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BACKGROUND AND OBJECTIVES: Greenhouse gas emissions are the primary cause of global warming. Under the Paris Agreement, all countries have developed programs to reduce anthropogenic impact on the environment. In the petrochemical industry, for example, isoprene, is a major contributor to the production of carbon dioxide, generating large amounts of acidic and hydrocarbon gases that are burned and released into the atmosphere. This study aimed to investigate the absorption of greenhouse gases from isoprene production by the marine microalgae Isochrysis galbana and Tetraselmis suecica, as well as the freshwater microalgae Chlorella vulgaris. METHODS: Microalgae cells were cultured in a bioreactor. The grown microalgae strains and mineralized water were fed to the bioreactor. Gases discharged from isoprene production were passed through the bioreactor. Inlet and outlet gas compositions were monitored by chromatography. FINDINGS: Absorption of gases discharged from isoprene production by microalgae was studied for the first time. Chlorella vulgaris microalgae reduced methane and carbon dioxide contents by an average of 20 times. A mixture of microalgae Tetraselmis suecica and Isochrysis galbana reduced methane and carbon dioxide contents by a factor of 10 but completely absorbed hydrocarbon gases from methane to pentane. CONCLUSION: The results indicate that microalgae cultivation can be used as a reliable and stable technology for the biofixation of the gases discharged in isoprene production. This technology can eliminate the combustion stage of hydrocarbon gases in isoprene production and significantly reduce carbon dioxide emissions into the atmosphere. [ABSTRACT FROM AUTHOR]

The dietary effects of the green microalga Tetraselmis suecica (TS) on the growth, digestive enzymes, immune and antioxidant responses, genes expression, and disease resistance of Nile tilapia (Oreochromis niloticus) fingerlings were investigated. This microalga was mixed with the diet' ingredients at doses of 0.0 (the control), 5, 10, 15, and 20 g/kg diet and then fed to fish daily for 84 days. After the feeding trial, fish were experimentally challenged with Aeromonas sobria, infection and fish mortalities were recorded for another 10 days. Dietary TS significantly (p < 0.05) enhanced growth, digestive enzymes activities, and blood proteins, particularly at the level of 15 g/kg diet. Feeding the fish on 15 TS/kg feed exhibited highest mRNA expressions of GH and IGF‐1 genes as well as SOD, CAT, and GPx genes compared to other TS groups. Moreover, highest levels of hepatic antioxidant and immune indices were found in the treatment of 15 g TS/kg feed. Significant downregulation of IL‐1β and IL‐8 genes expression and significant upregulation of IL‐10 gene expression were observed in TS‐fed fish, principally in fish groups fed on 15−20 g TS/kg feed. Conversely, hepatic malondialdehyde levels, blood glucose, and the activities of transaminases (ALT and AST) were significantly (p < 0.05) decreased in fish fed with 15−20 g TS/kg diet. Serum bactericidal activity against A. sobria was significantly higher in TS‐fed fish groups, and its highest levels were found in treatments of 15−20 g/kg diet. Of interest, the survival rates of fish groups fed diets with 10−20 g TS/kg feed were higher after the challenge with A. sobria infection than the control group. Accordingly, we can conclude that supplementing fish diets with a 15 g TS/kg diet enhanced the growth, antioxidant and immune activities, and resistance of Nile tilapia fingerlings to possible A. sobria infection. [ABSTRACT FROM AUTHOR]

ABSTRACT Microalgal microbiomes play vital roles in the growth and health of their host, however, their composition and functions remain only partially characterized, especially across microalgal phyla. In this study, a natural seawater microbiome was introduced to three distinct, axenic species of microalgae, the haptophyte Isochrysis galbana, the chlorophyte Tetraselmis suecica, and the diatom Conticribra weissflogii (previously Thalassiosira), and its divergence and assembly under constant illumination was monitored over 49 days using 16S rRNA amplicon and metagenomic analyses. The microbiomes had a high degree of host specificity in terms of taxonomic composition and potential functions, including CAZymes profiles. Rhodobacteraceae and Flavobacteriaceae families were abundant across all microalgal hosts, but I. galbana microbiomes diverged further from T. suecica and C. weissflogii microbiomes. I. galbana microbiomes had a much higher relative abundance of Flavobacteriaceae, whereas the two other algal microbiomes had higher relative abundances of Rhodobacteraceae. This could be due to the bacterivorous mixotrophic nature of I. galbana affecting the carbohydrate composition available to the microbiomes, which was supported by the CAZymes profile of I. galbana microbiomes diverging further from those of T. suecica and C. weissflogii microbiomes. Finally, the presence of denitrification and other anaerobic pathways was found exclusively in the microbiomes of C. weissflogii, which we speculate could be a result of anoxic microenvironments forming in aggregates formed by this diatom during the experiment. These results underline the significant role of the microalgal host species on microbiome composition and functional profiles along with other factors, such as the trophic mode of the microalgal host.IMPORTANCEAs the main primary producers of the oceans, microalgae serve as cornerstones of the ecosystems they are part of. Additionally, they are increasingly used for biotechnological purposes such as the production of nutraceuticals, pigments, and antioxidants. Since the bacterial microbiomes of microalgae can affect their hosts in beneficial and detrimental ways, understanding these microbiomes is crucial to both the ecological and applied roles of microalgae. The present study advances the understanding of microalgal microbiome assembly, composition, and functionality across microalgal phyla, which may inform the modeling and engineering of microalgal microbiomes for biotechnological purposes.

BACKGROUND AND OBJECTIVES: Greenhouse gas emissions are the primary cause of global warming. Under the Paris Agreement, all countries have developed programs to reduce anthropogenic impact on the environment. In the petrochemical industry, for example, isoprene, is a major contributor to the production of carbon dioxide, generating large amounts of acidic and hydrocarbon gases that are burned and released into the atmosphere. This study aimed to investigate the absorption of greenhouse gases from isoprene production by the marine microalgae Isochrysis galbana and Tetraselmis suecica, as well as the freshwater microalgae Chlorella vulgaris.METHODS: Microalgae cells were cultured in a bioreactor. The grown microalgae strains and mineralized water were fed to the bioreactor. Gases discharged from isoprene production were passed through the bioreactor. Inlet and outlet gas compositions were monitored by chromatography.FINDINGS: Absorption of gases discharged from isoprene production by microalgae was studied for the first time. Chlorella vulgaris microalgae reduced methane and carbon dioxide contents by an average of 20 times. A mixture of microalgae Tetraselmis suecica and Isochrysis galbana reduced methane and carbon dioxide contents by a factor of 10 but completely absorbed hydrocarbon gases from methane to pentane.CONCLUSIONS: The results indicate that microalgae cultivation can be used as a reliable and stable technology for the biofixation of the gases discharged in isoprene production. This technology can eliminate the combustion stage of hydrocarbon gases in isoprene production and significantly reduce carbon dioxide emissions into the atmosphere.

Regarding the widespread use of titanium dioxide nanoparticles (TiO2NPs) in industry, many concerns have been raised about the risks of their potential release into aquatic ecosystems. Among the marine primary producers, Tetraselmis suecica is an ecologically important microalgae species used also as live feed in the shrimp culture industry. In the present study, the impacts of TiO2NPs on growth performance, photosynthetic pigments, lipid and protein content and its interaction with the cells of T. suecica were assessed. Based on the preliminary tests and OECD suggestion, concentrations of 5, 10, 50, 100, 200 and 400 mg/L TiO2NPs were applied to algal cells for 10 days. With increasing concentration, a decrease in T. suecica cell density was observed each day. TiO2NPs induced a half-maximal inhibitory concentration (IC50) of 106.26 mg/L on algal cells on the 3rd day. Chlorophyll a and b contents of the microalga decreased up to 56.08% and 52.74%, respectively following the exposure to TiO2NPs at 400 mg/L. TiO2NPs also decreased the algal contents of protein and lipid up to 7.21% and 50.64%, respectively at the highest concentration. Based on FTIR, FESEM with EDS and mapping analyses, the interaction of TiO2NPs with the T. suecica cells was revealed. The stocks of T. suecica could be damaged by the toxic effects of the released TiO2NPs affecting their application as live feed in mariculture. [ABSTRACT FROM AUTHOR]

Microalgae are one of the promising feedstocks for biorefinery, contributing significantly to net-zero emissions through carbon capture and utilization. However, the disposal of microalgal byproducts from the manufacturing process causes additional environmental pollution, thus, a new application strategy is required. In this study, the Tetraselmis suecica byproduct from the carotenoid extraction process was carbonized and converted into biochar. The converted biochar was proved to be nitrogen-doped biochar (NDB), up to 4.69%, with a specific surface area of 206.59 m2/g and was used as an electrode for a supercapacitor. The NDB electrode (NDB-E) in half-cell showed a maximum specific capacitance of 191 F/g. In a full-cell test, the NDB-E exhibited a high energy density of 7.396 Wh/kg and a high-power density of 18,100 W/kg, and maintained specific capacity of 95.5% after charge and discharge of 10,000 cycles. In conclusion, our study demonstrated that the carotenoid-extracted microalgal byproducts are a useful resource for the supercapacitor production. This approach is the first to convert T. suecica into active materials for supercapacitors. [ABSTRACT FROM AUTHOR]

El Nutrilake y la urea se utilizaron como aporte de nitratos, en cultivos de cuatro especies de microalgas (Chaetoceros muelleri, Thalassiosira weissflogii, Isochrysis sp y Tetraselmis suecica), determinando su efecto y comparándolo con el obtenido usando el medio f. Los cultivos se repitieron tres veces utilizando cuatro réplicas por tratamiento y por especie. En cada experimento se determinó la concentración celular diaria por conteo directo al microscopio, las tasas de división acumulada y estandarizada, los pesos secos total y orgánico y la composición proximal de las microalgas. C. muelleri ofrece las mayores concentraciones celulares con urea y T. weissflogii con Nutrilake. Las tasas de división celular acumulada y estandarizada fueron mayores al final de los cuatro días en C. muelleri con urea y Nutrilake, en T. weissflogii con el medio f, en T. suecica con urea al tercer día y en Isochrysis sp. sólo con la tasa estandarizada al segundo día con Nutrilake. C. muelleri con urea e Isochrysis sp. con Nutrilake mostraron los mayores valores de biomasa seca total. El peso libre de cenizas para C. muelleri fue mayor con urea, para T. weissflogii lo fue con Nutrilake y con el medio f y urea para T. suecica. Los pesos unitarios solo fueron diferentes en T. suecica entre el Nutrilake y urea. La urea produce la mayor concentración proteica en T. weissflogii, Isochrysis sp. y T. suecica, ésta última también con el medio f. Para los carbohidratos T. weissflogii dio significativamente más alto con Nutrilake y el medio f. Los lípidos resultaron ser mayores para T. weissflogii y T. suecica con urea, y para esta última especie también con el medio f.

The anaerobic digestion, AD, process presents a solution for sustainable waste management, greenhouse gas mitigation and energy production for growing population needs and requirements. Adopting a biorefinery approach that utilises different feedstock may enhance energy production and support optimisation of the anaerobic digestion process. Algae is a promising feedstock that could be used for energy production via the anaerobic digestion process. Microalgal biomass is rich in carbohydrates and lipids; however, many species of algae exhibit tough cell walls that could also be difficult to digest and may influence or inhibit the efficiency of the AD process. This study concentrated on the comparison of AD remediation of two marine algal biomass species, Tetraselmis suecica and Nannochloropsis oceanica. The two species were pre-treated with an ultrasound technique and compared for their methane production using biochemical methane potential tests. For Tetraselmis, a specific methane production of 0.165 LCH4/KgVS was observed; however, for Nannochloropsis, a value of 0.101 LCH4/KgVS was observed for the samples treated with ultrasound. The BMP results from this study show that among the two micro-algae species tested, Tetraselmis suecica is found to be a better substrate for methane production potential. Contrary to increasing the specific methane production, ultrasound cavitation caused a slight decrease in the specific methane production values for both Nannochloropsis oceanica and Tetraselmis suecica biomass residues. The pre-treatment of the biomass using ultrasound techniques provided comparable results and can be recommended for effective bioenergy production. However, further research is required for the optimisation of the pre-treatment of microalgae and for the integration of microalgal biorefineries for circular economy. [ABSTRACT FROM AUTHOR]

[Display omitted] • An alternative to deactivate harmful green tide is proposed by employing AgSi and AgAl. • The synthesized AgSi and AgAl nanoparticles both have nanospherical morphology. • AgAl deposited on foamed waste glass achieve inactivation of green tide in 24 h. • AgAl/FWGS have good buoyancy and are easy to handle as a practical option for use in coastal waters. Nowadays harmful bloom tides affect greatly the economy of coastal states. For this reason, the present communication reports on a practical method for synthesizing SiO 2 and γ-alumina nanospheres, immobilized by sonochemistry on low-density porous foams and perlite granules, as a solution to this problem. A biostatic AgNP effect was incorporated into both materials, achieving AgSi and AgAl. The green-tide inactivation was performed by using Tetraselmis suecica under aqueous conditions. AgAl/FWGS displayed the best inactivation efficiency performance (94 %). Additionally, foams have significant buoyancy and are easy to handle, being an option for T. suecica inactivation for their easy recovering. [ABSTRACT FROM AUTHOR]

Change in medium salinity due to evaporation or water addition is one of the significant factors affecting algal culture growth and biomass quality. This study evaluates the effect of different salinities on growth and lipid, protein, and carbohydrate content in the green alga Tetraselmis suecica. Four different concentrations (15 g L−1, 30 g L−1, 60 g L−1, 90 g L−1) of artificial sea salt were used to prepare f medium for the outdoor cultivation of T. suecica. The highest growth (up to 0.66 g L−1 per day) was achieved using a medium with 15 g L−1 salinity, and at higher concentrations of salts, biomass yields tend to be reduced. The highest carbohydrate content (16.1%) was obtained when cultivating T. suecica in a medium with 15 g L−1 salinity. Protein content was significantly affected by the change in salinity, and it was found to be highest (56.9%) at 15 g L−1. Increasing salinity to 90 g L−1 significantly reduced protein content. The highest lipid content (27.7%) was reached with biomass cultivated at 30 g L−1 salinity, while further increase of salt concentration in the medium significantly reduced lipid content. Chlorophyll and total carotenoid content in the biomass varied from 2.8 to 5.5% and from 0.35 to 1.1%, respectively. Higher salinity resulted in a higher overall content of pigments (chlorophyll, carotenoids) but also a higher variation of concentration of these compounds during cultivation. [ABSTRACT FROM AUTHOR]

The anaerobic digestion, AD, process presents a solution for sustainable waste management, greenhouse gas mitigation and energy production for growing population needs and requirements. Adopting a biorefinery approach that utilises different feedstock may enhance energy production and support optimisation of the anaerobic digestion process. Algae is a promising feedstock that could be used for energy production via the anaerobic digestion process. Microalgal biomass is rich in carbohydrates and lipids; however, many species of algae exhibit tough cell walls that could also be difficult to digest and may influence or inhibit the efficiency of the AD process. This study concentrated on the comparison of AD remediation of two marine algal biomass species, Tetraselmis suecica and Nannochloropsis oceanica. The two species were pre-treated with an ultrasound technique and compared for their methane production using biochemical methane potential tests. For Tetraselmis, a specific methane production of 0.165 LCH4/KgVS was observed; however, for Nannochloropsis, a value of 0.101 LCH4/KgVS was observed for the samples treated with ultrasound. The BMP results from this study show that among the two micro-algae species tested, Tetraselmis suecica is found to be a better substrate for methane production potential. Contrary to increasing the specific methane production, ultrasound cavitation caused a slight decrease in the specific methane production values for both Nannochloropsis oceanica and Tetraselmis suecica biomass residues. The pre-treatment of the biomass using ultrasound techniques provided comparable results and can be recommended for effective bioenergy production. However, further research is required for the optimisation of the pre-treatment of microalgae and for the integration of microalgal biorefineries for circular economy.

Microalgal microbiomes play vital roles in the growth and health of their host, however, their composition and functions remain only partially characterized, especially across microalgal phyla. In this study, a natural seawater microbiome was introduced to three distinct, axenic species of microalgae, the haptophyte Isochrysis galbana, the chlorophyte Tetraselmis suecica, and the diatom Conticribra weissflogii (previously Thalassiosira ), and its divergence and assembly under constant illumination was monitored over 49 days using 16S rRNA amplicon and metagenomic analyses. The microbiomes had a high degree of host specificity in terms of taxonomic composition and potential functions, including CAZymes profiles. Rhodobacteraceae and Flavobacteriaceae families were abundant across all microalgal hosts, but I. galbana microbiomes diverged further from T. suecica and C. weissflogii microbiomes. I. galbana microbiomes had a much higher relative abundance of Flavobacteriaceae, whereas the two other algal microbiomes had higher relative abundances of Rhodobacteraceae. This could be due to the bacterivorous mixotrophic nature of I. galbana affecting the carbohydrate composition available to the microbiomes, which was supported by the CAZymes profile of I. galbana microbiomes diverging further from those of T. suecica and C. weissflogii microbiomes. Finally, the presence of denitrification and other anaerobic pathways was found exclusively in the microbiomes of C. weissflogii, which we speculate could be a result of anoxic microenvironments forming in aggregates formed by this diatom during the experiment. These results underline the significant role of the microalgal host species on microbiome composition and functional profiles along with other factors, such as the trophic mode of the microalgal host., Importance: As the main primary producers of the oceans, microalgae serve as cornerstones of the ecosystems they are part of. Additionally, they are increasingly used for biotechnological purposes such as the production of nutraceuticals, pigments, and antioxidants. Since the bacterial microbiomes of microalgae can affect their hosts in beneficial and detrimental ways, understanding these microbiomes is crucial to both the ecological and applied roles of microalgae. The present study advances the understanding of microalgal microbiome assembly, composition, and functionality across microalgal phyla, which may inform the modeling and engineering of microalgal microbiomes for biotechnological purposes., Competing Interests: The authors declare no conflict of interest.

The present study was aimed to assess the effect of gibberellic acids to enhance the growth, biomass, pigment, and exopolysaccharides production in Tetraselmis suecica under reciprocal nitrogen concentrations. For this study, the seven types of experimental media (N-P, NL-P/2GA3, N0-P/2GA3, NL-P/4GA3, N0-P/4GA3, NL-P/6GA3, and N0-P/6GA3) were prepared with the addition of gibberellic acids under various nitrogen concentrations. The experiment lasted for 15 days and the cell density, biomass, chlorophyll 'a', and exopolysaccharides (EPS) concentration of T. suecica were estimated for every 3 days. Then the EPS was subjected to the analyses of chemical (carbohydrate, protein, sulfate, and uronic acid), and antioxidant activity. In addition, nutrient removal efficiency was evaluated using different concentration of EPS. The highest DPPH (2,2-diphenyl-1-picrylhydrazyl) (86.7 ± 0.95%) and hydroxyl radical activity (85.7 ± 2.48%) were observed at the EPS concentrations 2.5 and 1.2 mg/mL, respectively. The immobilized magnetic Fe3O4–EPS (ferric oxide–exopolysaccharides) nanoparticles (5.0 and 10.0 g/L) have efficiently removed the excessive phosphate (89.5 ± 1.65%) and nitrate (73.5 ± 1.72%) from the Litopenaeus vannamei cultured wastewater. Thus, the application of gibberellic acids combined with limited nitrogen concentration could produce higher EPS that could exhibit excellent antioxidant activity, and nutrient removal efficacy in the form of Fe3O4–EPS magnetic nanoparticles. [ABSTRACT FROM AUTHOR]

The exposure-effect study was conducted to evaluate the effect of Co3O4 nanoparticles on Tetraselmis suecica. The growth suppressing effect has been observed during the interaction between nanoparticles and microalgae as indicated by 72 h EC50 (effective concentration of a chemical at which 50% of its effect is observed) value (45.13±3.95 mg/L) of Co3O4 nanoparticles for Tetraselmis suecica. Decline in chlorophyll a content also indicated the compromised photosynthetic ability and physiological state of microalgae. Further biochemical investigation such as increase in extracellular LDH (lactate dehydrogenase) level, ROS (reactive oxygen species), and levels of membrane lipid peroxidation in treated samples signifies the compromised cellular health and membrane disintegration caused by nanoparticles. Parallel to this, the cell entrapment, membrane damage, and attachment of nanoparticles on cell surface were also visualized by SEM-EDX (scanning electron microscope-energy dispersive X-ray) microscopy. The overall results of this study clearly indicated that Co3O4 nanoparticles might have toxic effects on growth of marine microalgae and other aquatic life forms as well. Hence, release of Co3O4 nanoparticles in aquatic ecosystem and resulting ecotoxic effect should be broadly addressed. [ABSTRACT FROM AUTHOR]

Tetraselmis suecica is a green microalga that thrives under a wide range of conditions, used in the commercial culture of fish, mollusk, and crustacean larvae for supplementing the demand for fertilizers. Its pigments have applications in human health care as drug products, vitamins, and cosmetics. Growth and pigment concentration of T. suecica were evaluated in experimental cultures with different nutrient concentrations and light intensities to determine the most appropriate culture conditions to optimize the production of biomass and pigments. Chlorophyll-a, chlorophyll-b, lutein, violaxanthin, a, ß-carotene, and neoxanthin concentrations were evaluated under three different nutrient conditions (441.5/18.1, 883/36.3, and 1766/76.2 µM of NaNO3/NaH2PO4) and four light intensities (50, 150, 300, and 750 µmol quanta m-2 s-1). Increases in either or both of these factors lead to increases in the concentration of all pigments. Chlorophyll-a reached up to 5×103 mg m-3, chlorophyll-b up to 2500 mg m-3, lutein 600 mg m-3, violaxanthin 300 mg m-3, a, ß-carotene 500 mg m-3, and neoxanthin 400 mg m-3. Growth rate (µ) attained values of 1.6 d-1. An index to evaluate the efficiency of pigment production by light intensity (called LER) was computed. The highest LER was recorded at 50 µmol quanta m-2 s-1 and a nutrient concentration of 1766/76.2 µM (NaNO3/NaH2PO4); this treatment optimizes pigment production with the lowest light intensity. Our results show that the optimum light intensity should be selected according to the objective of the culture, either maximizing pigment concentration for harvesting at higher concentrations or reducing production costs regarding light consumption. [ABSTRACT FROM AUTHOR]

The transfer of non-native, possibly invasive species in ship's ballast water is of global concern, and the International Maritime Organization and U.S. Coast Guard have adopted standards to minimize the environmental footprint caused by the maritime industry. In this study, seawater spiked with the phytoplankter Tetraselmis suecica, was treated with Knutsen Ballast Water Treatment Technology (KBAL), combining UV irradiation with an in-line vacuum drop. The test water was subsequently incubated in dark tanks, simulating what happens onboard a ship, where ballast water is treated at intake, stored in dark ballast tanks during the voyage, and then treated at discharge. Our results of the test water treated with KBAL and stored 5 days in the dark showed < 10 viable T. suecica cells ml−1 when assessing reproduction and > 10 living cells ml−1 when assessing metabolism. This highlights the challenge UV-based BWTS can encounter when meeting testing regimes assessing different characteristics of life. By comparing the effects caused by KBAL treatment with effects caused by UV irradiation only, we demonstrated that the pressure/vacuum technology seems to improve the disinfection effect. In addition, our investigations point out possible challenges with in situ conditions getting representative ballast water samples. [ABSTRACT FROM AUTHOR]

Algae and bacteria establish complex relationships reciprocally influencing their growth. Associated bacterial communities alter microalgae metabolism and physiology, affecting biomass yield and quality. In this study, 203 bacterial isolates (33 different genera), recovered from Tetraselmis suecica F&M-M33 cultures, were identified and phenotypically characterized in relation to the microalgal growth-promoting (MGP) features of indol-3-acetic acid (IAA) and siderophore production. IAA production was observed in 30 isolates belonging to 10 genera, whilst siderophore production was observed in 12 isolates belonging to nine genera, indicating that bacteria which are phylogenetically different within the phycosphere community may contribute in similar ways to boosting algal growth. Moreover, strains belonging to a single genus (e.g. Bacillus, Muricauda, Labrenzia and Amorphus) showed different MGP features, but none of these isolates were capable of producing both growth-promoting factors. Twenty-two selected strains were further tested in co-culture assays to evaluate their effect on T. suecica F&M-M33 growth; four induced an increase in microalgal productivity. The exo-metabolome of T. suecica F&M-M33 cultures, either axenically or when co-cultured with either Vitellibacter strain AAD2 or Sphingopyxis flavimaris strain AG5, was determined using a non-targeted metabolomics approach using an Ultra High Performance Liquid Chromatography (UHPLC) system. This allowed for the detection of 133 entities (small chemical molecules, e.g. metabolites), of which 84 were identified. Most of the entities were common in all three cultures, showing that the T. suecica F&M-M33 phycosphere was rich in small peptides and organic acids, and a high number of terpenes were also observed. Seventeen entities were culture-specific, suggesting that they were directly related to microalgae–bacteria interactions. [ABSTRACT FROM AUTHOR]

The present work aims to develop a fast and reliable procedure for motility analysis of a short-term effect of heavy metal cadmium on the algal cell response in laboratory conditions. Three unicellular motile species similar in cell length, while differing in the cell wall and the flagellar system are used as model algae. We quantitatively characterise motility in terms of swimming speed and search radius following addition of 1 mg Cd L−1. Both swimming speed and search radius determined in control algal cultures reflect morphological features of the corresponding flagellated system. After 1 h of cell exposure to a toxic concentration of cadmium, a statistically significant decrease in swimming speed is determined with predominant erratic cell movement on the spot in all examined cultures. After 3 h of cell exposure to cadmium, swimming speed in most of the examined cell cultures recovered close to the control value, indicating quick cell adaptation to elevated cadmium concentration. The results support the implementation of swimming speed and search radius as motility parameters for direct screening of cell physiological state, which is applicable to ecotoxicological studies providing insight into the mechanism of cell adaptation under stress, as well as a better understanding of the spatial distribution of algal cells in aquatic systems. [ABSTRACT FROM AUTHOR]

The eukaryotic green microalga Tetraselmis suecica is commonly used for aquaculture purposes because of its high stress tolerance and ease of culture in a wide spectrum of environments; they are therefore suitable candidates for biotechnology applications. To date, no data are available regarding chloroplast transformation vectors based on specific endogenous promoters and homologous targeting regions. We report on the identification of Tetraselmis suecica genes encoding the ribulose bisphosphate carboxylase/oxygenase large subunit protein, the photosystem II D1 protein and the ATP synthase CF1‐beta subunit protein together with their untranslated regions (5′UTR, 3′UTR). The full‐length ORFs of the putative genes with their regulatory sequences were obtained. We were also able to identify the downstream 3′ end of the large subunit ribosomal RNA gene (23S) along with the 5S RNA end‐to‐end with the psbA gene on the complementary strand. The intergenic region between these genes appears to be a good target site for the integration of target proteins. Moreover, we identified a back‐to‐back promoter region among the rbcL and atpB genes. To assess the bidirectionality activities of both promoters, a dual reporter vector was constructed for Tetraselmis suecica transformation containing the cat and TurboGFP genes driven by the 5′rbcL/5′atpB divergent promoter. The vector included the 23S‐5S and psbA nucleotide sequences as flanking regions. These flanking regions provided suitable insertion sites within the chloroplast genome for cassette integration via homologous recombination. Simultaneous expression of the chloramphenicol‐resistant conferring gene and the gene coding for TurboGFP driven by 5′rbcL/5′atpB showed a potent natural bidirectional promoter as a reliable genetic tool. [ABSTRACT FROM AUTHOR]

The marine flagellated Chlorophyta Tetraselmis suecica is among the most important live food species in marine aquaculture. In the present study, the effects of dietary supplementation of dried marine microalgae, Tetraselmis suecica, on growth performance; feed utilization; chemical composition; gene expression of superoxide dismutase (SOD), glutathione peroxidase (GPx) and insulin‐like growth factor 2 (IGF‐II) gene of Pacific white shrimp, Litopenaeus vannamei; muscle protein polymorphism; and microbial count were assessed and evaluated. Three hundred and sixty L. vannamei (postlarvae) Pls (0.124 ± 0.002 g) were randomly stocked into 40‐L glass aquaria (30 shrimp/aquarium) and fed three times daily four tested diets: a basal diet (control), diet incorporated with 2.5 g kg−1 dried T. suecica (T1), 5 g kg−1 dried T. suecica (T2) and 7.5 g kg−1 dried T. suecica (T3) in triplicates, for 90 days. At the end of the trial, the survival rate (SR) of L. vannamei fed diets supplemented with different levels of T. suecica was significantly (p <.05) higher than the control diet. The highest weight gain and specific growth rate and the best feed conversion ratio were recorded on L. vannamei fed a diet supplemented with a 7.5 g/kg dried T. suecica. The highest protein, lipid and ash contents were obtained in L. vannamei fed the diet containing 7.5 g/kg T. suecica, when compared with the remaining tested diets. The gene expression of antioxidant genes SOD and GPx was the lowest in the T3 group in comparison with the control group. Meanwhile, expression level of IGF‐II was higher in the T2 group. The total heterotrophic bacterial count was significantly (p <.05) increased with the cumulative T. suecica level, while no significant (p >.05) differences were found in the total Vibrio count among treatments. Overall, the present results have shown that the diet supplemented with the highest inclusion level of dried T. suecica resulted in improved growth and nutrient utilization. [ABSTRACT FROM AUTHOR]

In the present study we evaluated the effects of silver nanoparticles (AgNPs) and Tetraselmis suecica chloroform (CHL) crude extracts as single and co-applications against MCF-7 and 4 T1 breast cancer cells and normal Vero cell-lines. The AgNPs single application exhibited the highest cytotoxicity in a dose-dependent manner with IC50 of 5.3, 17.78, and 25.11 μg mL−1 against MCF-7, 4 T1 and Vero cell lines, respectively, after 72 h treatments. The AgNPs-T. suecica-CHL co-application at 2:1 ratio achieved the IC50 of 6.60 and 53.7 μg mL−1 on MCF-7 and 4 T1 cells, respectively, while the T. suecica-CHL single application only showed the IC50 of 46.77 and 83.17 μg mL−1, respectively. However, both the T. suecica-CHL and AgNPs-T. suecica-CHL showed no cytotoxic activity against the Vero cells. The AgNPs-T. suecica-CHL exhibited the highest late apoptotic events on MCF-7 (38.8%), followed by Tamoxifen (TMX), AgNPs and T. suecica-CHL. The cell cycle analysis of AgNPs-T. suecica-CHL–treated cells showed a significant increase in the accumulation of events at sub-G1 phase with increased ADP/ATP ratio and Caspase 3/7, suggesting the induction of apoptosis. The results brought new insights into the formulation of microalgal crude extracts (MCEs) and AgNPs co-applications in exerting strong cytotoxic effects on MCF-7 and 4 T1 cancer cells, but without having any cytotoxicity on the normal Vero cell-lines. [ABSTRACT FROM AUTHOR]

Marine microalgae or phytoplankton are marine microorganisms that act as producers. In addition to their important role in the sea, microalgae also have potential application in medicine and can be a good source of food. This study aims to determine the content of chlorophyll a and chlorophyll b pigments, carotenoids as well as antioxidant activity in samples of Tetraselmis suecica marine microalga using the DPPH (1, 1-diphenyl-2-picrylhydrazyl) method. The research samples were obtained from the Natural Feed Laboratory of the Brackish Water Aquaculture Center (BBPBAP), Jepara. The study included the following stages: sample preparation, sample extraction, and measurements of pigment content and antioxidant activity using DPPH method. The results showed that acetone extract of marine microalga Tetraselmis suecica contained 1.688 mg/g of chlorophyll a, 0.713 mg/g of chlorophyll b, and 5.380 µg/g of carotenoid, as well as an IC50 value of 37.320 ppm. It was concluded that the antioxidant activity of the Tetraselmis suecica was very strong, i.e. the IC50 value found was less than 50 ppm. [ABSTRACT FROM AUTHOR]

By answering the need for increasing sustainability in aquaculture, the present study aimed to compare growth, gene expression involved in appetite regulation, physical characteristics, and chemical composition of Sparus aurata fed alternative protein sources. Fish were fed ten iso-proteic, iso-lipidic, and isoenergetic diets: a vegetable-based (CV) and a marine ingredient-rich (CF) diet were set as control diets. The others were prepared by replacing graded levels (10, 20 or 40%) of the vegetable proteins in the CV with proteins from a commercial defatted Hermetia illucens pupae meal (H), poultry by-product meal (PBM) singly (H10, H20, H40, P20, P40) or in combination (H10P30), red swamp crayfish meal (RC10) and from a blend (2:1, w:w) of Tisochrysis lutea and Tetraselmis suecica (MA10) dried biomasses. The increase in ghre gene expression observed in MA10 fed fish matched with increased feed intake and increased feed conversion ratio. Besides, the MA10 diet conferred a lighter aspect to the fish skin (p < 0.05) than the others. Overall, no detrimental effects of H, PBM, and RC meal included in the diets were observed, and fish fatty acid profile resulted as comparable among these groups and CV, thus demonstrating the possibility to introduce H, PBM, and RC in partial replacement of vegetable proteins in the diet for Sparus aurata.

In this work, a marine microalga Tetraselmis suecica was pyrolyzed in a fixed-bed reactor in the presence of a series of zeolite (Si/Al = 30) supported Ni catalysts to increase the hydrocarbon composition of the pyrolysis oil by a two-step process - devolatilization followed by catalytic treatment. A 3 wt% Ni-loading on zeolite showed the highest hydrocarbon content of 55.38%, in which aliphatic hydrocarbons and aromatic hydrocarbons were 35.21% and 20.17%, respectively. Besides, the oxygen-containing compounds decreased from 42.88% to 9.55% while the nitrogen-containing compounds decreased from 40.68% to 35.07%. The activity of the Ni-loaded catalysts was found to increase up to 3 wt % Ni-loading and decrease at higher loadings in similar lines to catalyst acidity measurements. Besides, the catalytic activity decreased with an increase in crystallite size of Ni at higher Ni loadings. The results indicate that the Ni-loaded catalysts can deoxygenate pyrolysis oils, but it is necessary to address the removal of the nitrogenous compounds. Pyrolysis temperature and Ni-loading play an important role in the removal of oxygen and nitrogen from the bio-oil. The quality of the bio-oil can be affected by the presence of strong acid sites, nickel-loading and the pore size. Image 1 • Effects of different Ni-loadings in heteroatom removal investigated. • 3% Ni-loading zeolite contributed to high hydrocarbon production (55.38%). • Strong acid sites and large pore size facilitated catalyst performance. • Catalytic pyrolysis conditions optimized by Response Surface Methodology. • The minimum oxygen-containing compounds was 9.55% under optimum conditions. [ABSTRACT FROM AUTHOR]

The biosynthesis of metallic nanoparticles (NPs) has been previously reported using a variety of organic molecules produced by microalgae. However, the results obtained could vary due to the metabolic responses that microalgae have to different culture conditions which could affect the characteristics of the produced nanoparticles. In the present report, copper nanoparticle formation was evaluated by the microalgae Chlorella kessleri, Dunaliella tertiolecta, and Tetraselmis suecica, developed under combined conditions of low (L−) and high (L+) illumination, with low (S−) and high salinity (S+). The illumination was 12 h:12 h light/dark. NP formation was evaluated 72 h after exposure to copper salt. Cupric oxide (CuO) NPs were detected spectrophotometrically in both the culture media (extracellular NPs) and cells (intracellular NPs) of Ch. kessleri with absorbance in the range of 200 to 235 nm. Metallic copper NPs (Cun) were detected with an absorbance between 540 and 560 nm in treatments with cells of C. kessleri and D. tertiolecta which were grown in L+S−, while T. suecica cells showed Cun NPs formations in L−S−, L−S+, and L+S−. The size difference of the NPs was measured by scanning electron microscopy (SEM), in treatments with cells of C. kessleri, ranging in size from 15 to 25 nm (L−S−) and 55 to 65 nm (L+S−). In treatments with culture media, sizes from 35 to 45 nm (L−S−) of NPs were obtained. Differences in the biosynthesis of Cu-based NPs are possible, depending on the culture conditions and the strain of microalgae to be utilized. [ABSTRACT FROM AUTHOR]

Bacteria associated with microalgae strongly affect algal biomass and derived product yield and quality. Nevertheless, only a few studies have addressed the detailed phylogenetic characterization of bacterial communities associated with microalgae. In this study, the phycospheric bacterial communities associated with different Tetraselmis suecica F&M-M33 cultures, a green marine microalga with several industrial applications, were analysed using a metagenomic approach. The T. suecica F&M-M33 cultures used originated from the same ancestral microalgal non-axenic culture but were physically and geographically separated for years and maintained under different growing conditions. Despite the different history of the cultures, a 'core' bacterial community was identified, accounting for 70% of the total bacterial community and formed by at least 13 families. Among the 'core' operational taxonomic units (OTUs), 24 different genera were identified. Nevertheless, there was a high variability in the relative proportions of the taxa forming the 'core' community, indicating that the growing conditions and/or external contamination influence the relative abundance of these microorganisms. Our study allowed the identification of persistent taxa that may be used to deepen the knowledge of the complex relationship between T. suecica and its associated bacteria. [ABSTRACT FROM AUTHOR]

The carotenoid profiles of biomass from five eukaryotic microalgae, Porphyridium cruentum, Isochrysis galbana, Phaeodactylum tricornutum, Tetraselmis suecica and Nannochloropsis gaditana, produced at an industrial plant in outdoor photobioreactors, were investigated. Pigments were solvent-extracted after an ultrasonic pre-treatment and separated by HPLC-photodiode-array using a reversed-phase C18 column. Microalgae showed species-specific carotenoid profiles. Carotenoids were mostly in their free form, with a prevalence of xanthophylls over carotenes. Beta-carotene was the only carotenoid common to all species. The Rhodophyta P. cruentum exhibited the lowest total carotenoid content (167.2 mg 100 g−1 dw) and the simplest profile, with (all- E)-zeaxanthin (94.2 mg 100 g−1 dw, 56% of total carotenoids) and (all- E)- β – carotene (53.4 mg 100 g−1 dw, 32% of total carotenoids) as the major carotenoids. The Haptophyta Isochrysis galbana and the Bacillariophyta Phaeodactylum tricornutum were the species with the highest total carotenoid content (1760 mg and 1022 mg 100 g−1 dw, respectively). These species were characterized by similar carotenoid profiles, with (all- E)-fucoxanthin as the chief compound (1346 mg and 776.8 mg 100 g−1 dw for I. galbana and P. tricornutum , respectively), accounting for about 76% of total carotenoids. The Chlorophyta Tetraselmis suecica was the species showing the greatest variety of carotenoids, with both α - carotene and β - carotene and their derivatives present. (All- E)-lutein (85.4 mg 100 g−1 dw) and (all- E)-violaxanthin (81.8 mg 100 g−1 dw) were the major pigments in this species. In the Ochrophyta Nannochloropsis gaditana, (all- E)-violaxanthin was the prevalent carotenoid (336.7 mg 100 g−1 dw), followed by (all- E)-β-carotene (100.1 mg 100 g−1 algal dw). The carotenoid content of the microalgal biomass studied compared favourably to that of major vegetable sources. Due to their characteristics, these microalgae, most of them currently finding their main application in aquaculture, may be also regarded as valuable sources of carotenoids to be used in the formulation of functional food and nutraceuticals. Unlabelled Image • Microalgae showed species-specific carotenoid profiles. • Carotenoids were mostly in their free form, with a prevalence of xanthophylls over carotenes. • β-carotene was the only carotenoid common to all species. • Carotenoid levels compared favourably to those of high food sources. [ABSTRACT FROM AUTHOR]

• Toxicogenomic responses of HSPs in marine green algae Tetraselmis suecica. • TsHSPs were differentially involved in defense responses to environmental stress. • TsHSPs were not significantly upregulated by thermal and non-redox-active metals. • Redox-active metals considerably inhibit photosynthesis & induce considerable ROS. • Metal toxicity was specifically affected by the conjugated anion in metal compounds. Microalgae are capable of tolerating variations in water temperature and sudden exposures to toxic substances, and cellular heat shock proteins (HSPs) help to protect cells from such stress. Here, we determined the complete open reading frames (ORF) of small TsHSP20 and large TsHSP70 and 100 in the chlorophyte Tetraselmis suecica , and examined the expression levels of these genes after exposure to thermal stressors, redox-active metals, and non-redox-active metals. Putative TsHSP20, TsHSP70, and TsHSP100 proteins had conserved HSP-family motifs with different C-terminus motifs. Phylogenetic analyses of individual HSPs showed that T. suecica clustered well with other chlorophytes. Real-time PCR analysis showed that thermal stress did not significantly change the expression of all the tested TsHSPs. In addition, TsHSP20 showed little gene expression after being exposed to copper, whereas TsHSP70 and 100 genes greatly responded to the redox-active metals in CuSO 4 followed by CuCl 2 , but not to the non-redox active metals. Redox-active metals strongly affected the physiology of the cells, as judged by cell counting, reactive oxygen species imaging and photosynthetic efficiency. These findings suggest that small and large HSPs are differentially involved in the response against environmental stressors. Moreover, metal toxicity may be specifically controlled by the anions in the metal compounds. [ABSTRACT FROM AUTHOR]

Salinity is an important factor affecting microalgal production yield especially under the uncontrollable environments of outdoor cultivation systems. Elucidating the optimal salinity range for algal biomass and high-value biochemical production might help to increase the production potential and reduce cultivation cost. This study examined the effects of salinity changes from that of normal seawater level (30 ppt) to various salinities from 10 to 60 ppt on growth, biomass, photosynthesis, morphology, biochemical composition, fatty acid composition, and volumetric productivity of the marine microalga Tetraselmis suecica. The optimal salinity for biomass production of T. suecica was in the range from 20 to 60 ppt. Severe growth inhibition, alterations in cell morphology, and reduction of photosynthetic rate were found at low salinity of 10 ppt, suggesting that the algal cells suffered from osmotic and ionic imbalance. Total protein, carbohydrate, and lipid content were not significantly affected under the different salinities, although the increase in salinity from 30 to 50 and 60 ppt improved the total lipid productivity by nearly 22%. Fatty acid composition and content remained unchanged over the range of salinities. The predominant fatty acids were of C16 to C18 chain lengths, whereas eicosapentaenoic acid (EPA) was the major long-chain polyunsaturated fatty acid (LC-PUFA). Together these results demonstrate that a wide range of salinities are suitable for cultivation of in T. suecica without a compromise in biomass yield and biochemical composition. [ABSTRACT FROM AUTHOR]

The green microalga, Tetraselmis suecica, is commonly used in scientific, industrial, and aquacultural purposes because of its high stress tolerance and ease of culture in wide spectrums of environments. We hypothesized that carotenoids help to protect Tetraselmis cells from environmental stress by regulating genes in biosynthetic pathways. Here, we determined three major carotenogenic genes, phytoene synthase (PSY), phytoene desaturase (PDS), and β-lycopene cyclase (LCY-B) in T. suecica, and examined the physiological parameters and gene expression responses when exposed to redox-active metals and non-redox-active metals. Phylogenetic analyses of each gene indicated that T. suecica clustered well with other green algae. Real-time PCR analysis showed that TsPSY, TsPDS, and TsLCY-B genes greatly responded to the redox-active metals in CuSO4 followed by CuCl2, but not to the non-redox-active metals. The redox-active metals strongly affected the physiology of the cells, as determined by cell counting, reactive oxygen species (ROS) imaging, and photosynthetic efficiency. This suggests that carotenoids protect the cells from oxidative damage caused by metals, thereby contributing to cell survival under various stress conditions. [ABSTRACT FROM AUTHOR]

Bacteria are remarkably associated with the growth of green algae Tetraselmis which are used as a feed source in aquaculture, but Tetraselmis-associated bacterial community is characterized insufficiently. Here, as a first step towards characterization of the associated bacteria, we investigated the community composition of free-living (FLB) and particle-associated (PAB) bacteria in each growth phase (lag, exponential, stationary, and death) of Tetraselmis suecica P039 culture using pyrosequencing. The percentage of shared operational taxonomic units (OTUs) between FLB and PAB communities was substantially high (≥92.4%), but their bacterial community compositions were significantly (p = 0.05) different from each other. The PAB community was more variable than the FLB community depending on the growth phase of T. suecica. In the PAB community, the proportions of Marinobacter and Flavobacteriaceae were considerably varied in accordance with the cell number of T. suecica, but there was no clear variation in the FLB community composition. This suggests that the PAB community may have a stronger association with the algal growth than the FLB community. Interestingly, irrespective of the growth phase, Roseobacter clade and genus Muricauda were predominant in both FLB and PAB communities, indicating that bacterial communities in T. suecica culture may positively affect the algae growth and that they are potentially capable of enhancing the T. suecica growth.

Microalgae have been attracting attention as feedstock for biorefinery because they have various advantages, such as carbon fixation, high growth rate and high energy yield. The bioactive compounds and lutein contained in microalgae are known to be beneficial for human health, especially eye and brain health. In this study, in order to improve the recovery of bioactive extracts including lutein from Tetraselmis suecica with higher efficiency, an effective solvent was selected, and the extraction parameters such as temperature, time and solid loading were optimized by response surface methodology. The most effective solvent for lutein recovery was identified as 100% methanol, and the optimum condition was determined (42.4 °C, 4.0 h and 125 g/L biomass loading) by calculation of the multiple regression model. The maximum content of recovered lutein was found to be 2.79 mg/mL, and the ABTS radical scavenging activity (IC50) and ferric reducing antioxidant power (FRAP) value were about 3.36 mg/mL and 561.9 μmol/L, respectively. Finally, the maximum lutein recovery from T. suecica through statistical optimization was estimated to be 22.3 mg/g biomass, which was 3.1-fold improved compared to the control group.

Microalgae harvesting is an important part in microalgae cultivation system. Techniques for harvesting marine microalgae which are commonly used are centrifugation, filtration and flocculation. These techniques still have some disadvantages, such as not environment friendly, and high usage of energy and cost. Bio-flocculation harvesting technique using microalgae as a flocculant agent can be an alternative way to solve these problems. In this research, mixing of Tetraselmis suecica (flocculant) with Chlorella sp. and Nannochloropsis sp. (non-flocculant) in ratios of 1:4, 2:4, 3:4 and 4:4 (v/v) has been conducted to obtain percent recovery of marine microalgae harvest. The results showed that T. suecica as flocculant agent can fasten the harvesting of Chlorella sp. and Nannochloropsis sp. It was shown by the increase of percent recovery value of Chlorella sp. from 51.14 ± 1.07% to 67.34 ± 0.67% and Nannochloropsis sp. from 20.52 ± 1.17% to 42.43 ± 0.40% during the first hour of flocculating process. Our result showed that bio-flocculation is an environment friendly technique which can be applied to harvest marine microalgae.

The antioxidant activity of natural compounds consists in their ability to modulate gene and protein expression, thus inducing an integrated cell protective response and repair processes against oxidative stress. New screening tools and methodologies are crucial for the actual requirement of new products with antioxidant activity to boost endogenous oxidative stress responsive pathways, Reactive Oxygen Species (ROS) metabolism and immune system activity, preserving human health and wellness. In this study, we performed and tested an integrated oxidative stress analysis, using DPPH assay and PNT2 cells injured with DPPH. We firstly investigated the mechanism of action of the oxidising agent (DPPH) on PNT2 cells, studying the variation in cell viability, oxidative stress genes, inflammatory mediator and ROS levels. The results reveal that DPPH activated ROS production and release of Prostaglandin E2 in PNT2 at low and intermediate doses, while cells switched from survival to cell death signals at high doses of the oxidising agent. This new in vitro oxidative stress model was validated by using Trolox, β-carotene and total extract of the green microalga Testraselmis suecica. Only the T. suecica extract can completely counteract DPPH-induced injury, since its chemical complexity demonstrated a multilevel protecting and neutralising effect against oxidative stress in PNT2.

Marine microalgae produce extracellular metabolites such as exopolysaccharides (EPS) with potentially beneficial biological applications to human health, especially antioxidant and antitumor properties, which can be increased with changes in crop trophic conditions. This study aimed to develop the autotrophic and heterotrophic culture of Tetraselmis suecica (Kylin) Butcher in order to increase EPS production and to characterize its antioxidant activity and cytotoxic effects on tumor cells. The adaptation of autotrophic to heterotrophic culture was carried out by progressively reducing the photoperiod and adding glucose. EPS extraction and purification were performed. EPS were characterized by Fourier-transform infrared spectroscopy and gas chromatography-mass spectrometry. The antioxidant capacity of EPS was analyzed by the 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) method, and the antitumor capacity was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, showing high activity on human leukemia, breast and lung cancer cell lines. Although total EPS showed no cytotoxicity, acidic EPS showed cytotoxicity over the gingival fibroblasts cell line. Heterotrophic culture has advantages over autotrophic, such as increasing EPS yield, higher antioxidant capacity of the EPS and, to the best of our knowledge, this is the first probe that T. suecica EPS have cytotoxic effects on tumor cells; therefore, they could offer greater advantages as possible natural nutraceuticals for the pharmaceutical industry.

Studies considering broodstock conditioning of Ruditapes decussatus mostly used flagellates and diatoms for feeding, mainly Isochrysis galbana and Chaetoceros calcitrans, respectively. The present study evaluated the effect of different microalgal diets on gonadic maturation of R. decussatus including three microalgae species (C. calcitrans, Tetraselmis suecica, and Nannochloropsis oculata) which were used to prepare six diets: three monospecific and three bispecific mixed diets at a proportion of 1:1. Clams were daily fed at a ratio of 1% dry weight of algae/live weight of clam and unfed treatment was used as control. Results showed that clams fed C. calcitrans alone or mixed with T. suecica attained earlier full maturity with the highest response to spawning induction (after 34 conditioning days) and largest proportion in the partial spawning phase for both, followed by T. suecica alone after 48 days. In contrast, N. oculata alone or mixed diets demonstrated poor performance for gonadal maturation. Unfed treatment did not show any sign of maturation. The results indicated that T. suecica has high conditioning potential like C. calcitrans and their mixture gave the highest benefit. Therefore, T. suecica can be recommended for R. decussatus broodstock conditioning. [ABSTRACT FROM AUTHOR]

The marine green microalga, Tetraselmis suecica, is an important food source for aquaculture, lipid source for biofuel production, and a potential model organism for toxicity assays because of its rapid growth and ability to produce useful chemicals. In order to gain molecular toxicogenomic insights, we determined expressed sequence tags (ESTs) of T. suecica by pyrosequencing, and attained 741 K reads, including 290 Mb of cDNA information. Upon data processing, 24,651 contigs and 19,072 non-overlapping fragments were acquired and deposited to the NCBI non-redundant and gene ontology databases. Of these, 11,292 contigs and 1848 singletons were annotated. From the EST data, we found that many previously identified stress-responsive protein-coding genes were included. The data were further investigated with a focus on heat shock protein (HSP) gene families, with most characterized HSP genes present in our ESTs. In addition, the expression of HSP70 and HSP90 was significantly increased after T. suecica cells were exposed to metal contaminants. This work expands our understanding of stress-related genomics of T. suecica and further evaluates a potential use of oxidative stress-related genes as biomarkers, in particular HSP involvement in environmental genomics and marine toxicological assessment. [ABSTRACT FROM AUTHOR]

This paper presents a novel portable sample filtration/concentration system, designed for use on samples of microorganisms with very low cell concentrations and large volumes, such as water-borne parasites, pathogens associated with faecal matter, or toxic phytoplankton. The example application used for demonstration was the in-field collection and concentration of microalgae from seawater samples. This type of organism is responsible for Harmful Algal Blooms (HABs), an example of which is commonly referred to as “red tides”, which are typically the result of rapid proliferation and high biomass accumulation of harmful microalgal species in the water column or at the sea surface. For instance, Karenia brevis red tides are the cause of aquatic organism mortality and persistent blooms may cause widespread die-offs of populations of other organisms including vertebrates. In order to respond to, and adequately manage HABs, monitoring of toxic microalgae is required and large-volume sample concentrators would be a useful tool for in situ monitoring of HABs. The filtering system presented in this work enables consistent sample collection and concentration from 1 L to 1 mL in five minutes, allowing for subsequent benchtop sample extraction and analysis using molecular methods such as NASBA and IC-NASBA. The microalga Tetraselmis suecica was successfully detected at concentrations ranging from 2 × 10 5  cells/L to 20 cells/L. Karenia brevis was also detected and quantified at concentrations between 10 cells/L and 10 6  cells/L. Further analysis showed that the filter system, which concentrates cells from very large volumes with consequently more reliable sampling, produced samples that were more consistent than the independent non-filtered samples (benchtop controls), with a logarithmic dependency on increasing cell numbers. This filtering system provides simple, rapid, and consistent sample collection and concentration for further analysis, and could be applied to a wide range of different samples and target organisms in situations lacking laboratories. [ABSTRACT FROM AUTHOR]

Microalgae represent the most promising new source of biomass for the world’s growing demands. However, the biomass productivity and quality is significantly decreased by the presence of bacteria or other invading microalgae species in the cultures. We therefore report a low-cost spiral-microchannel that can effectively separate and purify Tetraselmis suecica (lipid-rich microalgae) cultures from Phaeodactylum tricornutum (invasive diatom). Fluorescent polystyrene-microbeads of 6 μm and 10 μm diameters were first used as surrogate particles to optimize the microchannel design by mimicking the microalgae cell behaviour. Using the optimum flowrate, up to 95% of the P. tricornutum cells were separated from the culture without affecting the cell viability. This study shows, for the first time, the potential of inertial microfluidics to sort microalgae species with minimal size difference. Additionally, this approach can also be applied as a pre-sorting technique for water quality analysis. [ABSTRACT FROM AUTHOR]

Dynamic filtration equipped with a perforated disk was adopted for the first time to dewater and concentrateTetraselmis suecica, from a typical solution of 2–100 g/L of dense biomass suited for the downstream process. An ultrafiltration membrane, polyethersulfone 150 kDa, was found to best perform in terms of high biomass retention and filtration rate. At 1600 rpm, the highest rotation speed of the disk we tested, plateau permeate flux increased up to 20.2 times higher than those with no rotation; this improvement was attributed to fouling reduction (up to 98%) via distinctively high-shear stress on the membrane surface. Even at a high biomass concentration (100 g/L) where fouling formation was very serious, the heightened shear stress caused high flux to be maintained and fouling resistance to be reduced in an effective way. When trans-membrane pressure was increased in a stepwise manner, flux continuously rose at high rotation speed; at low speed, on the other hand, the limiting flux was observed. The dynamic filtration with the perforated disk, which was an effective high-shear stress generator, was proven to be a promising dewatering means ofT. suecica, and especially so for the production of highly concentrated biomass. [ABSTRACT FROM AUTHOR]

The outburst of microbial resistance to antibiotics creates the need for new sources of active compounds for the treatment of pathogenic microorganisms. Marine microalgae are of particular interest in this context because they have developed tolerance and defense strategies to resist the exposure to pathogenic bacteria, viruses, and fungi in the aquatic environment. Although antimicrobial activities have been reported for some microalgae, natural algal bioactive peptides have not been described yet. In this work, acid extracts from the microalga Tetraselmis suecica with antibacterial activity were analyzed, and de novo sequences of peptides were determined. Synthetic peptides and their alanine and lysine analogs allowed identifying key residues and increasing their antibacterial activity. Additionally, it was determined that the localization of positive charges within the peptide sequence influences the secondary structure with tendency to form an alpha helical structure.

Algae have come into prominence over the last decade as a commercial biofuel feedstock due to their high production efficiencies compared to first and second feedstocks. However, algal investment is not economically feasible currently due to the operational and capital cost. There is still need for innovations for both high productivity and green productions. In order to decrease the cost of the algal processes, usage of some wastes as cultivation medium for algal productions and novel biofuel production methods should be considered according to green chemistry principals. In this study, seawater and wastewater supplied from Istanbul Water and Sewerage Administration (ISKI) were used and combined at different ratios to be utilized as a growth medium for Nannochloropsis oculata and Tetraselmis suecica microalgae strain under the same growth conditions, and its effect on cell proliferation and growth kinetics were investigated. It was found that, both N. oculata and T. suecica can tolerate and utilize the wastewater and, the specific growth rate of the cultures can up to 0.5430 d-1 (75% of wastewater) for N. oculata and 0.4778 d-1 (25% of wastewater) for T. suecica. Different concentrations show different results for the growth of two species due to the effect of higher concentrations of the fundamental sources on growth stage and change of ionic composition of the culture medium. To evaluate bioethanol production performance of these two strains, samples which included maximum carbohydrate content as well as control groups were chosen for further studies. The results showed that T. suecica is much suitable for ethanol production using municipal wastewater as a culture medium. [ABSTRACT FROM AUTHOR]

In the last years, applications for silver nanoparticles (Ag NPs) continue to increase together with the concerns about their potential input and hazards in aquatic ecosystems, where microalgae are key organisms. The aim of the present study was to assess the relative sensitivity of three marine microalgae species with differences in cell wall composition/structure exposed to Poly N-vinyl-2-pirrolidone/Polyethyleneimine (PVP/PEI) coated 5 nm Ag NPs and uncoated 47 nm Ag NP. As limited attention has been paid to the role of coating agents in NP toxicity, the effect of PVP/PEI alone was also evaluated. After 72 h in artificial seawater, 47 nm Ag NPs formed around 1400 nm size aggregates while PVP/PEI coated 5 nm Ag NPs reached around 90 nm. Ag + release in seawater was around 3% for 47 nm Ag NPs and 30% for PVP/PEI coated 5 nm Ag NPs. PVP/PEI coated 5 nm Ag NP aggregates entrapped the algal cells in a network of heteroaggregates, while uncoated 47 nm Ag NPs interacted to a lesser extent with algae. The concentration of PVP/PEI coated 5 nm Ag NPs that exerted the median effect (EC50) on algae growth pointed out differences in algae sensitivity: T . suecica was about 10 times more sensitive than I . galbana and P . tricornutum . Further, the coating agent alone was as toxic to algae as PVP/PEI coated 5 nm Ag NPs, suggesting that presence of the coating agent was the main driver of toxicity of coated NPs. Uncoated 47 nm Ag NPs instead, showed similar toxicity towards algae although P . tricornutum was slightly less sensitive than T . suecica and I . galbana , which agrees with the presence of a resistant silicified cell wall in the diatom. The present work demonstrates differences in sensitivity of three marine microalgae, possibly related to their cell surface and size characteristics. [ABSTRACT FROM AUTHOR]

The Biological CO2 assimilation process using marine phytoplankton and marine bivalve was evaluated by carbon assimilation of the green mussel Perna viridis fed with Tetraselmis suecica under laboratory condition. Incorporation of carbon dioxide into phytoplankton biomass was performed through aeration. The experiment consisted of three treatments i.e. mussels without feeding (Control), mussels fed with T. suecica cultured with air (Treatment 1: T-Air), and mussels fed with T. suecica cultured with 1.5% CO2 in air (Treatment 2: T-CO2). The results showed that growth of mussels in T-Air and T-CO2 was 22.4 ± 4.0 mg/individual/day and 28.9 ± 12.3 mg/individual/day, respectively, which was significantly higher than control (mussels without feeding). Growth of mussels in T-Air was significantly lower than in T-CO2. Carbon content in shell (15.59 ± 0.57 % D.W.) and meat (38.28 ± 1.72 % D.W.) of mussels fed with aerated T. suecica (T-Air) was significantly higher than that found in mussels fed with 1.5% CO2 T. suecica (14.2 ± 0.47 and 36.61± 0.43 % D.W. in shell and in meat, respectively) (p≤0.05). With T-Air, 1.95±0.27 and 9.36±1.24% of carbon from T. suecica cells was assimilated into shell and meat of the mussel, respectively, while in T-CO2 , carbon assimilation from T. suecica cells in shell and meat was 2.19±0.55 and 11.22±2.76% respectively.

The growth of Tetraselmis suecica was evaluated. The experiment was realized using the Response Surface Methodology (RSM) with Central Composite Rotational Design (CCRD) with two factors, pH and sanguaza/seawater concentration in the range of 7 - 9 and 2 - 5 % (v/v), respectively. The culture media were stirred by bubbling air constantly (0.07 L/s) and continuously illuminated with 40 W of fluorescent light in glass containers of 1.5 L capacity at a temperature of 22.5 ± 2.1 °C. Using the Gompertz mathematical model was determined that from an 8.0 of pH and a ratio of 3.5% of sanguaza/seawater, the Tetraselmis suecica achieves maximum growth. An 8.71 of pH and a ratio of 4.56% of sanguaza/seawater allow the Tetraselmis suecica maximum growth (logN/N0) of 0.659, with a 12.3% of prediction error by applying a mathematical model of 2nd order. According to the study, the values obtained in sanguaza/seawater as a culture medium outperformed the traditionally used culture medium (Guillard F/2 with seawater). The results demonstrate the potential use of the sanguaza/seawater medium in scalable studies on pilot scale production of Tetraselmis suecica, with a view to the production of biodiesel