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• Diatoms shaped by Si enrichment or low salinity accumulated more Cd and Cu. • Si-enriched cells under low salinity showed the highest instantaneous metal influx. • The adsorption capacity of diatoms is mediated by cell wall physicochemical traits. • Lower Si availability and salinity led to rougher cell walls with larger surface area. • Higher silicification level decreased cell surface potential with more silanol groups. Increasing nitrogen and phosphorus discharge and decreasing sediment input have made silicon (Si) a limiting element for diatoms in estuaries. Disturbances in nutrient structure and salinity fluctuation can greatly affect metal uptake by estuarine diatoms. However, the combined effects of Si and salinity on metal accumulation in these diatoms have not been evaluated. In this study, we aimed to investigate how salinity and Si availability combine to influence the adsorption of metals by a widely distributed diatom Phaeodactylum tricornutum. Our data indicate that replete Si and low salinity in seawater can enhance cadmium and copper adsorption onto the diatom surface. At the single-cell level, surface potential was a dominant factor determining metal adsorption, while surface roughness also contributed to the higher metal loading capacity at lower salinities. Using a combination of non-invasive micro-test technology, atomic force microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we demonstrate that the diversity and abundance of the functional groups embedded in diatom cell walls vary with salinity and Si supply. This results in a change in the cell surface potential and transient metal influx. Our study provides novel mechanisms to explain the highly variable metal adsorption capacity of a model estuarine diatom. [Display omitted] [ABSTRACT FROM AUTHOR]

Oil production and refining require very large quantities of fresh water. Therefore, the use of unconventional methods to exploit resources, such as seawater desalination, appears to be an interesting alternative to produce a controlled and conditioned quantity of water to meet the required quality for its use. In this context, the French Company "Société Anonyme de la Raffinerie des Antilles (SARA)", as being the main industrial consumer of fresh water in Martinique, became interested in this mode of production and implemented a project to build a seawater desalination unit. However, seawater desalination generates a discharge of brine concentrate that, by its nature, could lead to environmental problems in the surrounding aquatic environment. To minimize the effects, several measures were taken in the design of the unit, in particular the installation of a mixing basin to dilute the concentrate prior to discharge. The purpose of this study is to assess the potential chemical toxicity of this effluent. The physico-chemical composition on 32 selected parameters as well as toxicity tests using controlled and standardized marine aquatic biological models (Aliivibrio fischeri, Phaeodactylum tricornutum, and Crassostrea gigas) are presented. No chemical elements of concern are observed for the effluent. Moreover, no toxic effect is observed under the conditions of salinity tolerance of the model organisms. These results suggest that the effluent generated by the SARA desalination unit does not present any demonstrated ecotoxicity under the studied conditions. This original work constitutes the first toxico-chemical evaluation study of discharge after dilution in a mixing basin. [ABSTRACT FROM AUTHOR]

Dimethylsulfoniopropionate (DMSP) is one of the most abundant organosulfur‐containing molecules on earth. The DMSP synthesis by microalgae is of great significance for understanding the large-scale feedback between marine phytoplankton and the atmospheric chemistry and physical environment. In this study, temperature 4 °C and salinity 32‰ were more suitable for the growth and biomass accumulation of Phaeodactylum tricornutum ICE-H. Additionally, the DMSP synthesized by P. tricornutum ICE-H mainly exists in the form of particles, and the high salt environment is beneficial to DMSP biosynthesis. RNA-seq analysis revealed that the response of P. tricornutum ICE-H to hypersaline stress is a systematic work at global transcriptomic level, which may involve enhancements of photosynthesis, carbon fixation and ion transport processes, accelerated protein turnover, as well as fatty acid metabolism, glycolysis/gluconeogenesis. Meanwhile, several candidate DMSP synthesis genes were found that belong to the enzyme classes of the proposed algal assimilatory sulfur reduction pathway and transamination pathway. In conclusion, all the changes in these biological processes will help to recognize the new balance of P. tricornutum ICE-H adapting to hypersaline environment, and further understand the mechanism of the polar microalgae adapting to extreme environment and its unique phylogenetic status in polar habitats. [Display omitted] • Antarctic model diatom - Phaeodactylum tricornutum ICE-H was identified. • Dimethylsulfoniopropionate synthesis ability was characterized. • Transcriptome revealed the global gene expression pattern under hypersaline stress. • Homologous genes involved in DMSP synthesis pathways were found. [ABSTRACT FROM AUTHOR]

Sorption is here proposed as a promising approach for metal pre-concentration and recovery from wastewater. A study was carried out on the simultaneous sorption of Co2+, Cu2+, Ni2+ and Zn2+ on macroalgae, microalgae and cyanobacteria. The effect of pH, initial metal concentration, metal competition and time of contact on metal sorption were evaluated. Metal competition hampers sorption at the studied metal concentration ranges. The metal counterion (sulfate, chloride or acetate) did not influence metal sorption. The brown algae Sargassum sp. was the most promising sorbent (q max = 0.66 ± 0.03 mmol·g−1), followed by the microalgae Phaeodactylum tricornutum (q max = 0.36 ± 0.02 mmol·g−1) and the cyanobacteria Spirulina sp. (q max = 0.216 ± 0.007 mmol·g−1). All biomass samples showed preferential sorption of Cu2+. The experimental kinetic data were well described by Ho's model, showing chemisorption to be the main sorption mechanism. Ion-exchange of Ca2+, K+ and H+ also played a significant role in metal sorption. After sorption, metal recovery was achieved resorting to incineration. The metal content of the obtained biochar was 4639-fold higher when compared to the initial aqueous solution concentration. [Display omitted] • Metal pre-concentration onto macroalgae, microalgae and cyanobacteria was optimized. • Sargassum sp. had the greatest sorption capacity. • Chemisorption and ion-exchange played a key role in metal sorption. • Metal-laden biomass was incinerated into biochar to promote metal recovery. • The biochar had a metal concentration 4639-folds higher than the initial solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Our computational method identified solvents for microalgal biorefineries. • The solvents were experimentally validated on P. tricornutum biomass. • 2-butanol and water enable effective fractionation of wet P. tricornutum biomass. • The fractionation approach operates at ambient temperature using benign solvents. • No energy-intensive biomass drying step is required. Wet microalgal biomass was recently proposed as a feedstock to circumvent the energy-intensive drying step in biorefineries. However, solvents commonly applied to extract valuable target compounds from dried biomass are usually less effective when applied on wet biomass. In the present study, we investigated the potential of systematic solvent selection to increase pigment and lipid yields for the extraction of wet Phaeodactylum tricornutum biomass. The solvent selection was guided by a large-scale computational screening approach. Experiments revealed, that 2-butanol – a non-toxic, partially water-miscible solvent – extracted 99.4 wt% of lipids and 82.6 wt% of carotenoids from wet biomass. By using only 2-butanol and water as benign solvents, we developed a biorefinery approach that effectively fractionates wet microalgal biomass under ambient conditions into proteins, carbohydrates, carotenoids and lipids without the need for energy-intensive biomass drying. [ABSTRACT FROM AUTHOR]

[Display omitted] • Media formulations impacted Phaeodactylum tricornutum productivity. • Absorbance and 2D-fluorescence captured biological variance. • A comprehensive dataset was generated and machine learning models applied. • Spectroscopy-based models for monitoring P. tricornutum cultures were developed. • Robust and sensitive monitoring of P. tricornutum fucoxanthin and cell productivity. The development of sustainable and controlled microalgae bioprocesses relies on robust and rapid monitoring tools that facilitate continuous process optimization, ensuring high productivity and minimizing response times. In this work, we analyse the influence of medium formulation on the growth and productivity of axenic Phaeodactylum tricornutum cultures and use the resulting data to develop machine learning (ML) models based on spectroscopy. Our culture assays produced a comprehensive dataset of 255 observations, enabling us to train 55 (24+31) robust models that predict cells or fucoxanthin directly from either absorbance or 2D-fluorescence spectroscopy. We demonstrate that medium formulation significantly affects cell and fucoxanthin concentrations, and that these effects can be effectively monitored using the developed models, free of overfitting. On a separate data subset, the models demonstrated high accuracy (cell: R2 = 0.98, RMSEP = 2.41x106 cells/mL; fucoxanthin: R2 = 0.91 and RMSEP = 0.65 ppm), providing a practical, cost-effective, and environmentally friendly alternative to standard analytical methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stable perfusion cultivation through Vibro membrane filtration (up to 3.59 g L–1). • Bioremediating low nutrient concentrations through perfusion cultivation. • Life Cycle Assessment reveals lower environmental impact of perfusion cultivation. • Photobioreactor materials and cultivation energy impact sustainability the most. • Membrane filtration leads to significantly higher expenses. Effluent water from recirculating aquaculture systems (RAS) contains nutrients from fish excrements and leftover feed. This study investigated the nutrient remediation potential from RAS effluent water through microalgae cultivation in 25 L tubular reactors. We compared nutrient uptake and biomass productivity in continuous and perfusion cultivation modes for freshwater, brackish water and saltwater. Stable high biomass densities were achieved with additional nitrate during continuous cultivation (up to 3.88 g L–1) or by membrane filtration during perfusion cultivation (up to 3.59 g L–1). A life cycle assessment (LCA) compared the two different cultivation modes in terms of environmental sustainability on a 1 ha scale. The LCA and preliminary economic assessment showed that perfusion cultivation appears to have a lower environmental impact for relatively low nutrient concentrations, but additional equipment and higher energy demands are leading to increased operational (+6 %) and capital expenses (up to +60 %). [ABSTRACT FROM AUTHOR]

Microalgae have emerged as a promising supplement or feed additive and ensure sustainability standards in aquaculture. The present study aimed to investigate the effects of dietary marine microalgae, Phaeodactylum tricornutum and Tetraselmis sp., supplementation on growth performance, feed intake, tissue morphology, biochemical characteristics of some tissues and expression of immune related genes in hepatopancreas of Pacific white shrimp, Litopenaeus vannamei. L. vannamei (about 0.8 g) was fed six isonitrogenous and isolipidic diets including six dietary marine microalgae (P. tricornutum: Tetraselmis sp. = 1: 1) content 0 (CON), 1.5 % (MA-1.5 %), 3 % (MA-3 %), 4.5 % (MA-4.5 %), 6 % (MA-6 %) and 7.5 % (MA-7.5 %) for 9 weeks. Subsequently, the shrimp was challenged with Vibrio parahaemolyticus injection. Microalgae supplementation could increase the survival rate of from 78.33 % to 100 % and decrease the feed conversion ratio from 1.66 to 1.37. Additionally, microalgae significantly decreased the crude lipid and increased the content of n-3 PUFA in the muscle (P > 0.05). The intestinal villi in MA-4.5 % had the greatest height and maintained the most intact shape. Following 8 h of V. parahaemolyticus stress, the mortality rate of shrimp in MA-3 % group was 1/6 that in CON group. Furthermore, the MDA content in hepatopancreas was significantly lower in the MA-3 % group compared to the CON group (P > 0.05). Gene expression analysis revealed significant upregulation of antibacteria-related genes (alf1, alf2, crus, lyz, pen3a and pen4), proPO system-related genes (sp, pexn, propo1 and propo2), and antioxidant gene cat in the hepatopancreas of shrimp from the MA-3 % group (P > 0.05). In conclusion, the findings from this study indicate that the microalgal mixture is an effective dietary additive for L. vannamei, promoting improved growth performance, enhanced flesh quality, and stronger immunity. [ABSTRACT FROM AUTHOR]

Cocultivation of marine microalgae Nannochloropsis oculata and Phaeodactylum tricornutum enhanced biomass production, lipid accumulation, and flocculation efficiency. The coculture yielded 1.3 g L⁻1 biomass with 108.06 mg L⁻1 d⁻1 productivity, and 40.9 % lipid content, surpassing monocultures. Flocculation efficiency reached 78.82 % after 48 h, 1.75–3.20 times higher than monocultures, primarily due to increased loosely bound extracellular polymeric substances (LB-EPS). However, the extended settling time highlights the need for harvesting process optimization. Fatty acid profiling showed increased saturated (56.94 %), monounsaturated (24.99 %), and polyunsaturated (17.08 %) fatty acids, with notable increases in palmitic, myristic, stearic, and eicosapentaenoic acids. The derived biodiesel met international standards for cetane number, kinematic viscosity, and density. Elevated β-carotene and polyunsaturated fatty acids (PUFA) content suggest potential for functional foods and dietary supplements. This cocultivation strategy proves promising for augmenting biomass and lipid productivities, improving harvesting efficiency, and offering added value in food applications. Future research should focus on reducing harvesting time and scaling up production to enhance its viability for sustainable biodiesel production and functional food development. [Display omitted] • Algal coculture increased biomass yield and productivity compared to monocultures. • Lipid content in the coculture reached 40.9 %, higher than both monocultures. • Flocculation efficiency improved significantly in the coculture, reaching 78.82 %. • The biodiesel produced met international standards. • Elevated β carotene and PUFA content suggest potential for food applications. [ABSTRACT FROM AUTHOR]

The ongoing decline in seawater pH, driven by the absorption of excess atmospheric CO 2 , represents a major environmental issue. This reduction in pH can interact with metal pollution, resulting in complex effects on marine phytoplankton. In this study, we examined the combined impacts of seawater acidification and copper (Cu) exposure on the marine diatom Phaeodactylum tricornutum. Our data indicate that elevated p CO 2 had a minor effect on the growth and photochemistry and overall performance of P. tricornutum. However, seawater acidification significantly influenced cell size, surface roughness, and adhesion. Higher p CO 2 levels led to increased Cu accumulation in P. tricornutum under low ambient Cu concentrations, while significantly reducing Cu accumulation. The smaller cell size and reduced negative charge on the cell surface may explain the decreased Cu accumulation and toxicity. In response to metal stress, P. tricornutum upregulated Cu efflux to mitigate the increased Cu stress in acidified seawater. The expression of the metal transporter gene CTR1 and the reductase gene FRE1 were significantly downregulated, while ATPase5-1B was upregulated in cells exposed to elevated Cu concentrations at 1200 μatm p CO 2. Our study provides useful insights into the interactions between metals and diatoms in an increasingly acidified ocean. [Display omitted] • Seawater acidification reduced Cu uptake in marine diatom Phaeodactylum tricornutum. • Seawater acidification resulted in rougher surfaces, lower adhesion and modulus in the diatom. • Diatoms regulated Cu homeostasis via FRE1, CTR1, and ATPase 5-1B transporters. • The expression of CTR1 and FRE1 were significantly downregulated in response to seawater acidification. [ABSTRACT FROM AUTHOR]

In the intricate realm of aquatic ecosystems, biotic interactions play pivotal roles in shaping the physiological responses and survival strategies of microorganisms. This study investigates the effects of Gracilaria bailinae on photosynthesis and metabolism on the diatom Phaeodactylum tricornutum and the ecological significance. Our results reveal considerable suppression by G. bailinae on both its light-dependent and light-independent reactions of photosynthesis in P. tricornutum. A pronounced decline in carbon fixation was observed causing. the diatom to prioritize its carbon flux towards carbohydrate synthesis for its cellular energy needs. At high G. bailinae concentrations a marked reduction in lipid content indicated their importance as emergency energy sources. This response in lipid mobilization under photosynthetic stress is an evolutionary strategy for environmental adaptation. In addition, G. bailinae -induced stress amplified lysosomal activity in the diatom. Such an upsurge in oxidative stress appears to fast-track cellular death. We conclude that the ROS production, induced by G. bailinae , acts as a linchpin in mediating stress responses, thereby significantly reconfiguring the metabolism in the diatom. This study not only elucidates the physiological countermeasures of microalgae against biotic stressors but it also underscores the complex interactions between aquatic microorganisms. [Display omitted] • G. bailinae inhibits P. tricornutum growth by altering photosynthesis. • G. bailinae triggers ROS production, affecting diatom cellular homeostasis. • High ROS levels compromise microalgal cell membrane integrity. • Lipid peroxidation boosts lysosomal activity and shifts cell metabolism. [ABSTRACT FROM AUTHOR]

• MPs especially small sized MPs exacerbated SMR toxicity to microalgae. • Biodegradation was the main removal mechanism of SMR by P. tricornutum. • MPs especially 30 μm MPs promoted SMR photodegradation through leaching organic chemicals. • MPs especially small sized MPs inhibited SMR degradation by microalgae. • SMR bioaccumulation in the microalgae was low and affected by MPs. Antibiotics and microplastics (MPs) are two classes of emerging contaminants that are commonly found in various water environments. However, how different sized MPs affect the toxicity and biodegradation of antibiotics remains poorly understood. We investigated the effects of polystyrene (PS) MPs with different particle sizes (100 nm and 30 μm) on the physiological responses and degradation behavior of Phaeodactylum tricornutum to sulfamerazine (SMR). Results showed that microalgae growth was inhibited by SMR, and MPs especially those of smaller size exacerbated the inhibitory effects of SMR on microalgae, including decreasing the content of chlorophyll a, carotenoids, malondiadehyde and superoxide dismutase activity. MPs exhibited low adsorption towards SMR, and MPs especially 30 μm MPs strengthened SMR photodegradation through leaching more organic chemicals. In comparison, 100 nm MPs obstructed the light, resulting in insignificant effects on photodegradation. Apart from photodegradation, SMR could be bioaccumulated and biodegraded by microalgae, and biodegradation was the main removal mechanism. The overall influence of MPs on SMR degradation by microalgae was a balance of the promotion on photodegradation and negative effects on microalgae growth, with the degradation efficiency and rate of SMR significantly lower in treatment of 100 nm MPs (0.0128 ± 0.0012 day−1, 30.13 ± 0.36 %) than treatments without MPs (0.0155 ± 0.0011 day−1, 32.90 ± 3.11 %) or with 30 μm MPs (0.0165 ± 0.0013 day−1, 34.46 ± 2.52 %). Overall, this study reveals the size-specific effects of MPs on the toxicity and degradation behavior of SMR, providing novel insights into the combined effects of SMR and MPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • PtNRPS1-OE enhances resistance to SA pollution and its removal efficiency. • High binding affinity of rNRPS1 to SA pollutants confirmed. • MS/MS identifies amino acids binding SA pollutants. • Co-localization analysis elucidates pollutant removal mechanism. The accumulation of the emerging pollutant salicylic acid (SA) in the environment has gained much attention. In this study, overexpression of the non-ribosomal peptide synthase (NRPS) gene, PtNRPS1 in the marine diatom Phaeodactylum tricornutum (PtNRPS1-OE) increased resistance to SA pollutants. It was assumed that the enhanced tolerance was due to the high binding affinity between recombinant PtNRPS1 (rNRPS1) and SA pollutants. Moreover, tandem mass spectrometry analysis determined the amino acids that participated in the covalently binding of SA. The removal efficiency of SA pollutants by PtNRPS1-OE cells was found to be markedly elevated. The mechanism underlying the removal of SA and 5-substituted SA (5-sSA) was proposed, following the co-localization analysis of rNRPS1 and SA. The purpose of this study was not about using PtNRPS1 as an enzyme to catalyze the synthesis of metabolite. Rather, it explored the possibility of using PtNRPS1 to remove pollutants, which further improves practical feasibility of microalgae-mediated bioremediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • 6-BA could activate the resistant-system of microalgae under high-salinity stress. • 6-BA improved 38.3% biomass and enhanced IC, TN, TP removal by 85.2%, 27.4%, 31.9%. • 1 µM 6-BA enhanced Ca2+ transport ATPase and sensors to adjust osmotic balance. • 6-BA alleviated salt damage by promoting ion transportation and EPS production. • 6-BA boosted bioresource accumulation, supporting renewable energy and bioeconomy. High-salinity presents significant challenges in microalgal wastewater treatment and bioresource recovery due to salinity stress. This study explored the use of salt-tolerant microalgae in conjunction with phytohormone regulation. 1 µM 6-benzylaminopurine increased the biomass of Phaeodactylum tricornutum by 38.3 % and enhanced lipid production by 36.8 %. 6-benzylaminopurine significantly improved the removal of inorganic carbon, total nitrogen, and total phosphorus by 85.2 %, 27.4 %, and 31.9 %. Specifically, 6-benzylaminopurine improved K+ transportation by 71.0 %, increased the activity of Ca2+ transport ATPase and Ca2+ sensors by 49.0 %–83.0 %, optimized osmotic balance, and alleviated salt-induced damage. The contents of proline and extracellular polymers increased by 34.8 % and 35.5 %. A 38.4 % reduction in reactive oxygen species indicated that high-salinity stress was mitigated. The analysis of Sustainable Development Goals showed a 56.2 % improvement in Affordable and Clean Energy. Overall, these findings further highlighted the promising application of the phytohormone 6-benzylaminopurine in microalgal high-salinity wastewater treatment and lipid production. [ABSTRACT FROM AUTHOR]

• Cabo Verde Basin is dominated by deposit-feeding polychaetes that rewor and process organic matter on the seafloor. • Echinoderms and polychaetes exhibited higher 13C-uptake highlighting their efficiency in carbon processing at bathyal depths. • O.M. quality may affect macrofaunal feeding preferences and metabolism, but the precise impact of POC quality remains unclear. • Research on temperature and POC synergistic effects on macrofauna is needed, as deep-sea multi-stressor studies are limited. Deep-sea ecosystems are particularly important to the cycling of matter and energy in the oceans and therefore in regulating Earth's climate. The Atlantic Ocean is already experiencing significant abiotic changes, with expected warmer temperatures coupled with decreased particulate organic carbon (POC) export flux. However, there is yet a large gap in our understanding of warming impacts on deep benthic ecosystems and in the organic matter processing by benthic organisms in the seafloor. This study employed an experimental approach to assess the single and cumulative effects of two climate change stressors, temperature and POC quality, on macrofaunal benthic assemblages in the Cabo Verde Basin (CVB, Equatorial Atlantic) bathyal continental slope. Incubation enrichment experiments with 13C and 15N labelled diatoms Phaeodactylum tricornutum simulated climate projections for the next century with a balanced design, studying the effect of either increased temperature (+2°C), reduced POC quality (dialysed labile fraction), or both, against a control treatment. We found that echinoderms and polychaetes rapidly ingested labelled algae at rates between 0.02 and 21.9 µg C m−2 d-1. Given a strong spatial variability in macrofaunal biomass, the carbon and nitrogen incorporation by macrofauna was not affected by a + 2 °C warming, by a decreased organic matter quality, or the combination of both factors. Our study provides valuable insights into the biodiversity, biomass, and ecosystem functioning (C and N uptake rates) of deep-sea benthic ecosystems in the N Atlantic, and stress that potential effects of warmer temperatures and POC quality on carbon and nitrogen incorporation by macrofauna remain uncertain. We highlight the value of these experiments to better understand the effects of climate change on deep-sea ecosystems. [ABSTRACT FROM AUTHOR]

This research studied the growth of microalgae (Chlorella vulgaris and Phaeodactylum tricornutum) on a biofilm reactor using effluent water from salmon production in a recirculating aquaculture system (RAS). RAS effluent water contains considerable amounts of nitrate and small amounts of phosphate, that stem from dissolved excess feed and fish faeces. In microalgae growth experiments, we tested a twin-layer biofilm reactor, which has one layer for substrate distribution (RAS effluent water-based medium) and adhered onto that, a carrier layer for biofilm cultivation. First, we tested five different carrier materials (newsprint, filter paper, polypropylene, viscose/polyester mix, viscose) to assess the microalgae's attachment ability of the material, where the viscose fibre material proved to be the most suitable. The biofilm reactor design had to be improved for saltwater suitability, as water evaporation caused changes in salinity and nutrient concentrations and ultimately led to the formation of salt crusts on the biofilm and clogging of the irrigation system. A dilution of the medium with osmosis water compensated the evaporation rate and a technical improvement of the irrigation system established stable cultivation conditions. The biofilm reactor was then tested for all three water types (Chlorella for freshwater, Phaeodactylum for brackish water and saltwater) that are discharged during a RAS production cycle for salmon. Microalgae paste was used for inoculation of the biofilm carrier material and after a short maturation phase the biofilm reactor was harvested every three days. This study demonstrated that a complete uptake of nitrate and phosphate from RAS effluent water through microalgae cultivation is possible, and the biofilm reactor is able to handle changes in nutrient concentrations and salinity. Biomass productivity for Phaeodactylum cultivated on brackish RAS medium was highest (15.28 g m−2 d−1), compared to saltwater RAS medium (4.35 g m−2 d−1) and Chlorella on freshwater RAS medium (4.25 g m−2 d−1). • Nutrient uptake from aquaculture effluent water achieved through microalgal biofilms • Optimised microalgae biofilm reactor design for fresh and salt water cultivation • Five different carrier materials were tested, viscose fibre was most suitable • Easy inoculation procedure allows for fast biofilm establishment • Yields on light of P. tricornutum are comparable to suspended cultivation yields [ABSTRACT FROM AUTHOR]

Marine biological fouling is the undesirable accumulation on the surfaces of submerged objects and causes environmental and economic consequence to ships and marine facilities. However, traditional coatings achieve antifouling by releasing toxic heavy metal antifouling agents, causing ecological problems. And the static antifouling performance of self-polishing antifouling coating is not good. To overcome the shortcoming, a novel antifouling strategy to build a self-renewing multi-level microstructure on the coating surface was developed by dispersing GO-based quaternary polymer brushes in a self-polishing fluoro/silyl acrylate copolymer. Quaternized GO exhibits excellent dispersibility in the silyl-based acrylate copolymer. A dynamic self-renewing surface is realized for the coating via a self-polishing effect that exposes the filler inside the coating at the surface. The multi-level microstructure of the sharp edge of GO and quaternized "spear" structure destroys the cell wall of organisms. And a "water-shield" on amphoteric ion surface on quaternized GO inhibits adhesion of organisms. The antibacterial and anti-algae tests demonstrated the excellent antifouling effect of the coating at only 0.1% (mass) filler content, with anti-algae ratio against Nitzschia closterium (N. closterium), Phaeodactylum tricornutum (P. tricornutum) and Halamphora sp. of 83.7%, 52.4%, and 65.8%, respectively. The proposed preparation method is simple and potentially applicable to large-scale production for antifouling application. [Display omitted] • Multi-level microstructure was constructed for antifouling by quaternization-modified GO. • The coating exhibited a significant antifouling effect at only 0.1% (mass) filler content. • A GO surface killing-resistance mechanism is proposed for the first time. [ABSTRACT FROM AUTHOR]

Various protective coatings are applied to marine components to mitigate friction, wear, corrosion, and biofouling. However, these issues can arise simultaneously under certain operating conditions, posing significant challenges to the performance and durability of marine components. In this study, core-shell structured WC-Co-Cr/Cu powders were fabricated using electroless plating, and a high-velocity oxygen-fuel (HVOF) spraying technique was employed to deposit the WC-Co-Cr/Cu coating. The results demonstrated that the tribo-corrosion behavior of the WC-Co-Cr/Cu coating improved compared to that of the HVOF WC-10Co-4Cr coating, although there was a slight reduction in corrosion resistance. Additionally, the incorporation of Cu significantly reduced the adhesion rates of Bacillus subtilis and Phaeodactylum tricornutum , indicating that the WC-Co-Cr/Cu coating gained anti-biofouling properties from the presence of Cu. Overall, the development of this WC-Co-Cr/Cu coating presents a promising solution for marine components, providing enhanced tribo-corrosion performance and effective anti-biofouling properties. • Core-shell structured WC-Co-Cr/Cu powder were prepared by electroless plating. • HVOF-sprayed WC-Co-Cr/Cu coating showed enhanced tribo-corrosion behaviour. • HVOF-sprayed WC-Co-Cr/Cu coating exhibited good anti-fouling properties. [ABSTRACT FROM AUTHOR]

• 21T FT-ICR MS molecular formula library annotated 53% of diatom exometabolome. • Formula library increased annotations 10x relative to MS/MS spectra matching. • FT-ICR MS assignments corroborated 94% of MS/MS spectra matching assignments. • Novel approach identified 11 protein-like compounds exuded in response to Fe stress. Increased accessibility of liquid chromatography mass spectrometry (LC-MS) metabolomics instrumentation and software have expanded their use in studies of dissolved organic matter (DOM) and exometabolites released by microbes. Current strategies to annotate metabolomes generally rely on matching tandem MS/MS spectra to databases of authentic standards. However, spectral matching approaches typically have low annotation rates for DOM. An alternative approach is to annotate molecular formula based on accurate mass and isotopic fine structure measurements that can be obtained from state-of-the-art ultrahigh resolution Fourier Transform Ion Cyclotron Resonance mass spectrometry (FT-ICR MS), but instrument accessibility for large metabolomic studies is generally limited. Here, we describe a strategy to annotate exometabolomes obtained from lower resolution LC-MS systems by matching metabolomic features to a molecular formula library generated for a representative sample analyzed by LC 21T- FT-ICR MS. The molecular formula library approach successfully annotated 53% of exometabolome features of the marine diatom Phaeodactylum tricornutum – a nearly ten-fold increase over the 6% annotation rate achieved using a conventional MS/MS approach. There was 94% agreement between assigned formula that were annotated with both approaches, and mass error analysis of the discrepancies suggested that the FT-ICR MS formula assignments were more reliable. Differences in the exometabolome of P. tricornutum grown under iron replete and iron limited conditions revealed 668 significant metabolites, including a suite of peptide-like molecules released by P. tricornutum in response to iron deficiency. These findings demonstrate the utility of FT-ICR MS formula libraries for extending the accuracy and comprehensiveness of metabolome annotations. [ABSTRACT FROM AUTHOR]

The present work aims at providing a multi-disciplinary approach for environmental monitoring in marine-coastal areas. A monitoring campaign of 13 months (October 2022–October 2023) was carried out on sandy foreshore sediments (SFSs). The SFSs were analysed for potentially toxic elements (PTEs) and rare earth elements (REEs) content determination. In the investigated area, variable contamination trends were assessed through Friedman and Nemenyi tests. Further results also indicated the usefulness of statistical data elaboration in the identification of potential contamination sources. In fact, from Spearman test, significant positive correlations (between 0.650 and 0.981) were observed among PTEs of possible anthropogenic origin (such as Co, Cr, Cu, Pb, V, and Zn). For REEs, La and Nd showed strong correlations with Ce (0.909 and 0.920, respectively). The study also integrated luminescence inhibition (Aliivibrio fischeri), algal growth inhibition (Phaeodactylum tricornutum), and embryotoxicity assessment (Paracentrotus lividus) on sediment elutriates showing varying degrees of toxicity. Also these data were analysed through statistics in order to highlight possible correlations between contaminants and observed ecotoxicological effects on the involved bioindicators. The results outline an approach useful for more comprehensive monitoring of marine areas quality and identification of suitable environmental restoration strategies. • A multi-disciplinary approach was developed for marine environment monitoring. • Contamination of PTEs and REEs in sandy foreshore sediments was characterized. • Contamination sources and ecotoxicity effects were investigated through statistics. • The embryotoxicity of Paracentrotus lividus resulted as the most sensitive endpoint. • RQ values for all the sampled sites indicated ecotoxicological risk for aquatic biota. [ABSTRACT FROM AUTHOR]

• Ecological risks of SA pollutants and their impact on marine diatom. • SAs induced changes in photosynthetic pigments and fluorescence parameters. • Chlorophyll content declined, and PSII core damage reduced photosynthesis efficiency. • The antioxidant enzymes were enhanced significantly as a defense against SAs' toxicity. • Transcriptome data showed DEGs enriched in key pathways, inhibiting photosynthesis. Salicylate pollutants (SAs) poses a serious threat to marine ecosystems as emerging contaminants. However, the toxic effects of SAs on marine phytoplankton, as well as the potential mechanisms and their ecological risks linked with them, are remain largely unknown. In this study, we aimed to evaluate the toxic effects of salicylic acid (SA) and its 5-substituted derivatives (5-sSA) on the marine diatom Phaeodactylum tricornutum , as well as the potential molecular mechanism involved in the toxicity. Physiological assays conducted on P. tricornutum revealed significant changes in photosynthetic pigments, chlorophyll fluorescence parameters, and antioxidant enzyme activities. The results showed that exposure of P. tricornutum to SAs caused a significant decline in chlorophyll contents and damage to the photosystem II (PSII) core resulting in the decline of photosynthesis. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were enhanced, oxidative damage occurred. Transcriptome analysis showed that a large number of differentially expresses genes (DEGs) were significantly enriched in metabolic pathways such as porphyrin metabolism, terpenoid backbone biosynthesis, and carbon fixation in photosynthetic organisms after SA and 5-BrSA treatments. In addition, key genes in transcriptomic metabolic pathways were further analyzed and validated using weighted correlation network analysis (WGCNA) and real-time fluorescence quantitative PCR (qPCR). Considering the above results, SAs mainly inhibit the processes of photosynthesis by repressing the expression of genes involved in secondary metabolite synthesis and photosynthetic carbon sequestration pathways, thus exerting toxic effects on algal cells. The results of the study will provide key data for understanding the ecological risk and toxicity mechanisms of SA pollutants. [ABSTRACT FROM AUTHOR]

Antibacterial resistance causes around 1.27 million deaths annually around the globe and has been recognized as a top 3 priority health threat. Antimicrobial photodynamic therapy (aPDT) is considered a promising alternative to conventional antibiotic treatments. Algal lipid extracts have shown antibacterial effects when used as photosensitizers (PSs) in aPDT. In this work we assessed the photodynamic efficiency of lipidic extracts of microalgae belonging to different phyla (Bacillariophyta, Chlorophyta, Cyanobacteria, Haptophyta, Ochrophyta and Rhodophyta). All the extracts (at 1 mg mL−1) demonstrated a reduction of Staphylococcus aureus >3 log 10 (CFU mL−1), exhibiting bactericidal activity. Bacillariophyta and Haptophyta extracts were the top-performing phyla against S. aureus , achieving a reduction >6 log 10 (CFU mL−1) with light doses of 60 J cm−2 (Bacillariophyta) and 90 J cm−2 (Haptophyta). The photodynamic properties of the Bacillariophyta Phaeodactylum tricornutum and the Haptophyta Tisochrysis lutea , the best effective microalgae lipid extracts, were also assessed at lower concentrations (75 μg mL−1, 7.5 μg mL−1, and 3.75 μg mL−1), reaching, in general, inactivation rates higher than those obtained with the widely used PSs, such as Methylene Blue and Chlorine e6, at lower concentration and light dose. The presence of chlorophyll c , which can absorb a greater amount of energy than chlorophylls a and b; rich content of polyunsaturated fatty acids (PUFAs) and fucoxanthin, which can also produce ROS, e.g. singlet oxygen (1O 2), when photo-energized; a lack of photoprotective carotenoids such as β-carotene, and low content of tocopherol, were associated with the algal extracts with higher antimicrobial activity against S. aureus. The bactericidal activity exhibited by the extracts seems to result from the photooxidation of microalgae PUFAs by the 1O 2 and/or other ROS produced by irradiated chlorophylls/carotenoids, which eventually led to bacterial lipid peroxidation and cell death, but further studies are needed to confirm this hypothesis. These results revealed the potential of an unexplored source of natural photosensitizers (microalgae lipid extracts) that can be used as PSs in aPDT as an alternative to conventional antibiotic treatments, and even to conventional PSs, to combat antibacterial resistance. • Antibacterial resistance is a top health threat, causing 1.27 M deaths annually worldwide. • This work assessed the photodynamic efficiency of 11 microalgae lipidic extracts. • The lipidic extracts were obtained via Folch extraction and encapsulated in liposomes using a Thin-Film methodology. • Extracts from various microalgae phyla showed significant antibacterial effects. [ABSTRACT FROM AUTHOR]

Diatoms are a significant repository of lipids, primarily storing triacylglycerols (TAGs), and serve as a crucial source of polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as fucoxanthin. Their versatile applications across medicine, food, cosmetics, aquaculture, and biofuel production underscore their value as a vital biological resource. This study employs bibliometric analysis to explore the publication trends related to diatom fatty acids (FAs) and their associated compounds, offering a comprehensive understanding of research trajectories from past to present, and indicating future directions. Analyzing 2286 articles from the Scopus database, published between 1959 and 2023, we identified the United States as the leading country in diatom FA research, with France as the most productive institution. The USA also leads in fostering international collaborations, engaging with 41 countries. Keyword co-occurrence analysis revealed that EPA and DHA have dominated research interests over the decades, with Phaeodactylum tricornutum emerging as the most frequently studied diatom strain. Initially focused on aquaculture, diatom research expanded to include bioindicator, environmental, and biofuel applications. Recently, fucoxanthin and chrysolaminarin, in combination with FAs, have gained prominence in pharmaceutical research. Additionally, the exploration of metabolic pathways through transcriptomic analysis has become increasingly significant. This study identifies several research gaps in diatom FA research, paving the way for future investigations. We advocate for continued research to fully harness diatom FAs as sustainable biological resources for key industries, including biofuels, feed, food, and pharmaceuticals. • Diatoms: Crucial reservoir of triacylglycerols (TAGs), polyunsaturated fatty acids (PUFAs), fucoxanthin. • Bibliometric analysis unveils trends in diatom fatty acids (FAs) publications. • United States and China lead in diatom FA research and France most productive institution. • Research hotspots: EPA, DHA, fucoxanthin, chrysolaminarin, and metabolic pathways. [ABSTRACT FROM AUTHOR]

Phaeodactylum tricornutum have garnered significant attention for its ability to accumulate fucoxanthin (Fx) and eicosapentaenoic acid. However, its limited biomass in autotrophic culture becomes a restrictive factor for the large-scale production of Fx. Herein, 6-benzylaminopurine and 5-aminolevulinic acid at 1.0 mg/L, were proved conducive for promoting the Fx and biomass accumulation. Under the combined effect of the two, Fx and peaked at 36.01 mg/L after 10 d of cultivation, at which point biomass was 1.50 g/L and Fx content was 24.01 mg/g. Meanwhile, EPA production was elevated to 22.73 mg/L. Such combined effect was also found in regulating the transcriptional levels of Fx biosynthesis-related genes by the two plant hormones. This study demonstrates that Fx and biomass can be enhanced easily and efficiently under the combined effect of these two plant hormones, enabling massive Fx production in the autotrophic system. [Display omitted] [ABSTRACT FROM AUTHOR]

Blueberries are rich in polyphenolic compounds, mainly anthocyanins, responsible for strong antioxidant activities beneficial to human health. However, they are easily perishable after harvest due to microbial proliferation and certain insect pests such as Drosophila suzukii. In this study, a coating of organic blueberries with zinc oxide nanoparticles (ZnONPs), made from the culture supernatant of the marine microalga Phaeodactylum tricornutum , was used to increase their shelf life. Blueberries coated with solutions of 0.5–1.5 g L−1 ZnONPs and uncoated blueberries (controls) were stored at 15 °C for 15 d, and their physicochemical and microbiological properties, as well as the number of eggs, live larvae, pupae and adults of Drosophila suzukii , were determined. Compared to uncoated blueberries, coated blueberries showed lower weight loss and decay, as well as higher levels of ascorbic acid, anthocyanins, phenolic compounds and also higher antioxidant capacity. After a storage period of 15 d, blueberries coated with 1.5 g L−1 ZnONPs were characterized by the absence of aerobic mesophilic flora, molds and yeasts. The in vitro fungicidal effect of ZnONPs at a concentration of 1.5 g L−1 against Penicillium italicum and Cladosporium sp. isolated from decayed blueberries showed high percentages of mycelial growth inhibition of up to 89.9%. In terms of insecticidal activity, ZnONPs concentrations above 0.1 g L−1 significantly inhibited the hatching of eggs and the development of D. suzikii larvae contaminating organic blueberries. At a temperature of 15 °C, the shelf-life of untreated blueberries is only 2 d, but coating them with ZnONPs at a concentration of 1.5 g L−1 extends shelf life to 15 d. Coating organic blueberries with ZnO nanoparticles produced from the marine microalga Phaeodactylum tricornutum offers interesting potential as natural preservatives to improve the quality and shelf life of organic blueberries, paving the way for their application in the fight against post-harvest fruit deterioration in favor of sustainable agriculture. [Display omitted] • Biosynthesis of ZnONPs using supernatants from Phaeodactylum tricornutum. • The ZnONPs coating retained the fruit's nutritional and quality attributes. • ZnONPs coatings reduced microbial load of blueberry fruit. • ZnONPs have demonstrated antifungal activity. • ZnONPs acted as insecticides against Drosophila suzikii. [ABSTRACT FROM AUTHOR]

A cheap cultivation of microalgae greatly reduces the biodiesel production cost. Subsequently in this study, citric acid and effluents from sugar and tannery industries were used as the nutritional supplements for the improvement of biomass and TAG production in Phaeodactylum tricornutum using two-step cultivation. When compared to control (media without supplementation), a considerable increase in biomass and chlorophyll a was obtained with citric acid (CA) and sugar industry effluent (SIE) supplemented media. In the two-step cultivation method, biomass raised from CA (100 mg·L-1) and SIE (1.5 mL·L-1) supplementations in the first step, viz. biomass production (BP) step was allowed for lipid accumulation in the second step, viz. lipid production (LP) step, and thus yielded enhanced lipids of 11.5 ± 0.7 mg·L-1·day-1 and 13.5 ± 1.9 mg·L-1·day-1 respectively, with improved TAG synthesis. Further, differential expression analysis of TAG biosynthetic genes of P. tricornutum under single-step and two-step cultivation modes were performed, and the gene expression patterns were studied. • Two-step cultivation with cheap substrates, sugar industry effluent & citric acid. • Maximum biomass productivity via supplementation with sugar industry effluent. • Maximum yield of lipid and triacylglycerol (TAG) through two-step cultivation mode. • TAG biosynthetic genes showed differential expression in two-step cultivation mode. • N deficiency upregulated DGAT gene better than silicon deficiency. [ABSTRACT FROM AUTHOR]

The UV-induced DNA lesions, cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4 photoproducts), can be directly photorepaired by CPD photolyases and 6-4 photolyases, respectively. The fully reduced flavin (hydroquinone, HQ) cofactor is required for the catalysis of both types of these photolyases. On the other hand, flavin cofactor in the semireduced state, semiquinone, can be utilized by photolyase homologs, the cryptochromes. However, the evolutionary process of the transition of the functional states of flavin cofactors in photolyases and cryptochromes remains mysterious. In this work, we investigated three representative photolyases (Escherichia coli CPD photolyase, Microcystis aeruginosa DASH, and Phaeodactylum tricornutum 6-4 photolyase). We show that the residue at a single site adjacent to the flavin cofactor (corresponding to Ala377 in E. coli CPD photolyase, hereafter referred to as site 377) can fine-tune the stability of the HQ cofactor. We found that, in the presence of a polar residue (such as Ser or Asn) at site 377, HQ was stabilized against oxidation. Furthermore, this polar residue enhanced the photorepair activity of these photolyases both in vitro and in vivo. In contrast, substitution of hydrophobic residues, such as Ile, at site 377 in these photolyases adversely affected the stability of HQ. We speculate that these differential residue preferences at site 377 in photolyase proteins might reflect an important evolutionary event that altered the stability of HQ on the timeline from expression of photolyases to that of cryptochromes. [ABSTRACT FROM AUTHOR]

Diatoms are currently considered valuable feedstocks for different biotechnological applications. To deepen the knowledge on the production of these microalgae, the diel pattern of batch growth, photosystem II performance, and accumulation of target metabolites of two commercially relevant diatoms, Phaeodactylum tricornutum and Skeletonema costatum , were followed outdoors in 100-L flat panel photobioreactors. S. costatum presented a higher light-to-biomass conversion resulting in higher growth than P. tricornutum. Both fluorescence data and principal component analysis pointed to temperature as a limiting factor for the growth of P. tricornutum. Higher protein and carbohydrate contents were found in P. tricornutum , whereas S. costatum fatty acids were characterized by a higher unsaturation degree. Higher productivities were found at 1 p.m. for protein, lipid, and ash in the case of S. costatum. Overall, S. costatum showed great potential for outdoor cultivation, revealing a broader temperature tolerance and increased biomass productivity than P. tricornutum. • Two diatom species were successfully grown outdoors in flat panel photobioreactors. • S. costatum showed the best growth performance, with increased PUFA content. • Chl- a fluorescence and PCA identified the growth-limiting abiotic factor. • P. tricornutum productivity was significantly affected by minimum temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Literature differs on fucoxanthin-optimized supercritical extraction conditions. • Statistical analyses of literature data identify 3 predictors of fucoxanthin yield. • Experiments establish how tunable solvent polarity drives fucoxanthin recovery. • Extractions on fucoxanthin standard vs. algae show hindrance of the algae matrix. • Fucoxanthin selectivity over chlorophyll is observed in supercritical CO 2 systems. The emerging nutraceutical, fucoxanthin, shows promise as a high-value product to enable the integrated biorefinery. Fucoxanthin can be extracted from algae through supercritical fluid extraction (SFE), but literature does not agree on optimal extraction conditions. Here, a statistical analysis of literature identifies supercritical carbon dioxide (scCO 2) density, ethanol cosolvent amount, and polarity as significant predictors of fucoxanthin yield. Novel SFE experiments are then performed using a fucoxanthin standard, describing its fundamental solubility. These experiments establish solvent system polarity as the key knob to tune fucoxanthin recovery from 0% to 100% and give specific operating conditions for targeted fucoxanthin extraction. Further experiments compare extractions on fucoxanthin standard with extractions from Phaeodactylum tricornutum microalgae to elucidate the effect of the algae matrix. Results show selectivity of fucoxanthin over chlorophyll in scCO 2 microalgae extractions that was not seen in extractions with ethanol, indicating a benefit of scCO 2 to design selective extraction schemes. [ABSTRACT FROM AUTHOR]

Large-scale production of biofuels from oleaginous microalgal feedstocks in a commercially feasible manner is hampered by their relatively slow growth rates and overall lipid yield than the rapidly proliferating algal species. Therefore, it is pivotal to obviate this bottleneck by augmenting lipid overproduction in fast-growing microalgal species by heterologous overexpression lipogenic genes from model oleaginous species. In this regard, the pentose phosphate pathway of Tetradesmus obliquu s was perturbed by heterologous overexpression of glucose-6-phosphate dehydrogenase (PtG6PD) from the model pennate diatom Phaeodactylum tricornutum , known for its oleaginicity. The role of PtG6PD in increasing lipid production was reported in the heterologous T. obliquus. Total lipid content was increased by 2.09- and 2.31-fold in transgenic lines than WT by elevating the lipogenic NADPH, without any negative impact on their growth rates. Interestingly, lipid yields in the transgenic strains reached up to 93 mg/L and 103 mg/L which showed a further 2-fold enhancement under nitrogen-deficient conditions. Furthermore, it was demonstrated that PtG6PD overexpression also altered fatty acid composition, with a specific increment in total monounsaturated fatty acids. Our results uncovered the pivotal role of the pentose phosphate pathway in supplying lipogenic NADPH in T. obliquus and identified key genetic targets for lipid biosynthesis enhancement in alternative hosts. Altogether, these findings open avenues for metabolic engineering in non-model and fast-growing non-oleaginous microalgal species, thereby presenting a promising strategy for empowering commercially viable photosynthetic cell factories for biofuel production. • Heterologous PtG6PD enhanced lipogenic NADPH content in T. obliquus. • PtG6PD overexpressing strains accumulated up to 34.18 % of lipids CDW • Oxidative stress conditions were alleviated in transgenic strains than WT cells • Combinatorial approach under N-stress further elevated lipid content • Preferred source of lipogenic NADPH for T. obliquus was reported [ABSTRACT FROM AUTHOR]

Diatom has evolved response mechanisms to cope with multiple environmental stresses. Heat shock protein 40 (HSP40) plays a key role in these response mechanisms. HSP40 gene family in higher plants has been well-studied. However, the HSP40 gene family has not been systematically investigated in marine diatom. In this study, the bioinformatic characteristics, phylogenetic relationship, conserved motifs, gene structure, chromosome distribution and the transcriptional response of PtHSP40 to different environmental stresses were analyzed in the diatom Phaeodactylum tricornutum, and quantitative real-time PCR was conducted. Totally, 55 putative PtHSP40 genes are distributed to 21 chromosomes. All PtHSP40 proteins can be divided into four groups based on their evolutionary relationship, and 54 of them contain a conserved HPD (histidine-proline-aspartic acid tripeptide) motif. Additionally, six, eleven, ten and four PtHSP40 genes were significantly upregulated under the treatments of nitrogen starvation, phosphorus deprivation, 2,2′,4,4′-tetrabrominated biphenyl ether (BDE-47) and ocean acidification, respectively. More interestingly, the expression level of 9 PtHSP40 genes was obviously upregulated in response to nickel stress, suggesting the sensitive to metal stress. The different expression models of PtHSP40 genes to environmental stresses imply the specificity of PtHSP40 proteins under different stresses. This study provides a systematic understanding of the PtHSP40 gene family in P. tricornutum and a comprehensive cognition in its functions and response mechanisms to environmental stresses. [Display omitted] • Fifty-five heat shock protein 40 genes were identified in Phaeodactylum tricornutum. • HSP40s contain HPD conserved motif and are distributed to 21 chromosomes. • HSP40s are clustered into 4 independent clades in the phylogenetic tree. • HSP40s show different response mechanisms to five environmental stresses. • HSP40s are more sensitive to nickel than nutrient limit and ocean acidification. [ABSTRACT FROM AUTHOR]

Harmful algal blooms (HABs) of Alexandrium pacificum have affected the Marlborough Sounds in New Zealand since 2010, posing a threat to green-lipped mussel (GLM, Perna canaliculus) farming. Previous studies have shown A. pacificum has negative effects GLM embryos and larvae. To further investigate these toxic mechanisms, in vitro bioassays were conducted on GLM spermatozoa, hemocytes, and the diatom, Chaetoceros muelleri. The three cell types were exposed to several treatments of A. pacificum for 2 h and responses were measured using flow cytometry and pulse amplitude-modulated fluorometry. Significant spermatozoa mortality was recorded in treatments containing A. pacificum cells or fragments, while hemocyte and C. muelleri mortality was recorded in cell-free treatments of A. pacificum which contained paralytic shellfish toxins (PSTs). Variation in sensitivity between cell types as well as the sublethal effects observed, emphasise the diverse toxic mechanisms of A. pacificum on co-occurring species in the environment. [Display omitted] • In vitro bioassays were used to investigate the toxicity of Alexandrium pacificum. • Treatments containing Alexandrium pacificum fragments induced sperm mortality. • Treatments containing toxic compounds induced hemocyte mortality. • Toxins reduced metabolic activity and quantum yield in Chaetoceros muelleri. • Alexandrium pacificum imparted toxicity on cells via multiple mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonic probe method (5 min, ethanol) for extracting microalgal carotenoids. • Ultrasound as a greener and shorter alternative to the 24 h reference method. • AGREEprep™ software demonstrated the greenness of the ultrasonic method. • The application of ultrasound to defatted biomass shows potential for microalgal valorization. • Carotenoid and chlorophyll profiles varied depending on the species, biomass, and method. Carotenoids, versatile natural pigments with numerous health benefits, face environmental concerns associated with conventional petrochemical-based extraction methods and limitations of their synthetic equivalents. In this context, this study aims to introduce eco-friendly approaches using ultrasound-based strategies (probe and bath) for the extraction of carotenoids from microalgae, initially focusing on Microchloropsis gaditana and subsequently evaluating the versatility of the method by applying it to other microalgae species of interest (Tisochrysis lutea , Porphyridium cruentum , and Phaeodactylum tricornutum) and defatted microalgal residues. Among the approaches evaluated, the 5-min ultrasonic probe system with ethanol showed comparable carotenoid recovery efficiency to the reference method (agitation, 24 h, acetone) (9.4 ± 2.5 and 9.6 ± 3.2 mg g−1 carotenoids per dry biomass, for the green and the reference method, respectively). Moreover, the method's sustainability was demonstrated using the AGREEprep™ software (scored 0.62 out of 1), compared to the traditional method (0.22 out of 1). The developed method yielded high carotenoid contents across species with diverse cell wall compositions (3.1 ± 0.2, 2.1 ± 0.3, and 4.1 ± 0.1 mg g−1 carotenoid per dry biomass for T. lutea , P. cruentum , and P. tricornutum , respectively). Moreover, the application of the method to defatted biomass showed potential for microalgal valorization with carotenoid recovery rates of 41 %, 60 %, 61 %, and 100 % for M. gaditana , P. tricornutum , T. lutea , and P. cruentum , compared to the original biomass, respectively. Furthermore, by using high-performance liquid chromatography with a diode array detector (HPLC-DAD) and high-resolution mass spectrometry (HRMS), we reported the carotenoid and chlorophyll profiles of the different microalgae and evaluated the impact of the eco-friendly methods. The carotenoid and chlorophyll profiles varied depending on the species, biomass, and method used. In summary, this study advances a green extraction method with improved environmental sustainability and shorter extraction time, underscoring the potential of this approach as a valuable alternative for the extraction of microalgal pigments. [ABSTRACT FROM AUTHOR]

• Ecotoxicological impact of bisphenol a analogues. • BPA analogues-treated cells show chloroplast ultrastructural alterations. • Bisphenol a analogues induce ROS production and lipid accumulation. • Microalgae bioaccumulate bisphenol a analogues. As well-known, microalgae have a pivotal role in aquatic environments, being the primary producer. In this study, we investigated the effects of Bisphenol A (BPA) analogues on cell ultrastructure, reactive oxygen species (ROS) production and photosynthetic pigment responses in the diatom Phaeodactylum tricornutum. Microalgae were exposed during both exponential and stationary growth phases to an environmental relevant concentration (300 ng/L) of three differing BPA analogues (BPAF, BPF, and BPS) and their mixture (100 ng/L of each compound). Bioaccumulation of such compounds in microalgae was also analysed. During the stationary growth phase, a significant increase in the percentage of cells with hydrogen peroxide production was recorded after exposure to both BPS and MIX. Conversely, no significant effects on total chlorophylls and carotenoids were observed. During exponential growth phase we observed that control cultures had chloroplasts with well-organized thylakoid membranes and a central pyrenoid. On the contrary, the culture cells treated with BPA analogues and MIX showed chloroplasts characterized by evident dilation of thylakoid membranes. The presence of degeneration areas in the cytoplasm was also recorded. During the stationary growth phase, control and culture cells were characterized by chloroplasts with a regular thylakoid system, whereas BPA analogues-exposed cells were characterized by a deep degradation of the cytoplasm but showed chloroplasts without evident alterations of the thylakoid system. Lipid bodies were visible in treated microalgae. Lastly, microalgae bioaccumulated mainly BPS and BPF, alone or in the MIX. Overall, results obtained revealed that BPA analogues can affect some important biochemical and ultrastructure features of microalgae, promoting ROS production. Lastly, the capability of microalgae to bioaccumulate bisphenols suggest a potential ecotoxicological risk for filter-feeders organisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • High concentrations of selenite caused a negative impact on P. tricornutum. • Fulvic acid alleviated the damage by selenite. • High quality of biofuel was retrieved under selenite and fulvic acid treatment. • Se removal and SeCys accumulation capabilities were assisted by fulvic acid. In this study, the biochemical response of Phaeodactylum tricornutum to varying concentrations of inorganic selenium (Se) was investigated. It was observed that, when combined with fulvic acid, P. tricornutum exhibited enhanced uptake and biotransformation of inorganic Se, as well as increased microalgal lipid biosynthesis. Notably, when subjected to moderate (5 and 10 mg/L) and high (20 and 40 mg/L) concentrations of selenite under fulvic acid treatment, there was a discernible redirection of carbon flux towards lipogenesis and protein biosynthesis from carbohydrates. In addition, the key parameters of microalgae-based biofuels aligned with the necessary criteria outlined in biofuel regulations. Furthermore, the Se removal capabilities of P. tricornutum , assisted by fulvic acid, were coupled with the accumulation of substantial amounts of organic Se, specifically SeCys. These findings present a viable and successful approach to establish a microalgae-based system for Se uptake and biotransformation. [ABSTRACT FROM AUTHOR]

• TWPs showed low-dose stimulation and high-dose inhibition towards microalgae. • Aged TWPs induced stronger toxicity to microalgae than virgin TWPs. • First to prove that aging increased both particulate- and leachate-induced toxicity. • Particulate-induced toxicity was more obvious for high-dose K 2 S 2 O 8 aged TWPs. • Additives leached from TWPs at environmental concentrations exhibited toxicity. The toxic effects of tire wear particles (TWPs) on organisms have attracted widespread concerns over the past decade. However, the underlying toxicity mechanism of TWPs, especially aged TWPs to marine microalgae remains poorly understood. This study investigated the physiological and metabolic responses of Phaeodactylum tricornutum to different concentrations of TWPs (Experiment 1), virgin and differently aged TWPs (Experiment 2) as well as their leachates and leached particles (Experiment 3). Results demonstrated that TWPs promoted the growth of microalgae at low concentrations (0.6 and 3 mg L −1) and inhibited their growth at high concentrations (15 and 75 mg L −1). Moreover, aged TWPs induced more profound physiological effects on microalgae than virgin TWPs, including inhibiting microalgae growth, decreasing the content of Chla , promoting photosynthetic efficiency, and causing oxidative damage to algal cells. Untargeted metabolomics analysis confirmed that aged TWPs induced more pronounced metabolic changes than virgin TWPs. This study represented the first to demonstrate that both particulate- and leachate-induced toxicity of TWPs was increased after aging processes, which was confirmed by the changes in the surface morphology of TWPs and enhanced release of additives. Through the significant correlations between the additives and the microalgal metabolites, key additives responsible for the shift of microalgal metabolites were identified. These results broaden the understanding of the toxicity mechanism of aged TWPs to microalgae at the physiological and metabolic levels and appeal for considering the effects of long-term aging on TWP toxicity in risk assessment of TWPs. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • PO and LO reduced body weight gain, hyperlipemia, and fat accumulation in the HFD-fed mice. • PO and LO attenuated low-grade chronic inflammation in the HFD-fed mice. • PO and LO alleviated hyperglycemia and insulin resistance in the HFD-fed mice. • PO and LO modulated gut microbiota dysbiosis and increased the SCFAs production in the HFD-fed mice. The present study was aimed to investigate the effects of Phaeodactylum tricornutum oil (PO) and Laminaria japonica oil (LO) against obesity and other metabolic disorders in a high-fat diet (HFD) induced obese mouse model. The results revealed that PO or LO supplementation significantly reduced HFD-induced body weight gain, hyperlipemia, and fat accumulation in mice. PO or LO supplementation also inhibited SREBP-1-mediated de novo lipogenesis and PPAR γ -mediated adipogenesis, as well as enhanced PPAR α -mediated fatty acid β -oxidation in the WAT and liver of HFD-fed mice. Moreover, PO or LO supplementation attenuated low-grade chronic inflammation, hyperglycemia and insulin resistance in obese mice. Furthermore, Dietary PO or LO also modulated HFD-induced gut microbiota dysbiosis and increased the SCFAs production. More importantly, our results also manifested that the ameliorative effect of PO and LO against HFD-induced obesity, IR and gut microbiota dysbiosis was comparable, but was superior than that of krill oil and fish oil. [ABSTRACT FROM AUTHOR]

In this study, imaging flow cytometry (iFCM), confocal laser scanning microscopy (CLSM) and Raman microscopy were compared for their ability to detect lipid bodies in Phaeodactylum tricornutum (a diatom) and Nannochloropsis oculata. These two microalgae belonging to a different phylum were cultivated under standard growth conditions and analysed in the mid-exponential and early stationary growth phase. Lipids were detected using Nile red as a fluorescent dye. Spectral unmixing was applied in CLSM to separate the fluorescent signals from neutral lipids, polar lipids and pigments. CLSM was able to detect lipid bodies in a higher number of cells compared to iFCM or Raman microscopy. Pigments were interfering with the lipid body detection in iFCM while proteins were interfering in Raman microscopy. Nevertheless, the increase in lipid body area per cell from the mid-exponential phase to the early stationary growth phase follows a similar trend for both CLSM and iFCM. • Neutral lipid, polar lipid and pigment fluorescence were split by spectral unmixing. • CLSM detects lipid bodies in more cells compared to other techniques tested. • Similar increase of lipid body area per cell by CSLM and imaging flow cytometry • Lipid bodies smaller than 0.8 μm in radius were not detected by Raman microscopy. • Interference of proteins potentially hampers lipid detection in Raman microscopy. [ABSTRACT FROM AUTHOR]

The commercial exploitation of Phaeodactylum tricornutum and Chrysotila roscoffensis is hampered by their low biomass productivity. Microalgae-bacteria co-cultivation (MBC), as an emerging approach designed to boost microalgal growth, has recently gained considerable attention. Nevertheless, studies focusing on MBC with these two microalgae remain scarce. In this study, six bacterial strains were isolated from xenic microalgal cultures. Subsequent co-cultivation trials revealed two strains of Bacillus spp. and one of Agrobacterium sp. were found to promote the growth of axenic C. roscoffensis and P. tricornutum. Biochemical analysis, encompassing macromolecules, pigments, and fatty acids, indicated that the addition of these beneficial bacteria did not weaken the quality of microalgal biomass, but substantially increased the productivity of bioactive substances. To assess the feasibility of employing these bacteria in large-scale microalgal cultivation, further MBC trials using xenic microalgal cultures were conducted. The results confirmed that the beneficial bacteria were also effective in a non-axenic MBC context. • MBC is an efficient strategy to increase microalgal biomass productivity. • MBC shows no negative effects on the quality of microalgal biomass. • Effects of bacteria on algae need to be verified in both axenic and xenic systems. [ABSTRACT FROM AUTHOR]

Fucoxanthin (FX), a carotenoid with anti-inflammatory properties, has potential in tumor therapy. Its use in functional foods and nutraceuticals is limited by poor solubility, stability, and bioavailability. This study introduces an FX-targeted delivery system using a modified Phaeodactylum tricornutum (P. tricornutum) exosome. The system, enhanced with 1,2-distearoyl- sn -glycero-3-phosphoethanolamine- N -polyethyleneglycol-2000-triphenylphosphine (DSPE-PEG 2K -TPP, TPP), aims to improve FX bioavailability, stability, and targeted transport. Confocal laser scanning microscopy and Fourier transform infrared spectroscopy verified the effective attachment of TPP to the P. tricornutum exosome surface. Fluorescence imaging revealed efficient cellular uptake of the system, with notable targeting efficiency in RAW264.7 macrophages. The delivery system notably enhanced FX uptake in these macrophages, reducing oxidative cell damage and inducing macrophage polarization, compared to free FX. • Fucoxanthin were encapsulated by engineered P. tricornutum exosomes. • Modification of exosomes by TPP achieves precise targeting of inflammatory cells of fucoxanthin. • The inclusion of P. tricornutum exosomes enhances the gastrointestinal stability and bioavailability of fucoxanthin. • TPP-EXO-FX demonstrated the capacity to mitigate LPS-induced cellular inflammatory damage. [ABSTRACT FROM AUTHOR]

This paper investigated the cumulative impact of salinity, carbon source (glycerol and glucose) and photoperiod on the cultivation of the microalga Phaeodactylum tricornutum in mixotrophic growth in pure air supplied photobioreactors aiming at biomass output and lipid content enhancement for increased biodiesel productivity. For that, Phaeodactylum tricornutum was grown for 18 and 20 days in modified F2 medium which was supplied in the beginning of the culture, and with daily addition of glycerol (0.1 M) or glucose (0.05 M); salinity at 15 and 30‰, with the luminosity of 165 μmols photons m−2s−2 for 24 h day−1 or partial 12 h day−1. Biomass production was registered, total lipids quantified with the Bligh and Dyer methodology, and the lipids' drops observed with Nile Red staining. Regarding salinity, a value of 15‰ led to the highest microalgae growth. Glycerol 0.1 M was the carbon source which provided the best assimilation by the microalgae, reaching up to 1.3 g L−1 of biomass. The 24 h-illumination photoperiod with glycerol in mixotrophic cultivation led to 338.97 mg L−1 of lipids, which was roughly 80% higher than the lipid content obtained with autotrophic growth. In conclusion, the most effective conditions were glycerol 0.1 M (carbon source), 15‰ salinity, and 24 h-illumination. Image 1 • Salinity, carbon source and photoperiod effect on microalgae growth. • No CO 2 injection on microalgae mixotrophic cultivation outcome. • Lipids identification with Nile Red staining. • Glycerol and glucose comparative analysis on lipid production. • Glycerol addition produced 80% more lipid content than autotrophic growth. [ABSTRACT FROM AUTHOR]

• Microalgae production was proposed by simple biorefinery approach. • Glycerol and digestate ultrafiltrate were proposed as secondary C and N sources. • P. Tricornutum was cultivated both in autotrophic and mixotrophic batch mode. • Mixotrohpic productivity of P. tricornutum was 1.29 and 1.60 times than autotrophic. • Under mixotrophic condition carbohydrate content increased and lipid profile changed. Phaeodactylum tricornutum was cultivated mixotrophically in batch mode providing glycerol as the C source, i.e., 0.02, 0.03 and 0.04 Mol L−1 glycerol, and ultrafiltered digestate (UF) as an N source. Biomass productivity, biomass composition, N efficiency use and total energy balance were recorded and compared to those under autotrophic conditions. Under mixotrophic conditions (0.03 Mol L-1 and 0.04 Mol L-1 glycerol), biomass productivity of P. tricornutum increased by 1.29 and 1.60 times in comparison with autotrophic conditions. Algal protein content declined as glycerol concentration increased, contrary to the case of the carbohydrate content. Lipid content did not change but unexpectedly, a lower unsaturated fatty acid in mixotrophic culture was observed than that from autotrophic culture. Mixotrophic conditions offered a higher energy recovery efficiency (EF t) than autotrophic conditions (5.7 % in 0.04 Mol L−1 glycerol and 4.2 % in autotrophic trial, respectively). Additionally, the efficiency of glycerol conversion into biomass (EF gly) increased with the glycerol dose, achieving 22.8 % for 0.04 Mol L−1 glycerol. [ABSTRACT FROM AUTHOR]

Across the globe, heat waves are getting more intense and frequent. Diatoms are a major group of microalgae at the base of the marine food webs and an important source of long chain polyunsaturated fatty acids that are transferred through the food web. The present study investigates the possible impacts of temperature increase on lipid classes and expression of genes encoding enzymes related to lipid metabolism in Phaeodactylum tricornutum. The heat wave exposure caused an increase in the relative amounts of plastidial lipids such as the glycolipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulphoquinovosyldiacylglycerol (SQDG) in parallel with a decrease in the neutral lipid fraction, which includes triacylglycerols. In agreement, gene expression analyses revealed an up-regulation of a gene encoding one MGDG synthase and down-regulation of a diacylglycerol acyltransferase (DGAT), a key enzyme in triacylglycerol synthesis. Our results show that heat waves not only negatively impact the abundance of unsaturated fatty acids such as eicosapentaenoic acid (20:5n-3, EPA) and hexadecatrienoic acid (16:3n-4) as observed by the decrease in their relative abundance in MGDG and neutral lipids, respectively, but also induce changes in the relative amounts of the diverse membrane lipids as well as the proportion of membrane/storage lipids. The expression study of key genes indicates that some of the aforementioned alterations are regulated at the transcription level whereas others appear to be post-transcriptional. The changes observed in plastidial lipids are related to negative impacts on the photosynthesis. • Heat wave-exposed P. tricornutum cells presented higher galactolipid content. • The MGDG-eicosapentaenoic acid content severely decreased due to heat stress. • Monogalactosyldiacylglycerol (MGDG) synthase was upregulated under heat stress. • A diacylglycerol acyl transferase was downregulated in heat wave-exposed cells. • MGDG and sulfoquinovosyldiacylglycerol content reveals biotechnological potential. [ABSTRACT FROM AUTHOR]