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Life
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Algae—a Step Forward in the Sustainability of Resources
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Algae—a Step Forward in the Sustainability of Resources

A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Microbiology".

Deadline for manuscript submissions: closed (27 October 2023) | Viewed by 15640

Special Issue Editors

Dr. Helena Amaro

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Guest Editor
LEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, Universidade do Porto, Porto, Portugal
Interests: algal biotechnology; microalgae; cyanobacteria; seaweeds; bioactive compounds; algal process optimization; algal extraction; wastewater treatment; applications of algae biomass
Special Issues, Collections and Topics in MDPI journals
Dr. Graciliana Lopes

E-Mail Website
Guest Editor
CIIMAR/CIMAR, Interdisciplinary Centre of Marine and Environmental Research, Novo Edifício do Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos, S/N, 4450-208 Matosinhos, Portugal
Interests: antioxidants; free radicals; inflammation; iNOS; LOX; phlorotannins; carotenoids; phenols; seaweeds; HPLC
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Leonel Pereira

E-Mail Website
Guest Editor
Marine Resources, Conservation and Technology, Marine Algae Laboratory, Centre for Functional Ecology—Science for People & the Planet (CFE), Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
Interests: marine biotechnology; phycology; biodiversity; nutraceuticals
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Planet resources are being depleted earlier every year. Climate change, loss of biodiversity, loss of ecosystem services, land degradation, and air and water pollution is a part of our present and near future.

Eukaryotic and prokaryotic algae have a crucial role in ecosystems, not only because they are the energy base of the food web for all aquatic organisms, but also due to their ability to capture CO2 and produce oxygen. As autotrophic organisms, algae convert water, carbon dioxide, and some nitrogen and phosphorus sources into biomass that can be used as a source of high-value compounds, food/feed, and energy. Besides, their fast growth, and the no need for arable land or potable water, makes these organisms an exceptional sustainable source of eco-friendly products.

Hence, we welcome the submission of high-quality research articles, review articles, and short communications that provide recent insights into several aspects of how algae (seaweeds, microalgae, and cyanobacteria) can positively contribute, or have a role, towards more sustainable use of resources. We encourage submissions related to: algal biotechnology; algal processes or processes that include algae; screenings for exploitation of new species or new applications for known species; optimization of cultivation/production/extraction of algal biomass and their products; algal eco-services; algal products obtained in a biorefinery strategy; and with the role of algae in promotion of a circular economy, within the following topics:

- Health: Bioactive compounds from algae, source of pharmaceuticals, nutraceuticals and cosmetics.

- Food/Feed: ingredient for feed/food formulations, food/feed preservatives, nutraceuticals, algae as a food/feed source, Integrated Multithrophic Aquaculture (IMTA).

- Environment: Water treatment/polishing, biofuels production, ecosystems restoration, CO2 sequestration/capture, life cycle assessment of algal processes or involving algae, biofertilizers, biopesticides, green extraction of algal compounds.

Dr. Helena Amaro
Dr. Graciliana Lopes
Prof. Dr. Leonel Pereira
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Life is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • macroalgae
  • microalgae
  • cyanobacteria
  • bioactive compounds
  • biomass production
  • pharmaceuticals
  • nutraceuticals
  • cosmetics
  • food/feed
  • CO2 sequestrations
  • water treatment
  • imta
  • ecosystems services
  • biofuels
  • biopesticides
  • green extraction methods

Published Papers (9 papers)

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Research

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9 pages, 810 KiB  
Communication
The Impact of Non-Concentrated Storage on the Centrifugation Yield of Microchloropsis gaditana: A Pilot-Scale Study
by Joran Verspreet, Floris Schoeters and Leen Bastiaens
Life 2024, 14(1), 131; https://doi.org/10.3390/life14010131 - 17 Jan 2024
Viewed by 1208
Abstract
Non-concentrated algae storage can bridge the period between algae harvesting and processing while avoiding the stress conditions associated with the concentration step required for concentrate storage. This study aimed to examine organic matter losses during the non-concentrated storage of Microchloropsis gaditana at pilot-scale. [...] Read more.
Non-concentrated algae storage can bridge the period between algae harvesting and processing while avoiding the stress conditions associated with the concentration step required for concentrate storage. This study aimed to examine organic matter losses during the non-concentrated storage of Microchloropsis gaditana at pilot-scale. Algae cultures (400–500 L) were stored for up to 12 days either at an 8 °C target temperature or at 19 °C as the average temperature. The centrifugation yield of stored algal cultures decreased from day 5 or day 8 onwards for all storage conditions. After 12 days, the centrifugation yields were between 57% and 93% of the initial yields. Large differences in centrifugation yields were noted between the algae batches. The batch-to-batch difference outweighed the effect of storage temperature, and the highest yield loss was observed for the 8 °C cooled algae batch. The analysis of stored algae before and after centrifugation suggested that the decreasing yields were not related to respiration losses, but rather, the decreasing efficiency with which organic matter is collected during the centrifugation step. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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12 pages, 3571 KiB  
Article
Effects of Four Organic Carbon Sources on the Growth and Astaxanthin Accumulation of Haematococcus lacustris
by Huijeong Byeon, Yunji An, Taesoo Kim, Vijay Rayamajhi, Jihyun Lee, HyunWoung Shin and SangMok Jung
Life 2024, 14(1), 29; https://doi.org/10.3390/life14010029 - 24 Dec 2023
Cited by 1 | Viewed by 1451
Abstract
The microalga Haematococcus lacustris has a complex life cycle and a slow growth rate, hampering its mass cultivation. Culture of microalgae with organic carbon sources can increase the growth rate. Few studies have evaluated the effects of organic carbon sources on H. [...] Read more.
The microalga Haematococcus lacustris has a complex life cycle and a slow growth rate, hampering its mass cultivation. Culture of microalgae with organic carbon sources can increase the growth rate. Few studies have evaluated the effects of organic carbon sources on H. lacustris. We compared the vegetative and inductive stages of H. lacustris under autotrophic and mixotrophic conditions using four organic carbon sources: sodium acetate, glycerol, sodium gluconate, and ribose, each at various concentrations (0.325, 0.65, 1.3, and 2.6 g/L). The cell density was increased by 1.3 g/L of glycerol in the vegetative stage. The rapid transition to the inductive stage under nitrogen-depletion conditions caused by 1.3 or 2.6 g/L sodium acetate promoted the accumulation of astaxanthin. The production of astaxanthin by H. lacustris in mass culture using organic carbon sources could increase profitability. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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14 pages, 1459 KiB  
Article
Brine-Processed Caulerpa lentillifera Macroalgal Stability: Physicochemical, Nutritional and Microbiological Properties
by Wanida Pan-utai, Prajongwate Satmalee, Safiah Saah, Yupadee Paopun and Montakan Tamtin
Life 2023, 13(11), 2112; https://doi.org/10.3390/life13112112 - 25 Oct 2023
Viewed by 1050
Abstract
Caulerpa lentillifera is a type of green macroalga that is commonly consumed as fresh seaweed, particularly in Southeast Asia. The effects of different salt types and concentrations on C. lentillifera during brine processing were investigated using table, sea and flower salt at 10–30% [...] Read more.
Caulerpa lentillifera is a type of green macroalga that is commonly consumed as fresh seaweed, particularly in Southeast Asia. The effects of different salt types and concentrations on C. lentillifera during brine processing were investigated using table, sea and flower salt at 10–30% levels. The colour and texture of C. lentillifera varied across different treatments. After storage in brine for 12 weeks, lightness (L*) decreased, greenness (a*) decreased and yellowness (b*) increased while firmness increased in all treatments compared to fresh algae. The nutritional composition did not change significantly over time. To ensure the safety and quality of seaweed for consumption, the optimal salt level for brine processing should not exceed 30% table salt. The morphology and elements contained in different types of salt were also observed, and the microbiological safety of seaweed was evaluated. The popularity of Caulerpa macroalgae is rapidly increasing among consumers, leading to a growing demand for ready-to-eat Caulerpa products. However, food safety and security standards must be maintained. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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18 pages, 3823 KiB  
Article
A Comprehensive Study of Techniques to Optimize the Extraction of Lipids from the Autotrophic Strain of the Microalgae Chlorella vulgaris
by Ian Foerster, Wayne Seames, Jasmine Oleksik, Alena Kubatova and Andrew Ross
Life 2023, 13(10), 1997; https://doi.org/10.3390/life13101997 - 30 Sep 2023
Cited by 1 | Viewed by 1059
Abstract
Microalgae represent a promising source of triglycerides and free fatty acids, synthesized in the form of lipids, for use in renewable fuels and chemicals. One challenge is the ability to efficiently recover the lipids from within the microalgae cell. Although various techniques have [...] Read more.
Microalgae represent a promising source of triglycerides and free fatty acids, synthesized in the form of lipids, for use in renewable fuels and chemicals. One challenge is the ability to efficiently recover the lipids from within the microalgae cell. Although various techniques have been studied individually, a comprehensive study of extraction techniques using consistent experimental and analytical methodology is missing. This study aims to provide this unifying comparison using the common microalgae strain Chlorella vulgaris. The factors that were surveyed and then optimized to achieve maximum extraction efficiency included the solvent type; mechanical pre-treatment using a ball mill at a variety of grinding speeds; microalgae-to-solvent ratio; extraction facilitated by microwave; extraction facilitated by sonication; extraction facilitated using increased temperature; and extraction facilitated by in situ transesterification to convert the lipids into esters prior to extraction. The optimum conditions determined during these studies were utilizing methanol as the solvent, with ball mill pretreatment at a grinding speed of 500 rpm, and a 1:9 microalgae to solvent ratio. When used in combination with microwave-assisted extraction at a temperature of 140 °C, approximately 24 wt% of the initial lipids were recovered. Recoveries of over 70 wt% were obtained without a microwave at extraction temperatures of over 200 °C. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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13 pages, 1313 KiB  
Article
Blue-Green Algae as Stimulating and Attractive Feeding Substrates for a Mediterranean Commercial Sea Urchin Species, Paracentrotus lividus
by Paolo Solari, Giorgia Sollai, Viviana Pasquini, Angelica Giglioli, Roberto Crnjar and Piero Addis
Life 2023, 13(7), 1510; https://doi.org/10.3390/life13071510 - 05 Jul 2023
Viewed by 1376
Abstract
Sea urchins rely on chemical senses to localize suitable food resources, therefore representing model species for chemosensory studies. In the present study, we investigated the chemical sensitivity of the Mediterranean sea urchin Paracentrotus lividus to the blue-green alga Aphanizomenon flos-aquae, namely “Klamath”, [...] Read more.
Sea urchins rely on chemical senses to localize suitable food resources, therefore representing model species for chemosensory studies. In the present study, we investigated the chemical sensitivity of the Mediterranean sea urchin Paracentrotus lividus to the blue-green alga Aphanizomenon flos-aquae, namely “Klamath”, and to a few amino acids chosen from the biochemical composition of the same algae. To this end, we used the “urchinogram” method, which estimates the movement rate of the sea urchins in response to chemicals. Our results showed that Klamath represents a strong chemical stimulus for P. lividus as it elicits an overall movement of spines, pedicellariae, and tube feet coupled, in some cases, to a coordinated locomotion of the animals. Sea urchins also displayed a sensitivity, even if to a lesser extent, to leucine, threonine, arginine, and proline, thus implying that the amino acids contained in Klamath may account, at least in part, for the stimulating effects exerted by the whole algae. Additionally, our results show that Klamath, as well as spirulina, another blue-green alga with high nutritional value, is very attractive for this sea urchin species. These findings gain further importance considering the potential profit of echinoderms for commercial consumers and their growing role in aquaculture. Klamath and spirulina combine high nutritional profiles with attractive and stimulating abilities and may be considered potential valuable feed supplements in sea urchin aquaculture. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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21 pages, 1482 KiB  
Article
Laboratory- and Pilot-Scale Cultivation of Tetraselmis striata to Produce Valuable Metabolic Compounds
by Vasiliki Patrinou, Stefania Patsialou, Alexandra Daskalaki, Christina N. Economou, George Aggelis, Dimitris V. Vayenas and Athanasia G. Tekerlekopoulou
Life 2023, 13(2), 480; https://doi.org/10.3390/life13020480 - 09 Feb 2023
Cited by 6 | Viewed by 2105
Abstract
Marine microalgae are considered an important feedstock of multiple valuable metabolic compounds of high biotechnological potential. In this work, the marine microalga Tetraselmis striata was cultivated in different scaled photobioreactors (PBRs). Initially, experiments were performed using two different growth substrates (a modified F/2 [...] Read more.
Marine microalgae are considered an important feedstock of multiple valuable metabolic compounds of high biotechnological potential. In this work, the marine microalga Tetraselmis striata was cultivated in different scaled photobioreactors (PBRs). Initially, experiments were performed using two different growth substrates (a modified F/2 and the commercial fertilizer Nutri-Leaf (30% TN—10% P—10% K)) to identify the most efficient and low-cost growth medium. These experiments took place in 4 L glass aquariums at the laboratory scale and in a 9 L vertical tubular pilot column. Enhanced biomass productivities (up to 83.2 mg L−1 d−1) and improved biomass composition (up to 41.8% d.w. proteins, 18.7% d.w. carbohydrates, 25.7% d.w. lipids and 4.2% d.w. total chlorophylls) were found when the fertilizer was used. Pilot-scale experiments were then performed using Nutri-Leaf as a growth medium in different PBRs: (a) a paddle wheel, open, raceway pond of 40 L, and (b) a disposable polyethylene (plastic) bag of 280 L working volume. Biomass growth and composition were also monitored at the pilot scale, showing that high-quality biomass can be produced, with important lipids (up to 27.6% d.w.), protein (up to 45.3% d.w.), carbohydrate (up to 15.5% d.w.) and pigment contents (up to 4.2% d.w. total chlorophylls), and high percentages of eicosapentaenoic acid (EPA). The research revealed that the strain successfully escalated in larger volumes and the biochemical composition of its biomass presents high commercial interest and could potentially be used as a feed ingredient. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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22 pages, 3107 KiB  
Article
Development and Diversity of Epibiont Assemblages on Cultivated Sugar Kelp (Saccharina latissima) in Relation to Farming Schedules and Harvesting Techniques
by Sophie Corrigan, A. Ross Brown, Charles R. Tyler, Catherine Wilding, Carly Daniels, Ian G. C. Ashton and Dan A. Smale
Life 2023, 13(1), 209; https://doi.org/10.3390/life13010209 - 11 Jan 2023
Cited by 5 | Viewed by 2556
Abstract
Seaweed farming in Europe is growing and may provide environmental benefits, including habitat provisioning, coastal protection, and bioremediation. Habitat provisioning by seaweed farms remains largely unquantified, with previous research focused primarily on the detrimental effects of epibionts, rather than their roles in ecological [...] Read more.
Seaweed farming in Europe is growing and may provide environmental benefits, including habitat provisioning, coastal protection, and bioremediation. Habitat provisioning by seaweed farms remains largely unquantified, with previous research focused primarily on the detrimental effects of epibionts, rather than their roles in ecological functioning and ecosystem service provision. We monitored the development and diversity of epibiont assemblages on cultivated sugar kelp (Saccharina latissima) at a farm in Cornwall, southwest UK, and compared the effects of different harvesting techniques on epibiont assemblage structure. Increases in epibiont abundance (PERMANOVA, F4,25 = 100.56, p < 0.001) and diversity (PERMANOVA, F4,25 = 27.25, p < 0.001) were found on cultivated kelps over and beyond the growing season, reaching an average abundance of >6000 individuals per kelp plant with a taxonomic richness of ~9 phyla per kelp by late summer (August). Assemblages were dominated by crustaceans (mainly amphipods), molluscs (principally bivalves) and bryozoans, which provide important ecological roles, despite reducing crop quality. Partial harvesting techniques maintained, or increased, epibiont abundance and diversity beyond the farming season; however, these kelp plants were significantly fouled and would not be commercially viable in most markets. This paper improves understanding of epibiont assemblage development at European kelp farms, which can inform sustainable, ecosystem-based approaches to aquaculture. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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20 pages, 4250 KiB  
Article
Effects of Temperature, pH, and NaCl Concentration on Biomass and Bioactive Compound Production by Synechocystis salina
by Joana Assunção, Helena M. Amaro, Tânia Tavares, F. Xavier Malcata and A. Catarina Guedes
Life 2023, 13(1), 187; https://doi.org/10.3390/life13010187 - 09 Jan 2023
Cited by 3 | Viewed by 1880
Abstract
Synechocystis salina is a cyanobacterium that has biotechnological potential thanks to its ability to synthesize several bioactive compounds of interest. Therefore, this study aimed to find optimal conditions, in terms of temperature (15–25 °C), pH (6.5–9.5), and NaCl concentration (10–40 g·L−1), [...] Read more.
Synechocystis salina is a cyanobacterium that has biotechnological potential thanks to its ability to synthesize several bioactive compounds of interest. Therefore, this study aimed to find optimal conditions, in terms of temperature (15–25 °C), pH (6.5–9.5), and NaCl concentration (10–40 g·L−1), using as objective functions the productivities of biomass, total carotenoids, total PBPs, phycocyanin (PC), allophycocyanin (APC), phycoerythrin (PE), and antioxidants (AOXs) capacity of Synechocystis salina (S. salina) strain LEGE 06155, based in factorial design resorting to Box-Behnken. The model predicted higher biomass productivities under a temperature of 25 °C, a pH of 7.5, and low NaCl concentrations (10 g·L−1). Maximum productivities in terms of bioactive compounds were attained at lower NaCl concentrations (10 g·L−1) (except for PE), with the best temperature and pH in terms of carotenoids and total and individual PBPs ranging from 23–25 °C to 7.5–9.5, respectively. PE was the only pigment for which the best productivity was reached at a lower temperature (15 °C) and pH (6.5) and a higher concentration of NaCl (≈25 g·L−1). AOX productivities, determined in both ethanolic and aqueous extracts, were positively influenced by lower temperatures (15–19 °C) and higher salinities (≈15–25 g·L−1). However, ethanolic AOXs were better recovered at a higher pH (pH ≈ 9.5), while aqueous AOXs were favored by a pH of 8. The model showed that biomass production can be enhanced by 175% (compared to non-optimized conditions), total carotenoids by 91%, PC by 13%, APC by 50%, PE by 130%, and total PBPs by 39%; for AOX productivities, only water extracts exhibited a (marginal) improvement of 1.4%. This study provided insightful information for the eventual upgrading of Synechocystis salina biomass in the biotechnological market. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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Review

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15 pages, 1889 KiB  
Review
An Overview of Rhodoliths: Ecological Importance and Conservation Emergency
by Dimítri de Araújo Costa, Marina Dolbeth, Martin Lindsey Christoffersen, Pamela Tatiana Zúñiga-Upegui, Márcia Venâncio and Reinaldo Farias Paiva de Lucena
Life 2023, 13(7), 1556; https://doi.org/10.3390/life13071556 - 13 Jul 2023
Cited by 1 | Viewed by 1660
Abstract
Red calcareous algae create bio-aggregations ecosystems constituted by carbonate calcium, with two main morphotypes: geniculate and non-geniculate structures (rhodoliths may form bio-encrustations on hard substrata or unattached nodules). This study presents a bibliographic review of the order Corallinales (specifically, rhodoliths), highlighting on morphology, [...] Read more.
Red calcareous algae create bio-aggregations ecosystems constituted by carbonate calcium, with two main morphotypes: geniculate and non-geniculate structures (rhodoliths may form bio-encrustations on hard substrata or unattached nodules). This study presents a bibliographic review of the order Corallinales (specifically, rhodoliths), highlighting on morphology, ecology, diversity, related organisms, major anthropogenic influences on climate change and current conservation initiatives. These habitats are often widespread geographically and bathymetrically, occurring in the photic zone from the intertidal area to depths of 270 m. Due to its diverse morphology, this group offers a special biogenic environment that is favourable to epiphyte algae and a number of marine invertebrates. They also include holobiont microbiota made up of tiny eukaryotes, bacteria and viruses. The morphology of red calcareous algae and outside environmental conditions are thought to be the key forces regulating faunistic communities in algae reefs. The impacts of climate change, particularly those related to acidification, might substantially jeopardise the survival of the Corallinales. Despite the significance of these ecosystems, there are a number of anthropogenic stresses on them. Since there have been few attempts to conserve them, programs aimed at their conservation and management need to closely monitor their habitats, research the communities they are linked with and assess the effects they have on the environment. Full article
(This article belongs to the Special Issue Algae—a Step Forward in the Sustainability of Resources)
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