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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]

[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]

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 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]

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]

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 transfer of invasive organisms by ballast-water discharge has become a growing concern. UV treatment has become an attractive ballast water treatment technology due to its effectiveness, no harmful disinfection byproducts and easiness to handle. Two robust algae strains Microcystis viridis and Tetraselmis suecica were selected as indicator organisms to determine efficiency of medium-pressure (MP) UV-treatment on ballast water. Inactivation and potential repair of these two algae strains following MP UV irradiation were assessed under various turbidity, total organic carbon (TOC) and salinity conditions. The investigated range of UV doses was from 25 to 500 mJ/cm 2 . For M. viridis, results indicated that disinfection efficiency was negatively correlated with all of these three factors at low doses (25–200 mJ/cm 2 ). Photoreactivation and dark repair were promoted at high TOC levels (6–15 mg/L) with about 6–25% higher repair levels compared with those in distilled water, whereas no significant impacts were identified for turbidity and salinity on both of the photoreactivation and dark repair. For T. suecica, increased turbidity and TOC levels both hindered the performance of UV irradiation at high doses (200–500 mJ/cm 2 ). Suppressive effects on photoreactivation and dark repair were consistently observed with changes of all of the three factors. In conclusion, generally these three factors resulted in repressive effects on UV disinfection efficiency, and TOC played a more significant role in the levels of reactivation than the other two. The responses of T. suecica to these three factors were more sensitive than M. viridis . [ABSTRACT FROM AUTHOR]

This study investigates different UV doses (mJ/cm 2 ) and the effect of dark incubation on the survival of the algae Tetraselmis suecica , to simulate ballast water treatment and subsequent transport. Samples were UV irradiated and analyzed by flow cytometry and standard culturing methods. Doses of ≥ 400 mJ/cm 2 rendered inactivation after 1 day as measured by all analytical methods, and are recommended for ballast water treatment if immediate impairment is required. Irradiation with lower UV doses (100–200 mJ/cm 2 ) gave considerable differences of inactivation between experiments and analytical methods. Nevertheless, inactivation increased with increasing doses and incubation time. We argue that UV doses ≥ 100 mJ/cm 2 and ≤ 200 mJ/cm 2 can be sufficient if the water is treated at intake and left in dark ballast tanks. The variable results demonstrate the challenge of giving unambiguous recommendations on duration of dark incubation needed for inactivation when algae are treated with low UV doses. [ABSTRACT FROM AUTHOR]

Carbohydrate composition of the marine microalgae, Tetraselmis suecica was characterized following acidic and enzymatic hydrolysis. Monitoring intracellular starch as a function of cultivation time at varying nitrate concentrations showed a maximum cellular starch content of 45% of dry biomass when grown under nitrate depleted conditions. Characterization of the cell wall methanolysates using GC/MS showed that the monosaccharide composition did not change in response to the nitrate concentration and consisted of 54% 3-deoxy- d - manno -oct-2-ulosonic acid (Kdo), 17% 3-deoxy- lyxo -2-heptulosaric acid (Dha), 21% galacturonic acid and 6% galactose. Presence of up to 5% Kdo in the dry weight of T. suecica established in this study demonstrates the potential of the cell wall of this species as a feedstock for Kdo, a sugar that is difficult to obtain by chemical synthesis and that has applications in medicinal chemistry. [ABSTRACT FROM AUTHOR]

Wastewater from a fish farm was remediated in a continuously operated tubular photobioreactor in which Tetraselmis suecica was cultured. The N and P removal efficiencies and the productivity of T. suecica growing on the wastewater were determined. Possibilities to optimize the productivity by adding extra orthophosphate were investigated. At a biomass concentration of 0.5 g L −1 on only wastewater, the N and P removal efficiencies were 49.4% and 99.0%, respectively. When extra phosphate was dosed to the wastewater, a 95.7% N removal efficiency and a 99.7% P removal efficiency could be reached at a biomass concentration of 1.0 g L −1 . This also resulted in significantly higher average net volumetric productivity ranging from 0.35 g L −1 d −1 at a biomass concentration of 0.5 g L −1 to 0.46 and 0.52 g L −1 d −1 at biomass concentrations of 0.75 and 1.0 g L −1 , respectively. This study shows the feasibility of an integrated multi-trophic aquaculture approach where wastewater from the fish farms is used to produce feed for juvenile shellfish at high productivity and constant quality. [ABSTRACT FROM AUTHOR]

The effect of cooling at night on the 24 hour productivity and biochemical composition of Tetraselmis suecica cultivated in a tubular photobioreactor was determined. The hypothesis that cooling at night would decrease the night respiration rate and therefore enhance the net productivity was rejected. The productivity over a 24 hour period and biochemical composition were only influenced by the daily light input. Higher carbohydrate and lower protein content were observed in periods with more light. Carbohydrates produced during daylight were used for the protein synthesis at night, while the fatty acid content stayed constant during the day. The rate of carbohydrate loss at night was linearly related to the specific growth rate and therefore to the light history of the microalgae. [ABSTRACT FROM AUTHOR]

Abstract: The effect of biomass concentration on the net volumetric productivity, yield on light and nightly biomass loss rate of Tetraselmis suecica was studied using a pilot-scale tubular photobioreactor (PBR) under outdoor light conditions. The net average productivity and yield on light of Tetraselmis suecica were optimal at a biomass concentration of 0.7gL−1. Cultures grown at higher biomass concentrations showed a prolonged respiration period at low light periods, while light was wasted in more dilute cultures at high light intensities. At optimal biomass concentration of 0.7gL−1 the highest average net productivity and yield on light were 0.35±0.03gL−1 d−1 and 1.19±0.15gmol−1, respectively. The highest nightly biomass loss rate was measured for Tetraselmis suecica grown at an optimal biomass concentration, which can be explained by higher maintenance costs of the microalgae with a higher growth rate. This study shows that the productivity and yield on light can be enhanced by optimizing the biomass concentration. [Copyright &y& Elsevier]

Ensuring efficient growth performance and fish welfare, while improving aquafeed sustainability is a major challenge of the aquaculture sector. To reduce the dependence from unsustainable marine-derived raw materials and to counteract the negative side-effects of vegetable protein sources, functional feeds represent an interesting solution. The present study explored the nutraceutical effects of low dietary inclusions of conventional feed additives (nucleotides and sodium butyrate) and novel potential feed supplements such as Louisiana red claw crayfish (Procambarus clarkii) meal (RCM) and dried microbial biomass from Tetraselmis suecica (TS) and Artrhospira platensis (AP) during a 104-day-feeding trial performed on juvenile rainbow trout (Oncorhynchus mykiss). Four test diets were formulated starting from a basal diet rich in vegetal protein sources (CV) including 0.25% of conventional feed additives (CV plus) or replacing 10% of dietary crude protein supplied by plant protein-rich ingredients of the basal diet CV with the test ingredients (RCM, TS and AP). Through a multidisciplinary approach, fish responses to the different dietary formulations were evaluated in terms of growth performance, gut welfare and immune response. Results obtained showed that all the test diets exerted an ameliorative effect on fish responses compared to CV one. CV plus and AP diets did not impair growth but resulted only in a marginal amelioration of gut health status that remained highly affected. Differently, TS and RCM diets led to a slight worsening of zootechnical parameters compared to the CV diet but were able to improve the overall welfare and preserve the structural integrity of distal intestine. • A multidisciplinary approach was used to determine fish intestine and liver health in response to conventional and innovative feed additives. • The combination of sodium butyrate and nucleotide as supplement in a plant-protein based diet marginally ameliorate gut health. • The dietary inclusion of 9% A. platensis ensured the best fish growth performances among the feed supplements. • Fish fed 10% P. clarkii or T. suecica dietary inclusion showed a significant improve of distal intestine health status. [ABSTRACT FROM AUTHOR]

Abstract: As implementation of the Ballast Water Convention draws nearer a major challenge is the development of protocols which accurately assess compliance with the D-2 Standard. Many factors affect the accuracy of assessment: e.g. large volume of ballast water, the shape, size and number of ballast tanks and the heterogeneous distribution of organisms within tanks. These factors hinder efforts to obtain samples that truly represent the total ballast water onboard a vessel. A known cell density of Tetraselmis suecica was added to a storage tank and sampled at discharge. The factors holding period, initial cell density and sampling interval affected representativeness. Most samples underestimated cell density, and some tanks with an initial cell density of 100cellsml−1 showed <10cellsml−1 at discharge, i.e. met the D-2 standard. This highlights difficulties in achieving sample representativeness and when applied to a real ballast tank this will be much harder to achieve. [Copyright &y& Elsevier]

Abstract: Synthetic zero-valent nano-iron (nZVI) compounds are finding numerous applications in environmental remediation owing to their high chemical reactivity and versatile catalytic properties. Studies were carried out to assess the effects of three types of industrially relevant engineered nZVI on phytoplankton growth, cellular micromorphology and metabolic status. Three marine microalgae (Pavlova lutheri, Isochrysis galbana and Tetraselmis suecica) were grown on culture medium fortified with the nano-Fe compounds for 23days and subsequent alterations in their growth rate, size distribution, lipid profiles and cellular ultrastructure were assessed. The added nano Fe concentrations were either equimolar with the EDTA-Fe conventionally added to the generic f/2 medium (i.e. 1.17×10−5 M), or factor 10 lower and higher, respectively. We provide evidence for the: (1) broad size distribution of nZVI particles when added to the nutrient rich f/2 media with the higher relative percentage of the smallest particles with the coated forms; (2) normal algal growth in the presence of all three types of nZVIs with standard growth rates, cellular morphology and lipid content comparable or improved when compared to algae grown on f/2 with EDTA-Fe; (3) sustained algal growth and normal physiology at nZVI levels 10 fold below that in f/2, indicating preference to nanoparticles over EDTA-Fe; (4) increased total cellular lipid content in T. suecica grown on media enriched with uncoated nZVI25, and in P. lutheri with inorganically coated nZVIpowder, when compared at equimolar exposures; (5) significant change in fatty acid composition complementing the nZVIpowder-mediated increase in lipid content of P. lutheri; (6) a putative NP uptake mechanism is proposed for I. galbana via secretion of an extracellular matrix that binds nZVIs which then become bioavailable via phagocytotic membrane processes. [Copyright &y& Elsevier]

Abstract: Optimization of medium composition for the improvement of heterotrophic cultivation of green microalgae, Tetraselmis suecica, was performed using response surface methodology (RSM). Heterotrophic cultivation of T. suecica was conducted in total darkness using Walne medium formulated with natural sea water. Initially, the effect of two types of carbon source (glucose and sodium acetate) and various types of nitrogen source (peptone, yeast extract, meat extract, malt extract, urea, sodium nitrate and ammonium nitrate) on growth of T. suecica was studied. The concentration of medium component that was found to significantly influence the heterotrophic growth of T. suecica (glucose, peptone, yeast extract and meat extract) was further optimized using RSM. The medium that consists of 5.78g/L glucose, 9g/L peptone, 4.48g/L yeast extract and 3.01g/L meat extract was found optimal for heterotrophic cultivation of T. suecica. The final cell concentration (28.88g/L) obtained in heterotrophic cultivation using this optimized medium was about 3 and 2 times higher than obtained in photoautotrophic culture (8.40g/L) and non-optimized medium for heterotrophic cultivation (13.81g/L), respectively. In addition, the cell yield based on glucose consumed (9.31g cell/g glucose) was increased by about 3 times as compared to non-optimized medium (3.61g cell/g glucose). [ABSTRACT FROM AUTHOR]

Abstract: As fossil fuel prices increase and environmental concerns gain prominence, the development of alternative fuels from biomass has become more important. Biodiesel produced from microalgae is becoming an attractive alternative to share the role of petroleum. Currently it appears that the production of microalgal biodiesel is not economically viable in current environment because it costs more than conventional fuels. Therefore, a new concept is introduced in this article as an option to reduce the total production cost of microalgal biodiesel. The integration of biodiesel production system with methane production via anaerobic digestion is proved in improving the economics and sustainability of overall biodiesel stages. Anaerobic digestion of microalgae produces methane and further be converted to generate electricity. The generated electricity can surrogate the consumption of energy that require in microalgal cultivation, dewatering, extraction and transesterification process. From theoretical calculations, the electricity generated from methane is able to power all of the biodiesel production stages and will substantially reduce the cost of biodiesel production (33% reduction). The carbon emissions of biodiesel production systems are also reduced by approximately 75% when utilizing biogas electricity compared to when the electricity is otherwise purchased from the Victorian grid. The overall findings from this study indicate that the approach of digesting microalgal waste to produce biogas will make the production of biodiesel from algae more viable by reducing the overall cost of production per unit of biodiesel and hence enable biodiesel to be more competitive with existing fuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Basic Oxygen Furnace Slag (BOFS) as a novel attachment substrate for microalgae. • Attached cultivation of Tetraselmis suecica on BOFS yielded 2.52 mg/g slag. • Process parameter optimization increased the yield to 6.38 mg/g slag. • Slag with attached microalgae can be further used as seeds for regrowth. • BOFS slag with attached Tetraselmis biomass could be a potential artificial reef. Attached cultivation of microalgae is a suitable strategy for attaining high biomass productivity with effortless harvesting. This study evaluates the feasibility of using Basic Oxygen Furnace Slag (BOFS) as a carrier for microalgae cultivation. Among the three indigenous microalgae (namely, Chlorella sorokiniana PTC13, Tetraselmis suecica SC5, and Nannochloropsis oceanica DG), which were examined for their capability of attached growth on BOFS, T. suecica SC5 showed the best attached-growth performance (2.52 mg/g slag). Optimizing the cultivation parameters (agitation rate, 200 rpm; added sodium acetate, 1 g/L; light intensity, 300 µmol/m2/s) further enhanced the attached biomass yield to 6.38 mg/g slag. The microalgae-attached slag can be used as the seed for re-growth for three additional cycles and the biomass yield and productivity both enhanced from 6.00 to 11.58 mg/g slag and 497 to 760 mg/L/d, respectively. This study demonstrated the potential of using T. suecica SC5-attached BOFS to construct artificial reefs. [ABSTRACT FROM AUTHOR]

Abstract: In this study, 120-l annular columns were used to cultivate Tetraselmis suecica outdoors. The mass transfer at different aeration rates and the influence of the harvest rate on productivity and biochemical composition were investigated. The potential of the system was evaluated by estimating productivity at full-scale. Two different arrangements to simulate a full-scale plant and determine the “overall areal productivity” (OAP) were experimented with. In August 2003, one experimental column (full-scale column) was placed between seven dummy columns. All the reactors were positioned at a distance of 0.8 m wall to wall and centred at the vertices of equilateral triangles. A second experimental column (isolated column) was placed in a separate area under full sunlight. In August 2004, the columns were placed side by side in an east–west oriented row at a distance of 0.24 m wall to wall. In the first experiment, the mean volumetric productivity of the full-scale column was not significantly lower than that achieved by the isolated column (0.46 against 0.49 g l−1 day−1) in spite of the shading by the dummy units. The average OAP and efficiency of conversion of visible solar radiation (PE) were 36.3 g m−2 day−1 and 9.4%, respectively. In the second experiment, the full-scale column attained a mean volumetric productivity of 0.42 g l−1 day−1. The OAP and the PE were 38.2 g m−2 day−1 and 9.3%, respectively. [Copyright &y& Elsevier]

Batch experiments with Dunaliella tertiolecta and Tetraselmis suecica were performed to investigate alpha-tocopherol (α-T) production in time, in order to assess the effect of light availability per cell on the production of this antioxidant. In D. tertiolecta α-T content increased during growth, in other words, as the cell density increased and the light availability per cell decreased. In T. suecica the pattern was different: α-T content was highest during the exponential phase, decreased significantly during the linear phase and increased again towards the end of the cultivation. Chlorophyll (chl-a) content of T. suecica cells decreased after the exponential phase, instead of the expected increase typically observed in shade-adapted cells, suggesting that the culture was nutrient limited. An experiment with extra nutrients showed that chl-a and α-T content increased significantly during both the linear and the stationary phase when compared with values in nutrient-deficient conditions. No correlation between α-T and chl-a was observed. Our results indicate that diminished light availability does not limit α-T production in D. tertiolecta and T. suecica, opening up the possibility of using high cell density, light-limited cultures for the production of this commercially interesting compound. [Copyright &y& Elsevier]

The amount of ingredients of marine origin used in salmonid feed industry is rapidly decreasing and fish meal and fish oil have been largely replaced by vegetable ingredients. New potential protein rich ingredients for aquafeed formulations should therefore be alternative to vegetable ones. The pattern of fillet pigmentation was thus assessed in rainbow trout (Oncorhynchus mykiss) fed for 15 weeks isoproteic (42%) and isolipidic (24%) diets deprived of fish meal where 10% of protein from a blend of vegetable ingredients was replaced by cyanobacteria and microalgae dried biomass (Arthrospira platensis , Tisochrysis lutea and Tetraselmis suecica) or Louisiana red swamp crayfish (Procambarus clarkii) meal. An automatic, repeatable, and objective image analysis tool for the integrated determination and direct visualization of fillet colour was applied to digital images. Colour of fillets was also measured with a chromameter, recording data as L* , a* , b* indexes and used to validate image analysis results. Fillet carotenoid and lipid contents were determined, and their pattern of variation was compared to that obtained by image analysis. Fillet colouring capacity of crayfish meal was also compared to that of commercial synthetic astaxanthin included in rainbow trout feed. To this last aim, test diets were administered for 12 additional weeks. The image analysis and colorimetric data consistently indicated that, even if characterized by a significantly higher carotenoid content respect to fish fed a vegetable diet, fillets of trout fed the cyanobacteria and microalgae including diets displayed an undesirable yellowish colour. P. clarkii meal instead resulted a promising functional ingredient to supplement plant protein-based diets for trout, in view of its lipid composition and astaxanthin content. In fact, despite a relatively low dietary carotenoid level due to low percentage of inclusion, a desirable pink pigmentation was clearly detectable in fillets of trout fed the crayfish meal-including diet, which resulted in colour differences which were less obvious relative to those of fish given the astaxanthin-supplemented feeds at the end of the additional 12 weeks. • Appropriate inclusion of Procambarus clarkii meal in vegetable-based diets for rainbow trout improve fillet pigmentation; • The use of Arthrospira , Tetraselmis and Tisochrysis as a source of carotenoids is not optimal for rainbow trout; • A new image analysis tool was successfully applied to the characterization of fillet pigmentation. [ABSTRACT FROM AUTHOR]

Phytoplankton occupies a key trophic level in aquatic ecosystems. Chemical impacts on these primary producers can disrupt the integrity of an entire ecosystem. Two freshwater (Pseudokirchneriella subcapitata -Ps and Scenedesmus obliquus -S) and three marine (Phaeodactylum tricornutum -P, Isochrysis galbana -I , Tetraselmis suecica -T) microalgae species were exposed to dilutions of four chemicals: nanoparticles (n-TiO 2 , n-ZnO), amoxicillin (antibiotic), and white musk (personal care fragrance) to determine the half maximal effective concentration (EC 50) after 72 h of exposure under standardized and controlled environmental conditions. Cell cultures were exposed to EC 50 to determine sublethal effects (72 h) based on biochemical (chlorophylls a, b, c), molecular (changes in outer cell wall structure), and morphological alterations. We report for the first time EC 50 values for nanoparticles in not standardized species (S, I and T) and for amoxicillin and white musk in all tested species. Standardized species (Ps and P) were less sensitive than non-standardized in some cases. Fourier-transformed infrared spectroscopy showed a marked spectral alteration (from 10.44% to 90.93%) of treated cultures compared to negative controls; however, principal component analysis disclosed no differences in molecular alteration between the five microalgae species or the two aquatic habitats considered. There was a significant decrease in chlorophylls content in all species exposed to EC 50 compared to controls (Kruskal Wallis test; p < 0.05). There was a significant increase in cell-size (Mann–Whitney U test; p < 0.05) in I, P and T exposed to white musk and S exposed to amoxicillin. Findings highlight ecotoxicological risks from new generation pollutants for primary producers in aquatic ecosystems. [Display omitted] • Effects of new generation pollutants on five phytoplankton species were determined. • EC 50 values for amoxicillin and white musk were reported for the first time. • μFT-IR showed a marked spectral alteration of treated cultures compared to controls. • A significant decrease in chlorophylls in all species exposed to EC 50 was observed. • Changes in cell size, when significant, were an increase in maximum cell length. [ABSTRACT FROM AUTHOR]

Standardised microalgal toxicity assays are usually carried out with single-species cultures; however, multispecies bioassays are more faithful to environmental conditions. The aim of this study was to assess the toxicity of the emerging pollutant bisphenol A (BPA) in single- and multispecies bioassays with three marine microalgae (Tetraselmis suecica , Phaeodactylum tricornutum and Nannochloropsis gaditana) using an equivalent initial cell biovolume of each species. After conducting preliminary growth experiments on these microalgae, a BPA concentration of 1 mg L−1 was chosen to study the effects of this pollutant in uni- and multialgal cultures. Growth, cell viability, oxidative stress, and inherent cell properties (size, complexity and autofluorescence) were determined by flow cytometry after 24 h of exposure. Results showed that P. tricornutum was the most affected species in all analysed biomarkers in both single- and multispecies bioassays. However, in N. gaditana cultures no significant differences were observed in any of the parameters and conditions tested, indicating that this species was the least sensitive to BPA. Between the uni- and multialgal tests, significant differences were observed in controls and BPA treated cultures of P. tricornutum and T. suecica. Nevertheless, it seemed that the cells of these marine microalgae suffered a similar pattern of alterations in both toxicity tests. Unlabelled Image • Toxicity of bisphenol A on single- and multispecies microalgal cultures was tested. • P. tricornutum was the most sensitive species to the BPA concentration assayed. • The concentration of BPA tested did not cause cytotoxicity on N. gaditana. • Inherent cell properties were the most affected biomarkers. • Microalgae suffered a similar response pattern in uni- and multialgal bioassays. [ABSTRACT FROM AUTHOR]

Due to the increasing number of ecosystem invasions with the introduction of exogenous species via ballast water, the International Maritime Organization adopted the Ballast Water Convention (BWMC). The BWMC establishes standards for the concentration of viable organisms in a ballast water discharge. Ultraviolet (UV) irradiation is commonly used for treating ballast water; however, regrowth after UV irradiation and other drawbacks have been reported. In this study, improvement in UV treatment with the addition of hydrogen peroxide or peroxymonosulfate salt was investigated using the microalgae Tetraselmis suecica as the target organism. Results reported that each of these reagents added in a concentration of 10 ppm reduced the concentration of initial cells by more than 96%, increased the UV inactivation rate, and enabled reaching greater level of inactivation with the treatment. These improvements imply a reduction of the UV doses required for a consistent compliance with the BWMC standards. Unlabelled Image • We have treated Tetraselmis suecica with ultraviolet irradiation and reagents. • Reduction of viable organisms was determined by growth modeling. • Treatment with only UV had a maximum level of inactivation achievable. • Addition of hydrogen peroxide or peroxymonosulfate enhanced microalgae inactivation. • UV combined with reagents at 10 ppm enabled compliance with international standards. [ABSTRACT FROM AUTHOR]

Tetraselmis suecica was cultivated in a semi-continuously operated tubular photobioreactor fed on aquaculture wastewater (AW) testing two hydraulic retention times (HRT): 10 and 7 days (RUN_1 and RUN_2, respectively). The integrated mechanistic model BIO_ALGAE was validated with experimental data in order to simulate the biomass production and nutrient uptake of T. suecica. Moreover, AW was used as substitute synthetic cultivation medium to test the production of lipids, proteins, and carbohydrates in the microalgal biomass. Preliminary photo-respirometric tests were carried out on the AW suspension containing microalgae and bacteria. Dissolved Inorganic Nitrogen (DIN) and Dissolved Inorganic Phosphorus (DIP) were analyzed for the two RUNs, and no significant difference was highlighted (p > 0.05). On the contrary, the productivity of the Total suspended solids (TSS) was significantly higher (p < 0.05) for RUN_1 (900 mg TSS/L) than for RUN_2 (550 mg TSS/L). The analysis of the biochemical composition of biomass has demonstrated a higher content of proteins than of lipids and carbohydrates for the two RUNs. BIO_ALGAE model was validated by comparing simulated results to experimental data. The model was able to reproduce the pattern of these experimental data quite well, for both nutrient uptake and biomass production. The simulated curve follows the same pattern as the experimental data for both RUNs. The wavelike trend indicates the good accuracy of the simulated curves to reproduce the microalgae growth and nutrient uptake that occurring during daytime and at night. With this study, BIO_ALGAE Model was demonstrated to be useful to simulate bioremediation and microalgae production in aquaculture wastewater in a semi-continuous system with different environmental factors. The photo-respirometric outputs were compared with the process rates affecting dissolved oxygen dynamics computed by the mathematical model. Unlabelled Image • The microalga Tetraselmis suecica was grown in aquaculture wastewater (AW). • Microalgal content of proteins, lipids and carbohydrates cells was analyzed. • Oxygen uptake and production rates were measured by photo-respirometric tests. • BIO_ALGAE model simulated effectively nutrient uptake and biomass production. [ABSTRACT FROM AUTHOR]

Commercial microalgae production with conventional suspended cultures is still facing the challenge of high operational costs related to mixing and harvesting diluted biomass. Attached culture system is an emerging technology for replacing the suspended culture systems, were the biomass grows as a biofilm on a supporting belt that is continuously rotating between the liquid and gaseous phases. Immobilized culture systems have several advantages, when compared to suspended culture systems, such as higher biomass productivity and straightforward harvesting and concentration. Ready-to-use biomass with water content between 80 and 90% is harvested by simple scrapping, avoiding some dewatering steps. However, additional infrastructures are required increasing material and electricity demands. This study is a comparative pond to gate life cycle assessment of the environmental impacts, energetic and materials demands between the conventional Open Raceways Ponds (ORP) and Rotating Algal Biofilm (RAB), considering large-scale production of Tetraselmis suecica. Two products were analysed: microalgae biomass at 20%-DW and algae meal (protein concentrate powder). The results were also compared with the conventional protein sources, such as soymeal and fishmeal. Considering that both systems achieve the same productivity (20 g m−2·d−1), the environmental impacts, measured trough a single aggregated eco-point value, were 26% and 24% higher in attaching system than ORP, per kilogram of biomass at 20%-DW and protein powder (algae meal), respectively. Both solutions offer a significant environmental improvement when compared to soymeal and fishmeal. Productivities 40% higher in RAB are required to obtain lower environmental impacts than ORP system. Electrical demands reductions up to 83% and 62% per kilogram of biomass 20%-DW and kilogram of algae meal, respectively, were reached by RAB approach. If RAB can substantiate a 50% increase in productivity on the long run, then the eco-points gains will be 20%, with reductions higher than 55% in electricity requirements and around 30% in the water consumption. The efficient energy performance of RAB, and its considerable margin of improvement make it a promising alternative to conventional open raceway systems. • Algae protein has lower environmental impacts compared to soymeal and fishmeal. • Ready-to-use biomass after harvesting is a key environmental advantage in biofilms. • Biofilm has lower power demand compared to raceway at productivities >10 g m−2d−1. • Rotating biofilm require productivities 40% higher to outcompete with raceways. [ABSTRACT FROM AUTHOR]

A comparative study of food selectivity of the benthic copepod Tigriopus japonicus and the pelagic copepod Paracyclopina nana was performed by feeding four different microalgae (Tetraselmis suecica , Isochrysis galbana , Chlorella sp., and Nannochloropsis oculata). To examine whether the morphological characteristics of the microalga could influence the food selectivity, we investigated the movement, color, and size of the microalgae. The result indicated significant differences only in the movement of microalga. However, no significant differences in most of the microalgae were observed in feeding rate determination in 24 h, indicating plenty amounts of microalgae were administered to both copepods. In the T. suecica- and I. galbana- fed groups, no significant nitrogen isotopic turnover was observed, indicating both microalgae might be suitable for experimental copepods. However, the difference in the isotopic ratio of N. oculata and N. oculata -fed copepods showed that N. oculata was not a good food source. Various types of polyunsaturated fatty acids were successfully synthesized. However, the class of fatty acid conversion genes was different and the transcript level showed different trends according to each microalgal species in the two copepods. In developmental time, T. japonicus was not severely affected by the food types, while in P. nana , only T. suecica -fed group showed typical development progression. For further verification, both copepods were exposed to frozen- T. suecica. The result showed that T. japonicus was not affected by the frozen- T. suecica -fed condition, but no sign of development in P. nana was shown, suggesting that P. nana could not detect non-motile microalgae. • No significant nitrogen isotopic turnover was observed in the Tetraselmis suecica- and Isochrysis galbana- fed groups. • Various types of polyunsaturated fatty acids were successfully synthesized in both copepods. • The developmental time of T. japonicus was not severely affected by the food types. • In P. nana , only T. suecica -fed group showed typical development progression. • No sign of development was shown only in P. nana when frozen- T. suecica was administered. [ABSTRACT FROM AUTHOR]

This study investigated the role of the feeding regime on cellular (lysosomal membrane impairment), oxidative (superoxides and nitric oxides generation, as well as lipid peroxidation) and genotoxic (nuclear abnormalities) biomarkers measured in hemocytes of mussels Mytilus galloprovincialis treated with diclofenac (DCF). Specifically, unfed mussels, or mussels fed ad libitum with algal species Tisochrysis lutea or Tetraselmis suecica (Tiso/DCF- and Tetra/DCF- treated mussels, respectively) were exposed to DCF (20 μgL−1) for 4 days. The results showed that biomarkers' responsiveness against DCF, were more pronounced in unfed and Tetra/DCF-, rather than Tiso/DCF- treated mussel hemocytes, thus revealing food deprivation, changes in mussel feeding/filtration rate and digestion processes, as potent factors of mussels' immune efficiency and response against DCF. Those findings could provide valuable data for the optimization of mussels' feeding regime during laboratory studies, in order to assess reliably the effects of emerging contaminants on non-target sentinel organisms, such as mussels. • Biomarkers in hemocytes of diclofenac (DCF)-treated mussels were investigated. • Challenged mussels fed or not with Tetraselmis suecica or Tisochrysis lutea. • Feeding and digestion processes modify biomarkers in hemocytes of DCF-treated mussels. • Mussels immune and antioxidant efficiency is enhanced by Tisochrysis lutea diet. [ABSTRACT FROM AUTHOR]

• Viable organisms were quantified by modeling growth after exposure to UV. • Dark storage for 1–5 days after exposure to UV increased the efficacy of treatment. • The incremental effect of dark storage declined with time. • Results consistent with photorepair, mostly in the first 2 days, prevented in dark. Meeting the recent biological standards established by the Ballast Water Management Convention requires the application of ballast water treatment systems; ultraviolet irradiation is a frequently used option. However, organisms can repair the damage caused by ultraviolet irradiation primarily with photo-repair mechanisms that are dependent on the availability of light. The objective of this study is to quantify the impact of dark storage following ultraviolet irradiation on the viability of the microalgae Tetraselmis suecica. Results showed that one day of dark storage after ultraviolet irradiation enhanced the inactivation rate by 50% with respect to the absence of dark storage and increased up to the 84% with five days of dark storage. These results are consistent with photorepair, mostly in the first two days, prevented in the dark. The dose required to inactivate a determined ratio of organisms was correlated with the length of the dark post-treatment according to an inverse proportional function. This correlation may help to optimize the operation of ultraviolet ballast water treatment systems. Further, the results show that growth assays can detect organisms that are capable of repair after treatment with UV. [ABSTRACT FROM AUTHOR]