The outstanding capacity of Prasiola antarctica to thrive in contrasting harsh environments relies on the constitutive protection of thylakoids and on morphological plasticity.

The determination of physiological tolerance ranges of photosynthetic species and of the biochemical mechanisms underneath are fundamental to identify target processes and metabolites that will inspire enhanced plant management and production for the future. In this context, the terrestrial green algae within the genus Prasiola represent ideal models due to their success in harsh environments (polar tundras) and their extraordinary ecological plasticity. Here we focus on the outstanding Prasiola antarctica and compare two natural populations living in very contrasting microenvironments in Antarctica: the dry sandy substrate of a beach and the rocky bed of an ephemeral freshwater stream. Specifically, we assessed their photosynthetic performance at different temperatures, reporting for the first time gnsd values in algae and changes in thylakoid metabolites in response to extreme desiccation. Stream population showed lower α-tocopherol content and thicker cell walls and thus, lower gnsd and photosynthesis. Both populations had high temperatures for optimal photosynthesis (around +20°C) and strong constitutive tolerance to freezing and desiccation. This tolerance seems to be related to the high constitutive levels of xanthophylls and of the cylindrical lipids di- and tri-galactosyldiacylglycerol in thylakoids, very likely related to the effective protection and stability of membranes. Overall, P. antarctica shows a complex battery of constitutive and plastic protective mechanisms that enable it to thrive under harsh conditions and to acclimate to very contrasting microenvironments, respectively. Some of these anatomical and biochemical adaptations may partially limit photosynthesis, but this has a great potential to rise in a context of increasing temperature.

Choline Dehydrogenase Contributes to Salt Tolerance in Dunaliella through Betaine Synthesis.

In Dunaliella tertiolecta, a microalga renowned for its extraordinary tolerance to high salinity levels up to 4.5 M NaCl, the mechanisms underlying its stress response have largely remained a mystery. In a groundbreaking discovery, this study identifies a choline dehydrogenase enzyme, termed DtCHDH, capable of converting choline to betaine aldehyde. Remarkably, this is the first identification of such an enzyme not just in D. tertiolecta but across the entire Chlorophyta. A 3D model of DtCHDH was constructed, and molecular docking with choline was performed, revealing a potential binding site for the substrate. The enzyme was heterologously expressed in E. coli Rosetta (DE3) and subsequently purified, achieving enzyme activity of 672.2 U/mg. To elucidate the role of DtCHDH in the salt tolerance of D. tertiolecta, RNAi was employed to knock down DtCHDH gene expression. The results indicated that the Ri-12 strain exhibited compromised growth under both high and low salt conditions, along with consistent levels of DtCHDH gene expression and betaine content. Additionally, fatty acid analysis indicated that DtCHDH might also be a FAPs enzyme, catalyzing reactions with decarboxylase activity. This study not only illuminates the role of choline metabolism in D. tertiolecta's adaptation to high salinity but also identifies a novel target for enhancing the NaCl tolerance of microalgae in biotechnological applications.

Interaction between Haematococcus pluvialis microalgae and lead nitrate: lead adsorption from water.

Our study aims to investigate the response of the unicellular alga, Haematococcus pluvialis, to the toxicity of lead and propose a low-cost, highly efficient biological adsorbent for the purification of wastewater and lead-contaminated water. The first part examines the effects of lead toxicity on certain physiological indicators of this alga. In the second part, the potential of this alga in lead removal and its adsorption capacity was assessed. The alga was cultivated in a BG11 medium and treated with lead nitrate concentrations of 10, 50, and 200 mg/L during its exponential growth. The results showed that with an increase in lead concentration up to 200 mg/L, the growth rate, chlorophyll a, chlorophyll b, carotenoid and total protein content decreased, while malondialdehyde (MDA) content increased. The astaxanthin content slightly increased at the 10 mg/L but decreased at the 200 mg/L treatment. Maximum lead adsorption was observed at 98.69% under optimal conditions, including a pH of 6, an adsorbent dose of 1 g/L, a lead concentration of 25 mg/L, a temperature of 25 °C, and an exposure time of 120 min. The results of this study demonstrate that Haematococcus pluvialis has the potential for effective lead removal from aquatic environments.

While the influence of heavy metals on certain algae species has been explored, research on the impact of lead on Haematococcus pluvialis­a microalga of significant interest for astaxanthin production­remains uncharted territory. Therefore, understanding the impact of this heavy metal and the alga's metal absorption capabilities has profound implications for biotechnology and bioremediation applications. This study promotes H. pluvialis as an economically viable lead absorbent suitable for both industrial and domestic purposes.

Comparative Proteome Profiling of Extracellular Vesicles from Three Growth Phases of Haematococcus pluvialis under High Light and Sodium Acetate Stresses.

Extracellular vesicles (EVs) are nano-sized particles involved in intercellular communications that intrinsically possess many attributes as a modern drug delivery platform. Haematococcus pluvialis-derived EVs (HpEVs) can be potentially exploited as a high-value-added bioproduct during astaxanthin production. The encapsulation of HpEV cargo is a crucial key for the determination of their biological functions and therapeutic potentials. However, little is known about the composition of HpEVs, limiting insights into their biological properties and application characteristics. This study examined the protein composition of HpEVs from three growth phases of H. pluvialis grown under high light (350 µmol·m-2·s-1) and sodium acetate (45 mM) stresses. A total of 2038 proteins were identified, the majority of which were associated with biological processes including signal transduction, cell proliferation, cell metabolism, and the cell response to stress. Comparative analysis indicated that H. pluvialis cells sort variant proteins into HpEVs at different physiological states. It was revealed that HpEVs from the early growth stage of H. pluvialis contain more proteins associated with cellular functions involved in primary metabolite, cell division, and cellular energy metabolism, while HpEVs from the late growth stage of H. pluvialis were enriched in proteins involved in cell wall synthesis and secondary metabolism. This is the first study to report and compare the protein composition of HpEVs from different growth stages of H. pluvialis, providing important information on the development and production of functional microalgal-derived EVs.

Environmentally relevant copper concentrations stimulate photosynthesis in Monoraphidium sp.

Microalgae require copper (Cu) in trace levels for their growth and metabolism, it is a vital component of certain metalloproteins. Although this element has been widely studied concerning microalgae physiology, the effects of environmentally relevant levels have been less studied. We studied the photosynthesis and growth of the Chlorophyte Monoraphidium sp. exposed to Cu ranging from low (1.7 nM) to high (589.0 nM) free Cu ions (Cu2+) concentrations. The growth rate was unaffected by Cu concentrations in the range of 1.7-7.4 nM Cu2+, but decreased beyond it. The relative maximum electron transport rate (rETRm), saturation irradiance (Ek), photochemical quenching (qP and qL), and PSII operating efficiency [Formula: see text] were stimulated in the 3.4-7.4 nM Cu2+ range, concentrations slightly higher than the control, whereas non-photochemical quenching (NPQ) gradually increased with increasing Cu2+. The photosystem II antenna size [Sigma (II)440] increased under high Cu (589.0 nM), which resulted in a decrease in the quinone A (QA) reduction time (tau). In contrast, the QA re-oxidation time was unaffected by Cu exposure. These findings show that a slight increase in Cu stimulated photosynthesis in Monoraphidium sp., whereas high Cu reduced photosynthesis and increased the dissipation of captured light energy. This research is a contribution to the understanding of the dynamic photo-physiological responses of Monoraphidium sp. to Cu ions.

Asterarcys quadricellulare (Chlorophyceae) protects H9c2 cardiomyoblasts from H2O2-induced oxidative stress.

Oxidative stress has recently been identified as an important mediator of cardiovascular diseases. The need to find efficient antioxidant molecules is essential in the disease's prevention. Therefore, the present study aimed to evaluate the potential of microalgae bioactive in protecting H9c2 cardiomyoblasts from H2O2-induced oxidative stress. Four microalgal species were investigated for their antioxidant capacity. A qualitative assessment of oxidative stress in H9c2 cardiomyoblasts stained with DCFH-DA, treated with the highly active microalgae extracts, was performed. The protein expression of total caspase-3 was also examined to investigate whether the extract protects H9c2 cardimyoblasts from H2O2-induced apoptosis. High antioxidant activity was observed for the hexanoic extracts after 10 days of cultivation. Asterarcys quadricellulare exhibited the highest antioxidant capacity of 110.59 ± 1.75 mg TE g-1 dry weight and was tested against H9c2 cardiomyoblasts, which were initially subjected to H2O2-induced oxidative stress. This hexanoic extract protected against H2O2 induced oxidative stress with a similar scavenging capacity as N-Acetylcysteine. Furthermore, total caspase-3 was increased following treatment with the hexanoic extract, suggesting that A. quadricellulare also had anti-apoptotic properties. The outcome of our study highlighted the possible use of the local A. quadricellulare strain QUCCCM10 as a natural, safe, and efficient antioxidant to prevent cardiovascular diseases.

The Time-Resolved Salt Stress Response of Dunaliella tertiolecta-A Comprehensive System Biology Perspective.

Algae-driven processes, such as direct CO2 fixation into glycerol, provide new routes for sustainable chemical production in synergy with greenhouse gas mitigation. The marine microalgae Dunaliella tertiolecta is reported to accumulate high amounts of intracellular glycerol upon exposure to high salt concentrations. We have conducted a comprehensive, time-resolved systems biology study to decipher the metabolic response of D. tertiolecta up to 24 h under continuous light conditions. Initially, due to a lack of reference sequences required for MS/MS-based protein identification, a high-quality draft genome of D. tertiolecta was generated. Subsequently, a database was designed by combining the genome with transcriptome data obtained before and after salt stress. This database allowed for detection of differentially expressed proteins and identification of phosphorylated proteins, which are involved in the short- and long-term adaptation to salt stress, respectively. Specifically, in the rapid salt adaptation response, proteins linked to the Ca2+ signaling pathway and ion channel proteins were significantly increased. While phosphorylation is key in maintaining ion homeostasis during the rapid adaptation to salt stress, phosphofructokinase is required for long-term adaption. Lacking ß-carotene, synthesis under salt stress conditions might be substituted by the redox-sensitive protein CP12. Furthermore, salt stress induces upregulation of Calvin-Benson cycle-related proteins.

Enantioselective Toxic Effects of Prothioconazole toward Scenedesmus obliquus.

Prothioconazole (PTC) is a broad-spectrum triazole fungicide with one asymmetric center and consists of two enantiomers, R-(-)-PTC and S-(+)-PTC. To address the concern of its environmental safety, the enantioselective toxic effects of PTC on Scendesmus obliquus (S. obliquus) were investigated. PTC racemates (Rac-PTC) and enantiomers exhibited dose-dependent acute toxicity effects against S. obliquus at a concentration from 1 to 10 mg·L-1. The 72 h-EC50 value of Rac-, R-(-)-, and S-(+)-PTC is 8.15, 16.53, and 7.85 mg·L-1, respectively. The growth ratios and photosynthetic pigment contents of the R-(-)-PTC treatment groups were higher than the Rac- and S-(+)-PTC treatment groups. Both catalase (CAT) activities and esterase activities were inhibited in the Rac- and S-(+)-PTC treatment groups at high concentrations of 5 and 10 mg·L-1, and the levels of malondialdehyde (MDA) were elevated, which exceeded the levels in algal cells for the R-(-)-PTC treatment groups. PTC could disrupt the cell morphology of S. obliquus and induce cell membrane damage, following the order of S-(+)-PTC ≈ Rac-PTC > R-(-)-PTC. The enantioselective toxic effects of PTC on S. obliquus provide essential information for its ecological risk assessment.

A transfer learning approach for predictive modeling of bioprocesses using small data.

Predictive modeling of new biochemical systems with small data is a great challenge. To fill this gap, transfer learning, a subdomain of machine learning that serves to transfer knowledge from a generalized model to a more domain-specific model, provides a promising solution. While transfer learning has been used in natural language processing, image analysis, and chemical engineering fault detection, its application within biochemical engineering has not been systematically explored. In this study, we demonstrated the benefits of transfer learning when applied to predict dynamic behaviors of new biochemical processes. Two different case studies were presented to investigate the accuracy, reliability, and advantage of this innovative modeling approach. We thoroughly discussed the different transfer learning strategies and the effects of topology on transfer learning, comparing the performance of the transfer learning models against benchmark kinetic and data-driven models. Furthermore, strong connections between the underlying process mechanism and the transfer learning model's optimal structure were highlighted, suggesting the interpretability of transfer learning to enable more accurate prediction than a naive data-driven modeling approach. Therefore, this study shows a novel approach to effectively combining data from different resources for bioprocess simulation.

Evaluation of Cellular Uptake and Removal of Chlorpropham in the Treatment of Dunaliella salina for Phytoene Production.

Chlorpropham is a carbamate herbicide that inhibits cell division and has been widely used as a potato sprout suppressant. Recently we showed that the microalga Dunaliella salina treated with chlorpropham massively accumulated the colourless carotenoids phytoene and phytofluene. Phytoene and phytofluene are valued for their antioxidant, UV-absorption and skin protectant properties; however, they are present in very low quantities in nature. The low toxicity herbicide chlorpropham seems a promising catalyst to produce phytoene in large quantities from CO2 and solar energy with D. salina. This study explored chlorpropham uptake by the algal cells, the formation of potential intermediate metabolites, and the removal of residual chlorpropham from harvested D. salina biomass. Algal biomass rapidly concentrated chlorpropham from culture media. However, washing the harvested biomass with fresh culture medium twice and five times removed ~83 and ~97% of the chlorpropham from the biomass, respectively, and retained algal cell integrity. Furthermore, chloroaniline, a common metabolite of chlorpropham degradation, was not detected in chlorpropham-treated cultures, which were monitored every two days for thirty days. Cells treated with chlorpropham for either 10 min or 24 h continued to over-accumulate phytoene after resuspension in an herbicide-free medium. These data imply that whilst Dunaliella cells do not possess the intracellular capacity to degrade chlorpropham to chloroaniline, the effect of chlorpropham is irreversible on cell nuclear division and hence on carotenoid metabolism.

Coelastrella terrestris for Adonixanthin Production: Physiological Characterization and Evaluation of Secondary Carotenoid Productivity.

A novel strain of Coelastrella terrestris (Chlorophyta) was collected from red mucilage in a glacier foreland in Iceland. Its morphology showed characteristic single, ellipsoidal cells with apical wart-like wall thickenings. Physiological characterization revealed the presence of the rare keto-carotenoid adonixanthin, as well as high levels of unsaturated fatty acids of up to 85%. Initial screening experiments with different carbon sources for accelerated mixotrophic biomass growth were done. Consequently, a scale up to 1.25 L stirred photobioreactor cultivations yielded a maximum of 1.96 mg·L-1 adonixanthin in free and esterified forms. It could be shown that supplementing acetate to the medium increased the volumetric productivity after entering the nitrogen limitation phase compared to autotrophic control cultures. This study describes a promising way of biotechnological adonixanthin production using Coelastrella terrestris.

ß-Carotene from the Alga Dunaliella bardawil Decreases Gene Expression of Adipose Tissue Macrophage Recruitment Markers and Plasma Lipid Concentrations in Mice Fed a High-Fat Diet.

Vitamin A and provitamin A carotenoids are involved in the regulation of adipose tissue metabolism and inflammation. We examined the effect of dietary supplementation using all-trans and 9-cis ß-carotene-rich Dunaliella bardawil alga as the sole source of vitamin A on obesity-associated comorbidities and adipose tissue dysfunction in a diet-induced obesity mouse model. Three-week-old male mice (C57BL/6) were randomly allocated into two groups and fed a high-fat, vitamin A-deficient diet supplemented with either vitamin A (HFD) or ß-carotene (BC) (HFD-BC). Vitamin A levels in the liver, WATs, and BAT of the HFD-BC group were 1.5-2.4-fold higher than of the HFD group. BC concentrations were 5-6-fold greater in BAT compared to WAT in the HFD-BC group. The eWAT mRNA levels of the Mcp-1 and Cd68 were 1.6- and 2.1-fold lower, respectively, and the plasma cholesterol and triglyceride concentrations were 30% and 28% lower in the HFD-BC group compared with the HFD group. Dietary BC can be the exclusive vitamin A source in mice fed a high-fat diet, as shown by the vitamin A concentration in the plasma and tissues. Feeding BC rather than vitamin A reduces adipose tissue macrophage recruitment markers and plasma lipid concentrations.

Toxic effects and molecular mechanisms of sulfamethoxazole on Scenedesmus obliquus.

The antibiotic sulfamethoxazole (SMX) is a pollutant that is widely distributed in the global water environment.This substance has toxic effects on various aquatic organisms. Previous studies on SMX have focused on its acute toxicity towards algae and the changes induced at biological and cellular levels, rather than its biotoxicity and mechanisms at the molecular level. In this study, we investigated the effects of SMX on Scenedesmus obliquus as the model organism by performing transmission electron microscopy and transcriptome sequencing analyses. Exposure to SMX promoted gene expression, resulting in changes to algal cell ultrastructure. The cell walls became blurred, the chloroplast structure was seriously damaged, and the number and volume of mitochondria per cell increased. These changes were related to the inhibition of cell growth, decrease in chlorophyll content, increase in cell membrane permeability, and increased production of reactive oxygen species, which led to increased amounts of the lipid peroxidation product malondialdehyde, and higher activities of antioxidant enzymes. Our results suggest that SMX affects gene expression by influencing non-coding RNA metabolic processes, leading to changes in nuclear structures. Abnormally expressed long non-coding RNAs extensively regulate downstream gene expression through various mechanisms, such as chromatin recombination, thereby promoting tumor occurrence, invasion, and metastasis. This abnormal expression may be an important mechanism underlying the carcinogenic effects of SMX.

Effects of Tetracycline on Scenedesmus obliquus Microalgae Photosynthetic Processes.

Tetracycline (TC) antibiotics can be detected worldwide in the aquatic environment due to their extensive use and low utilization efficiency, and they may affect the physiological processes of non-target organisms. In this study, the acute and sub-acute toxicities of TC on the freshwater microalga Scenedesmus obliquus were investigated with an emphasis on algal photosynthesis and transcription alterations during an 8 d TC exposure. The results showed that the IC10, IC30 and IC50 values were 1.8, 4.1 and 6.9 mg/L, respectively. During sub-acute exposure, the microalgae of the IC10 treatment was able to recover comparable growth to that of the control by day 7, while significantly lower cell densities were observed in the IC30 and IC50 treatments at the end of the exposure. The photosynthetic efficiency Fv/FM of S. obliquus first decreased as the TC concentration increased and then returned to a level close to that of the control on day 8, accompanied by an increase in photosynthetic activities, including light harvesting, electron transport and energy dissipation. Transcriptomic analysis of the IC10 treatment (1.8 mg/L TC) revealed that 2157 differentially expressed genes were up-regulated and 1629 were down-regulated compared with the control. KEGG and GO enrichments demonstrated that 28 photosynthesis-related genes involving light-harvesting chlorophyll protein complex, photosystem I, photosystem II, photosynthetic electron transport and enzymes were up-regulated, which may be the factor responsible for the enhanced photosynthesis and recovery of the microalgae. Our work may be helpful not only for gaining a better understanding of the environmental risk of TC at concentrations close to the real levels in natural waters, but also for explaining photosynthesis and related gene transcription induced by antibiotics.

Optimization of culture conditions for enhanced Dunaliella salina productions in mixotrophic culture.

Dunaliella salina (D. salina) is a green microalga known for its tendency to produce lipid and ß-carotene. Fatty acid profile, lipid and ß-carotene productions of the microalga D. salina cultivated under different mixotrophic conditions were assayed. Notably, in spite of a broad spectrum of substrates served, mixotrophic cultivations slightly affected the fatty acid composition, and as a result C16:0 and C18:0, C18:1, C18:2 and C18:3 were identified as main fatty acids. Lipid in dry weight biomass (DWB) hit a high of 24.3% at 5% of NaCL and linolenic acid in lipid reached a peak of 9.15% at 15% of NaCL in medium containing glucose and equal amounts of yeast extract and soy bean powder. One-factor-at-a-time was applied to elucidate the substrates which had noticeable impacts on ß-carotene production. Glucose, meat peptone, titanium dioxide nanoparticles (TiO2 NPs), pH 7.5 and 5% NaCL were identified as key process parameters impacting ß-carotene production. Following, the concentration of glucose, meat peptone and TiO2 NPs were optimized by using response surface method. The highest content of ß-carotene, 25.23 mg/g DWB, was obtained in medium composed of (g/L); 22.92 glucose, 5 meat peptone and 0.002 TiO2 NPs.

The unusual di-domain structure of Dunaliella salina glycerol-3-phosphate dehydrogenase enables direct conversion of dihydroxyacetone phosphate to glycerol.

Dunaliella has been extensively studied due to its intriguing adaptation to high salinity. Its di-domain glycerol-3-phosphate dehydrogenase (GPDH) isoform is likely to underlie the rapid production of the osmoprotectant glycerol. Here, we report the structure of the chimeric Dunaliella salina GPDH (DsGPDH) protein featuring a phosphoserine phosphatase-like domain fused to the canonical glycerol-3-phosphate (G3P) dehydrogenase domain. Biochemical assays confirm that DsGPDH can convert dihydroxyacetone phosphate (DHAP) directly to glycerol, whereas a separate phosphatase protein is required for this conversion process in most organisms. The structure of DsGPDH in complex with its substrate DHAP and co-factor nicotinamide adenine dinucleotide (NAD) allows the identification of the residues that form the active sites. Furthermore, the structure reveals an intriguing homotetramer form that likely contributes to the rapid biosynthesis of glycerol.

Astaxanthin Is Ketolated from Zeaxanthin Independent of Fatty Acid Synthesis in Chromochloris zofingiensis.

The biosynthesis of astaxanthin, a high-value keto-carotenoid with broad industrial applications, remains unambiguous in algae. Here, we dissected the astaxanthin biosynthetic pathway and the coordination between astaxanthin and triacylglycerol (TAG) biosynthesis in the emerging model alga Chromochloris zofingiensis In vivo and in vitro experiments demonstrated that astaxanthin, utilizing the methylerythritol phosphate pathway-derived isopentenyl diphosphate as the building block, was synthesized from ß-carotenoid ketolase-mediated ketolation of zeaxanthin rather than ß-carotenoid hydroxylase-mediated hydroxylation of canthaxanthin, thus leading to the buildup of astaxanthin and canthaxanthin as end products in C. zofingiensis The synthesized astaxanthin, stored in TAG-filled lipid droplets, was esterified mainly with the fatty acid C18:1, which was not catalyzed by any acyltransferase previously proposed. Astaxanthin accumulated in a well-coordinated manner with TAG, supported by the coordinated up-regulation of both biosynthetic pathways at the transcriptional level. Nevertheless, astaxanthin and TAG showed no interdependence: inhibition of de novo fatty acid biosynthesis severely attenuated TAG biosynthesis but promoted the accumulation of astaxanthin, particularly in the diester form, leading to a fivefold increase in the astaxanthin/TAG ratio; however, inhibition of astaxanthin biosynthesis showed little effect on TAG accumulation. Our data suggest that an increase in astaxanthin accumulation following inhibition of de novo fatty acid biosynthesis, which is not regulated at the transcriptional level, is likely derived from the conversion of other carotenoids rather than from a shunt of carbon flux from lipid biosynthesis. Combined, these findings further our understanding of astaxanthin biosynthesis and provide a feasible strategy for promoting astaxanthin content and purity in algae.

Ameliorating effects of dietary Haematococcus pluvialis on arsenic-induced oxidative stress in rainbow trout (Oncorhynchus mykiss) fillet.

The current study was performed to investigate the protective effects of dietary Haematococcus pluvialis (H. pluvialis) on the oxidative stress induced by arsenic in rainbow trout (Oncorhynchus mykiss). The fish (20.70 ± 0.09 g) were fed with H. pluvialis at the levels of 0.28, 0.56, and 1.12 g 100 g-1 diet for 60 days. Then, each group was divided into two subgroups. In one of the subgroups, fish were exposed to arsenic challenge at a level of 9.1 mg/L. The other subset was used as the negative control. After the 96 h of toxicity test, protein and lipid oxidative levels, antioxidant-relevant gene expression as well as several chemical factors, including pH and peroxide value and moisture content, were evaluated in the fillet samples. Results showed that feeding with H. pluvialis decreased the levels of pH, peroxide value, as well as protein and lipid oxidation levels in treatment groups. Besides, the expression of antioxidant genes was significantly increased in the groups administrated with H. pluvialis. Based on the results of this study, feeding H. pluvialis attenuated the oxidative stress induced by arsenic in rainbow trout fillet through improving the antioxidant defense system.

New Models to Predict the Acute and Chronic Toxicities of Representative Species of the Main Trophic Levels of Aquatic Environments.

To assess the impact of chemicals on an aquatic environment, toxicological data for three trophic levels are needed to address the chronic and acute toxicities. The use of non-testing methods, such as predictive computational models, was proposed to avoid or reduce the need for animal models and speed up the process when there are many substances to be tested. We developed predictive models for Raphidocelis subcapitata, Daphnia magna, and fish for acute and chronic toxicities. The random forest machine learning approach gave the best results. The models gave good statistical quality for all endpoints. These models are freely available for use as individual models in the VEGA platform and for prioritization in JANUS software.

Toxicity of Zn-Fe Layered Double Hydroxide to Different Organisms in the Aquatic Environment.

The application of layered double hydroxide (LDH) nanomaterials as catalysts has attracted great interest due to their unique structural features. It also triggered the need to study their fate and behavior in the aquatic environment. In the present study, Zn-Fe nanolayered double hydroxides (Zn-Fe LDHs) were synthesized using a co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analyses. The toxicity of the home-made Zn-Fe LDHs catalyst was examined by employing a variety of aquatic organisms from different trophic levels, namely the marine photobacterium Vibrio fischeri, the freshwater microalga Pseudokirchneriella subcapitata, the freshwater crustacean Daphnia magna, and the duckweed Spirodela polyrhiza. From the experimental results, it was evident that the acute toxicity of the catalyst depended on the exposure time and type of selected test organism. Zn-Fe LDHs toxicity was also affected by its physical state in suspension, chemical composition, as well as interaction with the bioassay test medium.