Formation and toxicity alteration of halonitromethanes from Chlorella vulgaris during UV/chloramination process involving bromide ion.

Frequent algal blooms cause algal cells and their algal organic matter (AOM) to become critical precursors of disinfection by-products (DBPs) during water treatment. The presence of bromide ion (Br-) in water has been demonstrated to affect the formation laws and species distribution of DBPs. However, few researchers have addressed the formation and toxicity alteration of halonitromethanes (HNMs) from algae during disinfection in the presence of Br-. Therefore, in this work, Chlorella vulgaris was selected as a representative algal precursor to investigate the formation and toxicity alteration of HNMs during UV/chloramination involving Br-. The results showed that the formation concentration of HNMs increased and then decreased during UV/chloramination. The intracellular organic matter of Chlorella vulgaris was more susceptible to form HNMs than the extracellular organic matter. When the Br-: Cl2 mass ratio was raised from 0.004 to 0.08, the peak of HNMs total concentration increased 33.99%, and the cytotoxicity index and genotoxicity index of HNMs increased 67.94% and 22.80%. Besides, the formation concentration and toxicity of HNMs increased with increasing Chlorella vulgaris concentration but decreased with increasing solution pH. Possible formation pathways of HNMs from Chlorella vulgaris during UV/chloramination involving Br- were proposed based on the alteration of nitrogen species and fluorescence spectrum analysis. Furthermore, the formation laws of HNMs from Chlorella vulgaris in real water samples were similar to those in deionized water samples. This study contributes to a better comprehension of HNMs formation from Chlorella vulgaris and provides valuable information for water managers to reduce hazards associated with the formation of HNMs.

Impact of the biomass pretreatment and simulated gastrointestinal digestion on the digestibility and antioxidant activity of microalgae Chlorella vulgaris and Tetraselmis chuii.

Chlorella vulgaris and Tetraselmis chuii are two microalgae species already marketed because of their richness in high-value and health-beneficial compounds. Previous studies have demonstrated the biological properties of compounds isolated from both microalgae, although data are not yet available on the impact that pre-treatment and gastrointestinal digestion could exert on these properties. The aim of the present study was to analyze the impact of the biomass pre-treatment (freeze/thaw cycles plus ultrasounds) and simulated gastrointestinal digestion in the bioaccessibility and in vitro antioxidant activity (ABTS, ORAC, Q-FRAP, Q-DPPH) of the released digests. The cell wall from microalgae were susceptible to the pre-treatment and the action of saliva and gastric enzymes, releasing bioactive peptides and phenolic compounds that contributed to the potent antioxidant activity of digests through their radical scavenging and iron reduction capacities. Our findings suggest the potential of these microalgae against oxidative stress-associated diseases at both, intestinal and systemic level.

Enhancing the biodiesel production in the green alga Chlorella vulgaris by heavy metal stress and prediction of fuel properties from fatty acid profiles.

The green microalga Chlorella vulgaris was used as a test organism during this study for evaluation of the impact of different heavy metal stress, Mn2+, Co2+, and Zn2+, on enhancing the biodiesel production. The algal cultures were grown for 13 days under heavy metal stress after which were subjected to estimation of growth, some primary metabolites, lipid, and fatty acid profiles. The maximum lipid accumulation (283.30 mg/g CDW) was recorded in the algal culture treated with 3 µM cobalt nitrate. Application of 2 mM manganese chloride; 1, 2, and 3 µM cobalt nitrate; and 0.2, 0.4, and 0.6 mM zinc sulfate caused highly significant increases in the lipid contents amounting to 183.8, 191.4, 230.6, 283.3, 176.3, 226.0, and 212.1 mg/g CDW, respectively, in comparison to control (153.4 mg/g CDW). The maximum proportion of saturated fatty acids (SFA) (64.44%) was noted in the culture treated with 6 mM MnCl2 due to the existence of palmitic acid (C16:0), stearic acid (C18:0), and pentadecylic acid (C15:0) which are represented by 53.59%, 5.96%, and 1.37%, respectively, of the total FAs. Relative increase in energy compound (REEC) showed that 1, 2, and 3 µM Co2+ lead to the highest stimulation in lipid and carbohydrate contents to 0.207, 0.352, and 0.329 × 103%, respectively. Empirical formulas were used for the assessment of biodiesel fuel properties based on FAME composition. The estimated properties met the prescribed international standard criteria.

Exploring the potential nutritional benefits of Arthrospira maxima and Chlorella vulgaris: A focus on vitamin B12, amino acids, and micronutrients.

Arthrospira (Limnospira) maxima (A. maxima) and Chlorella vulgaris (Ch. vulgaris) are among the approved microalgae and cyanobacteria (MaC) in the food industry that are known to be safe for consumption. However, both organisms are controversial regarding their vitamin B12 content, due to the possible occurrence of pseudo-cobalamin. Concurrently, their nutrition profiles remain understudied. The main purpose of the present study was to identify their nutrition profiles, focusing mainly on vitamin B12, amino acids, and micronutrients under iron-induced hormesis (10 mg/L Fe in treated samples). Our findings indicate a higher B12 content in A. maxima compared to Ch. vulgaris (both control and treated samples). Using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the cyanocobalamin content was determined as 0.42 ± 0.09 µg/g dried weight (DW) in the A. maxima control and 0.55 ± 0.02 µg/g DW in treated A. maxima, resulting in an insignificant difference. In addition, the iron-enriched medium increased the amount of iron in both tested biomasses (p < 0.01). However, a more pronounced (approximately 100×) boost was observed in Ch. vulgaris, indicating a better absorption capacity (control Ch. vulgaris 0.16 ± 0.01 mg/g Fe, treated Ch. vulgaris 15.40 ± 0.34 mg/g Fe). Additionally, Ch. vulgaris also showed a higher micronutrient content. Using both tested microalgae, meeting the sufficient recommended daily mineral allowance for an adult is possible. By combining biomass from A. maxima and Ch. vulgaris in a ratio of 6:1, we can fulfill the recommended daily allowance of vitamin B12 and iron by consuming 6 tablets/6 g. Importantly, iron hormesis stimulated amino acid composition in both organisms. The profile of amino acids may suggest these biomasses as promising potential nutrition sources.

Therapeutic potential of Lactobacillus casei and Chlorella vulgaris in high-fat diet-induced non-alcoholic fatty liver disease (NAFLD)-associated kidney damages: a stereological study.

BACKGROUND: The non-alcoholic fatty liver disease (NAFLD) is prevalent in as many as 25% of adults who are afflicted with metabolic syndrome. Oxidative stress plays a significant role in the pathophysiology of hepatic and renal injury associated with NAFLD. Therefore, probiotics such as Lactobacillus casei (LBC) and the microalga Chlorella vulgaris (CV) may be beneficial in alleviating kidney injury related to NAFLD. MATERIALS AND METHODS: This animal study utilized 30 C57BL/6 mice, which were evenly distributed into five groups: the control group, the NAFLD group, the NAFLD + CV group, the NAFLD + LBC group, and the NAFLD + CV + LBC group. A high-fat diet (HFD) was administered to induce NAFLD for six weeks. The treatments with CV and LBC were continued for an additional 35 days. Biochemical parameters, total antioxidant capacity (TAC), and the expression of kidney damage marker genes (KIM 1 and NGAL) in serum and kidney tissue were determined, respectively. A stereological analysis was conducted to observe the structural changes in kidney tissues. RESULTS: A liver histopathological examination confirmed the successful induction of NAFLD. Biochemical investigations revealed that the NAFLD group exhibited increased ALT and AST levels, significantly reduced in the therapy groups (p < 0.001). The gene expression levels of KIM-1 and NGAL were elevated in NAFLD but were significantly reduced by CV and LBC therapies (p < 0.001). Stereological examinations revealed reduced kidney size, volume, and tissue composition in the NAFLD group, with significant improvements observed in the treated groups (p < 0.001). CONCLUSION: This study highlights the potential therapeutic efficacy of C. vulgaris and L. casei in mitigating kidney damage caused by NAFLD. These findings provide valuable insights for developing novel treatment approaches for managing NAFLD and its associated complications.

Chlorella vulgaris algae ameliorates chlorpyrifos toxicity in Nile tilapia with special reference to antioxidant enzymes and Streptococcus agalactiae infection.

BACKGROUND: Chlorpyrifos (CPF) is a widely used pesticide in the production of plant crops. Despite rapid CPF biodegradation, fish were exposed to wastewater containing detectable residues. Recently, medicinal plants and algae were intensively used in aquaculture to replace antibiotics and ameliorate stress impacts. METHODS AND RESULTS: An indoor experiment was conducted to evaluate the deleterious impacts of CPF pollution on Nile tilapia health and the potential mitigation role of Chlorella vulgaris algae. Firstly, the median lethal concentration LC50 - 72 h of CPF was determined to be 85.8 µg /L in Nile tilapia (35.6 ± 0.5 g body weight) at a water temperature of 27.5 °C. Secondly, fish were exposed to 10% of LC50 - 72 h for six weeks, and tissue samples were collected and examined every two weeks. Also, Nile tilapia were experimentally infected with Streptococcus agalactiae. Exposed fish were immunosuppressed expressed with a decrease in gene expressions of interleukin (IL) 1ß, IL-10, and tumor necrosis factor (TNF)-α. Also, a decline was recorded in glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) gene expression in the head kidney tissue. A high mortality rate (MR) of 100% was recorded in fish exposed to CPF for six weeks and challenged with S. agalactiae. Fish that received dietary C. vulgaris could restore gene expression cytokines and antioxidants compared to the control. After six weeks of CPF exposure, fish suffered from anemia as red blood cell count (RBCs), hemoglobin (Hb), and packed cell volume (PCV) significantly declined along with downregulation of serum total protein (TP), globulin (GLO), and albumin (ALB). Liver enzymes were significantly upregulated in fish exposed to CPF pollution, alanine aminotransferase (ALT) (42.5, 53.3, and 61.7 IU/L) and aspartate aminotransferase (AST) (30.1, 31.2, and 22.8) after 2, 4, and 6 weeks, respectively. On S. agalactiae challenge, high MR was recorded in Nile tilapia exposed to CPF (G3) 60%, 60%, and 100% in week 2, week 4, and week 6, and C. vulgaris provided a relative protection level (RPL) of 0, 14.29, and 20%, respectively. CONCLUSIONS: It was concluded that CPF pollution induces immunosuppressed status, oxidative stress, and anemic signs in Nile tilapia. In contrast, C. vulgaris at a 50 g/kg fish feed dose could partially ameliorate such withdrawals, restoring normal physiological parameters.

Microcystin-LR (MC-LR) inhibits green algae growth by regulating antioxidant and photosynthetic systems.

Microcystins release from bloom-forming cyanobacteria is considered a way to gain competitive advantage in Microcystis populations, which threaten water resources security and aquatic ecological balance. However, the effects of microcystins on microalgae are still largely unclear. Through simulated culture experiments and the use of UHPLC-MS-based metabolomics, the effects of two microcystin-LR (MC-LR) concentrations (400 and 1,600 µg/L) on the growth and antioxidant properties of three algae species, the toxic Microcystis aeruginosa, a non-toxic Microcystis sp., and Chlorella vulgaris, were studied. The MC-LR caused damage to the photosynthetic system and activated the protective mechanism of the photosynthetic system by decreasing the chlorophyll-a and carotenoid concentrations. Microcystins triggered oxidative stress in C. vulgaris, which was the most sensitive algae species studied, and secreted more glycolipids into the extracellular compartment, thereby destroying its cell structure. However, C. vulgaris eliminated reactive oxygen species (ROS) by secreting terpenoids, thereby resisting oxidative stress. In addition, two metabolic pathways, the vitamin B6 and the sphingolipid pathways, of C. vulgaris were significantly disturbed by microcystins, contributing to cell membrane and mitochondrial damage. Thus, both the low (400 µg/L) and the high (1,600 µg/L) MC-LR concentration inhibited algae growth within 3 to 7 days, and the inhibition rates increased with the increase in the MC-LR concentration. The above results indicate that the toxin-producing Microcystis species have a stronger toxin tolerance under longer-term toxin exposure in natural water environments. Thus, microcystins participates in interspecific interaction and phytoplankton population regulation and creates suitable conditions for the toxin-producing M. aeruginosa to become the dominant species in algae blooms.

A Comparative Analysis Assessing Growth Dynamics of Locally Isolated Chlorella sorokiniana and Chlorella vulgaris for Biomass and Lipid Production with Biodiesel Potential.

Prior research has emphasized the potential of microalgae in biodiesel production, driven by their ability to replace fossil fuels. However, the significant costs associated with microalgae cultivation present a major obstacle to scaling up production. This study aims to develop an eco-friendly microalgae cultivation system by integrating carbon dioxide from flue gas emissions with an affordable photobioreactor, providing a sustainable biomass production. The research evaluates the growth performance of Chlorella sorokiniana and Chlorella vulgaris across this integrated system for biomass and lipid production. Results indicate substantial biomass yields of 1.97 and 1.84 g/L, with lipid contents of 35 % and 41 % for C. sorokiniana and C. vulgaris, respectively. The macrobubble photobioreactor demonstrates high potential for microalgae biomass and lipid production, yielding quality fatty acid methyl esters such as palmitic, linoleic and stearic. This study presents an environmentally friendly system for efficient microalgae cultivation, generating lipid-rich biomass suitable for biodiesel production.

Alleviating binary toxicity of polystyrene nanoplastics and atrazine to Chlorella vulgaris through humic acid interaction: Long-term toxicity using environmentally relevant concentrations.

In this study, microalgae Chlorella vulgaris (C. vulgaris) were simultaneously exposed to environmental concentrations of amino-functionalized polystyrene nanoplastics (PS-NH2; 0.05, 0.1, 0.2, 0.3 and 0.4 mg/L) and the world's second most used pesticide, the herbicide atrazine (ATZ; 10 µg/L), in the absence and presence of humic acid (HA; 1 mg/L) for 21 days. Due to the low concentrations of PS-NH2, the majority of them could not cause a significant difference in the end-points of biomass, chlorophylls a and b, total antioxidant, total protein, and superoxide dismutase and malondialdehyde compared to the control group (p > 0.05). On the other hand, by adding ATZ to the PS-NH2, all the mentioned end-point values showed a considerable difference from the control (p < 0.05). The exposure of PS-NH2+ATZ treatments to the HA could remarkably reduce their toxicity, additionally, HA was able to decrease the changes in the expression of genes related to oxidative stress (e.g., superoxide dismutase, glutathione reductase, and catalase) in the C. vulgaris in the most toxic treatment group (e.g., PS-NH2+ATZ). The synergistic toxicity of the PS-NH2+ATZ group could be due to their enhanced bioavailability for algal cells. Nevertheless, the toxicity alleviation in the PS-NH2+ATZ treatment group after the addition of HA could be due to the eco-corona formation, and changes in their zeta potential from positive to negative value, which would increase their electrostatic repulsion with the C. vulgaris cells, in such a way that HA also caused a decrease in the formation of C. vulgaris-NPs hetero-aggregates. This research underscores the complex interplay between PS-NH2, ATZ, and HA in aquatic environments and their collective impact on microalgal communities.

Predicting the Structure of Enzymes with Metal Cofactors: The Example of [FeFe] Hydrogenases.

The advent of deep learning algorithms for protein folding opened a new era in the ability of predicting and optimizing the function of proteins once the sequence is known. The task is more intricate when cofactors like metal ions or small ligands are essential to functioning. In this case, the combined use of traditional simulation methods based on interatomic force fields and deep learning predictions is mandatory. We use the example of [FeFe] hydrogenases, enzymes of unicellular algae promising for biotechnology applications to illustrate this situation. [FeFe] hydrogenase is an iron-sulfur protein that catalyzes the chemical reduction of protons dissolved in liquid water into molecular hydrogen as a gas. Hydrogen production efficiency and cell sensitivity to dioxygen are important parameters to optimize the industrial applications of biological hydrogen production. Both parameters are related to the organization of iron-sulfur clusters within protein domains. In this work, we propose possible three-dimensional structures of Chlorella vulgaris 211/11P [FeFe] hydrogenase, the sequence of which was extracted from the recently published genome of the given strain. Initial structural models are built using: (i) the deep learning algorithm AlphaFold; (ii) the homology modeling server SwissModel; (iii) a manual construction based on the best known bacterial crystal structure. Missing iron-sulfur clusters are included and microsecond-long molecular dynamics of initial structures embedded into the water solution environment were performed. Multiple-walkers metadynamics was also used to enhance the sampling of structures encompassing both functional and non-functional organizations of iron-sulfur clusters. The resulting structural model provided by deep learning is consistent with functional [FeFe] hydrogenase characterized by peculiar interactions between cofactors and the protein matrix.

Impact of organic matter molecular weight on hexavalent chromium enrichment in green microalgae.

In lightly polluted water containing heavy metals, organic matter, and green microalgae, the molecular weight of organic matter may influence both the growth of green microalgae and the concentration of heavy metals. This study elucidates the effects and mechanisms by which different molecular weight fractions of fulvic acid (FA), a model dissolved organic matter component, facilitate the bioaccumulation of hexavalent chromium (Cr(VI)) in a typical green alga, Chlorella vulgaris. Findings show that the addition of FA fractions with molecular weights greater than 10 kDa significantly enhances the enrichment of total chromium and Cr(VI) in algal cells, reaching 21.58%-31.09 % and 16.17 %-22.63 %, respectively. Conversely, the efficiency of chromium enrichment in algal cells was found to decrease with decreasing molecular weight of FA. FA molecular weight within the range of 0.22 µm-30 kDa facilitated chromium enrichment primarily through the algal organic matter (AOM) pathway, with minor contributions from the algal cell proliferation and extracellular polymeric substances (EPS) pathways. However, with decreasing FA molecular weight, the AOM and EPS pathways become less prominent, whereas the algal cell proliferation pathway becomes dominant. These findings provide new insights into the mechanism of chromium enrichment in green algae enhanced by medium molecular weight FA.

Pulsed electric field (PEF) processing of microalga Chlorella vulgaris and its digestibility in broiler feed.

Microalgae have potentially beneficial effects on animal health and nutritional value when added to feed. Crucial hereby is that intracellular bio-active molecules are released in the intestinal tract. Digestibility of Chlorella vulgaris and its impact on total digestibility of broiler feed is a first step in assessing its characteristics as feed supplement. Different methods could be used to increase the digestibility of the algae. Among other, pulsed electric field (PEF) and freezing to disrupt autotrophic (A) and heterotrophic (H) Chlorella vulgaris cells was assessed to increase their availability followed by in-vivo trials. In these trials effect of algae type (A and H) and effect of PEF-processing was evaluated on the apparent nutrient digestibility. Pulsed electric field showed to have a disruption efficiency of 83.90% and 79.20% for heterotrophic and autotrophic C. vulgaris respectively. Freezing C. vulgaris only showed efficiencies ranging from 3.86 to 11.58%. In the in-vivo trials, microscopic counting of intact C. vulgaris cells showed an increase in digested intact C. vulgaris cells of PEF-processed C. vulgaris compared to nonprocessed cells ranging from 12.16% to 15.20%. Autotrophic C. vulgaris had a higher digestibility compared to heterotrophic C. vulgaris, with an increase of 7.29, 9.44, and 17.29% in digestibility of C. vulgaris in the 1, 2, and 5% feed respectively. Feeds with PEF-processed C. vulgaris showed no significant increase in digestibility compared to nonprocessed C. vulgaris supplemented feeds. The 5% C. vulgaris feeds showed lower fat digestibility than the 1 and 2% and control feeds. Protein digestibility was lower for all C. vulgaris feeds compared to the control feed. There was a significant linear decreasing effect (P < 0.001) for all digestibility parameters. Except for crude ash digestibility, which first lowered for the 1 and 2% feeds, but then increased at 5% inclusion. Considering this study, including low dosages of 1 and 2% of C. vulgaris in broiler feed does not compromise its digestibility.

Presence of humic acid in the environment holds promise as a potential mitigating factor for the joint toxicity of polystyrene nanoplastics and herbicide atrazine to Chlorella vulgaris: 96-H acute toxicity.

Increasing amounts of amino-functionalized polystyrene nanoplastics (PS-NH2) are entering aquatic ecosystems, raising concerns. Hence, this study investigated 96-h acute toxicity of PS-NH2 and its combination with the pesticide atrazine (ATZ) in the absence/presence of humic acid (HA) on the microalgae Chlorella vulgaris (C. vulgaris). Results showed that both PS-NH2 and PS-NH2+ATZ reduced algal growth, photosynthetic pigments, protein content, and antioxidant capacity, while increasing enzymatic activities. Gene expression related to oxidative stress was altered in C. vulgaris exposed to these treatments. Morphological and intracellular changes were also observed. The combined toxicity of PS-NH2+ATZ demonstrated a synergistic effect, but the addition of environmentally relevant concentration of HA significantly alleviated its toxicity to C. vulgaris, indicating an antagonistic effect due to the emergence of an eco-corona, and entrapment and sedimentation of PS-NH2+ATZ particles by HA. This study firstly highlights the role of HA in mitigating the toxicity of PS-NH2 when combined with other harmful compounds, enhancing our understanding of HA's presence in the environment.

Low-cost pyrolysis of biomass-derived nitrogen-doped porous carbon: Chlorella vulgaris replaces melamine as a nitrogen source.

Porous carbon generated from biomass has a rich pore structure, is inexpensive, and has a lot of promise for use as a carbon material for energy storage devices. In this work, nitrogen-doped porous carbon was prepared by co-pyrolysis using bagasse as the precursor and chlorella as the nitrogen source. ZnCl2 acts as both an activator and a nitrogen fixer during activation to generate pores and reduce nitrogen loss. The thermal weight loss experiments showed that the pyrolysis temperatures of bagasse and chlorella overlap, which created the possibility for the synthesis of nitrogen-rich biochar. The optimum sample (ZBC@C-5) possessed a surface area of 1508 m2g-1 with abundant nitrogen-containing functional groups. ZBC@C-5 in the three-electrode system exhibited 244.1F/g at 0.5A/g, which was extremely close to ZBC@M made with melamine as the nitrogen source. This provides new opportunities for the use of low-cost nitrogen sources. Furthermore, the devices exhibit better voltage retention (39%) and capacitance retention (96.3%). The goal of this research is to find a low cost, and effective method for creating nitrogen-doped porous carbon materials with better electrochemical performance for highly valuable applications using bagasse and chlorella.

Combined toxic effects of polystyrene nanoplastics and lead on Chlorella vulgaris growth, membrane lipid peroxidation, antioxidant capacity, and morphological alterations.

In recent years, there has been a significant rise in the utilization of amino-functionalized polystyrene nanoplastics (PS-NH2). This surge in usage can be attributed to their exceptional characteristics, including a substantial specific surface area, high energy, and strong reactivity. These properties make them highly suitable for a wide range of industrial and medical applications. Nevertheless, there is a growing apprehension regarding their potential toxicity to aquatic organisms, particularly when considering the potential impact of heavy metals like lead (Pb) on the toxicity of PS-NH2. Herein, we examined the toxic effects of sole PS-NH2 (90 nm) at five concentrations (e.g., 0, 0.125, 0.25, 0.5, and 1 mg/L), as well as the simultaneous exposure of PS-NH2 and Pb2+ (using two environmental concentrations, e.g., 20 µg/L for Pb low (PbL) and 80 µg/L for Pb higher (PbH)) to the microalga Chlorella vulgaris. After a 96-h exposure, significant differences in chlorophyll a content and algal growth (biomass) were observed between the control group and other treatments (ANOVA, p < 0.05). The algae exposed to PS-NH2, PS-NH2 + PbL, and PS-NH2 + PbH treatment groups exhibited dose-dependent toxicity responses to chlorophyll a content and biomass. According to the Abbott toxicity model, the combined toxicity of treatment groups of PS-NH2 and PbL,H showed synergistic effects. The largest morphological changes such as C. vulgaris' size reduction and cellular aggregation were evident in the medium treated with elevated concentrations of both PS-NH2 and Pb2+. The toxicity of the treatment groups followed the sequence PS-NH2 < PS-NH2 + PbL < PS-NH2 + PbH. These results contribute novel insights into co-exposure toxicity to PS-NH2 and Pb2+ in algae communities.

Prediction of acute toxicity for Chlorella vulgaris caused by tire wear particle-derived compounds using quantitative structure-activity relationship models.

Tire wear particles (TWPs) enter aquatic ecosystems through various pathways, such as rainwater and urban runoff. Additives in TWPs can harm aquatic organisms in these ecosystems. Therefore, it is essential to investigate their toxicity to aquatic organisms. In our study, we initially recorded the median effective concentrations of 21 TWP-derived compounds on Chlorella vulgaris growth, ranging from 0.04 to 8.60 mg/L. Subsequently, through an extensive review of the literature, we incorporated 112 compounds with specific toxicity endpoints to construct the QSAR model using genetic algorithm and multiple linear regression techniques, followed by the construction of the consensus model and the quantitative read-across structure-activity relationship (q-RASAR) model. Meanwhile, we employed rigorous internal and external validation measures to assess the performance of the model. The results indicated that the developed q-RASAR model exhibited strong adaptation, robustness, and reliable prediction, with q-RASAR indicators of Q2LOO = 0.7673, R2tr = 0.8079, R2test = 0.8610, Q2Fn = 0.8285-0.8614, and CCCtest = 0.9222. Based on an external dataset containing 128 emerging TWP-derived compounds, the model's applicability domain coverage was 90.6 %. The q-RASAR model predicted that the structure of diphenylamine was associated with higher toxicity, possibly liked to the SpMax2_Bhm and LogBCF descriptors. The established model reliably provides prediction and fills a critical data gap. These findings highlight the potential risks posed by emerging TWP-derived compounds to aquatic organisms.

Nutrients recovery from dairy wastewater by Chlorella vulgaris and comparison of the lipid's composition with various chlorella strains for biodiesel production.

Microalgae biomass is regarded as a promising feedstock for biodiesel production. The biomass lipid content and fatty acids composition are among the main selective criteria when screening microalgae strains for biodiesel production. In this study, three strains of Chlorella microalgae (C. kessleri, C. sorokiniana, C. vulgaris) were cultivated nutrient media with different nitrogen contents, and on a medium with the addition of dairy wastewater. Moreover, microalgae grown on dairy wastewater allowed the removal of azote and phosphorous. The removal efficiency of 90%, 53% and 95% of ammonium nitrogen, total nitrogen and phosphate ions, respectively, were reached. The efficiency of wastewater treatment from inorganic carbon was 55%, while the maximum growth of biomass was achieved. All four samples of microalgae had a similar fatty acid profile. Palmitic acid (C16:0) was the most abundant saturated fatty acid (SFA), and is suitable for the production of biodiesel. The main unsaturated fatty acids (UFA) present in the samples were oleic acid (C18:1 n9); linoleic acid (C18:2 n6) and alpha-linolenic acid (C18:3 n3), which belong to omega-9, omega-6, omega-3, respectively.

Inorganic carbon limitation decreases ammonium removal and N2O production in the algae-nitrifying bacteria symbiosis system.

Ammonium removal by a symbiosis system of algae (Chlorella vulgaris) and nitrifying bacteria was evaluated in a long-term photo-sequencing batch reactor under varying influent inorganic carbon (IC) concentrations (15, 10, 5 and 2.5 mmol L-1) and different nitrogen loading rate (NLR) conditions (270 and 540 mg-N L-1 d-1). The IC/N ratios provided were 2.33, 1.56, 0.78 and 0.39, respectively, for an influent NH4+-N concentration of 90 mg-N L-1 (6.43 mmol L-1). The results confirmed that both ammonium removal and N2O production were positively related with IC concentration. Satisfactory ammonium removal efficiencies (>98 %) and rates (29-34 mg-N gVSS-1 h-1) were achieved regardless of NLR levels under sufficient IC of 10 and 15 mmol L-1, while insufficient IC at 2.5 mmol L-1 led to the lowest ammonium removal rates of 0 mg-N gVSS-1 h-1. The ammonia oxidation process by ammonia oxidizing bacteria (AOB) played a predominant role over the algae assimilation process in ammonium removal. Long-time IC deficiency also resulted in the decrease in biomass and pigments of algae and nitrifying bacteria. IC limitation led to the decreasing N2O production, probably due to its negative effect on ammonia oxidation by AOB. The optimal IC concentration was determined to be 10 mmol L-1 (i.e., IC/N of 1.56, alkalinity of 500 mg CaCO3 L-1) in the algae-bacteria symbiosis reactor, corresponding to higher ammonia oxidation rate of ∼41 mg-N gVSS-1 h-1 and lower N2O emission factor of 0.13 %. This suggests regulating IC concentrations to achieve high ammonium removal and low carbon emission simultaneously in the algae-bacteria symbiosis wastewater treatment process.

Removal of polycyclic aromatic hydrocarbons (PAHs) from produced water using the microalgae Chlorella vulgaris cultivated in mixotrophic and heterotrophic conditions.

Chlorella vulgaris was cultivated for 15 days in 10 different treatments under mixotrophic and heterotrophic conditions, using wastewater from oil and poultry industries as the culture medium. The blends were made with produced water (PW), sterilized produced water (PWs), sterilized poultry wastewater (PoWs), sterilized seawater (SWs), and the addition of sodium nitrate to evaluate cell growth in treatments and the removal of PAHs. The heterotrophic condition showed more effective removal, having an initial concentration of 3.93 µg L-1 and a final concentration of 0.57 µg L-1 of total PAHs reporting 83%, during phycoremediation of (PW) than the mixotrophic condition, with an initial concentration of 3.93 µg L-1 and a final concentration of 1.96 and 43% removal for the PAHs. In the heterotrophic condition, the blend with (PWs + SWs) with an initial concentration of 0.90 µg L-1 and a final concentration of 0.32 µg L-1 had 64% removal of total PAHs compared to the mixotrophic condition with 37% removal having an initial concentration of 0.90 µg L-1 and a final concentration of 0.56 µg L-1. However, the best result in the mixotrophic condition was obtained using a blend of (PWs + PoWs) that had an initial cell concentration of 1.18 × 105 cells mL-1 and reached a final cell concentration of 4.39 × 105 cells mL-1, an initial concentration of 4.76 µg L-1 and a final concentration of 0.37 µg L-1 having a 92% total removal of PAHs. The biostimulation process increased the percentage of PAHs removal by 45% (PW) in the mixotrophic condition. This study showed that it is possible to allow an environmental remediation strategy that significantly reduces effluent toxicity and generates high value-added biomass in contaminated effluents rich in nutrients and carbon, based on a circular bioeconomy model.

Molecular mechanism of dissolvable metal nanoparticles-enhanced CO2 fixation by algae: Metal-chlorophyll synthesis.

Algae-driven photosynthetic CO2 fixation is a promising strategy to mitigate global climate changes and energy crises. Yet, the presence of metal nanoparticles (NPs), particularly dissolvable NPs, in aquatic ecosystems introduces new complexities due to their tendency to release metal ions that may perturb metabolic processes related to algal CO2 fixation. This study selected six representative metal NPs (Fe3O4, ZnO, CuO, NiO, MgO, and Ag) to investigate their impacts on CO2 fixation by algae (Chlorella vulgaris). We discovered an intriguing phenomenon that bivalent metal ions released from the metal NPs, especially from ZnO NPs, substituted Mg2+ within the porphyrin ring. This interaction led to 81.8% and 76.1% increases in Zinc-chlorophyll and Magnesium-chlorophyll contents within algal cells at 0.01 mM ZnO NPs, respectively. Integrating metabolomics and transcriptomics analyses revealed that ZnO NPs mainly promoted the photosynthesis-antenna protein pathway, porphyrin and chlorophyll metabolism, and carbon fixation pathway, thereby mitigating the adverse effects of Zn2+ substitution in light harvesting and energy transfer for CO2 fixation. Ultimately, the genes encoding Rubisco large subunit (rbcL) responsible for CO2 fixation were upregulated to 2.60-fold, resulting in a 76.3% increase in carbon fixation capacity. Similar upregulations of rbcL expression (1.13-fold) and carbon fixation capacity (76.1%) were observed in algal cells even at 0.001 mM ZnO NPs, accompanied by valuable lipid accumulation. This study offers novel insights into the molecular mechanism underlying NPs on CO2 fixation by algae and potentially introduces strategies for global carbon sequestration.