Search Results (603)

Bisphenol A (BPA) is a common plastic additive found in wastewater (WW) due to its extensive use in industrial and consumer products. As a known endocrine disruptor, BPA poses serious ecological and human health risks, yet its removal remains inefficient in conventional WW treatment plants. This novel study investigates the impact of high environmental BPA concentrations (5 mg/L and 25 mg/L) on Chlorella vulgaris in a WW-mimicking environment, assessing microalgal growth, metabolic activity, nutrient removal, and BPA degradation. Exposure to BPA led to a significant reduction in esterase activity and an increase in intracellular reactive oxygen species (ROS) levels, indicating cellular oxidative stress and metabolic disruption. Despite these effects, C. vulgaris maintained stable photosynthetic pigment levels, demonstrating a resilient photosynthetic function. The bioremediation potential of C. vulgaris was also compromised, with nitrogen and phosphorus removal efficiencies decreasing by up to 38% and 34% in the presence of 5 and 25 mg BPA/L, respectively. Nevertheless, the microalga exhibited the ability to degrade BPA, with removal efficiencies of 34% for 5 mg/L and 21% for 25 mg/L after 168 h, while abiotic degradation was minimal. These findings confirm the potential of C. vulgaris as a promising sustainable approach for BPA bioremediation but also highlight critical challenges at high contaminant concentrations. Full article

A series of 7-aminopyrazolo[1,5-d][1,2,4]triazin-4(5H)-ones was synthesized via a cascade condensation of methyl aroylpyruvates with 1,3-diaminoguanidine hydrochloride. The scope and limitations of this approach were investigated. Methyl mesitoylpyruvate bearing a sterically hindered mesityl substituent diverted the reaction pathway, affording a 1,2,4-triazine derivative. Diethyl 2,4,6-trioxoheptanedioate resulted in an unexpected pyrazolo[1,5-d][1,2,4]triazepine scaffold. All synthesized compounds were evaluated for growth-regulating activity using the green microalga Chlorella vulgaris as a model organism. 7-Amino-2-(4-methoxyphenyl)pyrazolo[1,5-d][1,2,4]triazin-4(5H)-one has shown the best results in the initial microplate screening, showing increased cell density at 10 μmol/L. However, subsequent validation in 50 mL flask cultures revealed no significant effect on biomass accumulation, photosynthetic pigment content, carbohydrate levels, or neutral lipid production compared to the negative control. Only a modest increase in protein content was observed at the concentration of 100 μmol/L. Full article

Microalgae represent a promising alternative as biofertilizers and biostimulants, providing essential nutrients and bioactive compounds that support plant growth. In this study, a screening of seven microalgal species—including Arthrospira platensis, Nannochloris sp., Chlorella sp., Chlorella vulgaris, Acutodesmus obliquus, Parachlorella kessleri, Coelastrella vacuolata—and one isolated mixed culture was conducted to evaluate their potential as biostimulants and biofertilizers under autotrophic cultivation conditions. Whole cultures and corresponding supernatants were directly applied, without any pretreatment, reducing potential processing costs. Their biostimulant activity was evaluated through multiple bioassays, including germination index and auxin- and cytokinin-like responses, while nitrogen, phosphorus, and potassium content was analyzed to assess biofertilizer potential. The results revealed that biostimulant effects were strongly influenced by species, concentration, and sample fraction. Chlorella species consistently showed high performance across assays, combining strong germination and rooting responses with high nitrogen content (8.2–8.8% w/w), while A. platensis and Nannochloris sp. showed inhibitory effects in many cases. Overall, under the cultivation and application conditions tested, C. vulgaris, mixed culture, and A. obliquus are identified as promising candidates for combined biostimulant and biofertilizer applications. This study is a primary step in identifying the most promising species as an alternative to synthetic fertilizers, enabling further optimization towards more sustainable agricultural practices. Full article

Ketoprofen (KET) is a non-steroidal anti-inflammatory drug frequently detected in surface waters and effluents, with the potential to impact trophic base organisms. This study evaluated the toxicity of KET, in its active pharmaceutical ingredient (API) form and in four commercial formulations (KET-1, KET-2, KET-3, and KET-4), on two freshwater species: the cyanobacterium Microcystis novacekii and the microalga Chlorella vulgaris. Cell growth assays, performed under acute (4 days) and chronic (14 days) conditions, showed that the API KET was the most toxic compound, especially for M. novacekii, with a chronic EC50 of 1.35 mg/L. The commercial formulations presented distinct toxicity profiles, suggesting the influence of excipients and synergistic or antagonistic interactions. For C. vulgaris, low acute toxicity was observed, with increased chronic effects at high concentrations and possible hormetic response at low doses. Risk quotient (RQ) calculations, based on environmental concentrations of KET, indicated low risk in surface and drinking water, but high risk in untreated hospital and wastewater treatment plant effluents, especially for M. novacekii. The results show that the complete formulation, exposure time, and target species are critical factors in the ecotoxicological risk assessment of pharmaceuticals in freshwater environments. Full article

Excessive concentrations of carbon dioxide (CO₂) in the atmosphere lead to adverse environmental effects. Biologically assisted processes that rely on organisms such as microalgae (i.e., Chlorella vulgaris) are common in capturing CO₂ from the atmosphere. Microalgae are rich in proteins, vitamins, minerals, and omega-3 fatty acids. Thus, microalgae production serves both health and environmental sectors. Varying light intensity and temperature are shown to influence algae growth. To quantify algae production under different light intensity and temperature conditions, and monitoring or scaling-up of biological reactors, reliable mathematical models are required. In this work, mathematical models that incorporate light intensity and temperature effects on algae growth in batch and continuous bioreactors are developed. Based on the modeling, the growth rate is maximum at T_opt = 25 °C, reaching the value of μ_max = 0.14 day⁻¹. The growth rate exponentially increases until light intensity (I) reaches around 150 ${\displaystyle \frac{\mathsf{\mu }\mathrm{m}\mathrm{o}\mathrm{l}}{{\mathrm{m}}^2\mathrm{s}}}$, which is approximately the optimal light intensity for Chlorella vulgaris. The effect of T on growth rate is found to be more sensitive than light intensity (I) in both batch and continuous reactor systems. When there are too many parameters in models, uncertainties exist and parameter estimation and model predictions become cumbersome. For these reasons analytical solutions to the models are presented in simplified forms and these models are more practical and easier to implement. The novelty of the work is also the presentation of the models in analytical forms. Analytical solutions to the two reactor models (batch and continuous) will help quantify biomass production as a function of time under the varying light intensity and temperature conditions encountered. Full article

Microalgae are photosynthetic organisms that produce bioproducts of commercial interest and are efficient sequestering CO₂. The monitoring and control processes are areas for improvement to increase the efficiency of its production. There are sensor options for monitoring microalgae cultures, but the vast majority rely on microcontrollers, often lacking the robustness required for applications in more demanding conditions. Also, commercial systems with industrial capabilities can fit the above purpose, but they require licensing and are expensive. Therefore, this work presents the technical details of developing an open-source platform to monitor environmental variables using Modbus industrial sensors and Python used to control the photoperiod and for measuring pH, dissolved oxygen, electrical conductivity, water and air temperatures, photosynthetic photon flux density, irradiance, and turbidity in three photobioreactors containing the microalgae Chlorella vulgaris. The resulting time series showed that the platform preserved data and had a low outlier rate. pH measurements showed that during photosynthesis, the microalgae used CO₂ as their carbon source. Dissolved oxygen and culture medium temperature had an almost perfect Pearson’s anticorrelation with air-sparging. However, with aeration interruption, the correlation was $-0.804$, because dissolved oxygen depends on illumination, aeration, temperature, and biomass quantity, as shown in the time series. Full article

Harvesting remains one of the main bottlenecks in microalgae-based technologies. Although microalgae hold great promise for industrial biotechnology, their growth in dilute suspensions makes biomass recovery challenging. Conventional harvesting methods are often energy-intensive and costly, limiting large-scale implementation. This study applies a life cycle assessment (LCA) to evaluate the environmental performance of a laboratory-scale magnetic harvesting process of Chlorella vulgaris (C. vulgaris) using Fe₃O₄ microparticles in combination with polyaluminum chloride (PAC) and polyacrylamide (PAM), followed by magnetic oscillation for particle detachment and subsequent reuse. Electricity consumption was identified as the dominant environmental hotspot across most impact categories, with the detachment step accounting for nearly two-thirds of the total energy demand, a step often overlooked in previous LCA studies. The global warming potential (GWP) is consistent with typical laboratory-scale assessments and is mainly driven by energy inefficiencies associated with small processing volumes. The values obtained and the scale-up literature indicate that further optimization and future industrial-scale production will decrease these values into a realistic and competitive range. Sensitivity analysis showed that replacing grid electricity with photovoltaic power significantly reduces environmental impacts. The use of NaOH as a reagent also contributed substantially to environmental impacts. Reusing magnetic particles (4 cycles) reduced material resource depletion by up to fourfold, which is a very relevant result bearing in mind the principles of sustainability and circularity. Full article

Cultivation knowledge deficiencies limit the appreciation of microalgae-based nutrient solutions on hydroponic plants. This study compared Chlorella vulgaris implications for lettuce growth and the production of high-value components through the use of four different co-cultivation hydroponic scenarios. The results of 30-day co-cultivation of Chlorella vulgaris and lettuce demonstrated the significance of controls of pH (7.0–7.75) and green microalgal cell density (10⁷ cells/mL) to improve the qualities in lettuce leaf growth, root vigor, and nutrient yield from days 15 to 30 during the co-cultivation. Plant height increased by 19%, leaf area by 4%, root cortex thickness by 14% (p < 0.05), total chlorophyll content by 49%, soluble sugar content by 12%, and protein content by 6% through the adoption of 1.0 × 10⁷~1.6 × 10⁷ cells/mL of microalgal solution during hydroponic cultivation. Furthermore, the aerated hydroponic device benefits of co-cultivating high-concentration Chlorella vulgaris and lettuce resulted in a 1.0-time increase in vitamin C compared to the cultivation of low-concentration Chlorella vulgaris. This study highlights the benefits of the sustainable strategy of the microalgal cultivation technique used in the hydroponic systems for nutritious and healthy leafy vegetable growers, which is also emphasized for eco-friendly bioactive compound production. Full article

Particulate emerging contaminants (PECs) pose increasing ecological risks due to their widespread occurrence and complex environmental behaviors, yet their heterogeneous toxic mechanisms remain poorly understood, especially under environmentally relevant conditions and concentration gradients. Here, Chlorella vulgaris was used as a model organism to systematically compare the effects of polystyrene nanoparticles (PSNPs), silver nanoparticles (AgNPs), and titanium dioxide nanoparticles (TiO₂NPs) across environmentally relevant and elevated concentrations (100 μg/L and 10 mg/L). Distinct toxicity pathways were identified among PEC types. PSNPs primarily induced chronic interference via particle–cell interactions, heteroaggregation, sedimentation-driven shading, and extracellular polymeric substance (EPS) regulation, rather than ROS-dominated toxicity. In contrast, AgNPs exhibited transformation-driven toxicity, undergoing intracellular speciation into Ag₂S, AgCl, and Ag⁺, which triggered oxidative stress, membrane damage, and lipid peroxidation. TiO₂NPs showed relatively high bioavailability and persistent oxidative stress effects. These results demonstrate that PEC toxicity evolves with particle type and concentration. Importantly, oxidative stress alone is insufficient to capture PEC ecotoxicity, which also involves the long-term impacts on algal behavior, sedimentation dynamics, and energy metabolism. This study provides mechanistic insights into PEC-induced algal toxicity and supports the source-oriented management of particulate pollutants in aquatic environments, particularly in hotspot scenarios such as wastewater discharge and sediment resuspension. Full article

The interfacial behavior of hybrid nanoparticles on biological substrates governs their functional performance. Here, we investigate how surface properties and colloidal stability dictate the pH-dependent adhesion of oxybenzone-loaded palygorskite nanohybrids to hair—a model biological interface. A series of hybrids with 5–50% oxybenzone loadings were prepared via melt impregnation. XRD and FTIR analyses confirm hydrogen bonding between oxybenzone and palygorskite, forming stable organic–inorganic hybrids. The colloidal stability of these nanohybrids varies non-monotonically with oxybenzone loading, governed by surface hydrophilicity and zeta potential, exhibiting a network-like behavior upon pH change. Optimal stability is achieved at an intermediate loading with a favorable balance of surface properties. While pristine hybrids show no affinity for hair, surface modification with cationic polyquaternium-7 (PQ-7) or non-ionic polyvinylpyrrolidone (PVP) enables effective deposition through distinct pH-dependent mechanisms: PQ-7 operates optimally at pH 10 via electrostatic attraction, whereas PVP performs best at pH 4 through hydrogen bonding, forming a protective coating layer on the hair surface. Deposition fails for PVP-modified hybrids at 50% loading due to excessive surface hydrophobicity. The deposited hybrids provide exceptional UV protection, significantly mitigating cuticle damage, suppressing photo-yellowing, and minimizing protein oxidation. Among the hybrids, hybrid-35 exhibited the best colloidal stability, whereas PQ-7-modified hybrid-50 gave the highest UV protection (color difference ΔE reduced from 10.51 to 1.60). The adhesion rates of the two best-performing hybrids were 2.70% and 2.85%, respectively. Beyond hair protection, we evaluate the environmental interface of these materials. While free oxybenzone is highly toxic to Chlorella vulgaris, hybridization drastically reduces its ecotoxicity. Remarkably, palygorskite and the hybrids promote algal growth, likely by acting as nutrient adsorbents and attachment sites. This work provides fundamental insights into particle–biointerface interactions and offers a strategy for designing functional hybrid materials with tailored surface properties for bio-related applications. Full article

The increasing demand for sustainable materials in additive manufacturing has driven the development of bioplastics derived from renewable biomass, including microalgae. In this study, the rheological behavior of a 20 wt.% aqueous gel prepared from native Chlorella vulgaris (C. vulgaris) starch, plasticized with 30 wt.% glycerol, was investigated to assess its suitability for extrusion-based 3D printing (direct-ink-writing, DIW). Steady shear analysis revealed a pronounced yield stress (${\tau }_0$ = 271.93 Pa) and strong shear-thinning behavior, described by the Herschel–Bulkley model (K = 59.47 Pa·sⁿ, n = 0.67), indicating structural stability at rest and efficient flow under shear. Oscillatory measurements confirmed a predominantly elastic response, with storage modulus (G′ $\approx$ 13,500 Pa) greatly exceeding loss modulus (G″) and a low loss factor (tan $\delta \approx$ 0.1), demonstrating gel integrity and shape retention. Temperature-dependent analysis indicated enhanced network strength without thermal softening, while thixotropic recovery tests showed rapid structural rebuilding after shear removal. Notably, a $~$50% increase in G′ during recovery highlights improved interlayer adhesion potential. These results show that C. vulgaris starch exhibits the key rheological characteristics required for DIW-type extrusion printing, including yield stress, shear-thinning behavior, viscoelastic stability, and rapid recovery, making it a promising candidate for this application. Full article

Ornamental fountains in the Alhambra and Generalife (Granada, Spain) constitute complex socio-ecological systems where water, stone, and biological communities interact, making them highly vulnerable to biodeterioration caused by phototrophic microorganisms such as cyanobacteria, green algae, and diatoms. Conventional chemical biocides, although widely applied, present significant drawbacks including toxicity, material degradation, ecological imbalance, and limited long-term effectiveness. In this context, this study evaluated the potential of algicidal bacteria as a sustainable alternative for controlling phototrophic growth in heritage environments. Water samples from eight ornamental fountains were analyzed using 16S ribosomal RNA (16S rRNA) gene sequencing to characterize bacterial communities and identify taxa previously reported with algicidal activity. Statistical analyses were conducted to assess relationships between microbial community structure and biofilm development. In parallel, functional screening assays using filtered fountain waters against Chlorella vulgaris were performed to evaluate intrinsic inhibitory capacity. The most active sample was selected for bacterial isolation and further validation through co-culture assays, cell density measurements, and pulse-amplitude-modulated (PAM) fluorometry. A total of 18 genera with reported algicidal capacity were detected, representing a substantial fraction of the microbiome across all samples. However, no significant association was found between these taxonomic metrics and biofilm development, highlighting a decoupling between taxonomic composition and functional activity. The most active isolate, identified as Stenotrophomonas maltophilia strain LIG25, caused a rapid decline in photosynthetic efficiency and achieved more than 98% inhibition of algal growth. These findings demonstrate that ornamental fountain microbiomes represent a reservoir of native biocontrol agents and support the development of eco-friendly strategies for cultural heritage conservation. Full article

Biological biogas upgrading using microalgae offers a sustainable route for simultaneous CO₂ removal and biomass production. This study sequentially evaluated liquid-to-gas ratios, L/G, of 0.6–4.0, photoperiods of 0:24–16:8 h, and light intensities of 150–400 µmol m⁻² s⁻¹ in a semi-continuous photobioreactor–absorption column (PBR-AC) with Chlorella vulgaris under moderate alkalinity conditions of 1053–1350 mg L⁻¹ CaCO₃. The system operated at D = 0.1 d⁻¹, a gas flow of 0.05 L min⁻¹, and GRT of 1.30 h. Increasing L/G from 0.6 to 4.0 improved CO₂-RE from 67.9% to 81.6% and CH₄ from 77.0% to 82.9%, showing that intensified recirculation partly compensated for the moderate carbonate-buffering capacity. Among illuminated photoperiods, 16:8 h performed best, reaching 81.4% CO₂-RE and 81.7% CH₄. At L/G = 4.0 and 16:8 h, increasing photosynthetic photon flux density (PPFD) from 200 to 300 µmol m⁻²·s⁻¹ further improved CO₂-RE from 81.4% to 82.86%, CH₄ from 81.7% to 84.4%, and biomass productivity from 0.230 to 0.250 g L⁻¹ d⁻¹. The dark control achieved 57.06% CO₂-RE, indicating substantial physicochemical CO₂ absorption, while illumination added up to 24.35 percentage points. Overall, the system showed strong upgrading potential under moderate alkalinity, although O₂ contamination, which was 1.5–2.5%, remains a key limitation. Full article

Microalgae are valuable biotechnological resources due to their high productivity and their capacity to synthesize compounds with nutritional and antioxidant functions. However, in the Santa Elena Peninsula (Ecuador), their use in aquaculture is limited to commercial strains. In this study, native microalgae were isolated and evaluated for their nutritional value in aquaculture. Samples were collected at five coastal sites, cultivated under controlled conditions, and characterized using optical microscopy and SEM, identified at the molecular level through the 28S rRNA gene, and their biochemical profiles were analyzed, including carotenoid quantification. The isolates were identified as PM-UPSE-006 (Tetradesmus obliquus), PM-UPSE-007 (Conticribra weissflogii), PM-UPSE-016 (Halamphora coffeiformis), PM018 (Dunaliella sp.), and PM-UPSE-022 (Chlorella vulgaris), with T. obliquus and H. coffeiformis being recorded for the first time in the peninsula. The highest growth rates were observed in T. obliquus, Dunaliella sp., and C. vulgaris, while Dunaliella sp. and C. vulgaris stood out for their protein content (57.28% DM and 55.37% DM), T. obliquus for carbohydrates (40.5% DM), and H. coffeiformis, Dunaliella sp., and C. vulgaris for carotenoids (0.53–1.60% DM). These results demonstrate their ex situ adaptability, competitive growth, and noteworthy biochemical profiles, establishing them as promising biotechnological resources for sustainable aquaculture. Full article

Heavy metal pollution poses a serious threat to aquatic ecosystems. Microalgae have attracted considerable attention due to their dual potential for heavy metal removal and lipid recovery. However, studies that simultaneously achieve both heavy metal removal and lipid accumulation remain very limited. The short-term (3 h) and long-term (3 days) effects of single and mixed Cu²⁺, Zn²⁺, and Pb²⁺ stress on Chlorella vulgaris FACHB-8 were investigated for heavy metal removal and lipid recovery. Removal rates varied with metal species, concentration, and single vs. mixed systems. At 3 h, the order was Pb²⁺ > Cu²⁺ > Zn²⁺; at 3 days, Pb²⁺ ≈ Zn²⁺ > Cu²⁺. The Zn²⁺+Pb²⁺ combination maintained >90% removal across all concentrations, whereas Cu²⁺ removal was impeded (65–85%). Long-term stress maximized lipid content at 30% under 1 mg/L Cu²⁺ or 0.5 mg/L Cu²⁺+Zn²⁺, while Pb²⁺ restricted it to ≤12.85%. Cu²⁺ (1 mg/L) produced the highest saturated fatty acids (69.95%, dominated by C16:0 and C18:0), favorable for biodiesel. Highly toxic Pb²⁺ impaired cellular integrity and suppressed carbon allocation to lipids, whereas moderate Cu²⁺ or Cu²⁺+Zn²⁺ stress induced synergistic lipid and SFA accumulation. This metabolic shift was associated with upregulated superoxide dismutase (SOD) and acetyl-CoA carboxylase (ACC) activities, mitigating oxidative damage and redirecting carbon flux toward lipid biosynthesis as a defense strategy. Full article