microalgae
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V současné době je celosvětově vynakládáno velké úsilí na nahrazení fosilních zdrojů energie obnovitelnými zdroji (biomasa, slunce, vítr atd.), které by navíc nezatěžovali zemskou atmosféru produkcí skleníkových plynů. Ukazuje se, že nelze očekávat příchod jedné univerzální technologie, ale je nutné využívat mnoho různých zdrojů tak, aby byla zohledněna geografická a ekonomická specifika konkrétní oblasti, kde se energie vyrábí. Jedním z možných zdrojů energie je produkce bioplynu z biomasy řas pěstovaných za tímto účelem ve speciálních reaktorech. Tento článek dává stručný přehled metod energetického využívání řas a zmiňuje hlavní ekonomické a technologické výzvy pro úspěšné zvládnutí této technologie. Zároveň je zmíněn evropský projekt „Renewable energy production through microalgae cultivation: Closing material cycles (ALGAENET)“, který spojuje výzkumná pracoviště v České republice (VŠCHT Praha), Španělsku a Chile.
Recently, a great eÍort is being put on the development of new technologies allowing energy production from renewable source that would not produce greenhouse gases. It is becoming increasingly apparent that one should not expect the advent of a new universal technology that would replace the entire energy production from fossil fuels. Instead, we need to develop many diÍerent technologies that would satisfy wide range of geographical and economical requirements. Biogas production from microalgae may become such a site-specific technology. This paper gives a brief list of diÍerent approaches to energy production from microalgae and describes the main economic and technological challenges for biogas production from microalgae. Moreover, an European project “Renewable energy production through microalgae cultivation: Closing material cycles (ALGAENET)“ that is currently being jointly executed by partners in the Czech Republic (ICT Prague), Spain and Chile.
The worldwide growing demand for energy permanently increases the pressure on industrial and scientific community to introduce new alternative biofuels on the global energy market. Besides the leading role of biodiesel and biogas, bioethanol receives more and more attention as first- and second-generation biofuel in the sustainable energy industry. Lately, microalgae (green algae and cyanobacteria) biomass has also remarkable potential as a feedstock for the third-generation biofuel production due to their high lipid and carbohydrate content. The third-generation bioethanol production technology can be divided into three major processing ways: (i) fermentation of pre-treated microalgae biomass, (ii) dark fermentation of reserved carbohydrates and (iii) direct "photo-fermentation" from carbon dioxide to bioethanol using light energy. All three technologies provide possible solutions, but from a practical point of view, traditional fermentation technology from microalgae biomass receives currently the most attention. This study mainly focusses on the latest advances in traditional fermentation processes including the steps of enhanced carbohydrate accumulation, biomass pre-treatment, starch and glycogen downstream processing and various fermentation approaches.
Centrifugation is the most commonly used method for harvesting autotrophically produced microalgae, but it is expensive due to high energy demands. With the aim of reducing these costs, we tested electrocoagulation with iron electrodes for harvesting Chlorella vulgaris. During extensive lab-scale experiments, the following factors were studied to achieve a high harvesting efficiency and a low iron content in the harvested biomass: electric charge, initial biomass concentration, pH, temperature, agitation intensity, residual salt content and electrolysis time. A harvesting efficiency greater than 95% was achieved over a broad range of conditions and the residual iron content in the biomass complied with legislative requirements for food. Using electrocoagulation as the pre-concentration step prior to centrifugation, total energy costs were reduced to 0.136 kWh/kg of dry biomass, which is less than 14% of that for centrifugation alone. Our data show that electrocoagulation is a suitable and cost-effective method for harvesting microalgae.
- MeSH
- biomasa MeSH
- Chlorella vulgaris * MeSH
- elektrokoagulace MeSH
- elektrolýza MeSH
- flokulace MeSH
- mikrořasy * MeSH
- Publikační typ
- časopisecké články MeSH
Contents 516 I. 516 II. 518 III. 518 IV. 521 V. 523 VI. 523 VII. 526 526 References 526 SUMMARY: The relevance of infochemicals in the relationships between organisms is emerging as a fundamental aspect of aquatic ecology. Exchanges of chemical cues are likely to occur not only between organisms of different species, but also between conspecific individuals. Especially intriguing is the investigation of chemical communication in microalgae, because of the relevance of these organisms for global primary production and their key role in trophic webs. Intraspecific communication between algae has been investigated mostly in relation to sexuality and mating. The literature also contains information on other types of intraspecific chemical communication that have not always been explicitly tagged as ways to communicate to conspecifics. However, the proposed role of certain compounds as intraspecific infochemicals appears questionable. In this article, we make use of this plethora of information to describe the various instances of intraspecific chemical communication between conspecific microalgae and to identify the common traits and ecological significance of intraspecific communication. We also discuss the evolutionary implications of intraspecific chemical communication and the mechanisms by which it can be inherited. A special focus is the genetic diversity among conspecific algae, including the possibility that genetic diversity is an absolute requirement for intraspecific chemical communication.
Microalgae are photosynthetic microorganisms with a major influence on global ecosystems. Further, owing to the production of various secondary metabolites, microalgae are also intensively studied for their enormous potential in biotechnology and its applications. While flow cytometry (FCM) is a fast and reliable method particularly suitable for genome size estimation in plant and animal studies, its application to microalgae often comes with many methodological challenges due to specific issues (e.g., cell wall composition, and presence of various secondary metabolites). Sample preparation requires considerable amounts of biomass, chemical fixation, and/or extraction of cellular components. In genome size estimation, appropriate methods for isolation of intact nuclei (using lysis buffers, razor-blade chopping, various enzymes, or bead-beating of cells) are essential for successful and high-quality analyses. Nuclear DNA amounts of microalgae diverge greatly, varying by almost 30,000-fold (0.01 to 286 pg). Even though new algal reference standards for genome size are now being introduced, animal red blood cells and nuclei from plant tissues are still predominantly used. Due to our limited knowledge of microalgal life cycles, particular caution should be taken during 1C/2C-value (or ploidy level) assignments.
- MeSH
- biomasa MeSH
- biotechnologie MeSH
- délka genomu MeSH
- ekosystém MeSH
- mikrořasy * MeSH
- průtoková cytometrie MeSH
- Publikační typ
- časopisecké články MeSH
Microalgae have traditionally been used in many biotechnological applications, where each new application required a different species or strain expressing the required properties; the challenge therefore is to isolate or develop, characterize and optimize species or strains that can express more than one specific property. In agriculture, breeding of natural variants has been successfully used for centuries to improve production traits in many existing plant and animal species. With the discovery of the concepts of classical genetics, these new ideas have been extensively used in selective breeding. However, many biotechnologically relevant algae do not possess the sexual characteristics required for traditional breeding/crossing, although they can be modified by chemical and physical mutagens. The resulting mutants are not considered as genetically modified organisms (GMOs) and their cultivation is therefore not limited by legislation. On the other hand, mutants prepared by random or specific insertion of foreign DNA are considered to be GMOs. This review will compare the effects of two genetic approaches on model algal species and will summarize their advantages in basic research. Furthermore, we will discuss the potential of mutagenesis to improve microalgae as a biotechnological resource, to accelerate the process from specific strain isolation to growth optimization, and discuss the production of new products. Finally, we will explore the potential of algae in synthetic biology.
To make magnetic harvesting a more viable option, a suspension of inexpensive iron oxide magnetic microparticles (IOMMs) prepared by microwave treatment is presented as a new agent for separating Chlorella vulgaris from a highly diluted suspension. Separation efficiencies were tested under various conditions (model environment, cultivation media, different pH), revealing not only a dependency on the pH and amount of IOMMs, but also the influence of the ions present in the culture medium. Phosphorus ions were identified as the medium component interfering with algae-IOMMs interactions that are essential for magnetic cell separations in the culture medium. Phosphorus limited C. vulgaris cells were magnetically separated from the medium at separation efficiencies of over 95% at a 3:1 mass ratio of IOMMs to microalgae. A rapid and complete demagnetization of harvested algae was achieved by acidic treatment (10vol.% H(2)SO(4)) at 40°C under the influence of ultrasound.
In this work, the key moments of the development of the so-called thin-layer cascades (TLC) for microalgae production are described. Development started at the end of the 1950s when the first generation of TLCs was set-up in former Czechoslovakia. Since, similar units for microalgae culturing, which are relatively simple, low-cost and highly productive, have been installed in a number of other countries worldwide. The TLCs are characterized by microalgae growth at a low depth (< 50 mm) and fast flow (0.4-0.5 m/s) of culture compared to mixed ponds or raceways. It guarantees a high ratio of exposed surface to total culture volume (> 100 1/m) and rapid light/dark cycling frequencies of cells which result in high biomass productivity (> 30 g/m2/day) and operating at high biomass density, > 10 g/L of dry mass (DW). In TLCs, microalgae culture is grown in the system of inclined platforms that combine the advantages of open systems-direct sun irradiance, easy heat derivation, simple cleaning and maintenance, and efficient degassing-with positive features of closed systems-operation at high biomass densities achieving high volumetric productivity. Among significant advantages of thin layer cascades compared to raceway ponds are the operation at much higher cell densities, very high daylight productivities, and the possibility to store the culture in retention tanks at night, or in unfavourable weather conditions. Concerning the limitations of TLCs, one has to consider contaminations by other microalgae that limit cultivation to robust, fast-growing strains, or those cultured in selective environments.
The majority of algal cells can interact with a wide range of nano- and microparticles. Upon interaction the modified cells usually maintain their viability and the presence of foreign material on their surfaces or in protoplasm can provide additional functionalities. Magnetic modification and labeling of microalgal biomass ensures a wide spectrum of biotechnological, bioanalytical and environmental applications. Different aspects of microalgal cell magnetic modification are covered in the review, followed by successful applications of magnetic algae. Modified cells can be employed during their harvesting and removal, applied in toxicity microscreening devices and also as efficient adsorbents of different types of xenobiotics.
Nitrogen is one of the most important nutrient sources for the growth of microalgae. We studied the effects of nitrogen starvation on the growth responses, biochemical composition, and fatty acid profile of Dunaliella tertiolecta, Phaeodactylum tricornutum, and Nannochloropsis oculata. The lack of nitrogen caused changes in carbohydrate, protein, lipid, and fatty acid composition in all examined microalgae. The carbohydrate content increased 59% in D. tertiolecta, while the lipid level increased 139% in P. tricornutum under nitrogen stress conditions compared to the control groups. Nitrogen starvation increased the oligosaccharide and polysaccharide contents of D. tertiolecta 4.1-fold and 3.6-fold, respectively. Furthermore, triacylglycerol (TAG) levels in N. oculata and P. tricornutum increased 2.3-fold and 7.4-fold, respectively. The dramatic increase in the amount of TAG is important for the use of these microalgae as raw materials in biodiesel. Nitrogen starvation increased the amounts of oligosaccharides and polysaccharides of D. tertiolecta, while increased eicosapentaenoic acid (EPA) in N. oculata and docosahexaenoic acid (DHA) content in P. tricornutum. The amount of polyunsaturated fatty acids (PUFAs), EPA, DHA, oligosaccharides, and polysaccharides in microalgal species can be increased without using the too costly nitrogen source in the culture conditions, which can reduce the most costly of living feeding.
