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Tetraselmis has been investigated as a potential source of lipids. This microalga possesses good growth characteristics and can be used to develop viable platforms for fatty acid production. This research aims to evaluate the effect of high photon flux density with light-dark cycles and light wavelength on biomass production and fatty acid profile in Tetraselmis subcordiformis. A low light control and treatments with high photon flux density with different light-dark cycles (24:0 h, 12:12 h, 1:1 h, and 15:15 min) and different light wavelength (white, green, red, and blue) were evaluated to determine cell concentration, nutrient consumption, chlorophyll content, photosynthetic yields, lipid content, and fatty acid profile. Significant differences were found in all variables, except for phosphate consumption. High photon flux density promotes cell growth with T. subcordiformis reaching biomass productivities of 0.10 g L-1 day-1 when continuous white light is used. However, no differences were observed in biomass productivities and lipid content for all high photon flux density treatments. On the other hand, red light resulted in higher cell growth, with a productivity of 0.12 g L-1 day-1, and the highest lipid content was achieved under white light. There was a significant effect on the fatty acid profile under different light conditions, with palmitic acid, oleic acid, and eicosapentaenoic acid being the most abundant. This study demonstrated that cellular growth and fatty acid profiles in T. subcordiformis can be influenced by different lighting schemes in the cultivation. [ABSTRACT FROM AUTHOR]

The use of functional feed additives is an important approach to both, prevent and fight, viral diseases in aquaculture. In this regard, microalgae-derived products, and, more specifically, microalgal exopolysaccharides (EPSs), have attracted attention, since multiple biotechnological applications are being described for these molecules. Furthermore, depending on culture conditions, the composition and, therefore, properties of EPSs can vary. In the present study, the antiviral activity of EPSs from Tetraselmis suecica and Porphyridium cruentum cultured under autotrophic and heterotrophic conditions has been evaluated in vitro against Viral Haemorrhagic Septicaemia Virus (VHSV), an important pathogen in fish farming. Results showed that EPSs from both species have anti-VHSV activity. T. suecica EPSs from autotrophic cultures showed the strongest effect, since both, adsorption and post-adsorption phases of the VHSV multiplication cycle were affected. In contrast, both, autotrophic and heterotrophic P. cruentum EPSs showed anti-VHSV activity only after the adsorption phase. These results pave the way to use these EPSs to fight VHSV infections, and animate to evaluate the EPS antiviral activity against other viral pathogens relevant to the aquaculture industry. [ABSTRACT FROM AUTHOR]

Acoels in the family Convolutidae are commonly found with microalgal symbionts. Convolutids can host green algal Tetraselmis and dinoflagellates within the family Symbiodiniaceae and the genus Amphidinium. The diversity of these microalgae has not been well surveyed. In this study, we used PCR and culture techniques to demonstrate the biodiversity of Tetraselmis and dinoflagellates in symbiosis with meiofaunal acoels. Here, 66 acoels were collected from seven localities around Okinawa, Ishigaki, and Kochi, Japan. While convolutids were heavily represented in this sampling, some acoels formed a clade outside Convolutidae and are potentially a new family of acoels harboring symbiotic microalgae. From the acoels collected, a total of 32 Tetraselmis and 26 Symbiodiniaceae cultures were established. Molecular phylogenies were constructed from cultured material (and from total host DNA) using the 18S rRNA gene (Tetraselmis) and 28S rRNA gene (dinoflagellates). The majority of Tetraselmis sequences grouped within the T. astigmatica clade but strains closely related to T. convolutae, T. marina, and T. gracilis were also observed. This is the first report of Tetraselmis species, other than T. convolutae, naturally associating with acoels. For dinoflagellates, members of Cladocopium and Miliolidium were observed, but most Symbiodiniaceae sequences formed clusters within Symbiodinium, grouping with S. natans, or sister to S. tridacnidorum. Several new Symbiodinium sequences from this study may represent novel species. This is the first molecular record of Miliolidium and Symbiodinium from acoels. Microalgal strains from this study will provide a necessary framework for future taxonomic studies and research on symbiotic relationships between acoels and microalgae. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainable sources for food, energy, and health products, microalgae have gained attention. In the present study, the lagoonal system of the Nestos River delta was selected as a sampling point in order to search for opportunistic and robust species. Two new strains of Tetraselmis are described with regards to their taxonomic features (as observed using light and transmission electron microscopy and molecular phylogenetics) and their biochemical properties (total lipid, total protein, and total carbohydrate content, photosynthetic pigments, and antioxidant capacity). The studied strains were identified as representatives of Tetraselmis verrucosa f. rubens. Furthermore, both strains exhibited an interesting biochemical profile coupled with high growth rates and promising antioxidant activity, without the use of enhancement and induction culture methods, warranting further investigation and showing potential for biotechnological use. [ABSTRACT FROM AUTHOR]

Se usó una zeolita natural cubana enriquecida para el cultivo de las microalgas marinas Tetraselmis suecica y Chaetoceros ceratosporum, especies utilizadas en la alimentación de larvas de camarón en cultivo. Se probaron diferentes concentraciones de zeolita (5, 10 y 25 mg/L) adicionándola al medio Guillard “f” (para C. ceratosporum) y “f/2” (para T. suecica) y se ensayaron diferentes porcentajes de utilización del medio (100, 75, 50 y 25% + zeolita en todos los casos). Se determinó velocidad de crecimiento (K), tiempo de duplicación (TD) yproducción (P) para la fase exponencial de los cultivos, que fueron desarrollados en condiciones controladas de iluminación, salinidad y temperatura. Los resultados demostraron que no hubo diferencias significativas, para α=0.05, entre los tratamientos con las diferentes proporciones de la zeolita, en ninguna de las dos especies. Todos los porcentajes de utilización del medio fueron diferentes al control, pero si comparamos los tratamientos de zeolitas, para el caso de T. suecica no se debe sustituir más del 25% del medio y para C. ceratosporum se puede sustituir hasta en un 50%. Los parámetros poblaciones no arrojaron diferencias significativas entre las diferentes proporciones de zeolita en ninguna de las especies. En T. suecica, cuando empleamos 75% del medio, se obtiene la mayor K y TD aunque la P para la fase exponencial fue menor significativamente que el control. Para C. ceratosporum la mayor K se obtuvo sustituyendo el 50% del medio, el TD fue similar para todos los tratamientos con zeolitas y la P fue mayor con el control porque no decayó el cultivo.

In the quest of finding local strains of marine ciliates that can be easily cultured under a broad range of salinity and fed with microalgae, Fabrea salina Henneguy, 1890 and Condylostoma sp. Bory de St. Vincent, 1826 were cultured for 22 days in small volumes at a temperature of 16–18 °C and fed with flagellated microalgae. F. salina presented a clear preference for the salinity of 40 ppt and Condylostoma. sp. for 20 ppt. Rhodomonas salina Hill and Wetherbee, 1989 were the most efficient feeds, resulting in 30 ind./mL in F. salina and 73 ind./mL in Condylostoma. Dunaliella salina Teodoresco, 1905 and Nephroselmis sp. F. Stein, 1878 also resulted in considerable ciliate densities while Isochrysis galbana Parke, 1949 came last with the highest density in Condylostoma. The strain of Tetraselmis sp. F. Stein, 1878 (var. red pappas) which is transformed in immobilized palmelloid cells and the dinoflagellate Amphidinium carterae Hulburt, 1957, which is suspected of toxin production, were inappropriate for both ciliates. These ciliates can be easily cultured and can serve as useful organisms in bioassays and probably as live food in marine fish hatcheries.

The spectrophotometric method is used to count the number of microalgal cells. Regression equations were obtained for four species of the genus Tetraselmis (Chlorophyta), that are widely used in biotechnology. The correlation coefficients between cell number and absorbance were 0.856, 0.941, 0.787, and 0.916 for Tetraselmis viridis, T. striata, T. maculata, and Tetraselmis sp. respectively, which demonstrates the precision of this method for cell counting. [ABSTRACT FROM AUTHOR]

Microalgae are considered sustainable resources for the production of biofuel, feed, and bioactive compounds. Among various microalgal genera, the Tetraselmis genus, containing predominantly marine microalgal species with wide tolerance to salinity and temperature, has a high potential for large-scale commercialization. Until now, Tetraselmis sp. are exploited at smaller levels for aquaculture hatcheries and bivalve production. However, its prolific growth rate leads to promising areal productivity and energy-dense biomass, so it is considered a viable source of third-generation biofuel. Also, microbial pathogens and contaminants are not generally associated with Tetraselmis sp. in outdoor conditions due to faster growth as well as dominance in the culture. Numerous studies revealed that the metabolite compositions of Tetraselmis could be altered favorably by changing the growth conditions, taking advantage of its acclimatization or adaptation ability in different conditions. Furthermore, the biorefinery approach produces multiple fractions that can be successfully upgraded into various value-added products along with biofuel. Overall, Tetraselmis sp. could be considered a potential strain for further algal biorefinery development under the circular bioeconomy framework. In this aspect, this review discusses the recent advancements in the cultivation and harvesting of Tetraselmis sp. for wider application in different sectors. Furthermore, this review highlights the key challenges associated with large-scale cultivation, biomass harvesting, and commercial applications for Tetraselmis sp. [Display omitted] • Tetraselmis strains are able to grow in a wider range of salinity and temperature. • Optimization of different strategies improves Tetraselmis sp. biomass production. • Tetraselmis could be a promising algal strain for aquaculture wastewater reclamation. • Integrated biorefinery of Tetraselmis biomass is needed for its broader applications. [ABSTRACT FROM AUTHOR]

Praesagittifera naikaiensis is an acoel flatworm that inhabits the sandy beaches in the intertidal zone of the Seto Inland Sea. This species carries Tetraselmis sp., a green unicellular chlorophyte, as a symbiont in its body, and depends on algal photosynthetic products to survive. However, the eggs of P. naikaiensis contain no symbiotic algae, and juvenile P. naikaiensis acquire symbionts from the surrounding environment through horizontal transfer after hatching, thereby establishing new symbiotic relationships in each generation. Other acoel species, Symsagittifera spp., also inhabit the Seto Inland Sea shores and acquire symbiotic green algae via horizontal transfers. To characterize their symbionts, these acoels were collected from a wide area of the Seto Inland Sea and partial nucleotide sequences of the chloroplast ribulose diphosphate carboxylase large subunit (rbcL) of the symbiotic algae were determined and used for molecular phylogenetic analysis. Symbionts of both P. naikaiensis and Symsagittifera spp. belonged to the genus Tetraselmis but were phylogenetically distant, and both species established symbiotic relationships with different symbionts even when they were sympatric. To test whether each species selects specific algae in the environment for symbiosis, we established algal strains from P. naikaiensis and Symsagittifera sp. symbionts and conducted uptake experiments on aposymbiotic juveniles of P. naikaiensis . The results suggest that symbiotic algae from Symsagittifera could be taken up by P. naikaiensis juveniles, but were unable to establish a normal symbiotic relationship with the juveniles.

In the pursuit of sustainable sources for food, energy, and health products, microalgae have gained attention. In the present study, the lagoonal system of the Nestos River delta was selected as a sampling point in order to search for opportunistic and robust species. Two new strains of Tetraselmis are described with regards to their taxonomic features (as observed using light and transmission electron microscopy and molecular phylogenetics) and their biochemical properties (total lipid, total protein, and total carbohydrate content, photosynthetic pigments, and antioxidant capacity). The studied strains were identified as representatives of Tetraselmis verrucosa f. rubens. Furthermore, both strains exhibited an interesting biochemical profile coupled with high growth rates and promising antioxidant activity, without the use of enhancement and induction culture methods, warranting further investigation and showing potential for biotechnological use.

In the quest of finding local strains of marine ciliates that can be easily cultured under a broad range of salinity and fed with microalgae, Fabrea salina Henneguy, 1890 and Condylostoma sp. Bory de St. Vincent, 1826 were cultured for 22 days in small volumes at a temperature of 16–18 °C and fed with flagellated microalgae. F. salina presented a clear preference for the salinity of 40 ppt and Condylostoma. sp. for 20 ppt. Rhodomonas salina Hill and Wetherbee, 1989 were the most efficient feeds, resulting in 30 ind./mL in F. salina and 73 ind./mL in Condylostoma. Dunaliella salina Teodoresco, 1905 and Nephroselmis sp. F. Stein, 1878 also resulted in considerable ciliate densities while Isochrysis galbana Parke, 1949 came last with the highest density in Condylostoma. The strain of Tetraselmis sp. F. Stein, 1878 (var. red pappas) which is transformed in immobilized palmelloid cells and the dinoflagellate Amphidinium carterae Hulburt, 1957, which is suspected of toxin production, were inappropriate for both ciliates. These ciliates can be easily cultured and can serve as useful organisms in bioassays and probably as live food in marine fish hatcheries. [ABSTRACT FROM AUTHOR]

Microalgal biomass is widely studied for its possible application in food and human nutrition due to its multiple potential health benefits, and to address raising sustainability concerns. An interesting field whereby to further explore the application of microalgae is that of beer brewing, due to the capacity of some species to accumulate large amounts of starch under specific growth conditions. The marine species Tetraselmis chui is a well-known starch producer, and was selected in this study for the production of biomass to be explored as an active ingredient in beer brewing. Cultivation was performed under nitrogen deprivation in 250 L tubular photobioreactors, producing a biomass containing 50% starch. The properties of high-starch microalgal biomass in a traditional mashing process were then assessed to identify critical steps and challenges, test the efficiency of fermentable sugar release, and develop a protocol for small-scale brewing trials. Finally, T. chui was successfully integrated at a small scale into the brewing process as an active ingredient, producing microalgae-enriched beer containing up to 20% algal biomass. The addition of microalgae had a noticeable effect on the beer properties, resulting in a product with distinct sensory properties. Regulation of pH proved to be a key parameter in the process. [ABSTRACT FROM AUTHOR]

This study investigated the hydrothermal liquefaction (HTL) of extracted major macromolecules from Tetraselmis sp. biomass. The carbohydrate fraction was first recovered from Tetraselmis biomass using pressurized heated water. The crude lipid fraction was then extracted from carbohydrate-free biomass by hexane. The remaining biomass was considered as protein extract. HTL runs were conducted from 275 to 350 °C and 30 min for each extract; the maximum biocrude yields for carbohydrate, lipid, and proteins were obtained at 325, 325, and 350 °C, respectively. Next, HTL runs of these macromolecules were conducted at 350 °C for 10–60 min. The highest biocrude yields from carbohydrate, lipid, and protein extracts were obtained at 45, 20, and 45 min, respectively. The optimal energy recovery, as biocrude, from carbohydrate, lipid, and protein extracts were 41, 85, and 81%, respectively. Therefore, microalgae biomass with low carbohydrate content or carbohydrate-extracted biomass could be used as feedstock for biocrude production. □ Carbohydrate, lipid, and proteins were extracted from Tetraselmis biomass for HTL. □ The liquefaction temperature for carbohydrate and lipid was lesser than protein. □ Higher holding times were required for liquefaction of carbohydrate, and protein than lipid. □ Energy recovery from extracted microalgal metabolites were 41–85%. □ 27–81% nitrogen of the microalgal metabolites could be recovered in aqueous phase. [ABSTRACT FROM AUTHOR]

Microalgae are a sustainable source of nutraceuticals such as omega-3 fatty acids and carotenoid pigments. Therefore, nutraceutical profiling of microalgae is essential to identify high-yielding candidates for cultivation upscaling and commercialisation. The present study investigated the pigment and fatty acid profiles of 10 marine species within the chlorophyte genus Tetraselmis, with a quantitative focus on the high-value nutraceuticals lutein, β-carotene and the omega-3 fatty acid eicosapentaenoic acid (EPA, C20:5 ω3). To achieve this, fatty acid and pigment analyses were carried out via GC-MS and HPLC, respectively. When comparing the 10 Tetraselmis species, identical fatty acid and pigment compositions were observed. Palmitic acid (C16:0), α-linolenic acid (C18:3 ω3) and oleic acid (C18:1) were the primary constituents of the fatty acid profile for the Tetraselmis species. Furthermore, the pigment profile observed for each Tetraselmis species was typical of Chlorophyceae algae and included common green algal carotenoids such as lutein, violaxanthin and neoxanthin. Significant variations in the yields of high-value nutraceuticals were observed. For example, T. suecica (CCAP 66/38) returned the highest yield of EPA (3.10 ± 0.20 mg EPA g−1dw). Moreover, T. suecica (CCAP 66/38) was one of the more prominent Tetraselmis species in relation to β -carotene (7.17 mg β- Car g−1dw) and lutein (0.39 mg lut g−1dw) content. Thus, the present intragenus study documents species-specific responses to common growth conditions and variations in nutraceutical biosynthesis potential. Of note, T. suecica (CCAP 66/38), subject to further cultivation optimisation strategies, may represent a promising commercial source of the bioactive xanthophyll lutein, the provitamin A carotenoid β -carotene and the omega-3 fatty acid EPA. [Display omitted] • The pigment and fatty acid biosynthesis potential of 10 marine Tetraselmis species was investigated. • A common genus-unique pigment and fatty acid profile was observed with species-specific variations in the production of individual bioactive metabolites. • T. suecica (CCAP 66/38) returned the highest yield for EPA (3.10 ± 0.20 mg g−1dw). • T. chuii , T. gracilis and T. suecica were the most prominent species in relation to the synthesis of β -carotene and lutein. [ABSTRACT FROM AUTHOR]

Tetraselmis sp. strain MD-01, a microalga isolated from the Tunisian marine coast, has been studied for autotrophic lipids production with two stage process. This strategy was conducted for maximum cells production under moderated conditions (2.12 g L−1), followed by cultivation under stressed conditions to induce lipid synthesis. High irradiance (300 μmol m−2 s−1) and nitrogen depletion (S mode) showed better carotenoids accumulation and lower chlorophylls content in microalgae compared to those obtained in biomass cultivated under high irradiance (Sg mode). This two-stage strategy allowed to increase of lipid content in cells cultivated in Sg and S modes from 18% DW (stage I) to 50 and 61.5% DW (stage II), respectively, with an increase of saturated and long chain fatty acids levels. Based on fluorometry analyses, an increase of lipids in Nile-Red stained cells and a decrease of chlorophylls auto-fluorescence under stressed conditions were shown. From spectral data, the lipids: amide I ratio obtained from S mode was 2.17 and 4.45 times higher than that from Sg mode and control conditions, respectively. These results revealed the potential of Tetraselmis strain MD-01 for biodiesel production. [Display omitted] [ABSTRACT FROM AUTHOR]

Microalgae are known producers of antioxidant and anti-inflammatory compounds, making them natural alternatives to be used as food and feed functional ingredients. This study aimed to valorise biomass and exploit new applications and commercial value for four commercially available microalgae: Isochrysis galbana, Nannochloropsis sp., Tetraselmis sp., and Phaeodactylum tricornutum. For that, five extracts were obtained: acetone (A), ethanol (E), water (W), ethanol:water (EW). The antioxidant capacity (ABTS•+/DPPH•/•NO/O2•−/ORAC-FL) and anti-inflammatory capacity (HBRC/COX-2) of the extracts were screened. The general biochemical composition (carbohydrates, soluble proteins, and lipids) and the main groups of bioactive compounds (carotenoids, phenolic compounds, and peptides) of extracts were quantified. The results of antioxidant assays revealed the potential of some microalgae extracts: in ABTS•+, Nannochloropsis sp. E and Tetraselmis sp. A, E, and P; in DPPH•, Tetraselmis sp. A and E; in •NO, P. tricornutum E and EW; in O2•−, Tetraselmis sp. W; and in ORAC-FL, I. galbana EW and P. tricornutum EW. Concerning anti-inflammatory capacity, P. tricornutum EW and Tetraselmis sp. W showed a promising HBRC protective effect and COX-2 inhibition. Hence, Tetraselmis sp. and P. tricornutum extracts seem to have potential to be incorporated as feed and food functional ingredients and preservatives.

[Display omitted] • Microbial profiling of large-scale algal culture was conducted using metagenomics. • Bacterial invaders increased gradually throughout Tetraselmis upscaling stages. • Balneola , Roseovarius , and Marinobacter had algae growth-promoting properties. • Ulvibacter , Aestuariicoccus and Defluviimonas demoted Tetraselmis growth. Microalgae have become a key source of valuable compounds, promoting commercial scale applications. However, biological contamination is one of the most critical problems associated with large scale algal production, especially in open systems such as raceway ponds. The current research is the first to assess the effectiveness of open raceway ponds in maintaining a pure culture of Tetraselmis sp. , starting from 20 L culture up to 10,000 L culture. Microbial profiling of each successive stage revealed lower abundance of eukaryotic organisms, whereas bacterial abundance increased notably resulting in a significant decrease in Tetraselmis sp. abundance. Furthermore , s everal bacteria with algae growth-promoting properties were found throughout the various culture stages including Balneola, Roseovarius, and Marinobacter. However, some algae-suppressive bacteria were evidenced at later stages such as Ulvibacter, Aestuariicoccus , and Defluviimonas. Overall, due to the increasing bacterial concentration, considerations limiting bacterial contamination need to be taken. [ABSTRACT FROM AUTHOR]

Microalgal biomass is widely studied for its possible application in food and human nutrition due to its multiple potential health benefits, and to address raising sustainability concerns. An interesting field whereby to further explore the application of microalgae is that of beer brewing, due to the capacity of some species to accumulate large amounts of starch under specific growth conditions. The marine species Tetraselmis chui is a well-known starch producer, and was selected in this study for the production of biomass to be explored as an active ingredient in beer brewing. Cultivation was performed under nitrogen deprivation in 250 L tubular photobioreactors, producing a biomass containing 50% starch. The properties of high-starch microalgal biomass in a traditional mashing process were then assessed to identify critical steps and challenges, test the efficiency of fermentable sugar release, and develop a protocol for small-scale brewing trials. Finally, T. chui was successfully integrated at a small scale into the brewing process as an active ingredient, producing microalgae-enriched beer containing up to 20% algal biomass. The addition of microalgae had a noticeable effect on the beer properties, resulting in a product with distinct sensory properties. Regulation of pH proved to be a key parameter in the process.

This study aims to determine the maximum specific biomass growth rates of Nannochloropsis gaditana and Tetraselmis chuii grown in sequential batch reactors. The maximum specific growth rates of N. gaditana and T. chuii were found to be 0.23 ± 0.04 gVSS/gVSS⋅d and 0.22 ± 0.05 gVSS/gVSS⋅d respectively. Optical density measured at 550 nm (OD550) accurately predict volatile suspended solids (VSS) concentration in N. gaditana growth media but not in T. chuii growth media. We observed decoupling of nitrate uptake from cell growth for both microalgae as growth continued well beyond the point where concentrations of nitrate in the growth media fell below the detection limit. This nitrate decoupling highlights the challenges in current microalgae growth models as growth was independent of the extracellular dissolved nitrogen in the system.

The aim of this paper was to develop high-protein vegetable creams through the incorporation of microalgae. Single-cell ingredients from Arthrospiraplatensis (spirulina), Chlorella vulgaris, Tetraselmis chui, and Nannochloropsis oceanica were incorporated at two levels of addition (1.5% and 3.0%) to a standard vegetable cream (STD). Effects of incorporation were assessed in terms of physicochemical and rheological attributes as well as nutritional labeling facts. Creams formulated with 3% A. platensis, N. oceanica, or T. chui showed strong color differences (6 < ΔE < 12) compared to STD; creams formulated with 1.5% A. platensis, T. chui, or N. oceanica showed perceptible differences (3 < ΔE < 6); and those made with C. vulgaris at 1.5 and 3% exhibited small differences (ΔE < 2). Moisture content, water activity, pH, syneresis, and °Brix did not show significant changes. Adding microalgae increased Bostwick consistency and decreased the consistency coefficient (K) except in creams made with A. platensis, which showed comparable values to STD. Principal component analysis indicated that creams made with 1.5% C. vulgaris were the most similar to STD considering all evaluated parameters. Estimation of the nutritional labeling facts showed that the four formulations could be labeled as having “high protein content” following the present EU legislation.

Featured Application: The following topics are assessed in this study: (1) microbial disturbance due to dissolved organic carbon secreted from T. striata; (2) risk of large-scale microalgae cultivation to marine environment; (3) relationship between bacteria and phytoplankton by dissolved organic carbon; (4) ecosystem impact assessment through mesocosm study. The green alga Tetraselmisstriata is regarded as a suitable candidate microalga for bio-diesel production. Recently, T. striata was cultured near Yeonghueung Island, Korea, in a "marine culturing field"; however, its environmental impacts are not yet studied. We estimated the amount of dissolved organic carbon (DOC) released from T. striata cultivation in the marine culturing field, and we investigated the changes in bacterial composition. Then, we designed and installed a mesocosm for further understanding. From the mesocosm results, the DOC released from the cultivation of T. striata led to changes in bacterial communities, disturbance of the microbial food web structure, rapid depletion of nutrients, and a decrease in dissolved oxygen (DO) and pH. Our novel work demonstrates that large amounts of DOC secreted by large-scale microalgal cultures such as that of T. striata can potentially have a significant impact on the structure and function of the surrounding microbial ecosystem. [ABSTRACT FROM AUTHOR]

Cittarium pica is an overexploited Caribbean top shell that is being produced at an experimental level by aquaculture for conservation purposes. To optimise nursery culture, the growth and survival of wild and hatchery-produced juveniles were assessed after feeding with different biofilm diets. The following three diets were tested over a 6-month period: (1) a microalgal biofilm of Nitzschia sp. and Tetraselmis chuii; (2) an artificial biofilm of dry seaweeds, Padina gymnospora and Laurencia obtusa, and the cyanobacterium Spirulina sp.; and (3) a mix of the microalgal and artificial biofilms. The biofilms were prepared and supplied on folded PVC plates, and treatments were administered in triplicated 10-L aquaria with down-welling systems at 25 ± 1 °C and a salinity of 36.5 ± 0.5 ppt. Higher growth rates were obtained in juveniles fed diets containing artificial biofilms, which had high protein and energy contents, whereas survival rates were higher in juveniles fed the mixed diet. The relatively high growth and survival values suggest that the nursery culture can be improved by feeding with the mix of microalgal and artificial biofilms and that the temporary translocation of wild juveniles to nursery conditions can be a tool for population enhancement. [ABSTRACT FROM AUTHOR]

Marine microalgae constitute a natural source of compounds (e.g., alkanes, triacylglycerols) useful for biodiesel production—yet improvement of lipid productivity by microalgae is a sine qua non for the economic feasibility of such a microalga-based process. Toward this goal, five Tetraselmis strains, Tetraselmis suecica UW605, T. suecia AROSA, and three Tetraselmis sp. strains, coded as lipogenic (63LG and 75LG) or non-lipogenic (46NLG) on the basis of stationary-phase cell flotation features, were cultured semi-continuously and subjected to 10 and 30% renewal rates; the effects upon growth rate and lipidic profile were accordingly assessed. As expected, cell productivity by all strains was higher under a renewal rate of 30%. Chlorophyll, protein, and total lipid content per cell also increased with the highest renewal rate. Conversely, cell content of neutral lipids, measured with Nile red staining, decreased with increasing renewal rate. The non-lipogenic strain 46NLG revealed a much lower total lipid content, at the 10% renewal rate, than all other strains, but a higher neutral lipid content. This result supports the use of the flotation method for the selection of lipogenic strains. The diverse profiles of the various Tetraselmis strains and the effect of renewal rate on their neutral lipid content emphasize the importance of strain screening to promote a suitable microalgae selection for biodiesel production purposes. [ABSTRACT FROM AUTHOR]

Acoels in the family Convolutidae are commonly found with microalgal symbionts. Convolutids can host green algal Tetraselmis and dinoflagellates within the family Symbiodiniaceae and the genus Amphidinium . The diversity of these microalgae has not been well surveyed. In this study, we used PCR and culture techniques to demonstrate the biodiversity of Tetraselmis and dinoflagellates in symbiosis with meiofaunal acoels. Here, 66 acoels were collected from seven localities around Okinawa, Ishigaki, and Kochi, Japan. While convolutids were heavily represented in this sampling, some acoels formed a clade outside Convolutidae and are potentially a new family of acoels harboring symbiotic microalgae. From the acoels collected, a total of 32 Tetraselmis and 26 Symbiodiniaceae cultures were established. Molecular phylogenies were constructed from cultured material (and from total host DNA) using the 18S rRNA gene ( Tetraselmis ) and 28S rRNA gene (dinoflagellates). The majority of Tetraselmis sequences grouped within the T . astigmatica clade but strains closely related to T . convolutae , T . marina , and T . gracilis were also observed. This is the first report of Tetraselmis species, other than T . convolutae , naturally associating with acoels. For dinoflagellates, members of Cladocopium and Miliolidium were observed, but most Symbiodiniaceae sequences formed clusters within Symbiodinium , grouping with S . natans , or sister to S . tridacnidorum . Several new Symbiodinium sequences from this study may represent novel species. This is the first molecular record of Miliolidium and Symbiodinium from acoels. Microalgal strains from this study will provide a necessary framework for future taxonomic studies and research on symbiotic relationships between acoels and microalgae., Competing Interests: The authors declare that there are no competing interests., (© 2023 Riewluang and Wakeman.)

Marine and freshwater algae and their products are in growing demand worldwide because of their nutritional and functional properties. Microalgae (unicellular algae) will constitute one of the major foods of the future for nutritional and environmental reasons. They are sources of high-quality protein and bioactive molecules with potential application in the modern epidemics of obesity and diabetes. They may also contribute decisively to sustainability through carbon dioxide fixation and minimization of agricultural land use. This paper reviews current knowledge of the effects of consuming edible microalgae on the metabolic alterations known as metabolic syndrome (MS). These microalgae include Chlorella, Spirulina (Arthrospira) and Tetraselmis as well as Isochrysis and Nannochloropsis as candidates for human consumption. Chlorella biomass has shown antioxidant, antidiabetic, immunomodulatory, antihypertensive, and antihyperlipidemic effects in humans and other mammals. The components of microalgae reviewed suggest that they may be effective against MS at two levels: in the early stages, to work against the development of insulin resistance (IR), and later, when pancreatic -cell function is already compromised. The active components at both stages are antioxidant scavengers and anti-inflammatory lipid mediators such as carotenoids and -3 PUFAs (eicosapentaenoic acid/docosahexaenoic acid; EPA/DHA), prebiotic polysaccharides, phenolics, antihypertensive peptides, several pigments such as phycobilins and phycocyanin, and some vitamins, such as folate. As a source of high-quality protein, including an array of bioactive molecules with potential activity against the modern epidemics of obesity and diabetes, microalgae are proposed as excellent foods for the future. Moreover, their incorporation into the human diet would decisively contribute to a more sustainable world because of their roles in carbon dioxide fixation and reducing the use of land for agricultural purposes.

To develop greener extraction alternatives for microalgae biomass, ultrasound assisted extraction (UAE) and pressurized liquid extraction (PLE) with different biobased solvents were investigated, demonstrating that both techniques are useful alternatives for algal lipid extraction. Specifically, Nannochloropsis gaditana lipids were extracted by UAE and PLE at different temperatures and extraction times with sustainable solvents like 2-Methyltetrahydrofuran (2-MeTHF) and its mixtures with ethanol and other alcohols. The best oil yields for both PLE and UAE of N. gaditana were achieved with the mixture of 2-MeTHF:ethanol (1:3), reaching yields of up to 16.3%, for UAE at 50 °C and up to 46.1% for PLE at 120 °C. Lipid composition of the extracts was analyzed by HPLC-ELSD and by GC-MS to determine lipid species and fatty acid profile, respectively. Different fractionation of lipid species was achieved with PLE and solvent mixtures of different polarity. Thus, for the extraction of glycolipids, ethanolic extracts contained higher amounts of glycolipids and EPA, probably due to the higher polarity of the solvent. The optimized method was applied to microalgae Isochrysis galbana and Tetraselmis chuii showing the potential of mixtures of biobased solvents like 2-methyl-THF and ethanol in different proportions to efficiently extract and fractionate lipids from microalgal biomass.

Highlights • The energy requirement for harvesting Tetraselmis sp. biomass was 0.49–4.65 MJ/kg. • Harvesting technique affected the microalgal biomass quality. • Microalgal biocrude yield and characteristic varied based on harvesting technique. • Excess Al in electrocoagulation and alum harvested biomass increased biocrude yield. • All microalgal biocrude samples had higher metal contents compared to petrocrude. Abstract A halo-tolerant Tetraselmis sp. was grown in a 100,000 L raceway pond in the Qatari desert environment. As the biomass density reached 0.679 g/L, after 7 days, five different harvesting methods (i.e., cross-flow filtration, electrocoagulation, and coagulation-flocculation by FeCl 3 , NaOH, and alum) were applied to harvest the biomass. Hydrothermal liquefaction, for all the harvested biomass, was conducted at 350 °C for 30 mins in 10 mL Swagelok unions. The biocrude yield from cross-flow processed biomass (i.e., control) was 50.8%. Biocrude yield from electrocoagulation and alum processed biomass were 62.7% and 60.4% respectively where aluminum could have a catalytic effect. Biocrude yield from FeCl 3 and NaOH processed biomass were 42.9% and 19.8% respectively. The total fraction of alkenes and alkanes was higher in the biocrude obtained from alum-harvested biomass, compared to other biocrude samples. However, the transition of metal species from biomass to biocrude was very low in all the biocrudes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Tetraselmis sp. could grow in extreme Qatar climate condition throughout the year. • The annual average biomass productivity of Tetraselmis sp. was 17.81 g/m2/d. • Recycling growth media had no effect on the biomass productivity of Tetraselmis sp. • Iron content in ferric chloride assisted harvested Tetraselmis biomass was 1.5–3.3%. • Acid solution could leach >91% iron from freshly harvested Tetraselmis biomass. Abstract In this study, a halotolerant Tetraselmis sp. was selected for 11-month outdoor semi-continuous cultivation in one sq. m raceway tank in the Qatari desert. A fraction of the culture was harvested using ferric chloride, and the growth media was returned to the tank. The recycling of culture media continued till the culture salinity reached 8% NaCl; 90% culture was then harvested, and the remaining culture fraction was used as inoculum for a new cultivation cycle. The growth of Tetraselmis sp. was not affected by incremental salinity although the intracellular metabolites varied; the average biomass productivity was 17.8 g/m2/d. Harvesting efficiency was slightly affected by the increase in salinity. Iron content in the harvested biomass was in the range of 1.5–3.3%, and acidic solution (pH = 1.48) was able to recover 91.3% iron from the harvested biomass. Nonetheless, Tetraselmis sp. could be grown continuously throughout the year in Qatar's climate condition. [ABSTRACT FROM AUTHOR]

Date palm (Phoenix dactylifera L.) is the main fruit crop found in the arid and semi-arid regions of the world. It naturally adapts to the adverse environments of extreme heat and water scarcity and prevents further desertification in addition to producing fruits with high nutritional value. It is seen in many parts of the world that traditional cultivation practices such as mixed planting and chemical fertilizers have led to low fruit quality resulting in low market values. Long generation time also hinders production of the dates. Tissue culture is therefore considered the most promising solution for rapid large-scale production of true-to-type clonal plants. The plantlets originating from in vitro callus proliferation are transferred from synthetic media to soil. The conventional method of using chemical fertilizers also leads to low plantlet viability with increased environmental and health risk. The current research targets the use of a local microalga, Tetraselmis sp. QUCCCM8, identified as an organic source of nutrients, a substitute for chemical fertilizers to acclimatize cultured date palmlets to soil. Soil was supplemented with different concentrations of algal biomass and plant growth was monitored for 3 months. Soil without any fertilizer and soil amended with 1 g conventional fertilizer were used as negative and positive control, respectively. Supplementation with 0.5 g of algal biomass led to higher plant growth rates, 100% survival rates, high ability of rooting (3.17 ± 0.14 roots), higher number of leaves (2.5 ± 0.25 leaves), largest stem thickness, longer shoot (33.75 ± 1.56 cm), and higher total chlorophyll (159.61 ± 9.6 mg L−1) as compared to conventional fertilizer. These stated findings are significantly higher than the control. Furthermore, elemental analysis of the soil showed that supplementation with algal biomass increased the soil total nitrogen, potassium, and phosphorus contents essential for plant growth. Finally, the comparison of heavy metals composition between soils amended with conventional fertilizer and algae-based fertilizer highlights the potential use of algae as a safe and efficient biofertilizer post tissue culture mode of plantlet generation. This enhanced the viability of healthy plantlets without affecting the environment, averting usage of chemical fertilizers. [ABSTRACT FROM AUTHOR]

The green alga Tetraselmis striata is regarded as a suitable candidate microalga for bio-diesel production. Recently, T. striata was cultured near Yeonghueung Island, Korea, in a “marine culturing field”; however, its environmental impacts are not yet studied. We estimated the amount of dissolved organic carbon (DOC) released from T. striata cultivation in the marine culturing field, and we investigated the changes in bacterial composition. Then, we designed and installed a mesocosm for further understanding. From the mesocosm results, the DOC released from the cultivation of T. striata led to changes in bacterial communities, disturbance of the microbial food web structure, rapid depletion of nutrients, and a decrease in dissolved oxygen (DO) and pH. Our novel work demonstrates that large amounts of DOC secreted by large-scale microalgal cultures such as that of T. striata can potentially have a significant impact on the structure and function of the surrounding microbial ecosystem.

The use of microalgae in biotechnological processes has received much attention worldwide. This is primarily due to the fact that they are inexpensive to grow, requiring only sunlight and CO2, whilst lending themselves to a range of uses, such as to reduce CO2 levels, as fish feed, in biofuel production, for the generation of secondary metabolites of interest, and in bioremediation. These features mean that microalgae are excellent candidates for the implementation of a range of eco-friendly technologies. Here, we investigated the behavior and feasibility of the use of the microalgal strain Tetraselmis marina AC16-MESO against heavy metal contamination focused on potential use in bioremediation. The following key parameters were recorded: (i) the sedimentation efficiency, which reached 95.6% after five hours of decantation; (ii) the ion tolerance (Ca2+, Co2+, Cu2+, Fe3+, Mn2+ and Ni2+) at concentrations of 0.1, 1.0, 5.0, 10.0 and 20.0 mg*L−1 and (iii) ion removal efficiency (Cu2+, Fe3+ and Mn2+). Our results indicated a higher tolerance for iron and calcium (20 ± 1.10 mg*L−1; 100 ± 8.10 mg*L−1), partial to nickel, manganese and copper (4.4 ± 0.10 mg*L−1; 4.4 ± 0.15 mg*L−1; 5 ± 1.25 mg*L−1) and less for cobalt (0.1 ± 0.20 mg*L−1). Moreover, removal efficiency of 40–90% for Cu2+, 100% for Fe3+, and 20–50% for Mn2+ over a 72 hours period, for ion concentrations of 1.0 and 5.0 mg*L−1.

Tetraselmis desikacharyi is a marine alga, known as an important plankton for aquaculture as a feed organism. However, the genomic study on this class is rare. Here, we present a complete chloroplast genome of T. desikacharyi, belonging to Chlorodendrophyceae with a full length of 149,934 bp, characterized by a very small single-copy (SSC) region without any genes and a large inverted repeat (IR) region. A maximum-likelihood (ML) phylogenetic analysis was performed using three kinds of data comprising 50 protein-coding genes, which placed the Chlorodendrophyceae as a deep-diverging lineage of the core Chlorophyta.

Identifying sources of renewable energy is extremely important. The potential of Tetraselmis sp. in biodiesel production was investigated using a completely randomized design with four treatments. Tetraselmis sp. was cultured on media containing different concentrations of nitrate there are 2 mM and 15 Mm and s 25 ‰ and 35 ‰ salinity. The treatments namely are (N2S25), (N2S35), N15S25) and (N15S35). Analysis of the fatty acid content using gas chromatography-mass spectrometry (GC-MS). The results showed that the highest growth occurred in culture that contained 15 mM of nitrate and 35 ‰ salinity. The lowest growth occurred in culture containing 2 mM of nitrate and 25‰ of salinity. The highest lipid content was found in cultures containing 2 mM of nitrate and 25‰ salinity, it is 34.83%. Seven fatty acids were detected in culture containing 2 mM of nitrate and 25‰ salinity namely myristic acid (4.02%), palmitic acid (40.59%), palmitoleic acid (29.06%), stearic acid (0.95%), oleic acid (12.52%), gamma-linolenic acid (2.56%), and arachidonic acid (9.38%). Four fatty acids palmitoleic acid (8.99%), palmitic acid (37.34%), oleic acid(44.89%), and stearic acid (8.78%) were detected in 2 mM of nitrate with 35‰ salinity. The fatty acids have potential to be used as raw material for biodiesel production.

The use of microalgae in biotechnological processes has received much attention worldwide. This is primarily due to the fact that they are inexpensive to grow, requiring only sunlight and CO2, whilst lending themselves to a range of uses, such as to reduce CO2 levels, as fish feed, in biofuel production, for the generation of secondary metabolites of interest, and in bioremediation. These features mean that microalgae are excellent candidates for the implementation of a range of eco-friendly technologies. Here, we investigated the behavior and feasibility of the use of the microalgal strain Tetraselmis marina AC16-MESO against heavy metal contamination focused on potential use in bioremediation. The following key parameters were recorded: (i) the sedimentation efficiency, which reached 95.6% after five hours of decantation; (ii) the ion tolerance (Ca2+, Co2+, Cu2+, Fe3+, Mn2+ and Ni2+) at concentrations of 0.1, 1.0, 5.0, 10.0 and 20.0 mg*L-1 and (iii) ion removal efficiency (Cu2+, Fe3+ and Mn2+). Our results indicated a higher tolerance for iron and calcium (20 ± 1.10 mg*L-1; 100 ± 8.10 mg*L-1), partial to nickel, manganese and copper (4.4 ± 0.10 mg*L-1; 4.4 ± 0.15 mg*L-1; 5 ± 1.25 mg*L-1) and less for cobalt (0.1 ± 0.20 mg*L-1). Moreover, removal efficiency of 40-90% for Cu2+, 100% for Fe3+, and 20-50% for Mn2+ over a 72 hours period, for ion concentrations of 1.0 and 5.0 mg*L-1. [ABSTRACT FROM AUTHOR]

Cell walls of microalgae differ both in terms of chemical composition and architecture. Certain characteristics of cell walls limit both the effectiveness of extraction of valuable constituents and nutrient bioavailability and bioaccessibility in fish. We first investigated the potential of bead milling to disrupt cell walls to improve extractability of bioactive compounds from Phaeodactylum tricornutum and Tetraselmis chui. We also evaluated the effect of the mechanical treatment on i) digestibility of nutrients in the two microalgae and ii) fatty acid and pigment content of fillet of Atlantic salmon fed the algae diets. Cell wall disruption facilitated efficient release of total phenolic compounds (TPC), chlorophyll A, chlorophyll B and total carotenoids from both microalgae species, but increased only the total antioxidant capacity (TAC) of T. chuii. The polyphenol profile varied between the two species; we identified 2 and 6 polyphenols from P. tricornutum and T. chui , respectively. For the feeding experiment, microalgae biomass, intact or cell wall disrupted (90.7 and 76.4% disruption degree for T. chui and P. tricornutum , respectively), were mixed with the other feed ingredients. Atlantic salmon (315 g start weight / 55 fish per tank) were fed one of the five extruded experimental diets (a fishmeal-based reference diet and four feeds with 30% of the whole or broken microalgae biomass added to the reference diet). The digestibility of protein in the P. tricornutum was significantly higher compared to that of T. chui. Breaking the cell walls by bead milling caused a significant improvement in digestibility of protein in T. chui. The apparent digestibility coefficient of lipid was higher in P. tricornutum and bead milling improved the digestibility of the two algae. However, bead milling did not favourably change the fatty acid profile of Atlantic salmon. At the end of the feeding trial, P. tricornutum -fed fish had significantly improved pigmentation, probably due to the higher content of fucoxanthin and fucoxanthinol compared to the fish fed the reference diet. The main conclusion from the mechanical processing of the microalgae is that bead milling can increase i) the extractability of polyphenols and pigments, ii) the digestibility of lipid in both algae while the effect on protein was improved only for T. chui. Furthermore, P. tricornutum can be considered a natural pigment source in the feeds of Atlantic salmon. • The extractability of polyphenols and carotenoids from P. tricornutum and T. chui • The digestibility of lipid in both algae • The digestibility of protein in T. chui • The carotenoid bioavailability in P. tricornutum [ABSTRACT FROM AUTHOR]

Con el fin de crear una colección de microalgas bentónicas marinas del Caribe colombiano, algunas cepas fueron aisladas y cultivadas bajo diferentes condiciones de temperatura. A partir de muestras de perifiton de placas de PVC colocadas en el intermareal rocoso de Taganga, Santa Marta (Colombia), se evaluó el tipo y número de microalgas aisladas, así como la densidad y la constante de crecimiento relativo (K) de tres de las cepas aisladas bajo tres temperaturas de cultivo (20, 25 y 28 °C). Se mantuvieron condiciones constantes de medio de cultivo F/2 de Guillard, iluminación artificial (1500 lux) y valores iniciales de salinidad de 30‰ y pH de 7,0. Se logró el aislamiento de cinco cepas de microalgas a una temperatura de 20 °C (Cylindrotheca closterium, Komvophoron crassum, Tetraselmis sp. y 2 morfotipos de la familia Bacillariaceae); a 25 y 28 °C ninguna cepa fue obtenida. En la diatomea identificada como Bacillariaceae morfotipo 1, los valores mayores de densidad celular (96,3 x 105 cel.ml-1) y K (1,03 div. día-1), se obtuvieron a temperaturas de 20 y 25 °C, mientras que a 28 °C fue imposible obtener su crecimiento. Contrariamente, en las microalgas Cylindrotheca closterium y Tetraselmis sp., los valores mayores de densidad (2,6 y 7,7 x 105 cel.ml-1, respectivamente) se obtuvieron en el tratamiento de 25 °C, mientras que los mayores valores de K ocurrieron a 28 °C (0,64 y 0,60 div. d-1, respectivamente). Este estudio permitió iniciar un cepario de microalgas bentónicas del Caribe colombiano, así como determinar las temperaturas más apropiadas para el aislamiento microalgal (20 °C) y para la producción de células de Bacillariaceae morfotipo 1, Cylindrotheca closterium y Tetraselmis sp. (25 °C).

Transport and release of waterborne organisms as a result of ballasting and de-ballasting operations is widely acknowledged to represent an important mechanism for invasions by non-indigenous species. Regulatory requirements have been implemented globally to require treatment of ballast water before its release to the environment as a means of minimizing risks of invasion. UV-based processes represent an option for ballast water treatment; however, their use will require development of appropriate methods for reactor validation. To address this need, Tetraselmis was examined as challenge organism using a most probable number (MPN) assay for quantification of the concentration of viable (reproductively active) cells in suspension. A low pressure collimated-beam reactor was used to investigate UV 254 dose-response behavior of Tetraselmis. Based on the experimental conditions applied, Tetraselmis indicated 4.5–5 log 10 units of inactivation for UV 254 doses of approximately 120 mJ/cm 2 , with no apparent change of resistance resulting from repeated exposure. A medium pressure UV collimated-beam reactor equipped with a series of narrow bandpass optical filters was used to investigate the action spectrum of Tetraselmis for wavelengths ranging from 228 nm–297 nm. Radiation with wavelengths in the range 254–280 nm was observed to be most efficient for inactivation of Tetraselmis. Additionally, DNA was extracted from Tetraselmis to allow measurement of its absorption spectrum. These results indicated strong absorbance from 254 nm to 280 nm, thereby suggesting that damage to DNA plays an important role in the inactivation of Tetraselmis sp. However, deviations of the action spectrum shape from the shape of the DNA absorption spectrum suggest that UV-induced damage to biomolecules other than DNA may contribute to Tetraselmis inactivation at some wavelengths in the UVC range. [ABSTRACT FROM AUTHOR]