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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]

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 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]

[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]

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]

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]

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]

The objective of this techno-economic analysis (TEA) was to define the production cost of the microalga Tetraselmis suecica in a 1-ha plant made of “Green Wall Panel-II” (GWP®-II) photobioreactors. The study was based on an energy analysis carried out for a similar plant located in Tuscany (Italy) and considers the steps from inoculum preparation to the wet algal paste. Costs of equipment and materials were obtained from manufacturers and suppliers, while operating costs and output data (e.g. biomass composition and productivity) were collected during several years of trials at the Fotosintetica & Microbiologica S.r.l. facilities (Florence, Italy). Other data were obtained from Microalghe Camporosso S.r.l. (Imperia, Italy), where a commercial 1500-m 2 GWP®-I plant is in operation and two 250-m 2 GWP®-II modules were built and used in the framework of the EU project BIOFAT. This TEA shows that, given a productivity of 36 tonnes per hectare per year, T. suecica biomass can be produced at a cost of €12.4 kg − 1 (dry weight). Using conservative assumptions it was estimated that at the 100-ha scale the cost will be €5.1 kg − 1 . Locating the plant in more favorable climatic conditions (e.g. in Tunisia) will allow reaching 54 tonnes per hectare annually and reducing cost to €6.2 kg − 1 at the 1-ha scale and to €3.2 kg − 1 at the 100-ha scale. The major cost factors are labor at 1-ha scale in Tuscany and capital expenses in all the other cases. This TEA confirms that microalgal technologies have high potential not only for high-value, but also for medium- and low-value products, while the production of biofuels, protein, food and feed seems currently out of reach. However, the global scenario of agriculture commodities is rapidly changing and other factors (e.g. sustainability), besides a pure economic evaluation, will assume greater importance in the future. [ABSTRACT FROM AUTHOR]

The cell growth rate and cellular lipid content of microalgae are affected by the nitrogen levels during cultivation. The growth rate and lipid content of marine microalga Tetraselmis sp. was found to increase under nitrate replete conditions, but not under deplete conditions. Thus, in order to enhance the lipid productivity of Tetraselmis sp., a two-stage culture process utilizing nitrate replete condition was applied. When the cells were cultivated in F/2 medium for five days in the first stage, the obtained lipid content and productivity were 22.4% and 26.7 mg L −1 d −1 , respectively. After second stage of cultivation for a further 36 h under nitrate replete conditions with 8.82 mM NaNO 3 , increased biomass concentration of 1.32 g L −1 and lipid content of 30.5% were obtained, with an enhanced lipid productivity of 47.3 mg L −1 d −1 . [ABSTRACT FROM AUTHOR]

Demand for long chain ω-3 fatty acids from non-fish source for vegetarians has increased recently. Marine microalgae are the primary producers of EPA/DHA and promising alternatives for fish oil. Tropical areas have abundant sunlight throughout the year for microalgal cultivation but this practice can be hindered by high temperature. Discovery of heat-tolerant marine microalgae that can synthesize EPA/DHA will solve these problems. A new species of microalga was isolated from a high temperature lagoon and identified as Tetraselmis sp. DS3. These cells could grow at 40 °C, the highest temperature for marine microalgal growth ever reported. Its ω-3 fatty acids and EPA accounted for 33 and 10% of total lipids, respectively, grown in nitrogen-depleted conditions. These cells also accumulated more than 5% β-carotene and 0.48% lutein in biomass. This new microalga can be cultivated for long chain ω-3 fatty acids and lutein production in the tropical areas. [ABSTRACT FROM AUTHOR]

The annual productivity of Tetraselmis suecica in a 1-ha Green Wall Panel-II (GWP-II) plant in Tuscany (Italy) is 36 t (dry weight) ha − 1 year − 1 , which corresponds to an energy output of 799 GJ ha − 1 year − 1 . The energy inputs necessary to attain that productivity amount to 1362 GJ ha − 1 year − 1 , mainly given by the embodied energy of the reactor (about 30%), mixing (about 40%), fertilizers (11%) and harvesting (10%). The Net Energy Ratio (NER) of T. suecica production is thus 0.6. In a more suitable location (North Africa) productivity nearly doubles, reaching 66 t ha − 1 year − 1 , but the NER increases only by 40% and the gain (difference between output and inputs) remains negative. In a GWP-II integrated with photovoltaics (PV), the NER becomes 1.7 and the gain surpasses 600 GJ ha − 1 year − 1 . Marine microalgae cultivation in a GWP plant, in a suitable location, can attain high biomass productivities and protein yields 30 times higher than those achievable with traditional crops (soya). When the GWP reactor is integrated with PV, the process attains a positive energy balance, which substantially enhances its sustainability. [ABSTRACT FROM AUTHOR]

• T. chui efficiently accumulates up to 59% starch under nitrogen deprivation. • Recovery from stress begins within 12 h after nutrient replenishment. • Nitrogen deprivation has a strong impact on regulation of starch-related genes. • Gene expression results challenge the traditional starch metabolism model. • Post-transcriptional regulatory mechanisms seem to play a crucial role in T. chui. Tetraselmis chui is known to accumulate starch when subjected to stress. This phenomenon is widely studied for the purpose of industrial production and process development. Yet, knowledge about the metabolic pathways involved is still immature. Hence, in this study, transcription of 27 starch-related genes was monitored under nitrogen deprivation and resupply in 25 L tubular photobioreactors. T. chui proved to be an efficient starch producer under nitrogen deprivation, accumulating starch up to 56% of relative biomass content. The prolonged absence of nitrogen led to an overall down-regulation of the tested genes, in most instances maintained even after nitrogen replenishment when starch was actively degraded. These gene expression patterns suggest post-transcriptional regulatory mechanisms play a key role in T. chui under nutrient stress. Finally, the high productivity combined with an efficient recovery after nitrogen restitution makes this species a suitable candidate for industrial production of high-starch biomass. [ABSTRACT FROM AUTHOR]

Highlights: [•] Bacteria were present over the whole harvest/recycle process at large scale. [•] Electroflocculation had little effect over the bacterial community. [•] Bacteria found within this study are a symbiotic partner to Tetraselmis sp. [ABSTRACT FROM AUTHOR]

Abstract: The iron uptake and storage systems of terrestrial/higher plants are now reasonably well understood with two basic strategies being distinguished: strategy I involves the induction of a Fe(III)-chelate reductase (ferrireductase) along with Fe(II) or Fe(III) transporter proteins while strategy II plants have evolved sophisticated systems based on high-affinity, iron specific, binding compounds called phytosiderophores. In contrast, there is little knowledge about the corresponding systems in marine, plant-like lineages. Herein we report a study of the iron uptake and storage mechanisms in the green alga Tetraselmis suecica. Short term radio-iron uptake studies indicate that iron is taken up by Tetraselmis in a time and concentration dependent manner consistent with an active transport process. Based on inhibitor and other studies it appears that a reductive–oxidative pathway such as that found in yeast and the green alga Chlamydomonas reinhardtii is likely. Upon long term exposure to 57Fe we have been able, using a combination of Mössbauer and X-ray absorption spectroscopies, to identify three metabolites. The first exhibits Mössbauer parameters typical of a [Fe4S4]2+ cluster and which accounts for approximately 10% of the total intracellular iron pool. The second displays a spectrum typical of a [FeIIO6] system accounting for approximately 2% of the total pool. The largest component (ca. 85+%) consists of polymeric iron-oxo mineral species with parameters between that of the crystalline ferrihydrite core of animal ferritins and the amorphous hydrated ferric phosphate of bacterial and plant ferritins. [Copyright &y& Elsevier]

Abstract: Nannochloropsis sp. F&M-M24 and Tetraselmis suecica F&M-M33 were cultivated outdoors in Green Wall Panels under nutrient deficiency to stimulate oil synthesis. Under nitrogen deprivation, Nannochloropsis attained average biomass and lipid productivities of 9.9 and 6.5gm−2 day−1, respectively. Starved Tetraselmis cultures achieved a biomass productivity of about 7.6gm−2 day−1 and a lipid productivity of 1.7gm−2 day−1. Lipids represented 39.1% and 68.5% of non-starved and starved Nannochloropsis biomass, respectively. Starvation did not increase lipid content in Tetraselmis biomass. Important differences in lipid classes and in fatty acid composition were observed under the different cultivation conditions for both microalgae. [Copyright &y& Elsevier]

Abstract: The marine prasinophyte Tetraselmis suecica was grown in a chemostat culture system over a series of phosphate-limited growth rates ranging from 0.164 to 0.755d−1. The relationship between phosphate concentration and growth rate was well described by the Monod equation with a half-saturation constant of 3.45nM. The kinetics of short-term uptake of phosphate spikes were well described by the Michaelis–Menten equation, maximum uptake rates being 2–3 orders of magnitude higher than associated growth rates. The relationship between cellular carbon-to-phosphorus ratios and growth rates was consistent with the Droop formulation of nutrient-limited growth, and chlorophyll a/carbon ratios were linearly related to growth rate. The protein content of the cells inferred from calculated nitrogen-to-carbon ratios ranged from a minimum of ~7% at zero growth rate to a maximum of ~59% at a relative growth rate of 1.0. Control of the relative growth rate of T. suecica via selection of the phosphate concentration in the growth medium and dilution rate of the culture appears to be an effective and practical way to manipulate the biochemical composition of this species in order to maximize its nutritional value to invertebrate consumers in aquaculture systems. [Copyright &y& Elsevier]

Abstract: Juvenile or adult Artemia sp. are often used as live prey for the rearing of early life stages of some crustacean, fish and cephalopod species. The improvements of both Artemia growth and its biochemical composition are key issues for the suitable use of Artemia biomass in these rearing processes. In this study we evaluated the growth and survival rates of Artemia fed with the cryptophyte Rhodomonas lens in comparison with different microalgal species commonly used in aquaculture: the prasinophyte Tetraselmis suecica, the prymnesiophyte Isochrysis galbana Parke, and the eustigmatophyte Nannochloropsis gaditana. Microalgae were cultured semi-continuously in nutrient saturated conditions and with a daily renewal rate of 30% of the volume of cultures, to obtain biomass of controlled and optimized composition. Considerable differences in Artemia growth were observed, as well as in the survival rate. At day 8 of rearing, Artemia fed R. lens had the highest length (4.9±0.6mm, P <0.001), followed by individuals fed T. suecica (4.2±0.7mm), I. galbana (3.6±0.7mm) and finally those fed N. gaditana (1.5±0.2mm). The survival rate of Artemia fed N. gaditana (18±3%) was much lower (P <0.001) than values found for the remaining groups (69 to 88%). The growth rate of Artemia obtained with R. lens was in general much higher than with other microalgal diets previously reported in the literature. The higher protein content of R. lens could explain the higher growth obtained with this species, but differences of Artemia growth with the different diets could not be explained solely on the basis of the gross composition of microalgae. Factors such as cell size and digestibility all seem to contribute to the results observed. Another trial was carried out to investigate differences in Artemia growth and on its biochemical composition when fed the best two diets: R. lens or T. suecica. The fatty acid (FA) and total amino acid (AA) composition of both microalgal species and the composition of Artemia were assessed as well. As found in the first experiment individuals fed R. lens (group ARHO) grew faster than those fed T. suecica (group ATET), attaining 3.6±0.3mm and 3.2±0.4mm (P <0.001), respectively, after 5days of rearing. The much higher AA content obtained in R. lens may be on the basis of the higher growth obtained with this species. Protein and carbohydrate levels in Artemia juveniles were very similar in both groups (64–68% of dry weight, and 8–10%, respectively). Lipid was slightly lower in ARHO (12%) than in ATET (15%, P <0.01). Regarding the FA composition, juveniles from group ARHO contained higher levels of eicosapentaenoic acid (EPA, 6.2%) than juveniles from ATET (4.1%, P <0.01), whereas docosahexaenoic acid (DHA) was only found in juveniles from ARHO (1.1%). Taking into account that the daily productivity of R. lens culture was higher than, or at least equal, the remaining microalgal species this cryptophyte is confirmed as an excellent diet to optimize the growth of Artemia, as well as to improve its biochemical composition. [Copyright &y& Elsevier]

Abstract: ECOTOX is an automatic early warning system to monitor potential pollution of freshwater, municipal or industrial waste waters or aquatic ecosystems. It is based on a real time image analysis of the motility and orientation parameters of the unicellular, photosynthetic flagellate Euglena gracilis. In order to widen the use of the device to marine habitats and saline waters nine marine flagellates were evaluated as putative bioassay organisms, viz. Dunaliella salina, Dunaliella viridis, Dunaliella bardawil, Prorocentrum minimum Kattegat, P. minimum Lissabon, Tetraselmis suecica, Heterocapsa triquetra, Gyrodinium dorsum and Cryptomonas maculata. Because of their slow growth the last three strains were excluded from further evaluation. Selection criteria were ease of culture, density of cell suspension, stability of motility and gravitactic orientation. The sensitivity toward toxins was tested using copper(II) ions. The instrument allows the user to automatically determine effect-concentration (EC) curves from which the EC50 values can be calculated. For the interpretation of the EC curves a sigmoid logistic model was proposed which proved to be satisfactory for all tested strains. The inhibition of the motility was considered as the most appropriate movement parameter as an endpoint. The Dunaliella species had the lowest sensitivity to copper with EC50 values of 220, 198 and 176mg/L for D. salina, D. bardawil and D. viridis, respectively, followed by T. suecica with an EC50 value of 40mg/L. The Prorocentrum species were found to be the most sensitive with an EC50 value of 13.5mg/L for P. minimum Lissabon and 7.5mg/L for P. minimum Kattegat. [Copyright &y& Elsevier]

This paper reports the results of a complete kinetic study, based on thermogravimetric characterisation, to compare the performance of Nannochloropsis sp. and Tetraselmis sp. microalgae during pyrolysis and combustion with air, enriched air and oxygen. The analysis has been carried out including both the single- and multi-step approach studying the effect of different model-free methods and heating rates. In addition, the study brings together the pseudo-components (obtained by peaks deconvolution) model and master plot methodology to discriminate the kinetic model followed by the different processes with the aim to determine the kinetic triplet (activation energy, reaction order and pre-exponential factor). It results that the thermal decomposition of the microalgae cannot be represented by a single reaction mechanism for the whole conversion range, but several parallel decomposition reactions have been taken into account, and the kinetics have been assessed from each decomposition kinetic of the pseudo-components. The kinetic profiles can be interpreted as the combined effects of reaction-order (F), nucleation (A), exponential nucleation (P) and geometrical contraction (R) mechanisms. Image 1 • Pyrolysis and combustion processes with air, enriched air and oxygen are compared. • Single- and multi-step approach studying the effect of different model-free methods. • Deconvolution DTG-peaks and integral-master plot methodology. • Effect of the model-free methods on the accuracy of the master plot method. • Kinetic profile interpreted as combined effect of F, A, P and R reaction mechanisms. [ABSTRACT FROM AUTHOR]

Several species of the genus Tetraselmis (Chlorodendrophyceae, Chlorophyta) were recently discovered to possess unsuspected biomineralization capacities: they produce multiple intracellular inclusions of amorphous calcium carbonate (ACC), called micropearls. Early light-microscopists had spotted rows of refractive granules in some species, although without identifying their mineral nature. Scanning electron microscope (SEM) observations showed that the distribution of the micropearls in the cell forms a pattern, which appears to be characteristic for a given species. The present study shows that this pattern correlates with the shape of the chloroplast, which differs between Tetraselmis species, because micropearls align themselves along the incisions between chloroplast lobes. This was observed both by SEM and in live cells by light microscopy (LM) using Nomarski differential interference contrast. Additionally, molecular phylogenetic analyses, of rbcL and ITS2 gene sequences from diverse strains of Chlorodendrophyceae, corroborated the morphological observations by identifying two groups among nominal Tetraselmis spp. that differ in chloroplast morphology, micropearl arrangement, and ITS2 RNA secondary structure. [ABSTRACT FROM AUTHOR]