical water gasification. The long term aim is to gain higher process efficiency through recycling of byproducts of supercritical water gasification and waste water during the cultivation of microalgae. The first step of the project, the general feasibility of conversion of microalgae Scenedesmus obliquus via supercritical water gasification to a hydrogen‐rich combustible gas is presented. The product gas had a higher heating value and consisted of hydrogen, methane, carbon dioxide, and ethane.
Green microalgae are gaining increased interest due to their ability to accumulate high-value com... more Green microalgae are gaining increased interest due to their ability to accumulate high-value compounds such as pigments, oils, antioxidants, and aromatics. These hydrophobic compounds can be extracted from the culture by the means of the biocompatible surfactantbased in situ cloud point extraction. In this study, we developed a continuous cloud point extraction using the nonionic surfactant Triton X-114, in order to extract the lipophilic substances from a green microalgae culture and accumulate these in the surfactant-rich phase. Cinnamic acid was applied as tracer in order to determine the optimal operating conditions for the extraction in a stirred extraction column. This model substance shows satisfying partitioning in the micellar phase (= 1.2 ± 0.2) and the maximal yield of 79.1 ± 0.2 % in a corresponding batch experiment. The process window for the continuous extraction was developed based on three parameter ranges: feed-to-solvent ratio of 6-10, a total column capacity of 1-2 l•h-1 , and a stirring speed of 20-60 rpm. Statistical experimental design utilizing a response surface method was applied to investigate the influence of the three process parameters mentioned above on the yield and productivity of cinnamic acid. The optimal conditions for the in situ extraction of the microalgae were validated with an Acutodesmus obliquus culture (cell dry weight = 1 g•l-1). A total amount of 0.2 ± 0.1 gAlgae product/kgCulture (0.2 ± 0.1 gAlgae product/gcell dry weight) accumulated in the extract phase. A good biocompatibility of the surfactant with the microalgae cells in raffinate was demonstrated by measuring the photosynthetic activity with a pulse amplitude measurement. This study demonstrated for the first time a successful application of a surfactant-based cloud point extraction of microalgae in a continuous mode. The presented results proved the potential of the in situ surfactant-based extraction of microalgae products as an alternative to conventional extraction techniques. Highlights Cloud point extraction as an in situ method for separation of algae products Optimization of the continuous Triton X-114 extraction for enhanced productivity Biocompatible continuous cloud point extraction with Acutodesmus obliquus Accumulation of algae products in the micellar phase of Triton X-114 Influence of the cloud point extraction with Triton X-114 on the cell morphology
Separation and Purification Technology, Oct 1, 2014
ABSTRACT In this work micelle-mediated extraction was investigated in order to develop an alterna... more ABSTRACT In this work micelle-mediated extraction was investigated in order to develop an alternative process for the in situ extraction of hydrophobic substances from microalgae cultures. The main requirements for an in situ extraction process such as biocompatibility, phase separation behavior and partitioning of the hydrophobic target substance between micellar- and aqueous phases were studied for a number of surfactants. The cloud point temperatures (CPT) as well as the biocompatibility of seven nonionic surfactants with the microalgae Scenedesmusobliquus were determined as a function of time. For the most biocompatible surfactant, Triton X-114 with a biocompatibility of 98%, the kinetics of phase separation in the temperature range between 30 and 40 °C have been investigated. The fastest phase separation (12 min) took place at a Triton X-114 concentration of 3 wt% at 40 °C, in contrast to the slowest (55 min) at a Triton X-114 concentration of 5 wt% at 30 °C. The partitioning of representative hydrophobic substances between the both phases was predicted using the model COSMO-RS, the results were compared to experimental data with satisfying accordance (LogPcalc. palmitic acid: 0.82; LogPexp. palmitic acid: 0.75). Based on these results the extraction of valuable compounds from the microalgae S.obliquus was realized on a pilot plant and compared to the lab scale experiments.
In the present study a control system was developed and tested which allowed to maintain an optim... more In the present study a control system was developed and tested which allowed to maintain an optimum of both heat and microalgae production in a bioenergy façade and use of the heat to supply a residential building with hot water and heating. The control was developed for and implemented in the residential building BIQ Das Algenhaus , Hamburg, Germany. It automatically operates all system components of the 170 m ² bioenergy façade as well as the management utilities which supply the building with heat. During a one-year monitoring in 2017/18, it was shown that the temperature in the culture medium of the bioenergy façade could be kept at the optimal cultivation temperature range between 20 and 35 °C. In addition to the biomass production, the façade produced heat as a result of the solar radiation. This heat has been extracted from the façade and utilized as a heat source for the building's supply system. The ratio between the solar radiation on the façade's surface and the heat produced-called energy conversion coefficient-was 0,38 across the year. The system supplied 59 % of the building's annual total heat consumption of 63 MWh/a for hot water and heating. In the months May to August, the bioenergy façade served as the sole primary heat source for the building and the 50% surplus heat were stored in the soil below the building. The heat stored in the soil resulted in a regeneration of the soil temperature and allowed to cover the heat demand during winter. 80% of the heat extracted from the façade were used instantaneously and without intermediate storage. This indicates that the control optimally regulates the heat flows for direct use and thus minimizes storage losses. The results show that bioenergy façades can be perfectly integrated into cities to help transfer them from being places of abundant resource consumption to places of production of resources by producing heat and biomass concomitantly.
ABSTRACT The micellar in situ extraction of hydrophobic compounds from microalgae cultures (Chlam... more ABSTRACT The micellar in situ extraction of hydrophobic compounds from microalgae cultures (Chlamydomonas reinhardtii, Chlorella vulgaris, Scenedesmus obliquus) using nonionic surfactants (Triton X-114, Tergitol TMN 6, Tergitol 15-s-7) was studied in lab- and pilot scale. Therefore, phase separation behavior of the cloud point systems as well as the biocompatibility of the surfactants was investigated. It was shown that algae cells are concentrated in the aqueous phase, whereas the hydrophobic compounds (fatty acids) are enriched in the micellar phase. The thermodynamic model COSMO-RS was used to calculate partitioning coefficients of fatty acids between the phases. The biocompatibility of the surfactants applied was studied by monitoring the photosynthetic activity of algae upon contact with surfactants using puls amplitude modulation. Significant differences in growth and the photosynthetic activity of different algae strains after exposure to surfactants were determined. Whereas the photosynthetic activity of C. reinhardtii decreased rapidly upon contact with surfactants, the photosynthetic activity of S. obliquus, was 90% in comparison to a control after exposure for 240 min to all tested surfactants. C. vulgaris showed an intermediate decrease. Thus, besides extraction, surfactants might be applied to control the growth of certain algae enabling the monoalgal culturing in outdoor cultivation of microalgae since the growth of the less surfactant-tolerant microalgae could be suppressed. Overall, the results indicate that a micellar extraction with nonionic surfactants offers the opportunity for an in situ extraction of hydrophobic substances directly from the culture medium and might be a promising alternative to a classic solvent extraction of dried algal biomass.
Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supe... more Microalgae (Scenedesmus obliquus) produced in flat panel photobioreactors were converted via supercritical water gasification at 650°C, 28 MPa and a residence time of 3 minutes. The long term aim is to gain a higher process efficiency through recycling of byproducts of supercritical water gasification and waste water during the cultivation of microalgae. The first step of the project, the general feasibility of conversion of microalgae via supercritical water gasification to a hydrogen-rich combustible gas is presented. The product gas consisted of hydrogen, methane, carbon dioxide, and ethane. A product gas with a higher heating value of 36 to 38 MJ/kg TOC could be reached, the carbon gasification yield was 64% respectively 69,5% in the two first experiments.
Environmental pollutants might significantly affect the ecological integrity of coastal waters. B... more Environmental pollutants might significantly affect the ecological integrity of coastal waters. Biological indicators like seaweeds have been used globally to assess water pollution. In the present work, the seaweed Ellisolandia elongata was used to evaluate the pollution status in coastal waters around Essaouira city. Three sites were chosen: One as reference station (S1) and two polluted ones (S2 and S3). Seaweed biodiversity, physiologic parameters of E. elongata, as well as, abiotic parameters were studied. Results showed that at the polluted stations, seaweed biodiversity was significantly lower than in S1. However, the concentrations of Total Suspended Solids, Electrical Conductivity, Biological Oxygen Demand, Chemical Oxygen Demand, Ammonium, and Orthophosphates at S2 were significantly higher than at S1. Metal content of E. elongata remained below detection limit at all stations except for Zn and Cu at S2 considered the most polluted station. With respect to the physiologic parameters, Proline, Glycine Betaine and Polyphenol contents at S2 were above, whereas, Chlorophyll a content and axis length were below those determined at the reference station. From the results it can be concluded that seaweed E. elongata could be a good indicator to determine organic pollution in marine ecosystems.
Early microbial degradation processes and accumulation of carbonyl compounds and carboxylic acids... more Early microbial degradation processes and accumulation of carbonyl compounds and carboxylic acids in seston aggregates under oxic and suboxic environmental conditions were studied. In laboratory experiments, aerobic decomposition of seston material increased after aggregation and maximum rates were reached after about 70 h. Seston material that became refractory to aerobic degradation was mineralized anaerobically with nitrate as the terminal electron acceptor at a rate amounting to about 50% of the maximum rate during the previous aerobic incubation. During both early aerobic and anaerobic degradation of seston, a decrease in particulate organic carbon (POC) and the C:N ratio was observed. A net production of glyoxylate and glycolaldehyde occurred under anaerobic heterotrophic conditions and concentrations up to 4 and 30 pg 1-', respectively, were detected in the field when dissolved oxygen concentrations were below 3 mg I-'. Glycolaldehyde was identified as an indicator of anaerob~c degradation processes which occurred in the open water of the Elbe estuary for suspended seston aggregates 5 2 mm in diameter. Results indicate a strong coupling between aerobic and anaerobic processes in the aggregates whereby anaerobic net production of DOC could significantly enhance O2 consun~ption.
This study investigates the feasibility of microalgae cultivation with the effluent (permeate) of... more This study investigates the feasibility of microalgae cultivation with the effluent (permeate) of a decentralized anaerobic membrane bioreactor (AnMBR) treating high strength domestic wastewater. Two experiments, consisting of three and two successive batch experiments with incubation times varying between 5 and 9 days, were conducted. Nutrient removal and growth of the microalgae species Acutodesmus obliquus were studied for the following culture media: (A) permeate, (B) permeate enriched with iron (Fe), magnesium (Mg), manganese (Mn), sulfur (S) and the chelating agent EDTA, (C) commercial fertilizer as control culture. Initial nutrient concentrations in the culture media ranged from 9.3 to 16.6 mg•L À1 total phosphorus (TP) and from 85.1 to 126.2 mg•L À1 total nitrogen (TN). TP reached an average removal of 97%, 98% and 99% in (A), (B) and (C) respectively. An average TN removal of 94% and 96% was achieved in (B) and (C). Starting from the third batch of the first experiment and the second batch of the second experiment, the culture with permeate (A) showed a decrease in TN removal. Further batch experiments showed the need to add iron to ensure an optimal TN removal from the permeate.
Flat panel photobioreactors consisting of different layers of glass panes, designed to allow heat... more Flat panel photobioreactors consisting of different layers of glass panes, designed to allow heat and microalgae biomass production in a water layer by solar radiation at the facade of buildings (i.e. bioenergy facade), were acoustically examined and further developed for increased sound insulation against external noise exposure. The sound insulation was first examined by simulations on double-, triple-and four-skin bioreactor variants. Parameters such as the distance between panes, the number and types of layers, as well as the material and thickness of the glass panes, were varied. Especially the influence of decoupling layers and an airlift on the sound reduction index was evaluated. Based on the simulation results, a modular prototype was developed which could be converted into a double-, triple-or four-skin structure as required. The sound reduction of these was studied in an acoustic window laboratory experimentally. The highest measured weighted sound reduction index of 51 dB was obtained with a four-skin photobioreactor variant with four glass pane layers and a water layer. The weighted sound reduction indexes for alternative four-skin opaque prototype variants with a plasterboard layer were 2-3 dB lower. The double-and triple-skin variants achieved 43-47 dB. The use of XPS as insulation material in the outer air layers of the triple-and four-skin variants reduced the weighted sound reduction index by 2 dB. The airlift needed for turbulent mixing of the microalgae had no effect on the sound insulation but increased the average ambient noise level by up to 10 dB. With 51 dB, the four-shell photobioreactor prototype achieves sound insulation class 5 according to the german regulation VDI 2719 for windows and thus fulfills the function of a sound insulation element in the facade of buildings or in a soundproof wall. Highlights • Sound insulation of flat panel photobioreactors can be increased to 51 dB by two additional glass panes to a four skin type. • A four skin type is also favourable with respect to thermal insulation and allows higher solar heat gains. • The sound propagation speed in the water interlayer and therefore the dynamic stiffness changes with the filling stage of the intermediate water layer and the amount of bubbles of the airlift. • The influence of dynamic stiffness of the intermediate layer on the weighted sound reduction index decreases as the thickness of the prototype and the number of layers increases. • An increase in the thickness of the air layer between the panes from 5 to 40 mm increases the sound reduction index for all frequencies.
Blue-green light is known to maximize the degree of fatty acid (FA) unsaturation in microalgae. H... more Blue-green light is known to maximize the degree of fatty acid (FA) unsaturation in microalgae. However, knowledge on the particular waveband responsible for this stimulation of FA desaturation and its impact on the pigment composition in microalgae remains limited. In this study, Acutodesmus obliquus was cultivated for 96 h at 15°C with different light spectra (380-700 nm, 470-700 nm, 520-700 nm, 600-700 nm, and dark controls). Growth was monitored daily, and qualitative characterization of the microalgal FA composition was achieved via gas chromatography coupled with electron impact ionization mass spectrometry (GC-EI/MS). Additionally, a quantitative analysis of microalgal pigments was performed using high-performance liquid chromatography with diode array detection (HPLC-DAD). Spectra that included wavelengths between 470 and 520 nm led to a significantly higher percentage of the polyunsaturated fatty acids (PUFA) 18:3 and 16:4, compared to all other light conditions. However, no significant differences between the red light cultivations and the heterotrophic dark controls were observed for the FA 18:3 and 16:4. These results indicate, that exclusively the blue-green light waveband between 470 and 520 nm is responsible for a maximized FA unsaturation in A. obliquus. Furthermore, the growth and production of pigments were impaired if blue-green light (380-520 nm) was absent in the light spectrum. This knowledge can contribute to achieving a suitable microalgal pigment and FA composition for industrial purposes and must be considered in spectrally selective microalgae cultivation systems.
Microalgae have been considered as a potential feedstock for biomaterial compounds production. In... more Microalgae have been considered as a potential feedstock for biomaterial compounds production. In the southern Mediterranean region, which suffers from water scarcity, using wastewaters as culture media for microalgae cultivation is recommended. Hence, an algal strain is needed, which exhibits high growth under the prevailing temperature and light conditions. To obtain such strains, natural samples were collected from a maturation pond in the Peri-Urban Area of Marrakech (Morocco) and cultivated in different types of wastewaters at light intensity of 1,500 µmol m-2 s-1 and temperature up to 45°C in a batch system. Three types of wastewaters were used: raw, treated, not sterilized treated domestic wastewater from muti-soil layering system and tap water, started with the same concentrations of nitrogen and phosphorus. Results showed Chlorella was the only strain able to grow under the cultivation conditions established. This microalgae was identified by partial rbcL-gene as Chlorella sorokiniana with a genetic similarity of 98.8%, and registered under UCAM 001 (GenBank number MT999855). This finding indicates that the strain can be used for biomass production and phycoremediation process in semi-arid area. In addition, microalgae isolation by dominance could be a fast approach to obtain adapted strains for outdoor mass cultivation.
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