Search Results (611)

Green synthesis has emerged as a sustainable alternative to conventional nanoparticle production by utilizing biological resources as reducing and stabilizing agents. In this study, extracts of Chlorella vulgaris cultured at different incubation temperatures and light periods were evaluated for their total phenolic content, total flavonoid content, and antioxidant capacity to identify the most suitable extract for the green synthesis of zirconium dioxide (ZrO₂) nanoparticles. The extract prepared at 25 °C under a 12 h light/12 h dark photoperiod exhibited the highest antioxidant activity and flavonoid content and was selected for nanoparticle synthesis. ZrO₂ nanoparticles were successfully synthesized using a green approach and characterized by dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-Ray diffraction (XRD). DLS analysis revealed hydrodynamic particle sizes ranging from 419 to 570 nm with polydispersity index values between 0.27 and 0.44. FTIR analysis confirmed the formation of ZrO₂ through characteristic Zr–O and Zr–O–Zr vibrational bands, while SEM images demonstrated predominantly spherical particles with a heterogeneous size distribution. The synthesized nanoparticles retained considerable phenolic and flavonoid contents and exhibited enhanced antioxidant activity compared with the corresponding algal extracts. Furthermore, the nanoparticles demonstrated broad-spectrum antibacterial activity against both Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria, as well as antifungal activity against Candida albicans and Saccharomyces cerevisiae. Nanoparticles synthesized by incubation at 40 °C for 12 h showed the strongest antimicrobial activity. These findings demonstrate that cultivation conditions of C. vulgaris and the synthesis conditions of the nanoparticles significantly influence nanoparticle properties and biological activity, highlighting the potential of microalgae-mediated green synthesis for developing environmentally friendly antimicrobial nanomaterials. Full article

The growing demand for sustainable, non-animal-derived, and low-allergenic protein alternatives has driven research into innovative sources such as microalgae. This review focuses on three key microalgal species Arthrospira platensis (Spirulina), Chlorella vulgaris, and Tetraselmis chuii. It examines their cell wall structures, protein content, and amino acid profiles. Protein extraction methods, including physical, enzymatic, and chemical approaches, are critically discussed. Downstream purification techniques aimed at improving protein purity and quality are also reviewed. Protein characterization methods are discussed, highlighting their relevance to food applications. The potential applications of microalgal biomass and protein extracts in food and beverage products are evaluated, with consideration given to their functionality, safety, and regulatory aspects. Despite significant advances in this field, further research is essential to optimize extraction and processing technologies, facilitate their integration into mainstream food production, and improve overall process efficiency. Full article

The development of sustainable, nutrient-dense food systems requires a comprehensive understanding of how microalgae influence the mechanical properties of starch hydrogels. While certain microalgae are common food additives, a critical research gap remains regarding their effect on the rheological behavior and structural integrity of potato starch gels specifically. This study addressed this gap by evaluating the mechanical, microstructural and optical impacts of Arthrospira platensis (commonly known as Spirulina) and Chlorella vulgaris at 0.5%, 1% and 2% (w/w). Utilizing steady-shear flow tests, colorimetry, NIR spectroscopy and microscopy, we characterized changes in steady rheological parameters, color, chemical changes and microstructure of fortified hydrogels. Results indicated that filamentous Arthrospira platensis reinforces the matrix, significantly increasing yield stress from 10.2 Pa in the control to 32.4 Pa at 2% inclusion. In contrast, spherical Chlorella vulgaris appears to act as a structural filler, reducing yield stress to 4.8 Pa at 2%. Microscopy confirmed these morphological influences, showing Arthrospira platensis filaments entangling granules while Chlorella cells integrated into inter-granular spaces. Colorimetry revealed significant darkening (L* decreased from 31.59 to 18.54 at 2% Spirulina addition) and significant greening (p < 0.05). NIR spectroscopy demonstrated potential physical interactions via vibrational markers at 5172 cm⁻¹ and 5646 cm⁻¹, indicating water matrix redistribution within the system. This research demonstrates how incorporating Spirulina and Chlorella vulgaris provides a viable approach for modifying the physical properties of starch-based matrices. The findings indicate that Spirulina enhances flow resistance and structural stability under steady shear, whereas Chlorella vulgaris reduces flow barriers, thereby increasing the spreadability of these composite food systems. Full article

Global population growth has emphasised the need to have sustainable and alternative sources of nutrients. In this context, microalgae have emerged as a potential solution due to their rich biochemical composition, including high-quality proteins, carbohydrates, lipids, and pigments. This study investigates the variation in microalgal growth and biochemical composition over a light:dark cycle, with a focus on the night period. Batch experiments were performed with eight Chlorella vulgaris cultures over a 7-day period. On the seventh day, biomass samples were collected at four time points in four-hour intervals and stored for subsequent biochemical analyses. During the eight-hour dark period, biomass, carbohydrate, and total chlorophyll concentrations decreased by 9%, 12.5%, and 14.4%, respectively. After four hours of light exposure, these parameters increased significantly by 6%, 15.4%, and 12.7%, respectively. Total protein, carotenoids, and fatty acid contents remained relatively stable throughout the evaluated cycle, although variations were observed in the carotenoid profile. During the dark phase, zeaxanthin decreased by 38.0%, whereas violaxanthin increased by 27.2%, suggesting complementary pigment interconversion consistent with xanthophyll cycle activity. Overall, these results highlight the importance of optimising harvesting time to enhance the production of target compounds in a sustainable production of microalgal biomass. Full article

Interactions between cyanobacteria and eukaryotic algae are traditionally viewed as favoring cyanobacteria, which are often the dominant competitors in freshwater ecosystems. However, increasing evidence suggests that eukaryotic algae also possess effective chemical defenses capable of suppressing cyanobacterial proliferation. In this study, the anti-cyanobacterial potential of a methanolic biomass extract of the green microalga Chlorella vulgaris against the bloom-forming cyanobacterium Microcystis aeruginosa was investigated. Optical density measurements revealed the inhibition of cyanobacterial growth, with extract concentrations of 0.4–1.6 mg mL⁻¹ significantly reducing biomass accumulation. The lowest concentration (0.2 mg mL⁻¹) stimulated the accumulation of phycobiliproteins, whereas concentrations of 0.8–1.6 mg mL⁻¹ significantly decreased phycobiliprotein content, indicating progressive physiological impairment. The results suggest that the highest extract concentration applied may also cause alteration in phosphate acquisition. Lipid profiling of the Chlorella biomass showed that 97% of the extractable lipids consisted of methanol-soluble fatty acids, with C18 fatty acids predominating among the 20 identified compounds. These metabolites are reported to possess allelopathic activity and therefore represent plausible contributors to the observed inhibition. These findings support that anti-cyanobacterial activity may represent a widespread ecological trait of Chlorella and potentially other green microalgae, providing a promising foundation for environmentally friendly cyanobacterial bloom management. Full article

The objective of the present study was to evaluate the impact of high-density polyethylene (HDPE) used in two particle sizes (40 and 125 µm) on selected biochemical parameters in two species of green algae: Chlorella vulgaris and Scenedesmus quadricauda. Exposure to microplastics resulted in decreased cell numbers (up to 43%) and reductions in protein (up to 42%), monosaccharide, and chlorophyll contents in both algal species. Oxidative stress, as reflected by increased hydrogen peroxide levels (up to 120%) and enhanced lipid peroxidation, was observed in HDPE-treated cells. This was accompanied by elevated antioxidant enzyme activity, changes in ascorbate and proline content, and alterations in carotenoid composition. Thus, toxicity of HDPE and the induction of defense mechanisms involved in adaptation to environmental pollutants were confirmed in both microalgae. Changes in the physicochemical properties of the tested polymer surface were investigated using Fourier-Transform Infrared Spectroscopy, scanning electron microscopy (SEM), and porosimetry analysis. The presence of biofilm, hydroxyl groups, higher total pore volume, and maximum pore width on the surface of the microplastic confirmed that green algae may be responsible for the first step in HDPE structure modifications. Understanding the interactions between such micropollutants and green algae, key primary producers in aquatic food webs, is therefore essential. Full article

This study systematically investigated the hydrothermal liquefaction (HTL) of Chlorella vulgaris to understand how operating conditions influence bio-crude oil yield, nitrogen behavior, fuel properties, and compositional changes. A Box–Behnken design (BBD) was used, with temperature (200–300 °C), pressure (50–200 bar), and reaction time (15–45 min) as the process variables. Bio-crude oil yields ranged from 11.10 to 40.79 wt% (dry basis), and nitrogen content varied between 2.34 and 6.22 wt%. Temperature was the primary factor affecting both bio-crude oil yield and nitrogen content. Higher temperatures increasedbio-crude oil production but also led to more nitrogen incorporating into the oil phase, indicating a trade-off between yield and nitrogen retention. Van Krevelen analysis showed that HTL bio-crude had lower O/C ratios than the raw microalgal feedstock, suggesting progressive deoxygenation under more severe HTL conditions. GC–MS analysis revealed that hydrocarbons increased and fatty acids decreased with rising temperature. Nitrogen-containing compounds such as amides and N-heterocyclic compounds, were still detectable at high temperatures. Multi-response optimization identified 300 °C, 200 bar, and 15 min as the optimal conditions, balancing maximized bio-crude oil yield with minimized nitrogen content. These results suggest that HTL bio-crude oil is regarded as an intermediate feedstock requiring further upgrading. Therefore, optimizing the HTL process should simultaneously consider both fuel-related properties and nitrogen behavior. Full article

Microalgae of the genus Chlorella are widely used in biotechnology for biofuel production, wastewater treatment, and biomass generation. This study examined the effect of initial biomass concentration on the growth kinetics of Chlorella vulgaris cultivated in cylindrical photobioreactors. Experiments were performed in identical 4 L reactors under constant illumination (~300 µmol·m⁻²·s⁻¹), aeration (0.5 vvm), and atmospheric CO₂ (~0.04%). Four initial biomass concentrations (0.012, 0.053, 0.110, and 0.530 g·L⁻¹) were tested in duplicate. Growth curves were fitted using the logistic, Gompertz, and Baranyi–Roberts models. The best-performing Gompertz model was further extended by relating its kinetic parameters to the initial biomass concentration, allowing biomass productivity to be evaluated as a continuous function of cultivation time and inoculum level. Initial biomass strongly affected growth dynamics. Increasing the initial concentration from 0.012 to 0.110 g·L⁻¹ reduced the lag phase from 53.9 ± 5.1 h to 4.0 ± 6.9 h, while no distinct lag phase was observed at 0.530 g·L⁻¹. Meanwhile, the maximum specific growth rate decreased from 0.0507 to 0.0251 h⁻¹. The model-based analysis indicated that the optimal initial biomass concentration is time-dependent: higher values are preferable for short cultivations, whereas lower values become advantageous during prolonged cultivation. Although the predicted optimum partly lies between experimentally tested values and should be interpreted as exploratory rather than predictive, the proposed approach demonstrates the potential of model-assisted optimization for future process design, pending experimental validation. Full article

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