Algae
Algae are a diverse group of photosynthetic organisms that can be found in various aquatic environments, including freshwater and marine habitats. They can range from single-celled microalgae to large, multicellular seaweeds. Algae play a crucial role in the ecosystem by producing oxygen and serving as a food source for various aquatic organisms.
6 Key excerpts on "Algae"
eBook - ePub- Britannica Educational Publishing, Kara Rogers(Authors)
- 2010(Publication Date)
- Britannica Educational Publishing(Publisher)
...CHAPTER 6 Algae A lgae are eukaryotic and predominantly aquatic, photosynthetic organisms. They range in size from the tiny flagellate Micromonas that is 1 micrometre (0.000039 inch) in diameter to giant kelps that reach 60 metres (200 feet) in length. Algae provide much of Earth’s oxygen, they are the food base for almost all aquatic life, they are a source of crude oil, and they provide foods and pharmaceutical and industrial products for humans. The Algae have many types of life cycles. Their photosynthetic pigments are more varied than those of plants, and their cells have features not found among plants and animals. Some groups of Algae are ancient, whereas other groups appear to have evolved more recently. The taxonomy of Algae is subject to rapid change because new information is constantly being discovered. The study of Algae is termed phycology, and one who studies Algae is known as a phycologist. Although Algae are photosynthetic organisms, they lack the specialized reproductive structures of plants, which always have multicellular reproductive structures that contain fertile gamete-producing cells surrounded by sterile cells. Algae also lack true roots, stems, and leaves—features they share with plants known as bryophytes (e.g., mosses and liverworts). In the past, the prokaryotic (nucleus-lacking) cyanobacteria (blue-green Algae), a group that includes photosynthetic marine organisms in the genus Prochlorococcus, were considered to be Algae. Beginning in the 1970s, some scientists suggested that the study of the prokaryotic Algae should be incorporated into the study of bacteria because of certain shared cellular features. In fact, today cyanobacteria and Prochlorococcus are known to be more closely related to bacteria than to Algae, and for this reason they are now classified with the bacteria...
eBook - ePubMarine Macro- and Microalgae
An Overview
- F. Xavier Malcata, Isabel Sousa Pinto, A. Catarina Guedes, F. Xavier Malcata, Isabel Sousa Pinto, A. Catarina Guedes(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
...In a simplistic approach, the term Algae refer to both macroAlgae and a highly diversified group of microorganisms known as microAlgae. Species and environments A conservative approach estimates the number of algal species in 72,500, most of them being microAlgae (Guiry 2012). Algae most commonly occur in water—marine, freshwater, and brackish—but they can also be found in almost every other environment on earth, for example, growing on snow in some high mountains and in the Arctic or living in lichen associations on bare rocks, in desert soils, and in hot springs (Lee 2008). In most habitats, Algae are extremely important as they function as primary producers in the food chains and produce the oxygen necessary for their metabolism and that of the consumer organisms. Algae also form mutually beneficial partnerships with other organisms in which they provide oxygen and organic compounds and receive protection and nutrients. This is the case of the zooxanthellae that live inside the cells of reef-building corals, and of the green Algae or cyanobacteria that associate with fungi to form lichens (Barsanti and Gualtieri 2014). Algae cells contain the green pigment chlorophyll that captures the sun’s energy for photosynthesis, that is, the process of building energy-rich compounds from water and carbon dioxide. Photosynthetic Algae will therefore grow only where there is light. In marine environments below low tide level, the amount and quality of light decreases with increasing depth to a point where the light level is not enough for algal growth. Some species contain additional pigments that enable them to absorb different light wavelengths and to use faint levels of light. This is the case of a coralline red Algae collected at 268 m deep, the depth record for marine macrophytes (Littler et al. 1985). Due to these additional pigments, Algae can exhibit different colors, the more common being red or brown...
eBook - ePubSeaweed Sustainability
Food and Non-Food Applications
- Brijesh K. Tiwari, Brijesh K. Tiwari(Authors)
- 2015(Publication Date)
- Academic Press(Publisher)
...Their dimension ranges from micrometers to meters, providing an obvious size division between microAlgae and macroAlgae. The latter, commonly known as seaweed, are multicellular organisms similar to plants, growing predominantly in the marine environment. MicroAlgae, or phytoplankton, include small unicellular organisms found in water, representing the primary source of food for most aquatic fauna and causing seasonal algal blooms in rivers, lakes, and ponds under eutrophic conditions. Early hunter–gatherers benefited from the nutritional and medicinal qualities of Algae as well as from the rich habitats associated with them. Analysis of ancient remnants of a number of species of Algae excavated in southern Chile and dated to approximately 14,000 years BP suggests it was used in food and medicine (Dillehay et al., 2008). There is no doubt that a diet rich in the essential amino acids, particularly the super unsaturated omega-3 fatty acids, most importantly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), contributed to the early development and growth of the human brain. Nowadays, Algae are commercially cultivated for the production of a number of different goods, including human and animal food additives and biochemicals. However, Algae biomass has the potential to deliver a wider range of products, which include bioenergy, biofuels, and biobased products (bioplastics, biocosmetics, biosolvents). The special gelling and lubricating properties of seaweeds have also been exploited. Agar, and then carrageenan, which had traditionally been used as a thickener in cooking, became important gelling agents utilized in medicine and in science (Marshall et al., 1949). The extensive rheological properties of the sulfated polysaccharide components of Algae are indicative of its value as a superior biolubricant, which is stable over a range of temperatures, pH values, and salinities (Arad et al., 2006)...
eBook - ePubMicroalgae
From Future Food to Cellular Factory
- Joel Fleurence(Author)
- 2021(Publication Date)
- Wiley-ISTE(Publisher)
...1 Biology and Ecology of MicroAlgae 1.1. Biological characteristics 1.1.1. General characteristics MicroAlgae are mainly photo-synthetic single-celled organisms living in aquatic environments (marine, brackish, fresh water) or humid or aerial terrestrial environments (atmosphere, soils, trees, building facades, etc.) (Sharma et al. 2006). They can also associate together to form colonies or undifferentiated multicellular organisms. The morphology and size of microAlgae vary greatly according to species and taxonomic groups. MicroAlgae are eukaryotic organisms that possess the main characteristics of the vegetable eukaryotic cell. They can be flagellated as in the case of Algae belonging to the genus Chlamydomonas (see Figure 1.1) or not (see Figure 1.2). As eukaryotes, microAlgae can be distinguished from cyanobacteria, which are prokaryotic organisms with a long life span and are called “blue-green Algae” or Cyanophyceae. Spirulina (Arthrospira sp.), a well-known representative of this group, is, therefore, a photosynthetic bacterium and not an alga, as is often stated in commercial communication (Fleurence 2018). MicroAlgae are also characterized by a great morphological diversity. This is the case of diatoms, which are distinguished from other Algae by the presence of a siliceous shell called a frustule and whose architecture differs according to the species considered (see Figure 1.3) (Loir 2004). This unique morphological feature is the biological signature of diatoms, which are also known as “siliceous Algae”. This morphological heterogeneity is also found in size since microAlgae generally vary in size from less than 1 μm to 1 mm. The smallest size, 0.8 μm, is observed for the marine species Ostreococcus tauri (Borowitzka 2018a). Figure 1.1. Cellular organization of the microalga Chlamydomonas sp. (source: Pouchus Y.-F.). For a color version of this figure, see www.iste.co.uk/fleurence/microAlgae Figure 1.2. Cellular organization of the microalga Chlorella sp...
eBook - ePubBiomass, Biofuels, Biochemicals
Biofuels from Algae
- Ashok Pandey, Duu Jong Lee, Jo-Shu Chang, Yusuf Chisti, Carlos Ricardo Soccol, Ashok Pandey, Duu Jong Lee, Jo-Shu Chang, Yusuf Chisti, Carlos Ricardo Soccol(Authors)
- 2018(Publication Date)
- Elsevier(Publisher)
...These biomolecules can then be used to generate biomass, rich in fuel-like metabolites, which may be extracted [1, 2]. However, the problem remains, what to do with the spent biomass. In particular, third-generation biofuels based on micro- and macroAlgae offer an excellent possibility to displace fossil fuels; it is even believed that ancestors of marine microorganisms were responsible for formation of petroleum in the first place [3]. MacroAlgae (or seaweeds) are multicellular organisms that take many forms and sizes; they are classified into three broad groups, based on their pigmentation: brown Algae (Phaeophyceae), red Algae (Rhodophyta), and green Algae (Chlorophyta). Conversely, microAlgae are microscopic organisms, which, besides Rhodophyta and Chlorophyta, may belong to another three specific groups of unicellular organisms: blue-green Algae (Cyanobacteria), diatoms (Bacillariophyta), and dinoflagellates (Dinophyceae); these species are commonly referred to as phytoplankton [4, 5]. Despite looking similar to land plants, microAlgae miss the lignin crosslinking in their cellulose structures, because their growth in aquatic environments does not require strong supports [6]. On the other hand, macroAlgae contain significant amounts of sugars (at least 50%) suitable for fermentation [7]. In certain marine Algae (e.g., red Algae), the carbohydrate content is strongly influenced by the presence of agar—a polymer of galactose and galactopyranose. Recent research has attempted to develop methods of saccharification to release galactose from agar, and release glucose from cellulose, so as to increase fermentation yields in terms of bioethanol [1]. Other studies have shown that red Algae, like Gelidium amansii, and the brown Algae Saccharina japonica, are both potential sources of biohydrogen via anaerobic fermentation [1]...
eBook - ePubAlgal Biorefineries and the Circular Bioeconomy
Algal Products and Processes
- Sanjeet Mehariya, Obulisamy Parthiba Karthikeyan, Shashi Kant Bhatia, Sanjeet Mehariya, Obulisamy Parthiba Karthikeyan, Shashi Kant Bhatia(Authors)
- 2022(Publication Date)
- CRC Press(Publisher)
...Generally, three distinct groups of pigments may be considered: chlorophylls – greenish, photosynthetic, and lipid-soluble; carotenoids – hydrocarbons (lipids) in a range of yellow to red colours; and phycobiliproteins – blue-green pigments that are only known to exist in cyanobacteria and the phylum Rhodophyta (Cuellar-Bermudez et al., 2015). Still, the diversity of chemicals produced by so many species and their potential as valuable compounds, especially as bioactive compounds is yet to be unveiled (Del Mondo et al., 2020 ; Tudor et al., 2021). MicroAlgae ubiquity, diversity, completeness in nutrition value, and availability makes them attractive as a food source, especially as functional foods and nutraceuticals (Galasso et al., 2019 ; García et al., 2017 ; Torres-Tiji et al., 2020). The interest of microAlgae biomass as a food source is quite ancient: the Aztecs, from Lake Texcoco (Mexico), and the indigenous Kanembu tribe, from Lake Kossorom (Chad), harvested Spirulina (cyanobacteria) and included it in their diet in the form of a dried cake (Habib and Ahsan, 2008 ; Vonshak and Richmond, 1988). Other microAlgae, such as Chlorella, were also commonly consumed as food in other areas of the globe, especially in Asia (Borowitzka, 2013a ; García et al., 2017), because Algae-dried biomass is very well digested and tolerated by humans (Gurev et al., 2020 ; Hemantkumar and Rahimbhai, 2019). Notwithstanding, industrial mass cultivation of microAlgae in photobioreactors has started only in the 1950s of the 20th century, propelled by the first Algal Mass-Culture Symposium held at the Stanford University and by a dedicated project of the Carnegie Institute (Burlew, 1953) that led to the establishment, in California, of one of the world's first research institutions and microAlgae laboratories...
