Search Results (37)

Studies of complex natural environments often focus on either biodiversity or on isolating organisms with specific properties. In this study, we sought to widen this perspective and achieve both. In particular, hypersaline ecosystems, such as the Sečovlje salt pans (Slovenia), are particularly promising sources of novel bioactive compounds, as their microorganisms have evolved adaptations to desiccation and high light intensity stress. We applied shotgun metagenomics to assess microbial biodiversity under low- and high-salinity conditions, complemented by isolation and cultivation of photosynthetic microorganisms. Metagenomic analyses revealed major shifts in community composition with increasing salinity: halophilic Archaea became dominant, while bacterial abundance decreased. Eukaryotic assemblages also changed, with greater representation of salt-tolerant genera such as Dunaliella sp. Numerous additional microorganisms with biotechnological potential were identified. Samples from both petola and brine led to the isolation and cultivation of Dunaliella sp., Tetradesmus obliquus, Tetraselmis sp. and cyanobacteria Phormidium sp./Sodalinema stali, Leptolyngbya sp., and Capilliphycus guerandensis. The newly established cultures are the first collection from this hypersaline environment and provide a foundation for future biodiscovery, production optimization, and sustainable bioprocess development. The methods developed in this study constitute a Toolbox Solution that can be easily replicated in other habitats. Full article

Incorporating microalgae into integrated biotechnologies facilitates rational resource management. Cultivation of microalgae in various types of wastewater offers a number of advantages: safe disposal of liquid waste, restoration of water resources, and the production of valuable products. This study presents a comparative analysis of the growth and biomass productivity of various algal strains in an unsterilized fish processing plant wastewater. Desmodesmus sp. EE-M8 demonstrated the most efficient growth, with a biomass yield of 2.21 ± 0.09 g L⁻¹. The average biomass yield obtained during the growth of Chlorella vulgaris SB-M4, Chlorella sp. EE-P5, Micractinium inermum EE-M2, and Tetradesmus obliquus EZ-B11 ranged from 1.42 to 1.96 g L⁻¹. Ammonium, phosphate, and sulfate ions were completely utilized from the wastewater during algal growth. In addition, the bacterial community structure of wastewater was found to change drastically toward the dominance of Alphaproteobacteria during the microalgal growth. The algal strains (in combination with bacterial partners) used to determine their biostimulant potential demonstrated a positive effect on the germination of garden cress seeds. These findings demonstrate that incorporating algae into the wastewater purification process will reduce the negative impact on the environment and produce valuable biomass for various purposes. Full article

The filtration of microalgae generates fouling through algal matter and exopolymer particles with consequences for the flow rate. Therefore, regeneration that is as complete and continuous as possible is necessary. For this purpose, a commercial membrane with a pore size of 0.8 µm is contaminated with the microalgae mixture Haematoccocus Pluvialis and Tetradesmus obliquus, and then regenerated with mechanical (backwashing), chemical (HCl, NaOH, NaClO, P3-Ultrasil) and biological (dishwashing and laundry detergents) cleaning methods. The filtration time of the individual experiments is compared with a new membrane, and the increase is determined. Backwashing cleans the pores, but the biofilm sticks to the membrane surface and blocks the pores shortly after a new cycle. It was shown that the biofilm can only be removed chemically through oxidative effects or anionic surfactants. Hydrolysis does not remove the biofilm, and it can actually make the blockage worse. Bigger cellular residues can only be removed with enzymes. This improves cleaning performance by 61% compared to commercial cleaning agents for membranes and 42% compared to backwashing. Full article

Microalgae have attracted the interest of researchers due to their high amounts of bioactive compounds with potential anti-obesity effects. In this context, the aim of this study is to analyse the effects of pigment extracts of Tetradesmus obliquus, Phaeodactylum tricornutum and Desmodesmus armatus on triglyceride accumulation in 3T3-L1 pre-adipocytes. Pigments were extracted and the chlorophyll and carotenoid profiles were analysed by HPLC-DAD-APCI-QTOF-MS analysis. Next, the three extracts were tested in maturing 3T3-L1 pre-adipocytes treated during 8 days at doses of 6.25, 12.5, 25 and 50 µg/mL. Cell viability was evaluated and triglyceride content of cells was measured by a commercial kit. Furthermore, adipogenic gene expression was measured in cells treated with the highest dose of the three extracts. The characterisation showed that the predominant pigments in each extract were different among the microalgae, with fucoxanthin being the main one in Phaeodactylum tricornutum and chlorophylls, lutein and violaxanthin/neoxanthin in the other two microalgae. All the tested microalgae extracts reduced triglyceride content of pre-adipocytes, although differing in the minimum effective dose. The underlying mechanism depends on the analysed extract, but the three extracts reduced adipogenesis via Pparg inhibition. In conclusion, the pigment extracts of the three microalgae exert anti-adipogenic effects in 3T3-L1 pre-adipocytes. Full article

This study uses industrial wastewater from an aluminum factory to evaluate the phycoremediation efficiency of two green microalgal strains, Dictyosphaerium sp. and Tetradesmus obliquus. The industrial wastewater contained high levels of pollutants, including COD, ammonium, nitrate, phosphate, and heavy metal ions (Al³⁺, Cu²⁺, Cr³⁺, Zn²⁺, Mn²⁺, Cd²⁺). Four biomass conditions were tested: free-living cells (active living cells), immobilized cells (entrapped within alginate), dried biomass (non-living dried cells), and acid-treated dried biomass (chemically modified for enhanced adsorption). Both strains demonstrated significant pollutant removal, with living biomass (free and immobilized) achieving the highest nutrient and organic pollutant removal, and non-living biomass (dried and acid-treated) being more efficient for rapid heavy metal removal. Tetradesmus obliquus showed superior performance across most parameters, while Dictyosphaerium sp. exhibited the highest aluminum removal (99.4%, reducing Al from 481.2 mg/L to 10.2 mg/L). These findings highlight the potential of microalgae-based approaches and support species-specific strategies for cost-effective and sustainable phycoremediation of industrial wastewater. Full article

The soft drink industry generates effluents with high organic loads and contaminants such as nitrogen and phosphorus, requiring sequential secondary and tertiary treatments to meet international discharge standards. Moving beyond traditional monocultures, this study developed a microbial consortium (forming microalga–fungus pellets), demonstrating a synergistic combination due to the resistance of the pellets, enhancing the treatment efficiency, and facilitating the recovery of the microbial sludge produced. Specifically, the treatment of anaerobic effluents (tertiary treatment) from the soft drink industry using consortia of the fungus Penicillium gravinicasei and the microalgae Tetradesmus obliquus and Chlorella sp. in aerated reactors was evaluated, analyzing the impact of aeration rates (0.5–3.5 vvm) on pollutant removal and microbial sludge production. The results showed that moderate aeration rates (1.5 vvm) optimized the removal of COD (up to 92.5%), total nitrogen (TN) (up to 79.3%), and total phosphorus (TP) (up to 83.4%) in just 2.5 h. Furthermore, excessive aeration reduced treatment efficiency due to microbial stress and difficulty in forming microalga–fungus pellets. The Chlorella sp. consortium showed greater stability, while T. obliquus was more sensitive to the aeration rate. Microbial sludge production was also optimized at around 1.5 vvm, consequence of the pollutant removal, with the formation of pellets that facilitated biomass harvesting. Full article

The study of microalgae has led to significant progress in recent decades. The current microalgal biomass yield is unsatisfactory, except for certain species that are cultivated for the nutraceutical and pharmaceutical industries. In this study, the growth efficiency and biochemical composition of Tetradesmus obliquus at high levels of nutrients were characterized. Increasing the NH₄⁺-N content in the medium to 164 mg L⁻¹ allowed the algae to steadily accumulate biomass (6.14 ± 0.28 g L⁻¹) with a moderate content of starch. Optimizing the levels of N, P, and S allowed the biomass productivity to increase from the average 0.45 to 0.88 g L⁻¹ day⁻¹. A further increase of NH₄⁺-N to 410 mg L⁻¹ and other nutrients’ concentration allowed the algae to accumulate biomass (7.50 ± 0.28 g L⁻¹), enriched with protein and pigments. The algae cultivated with the high load of nutrients reached 100%, 84%, and 96% removal of N, P, and S, respectively. Adding the NaHCO₃ to the photobioreactor for pH adjustment (instead of NaOH) did not significantly improve the growth parameters or affect the composition of the algal cells. In general, our study will improve the comprehensive understanding of culture-based approaches to study the perspective use of the alga T. obliquus. Full article

The microalga Tetradesmus obliquus has emerged as a promising candidate for biotechnological and industrial applications due to its rapid growth, resilience under diverse environmental conditions, and potential for bioactive compound production. This study presents a multiparametric characterization of dry T. obliquus biomass cultivated in patented industrial-scale photobioreactors, integrating thermochemical, elemental, antioxidant, and protein analyses. Proximate and ultimate analyses were conducted to assess fuel potential, revealing favorable volatile matter (VM = 64.80–72.44%) and fixed carbon (FC = 15.77–21.23%) contents. The HHV (18.32–22.75 MJ·kg⁻¹) and LHV (16.86–21.24 MJ·kg⁻¹) confirmed the biomass as a viable candidate for solid biofuel. The elemental composition provided the total nitrogen values, subsequently used to estimate the protein content via both the Kjeldahl and Dumas methods, with results ranging from 36.66% to 40.02%, in line with the literature. Despite the absence of detectable antioxidant activity under the tested DPPH conditions, the biomass demonstrated a robust nutritional profile and energy potential. These findings support the industrial relevance of T. obliquus biomass, particularly for applications targeting sustainable protein sources and bioenergy solutions. Full article

The microstructures of microalgae biofilms affect biofilms’ growth, which is critical in developing efficient microalgae biofilm-based culture systems. Herein, the microstructures of Tetradesmus obliquus biofilms cultured under different nutrients were in situ observed with confocal laser scanning microscopes. The surface structures and internal pore structures for these biofilms were determined quantitatively. The results indicated that the surfaces of these biofilms were all wrinkled with many folds in micrometres. The biofilms cultured under BG11, BG11^+glycerine, BG11^+urea, and BG11^+NH₄Cl nutrients had small pores with diameters of 15~30 μm, whereas the biofilms formed under BG11^+NaHCO₃ and BG11^+NaNO₃ presented many large pores with diameters of 50~150 μm. The mechanism of forming different microstructures of these nutrients was interpreted by analyzing cell surface properties. We found that the cells cultured under BG11^+NaHCO₃ and BG11^+NaNO₃ had more hydrophobic surface groups. The high cell–cell interactions between hydrophobic cells made cells tend to aggregate together and form biofilms with more inner pores, which may be conducive to cell growth and biofilm development. The study offers new insights into understanding the microstructural characteristics of microalgae biofilms cultured under different nutrients, providing important guidance for the development of biofilm-based culture systems. Full article

Heavy metal wastewater often contains multiple metal ions, and competition among them reduces the adsorption efficiency of microalgae. Enhancing this efficiency is crucial for improving heavy metal removal. This study optimized lysine addition to facilitating the formation of a ternary complex between microalgae, lysine, and heavy metals, thereby enhancing adsorption in both single- and mixed-metal systems. In a single-metal system at 64 mg/L, lysine improved the removal rates of copper, zinc, and cadmium by 13.96%, 41.21%, and 33.26%, respectively. In binary systems (Cu-Zn, Cu-Cd, and Cu-Pb) at 32 mg/L, lysine increased copper adsorption by 11.81%, 15.71%, and 25.25%, while improving zinc, cadmium, and lead adsorption by 15.41%, 12.51%, and 3.93%, respectively. Competitive adsorption analysis revealed that lead most strongly inhibited copper adsorption, while copper significantly suppressed zinc adsorption. Mechanistic investigations using 3D-EEM, FTIR, and XPS demonstrated that humic substances in the extracellular polymeric substances (EPSs) of microalgae play a key role in lysine binding. This interaction increases the number of carboxyl functional groups on the cell surface, thereby enhancing the microalgae’s capacity to adsorb heavy metals. Full article

Microalgae, a marine-derived natural ingredient, has emerged as a rich source of bioactive compounds with the potential to modulate gut–brain axis activities. The objective of this study was to investigate whether supplementation with a microalgae extract from Tetradesmus obliquus strain Mi175.B1.a (TOME) influences gut health and reduces stress and anxiety in healthy adults experiencing mild to moderate gastrointestinal (GI) distress. Methods: Fifty-six healthy adults (age: 31.9 ± 7.7 years; body weight: 71.8 ± 12.6 kg; BMI: 24.6 ± 2.8 kg/m²) were enrolled in a randomized, double-blind, placebo-controlled, parallel-arm clinical trial. Participants were randomly allocated to receive capsules containing either 250 mg/day of TOME or a placebo for four weeks. Primary outcomes included the assessment of GI symptoms using the Gastrointestinal Symptom Rating Scale (GSRS) and Bristol Stool Scale (BSS). Secondary outcomes focused on subjective evaluation of mood, stress, and anxiety, as well as blood pressure responses to sympathetic nervous system activation induced by the cold pressor test (CPT). In addition, stool, plasma, and saliva samples were collected to assess biomarkers associated with stress, sympathetic activation, intestinal permeability, and GI health. 16S rRNA sequencing was performed to analyze changes in gut microbial populations. Results: Daily supplementation for four weeks with TOME was safe and well tolerated in the study population. In addition, TOME significantly reduced GSRS global scores (p = 0.02), as well as constipation (p = 0.05) and indigestion (p = 0.03) subcomponent scores compared to Placebo. There was also a significant increase in Shannon’s index before FDR correction (p = 0.05; FDR = 0.12) and stool butyrate level was significantly lower in the TOME group than in Placebo after 4 weeks of supplementation (p = 0.039). Both groups showed a significant reduction in perceived stress scores, but the TOME intervention group also had reduced Negative Affect scores (p < 0.001). In addition, plasma chromogranin A, a stress biomarker, was significantly reduced after TOME intervention (p = 0.03). There were no negative effects on blood lipids or other parameters related to sympathetic activation or cardiovascular health. Conclusions: Overall, these results suggest that 4-week supplementation with T. obliquus strain Mi175.B1.a improves GI symptoms, potentially through effects on the gut microbiota, and may promote positive effects on mental health. Additional research should follow up on mental health outcomes in populations with increased stress and anxiety and investigate mechanisms underlying improvements in GI health. This trial was registered at clinicaltrials.gov as NCT06425094. Full article

The present study aimed to chemically profile the hydroalcoholic extracts from the microalgae (MEs) Nannochloropsis oculata, Phaeodactylum tricornutum, Tetradesmus obliquus, and Tetraselmis tetrathele and evaluate their effects on the development of Colletotrichum lindemuthianum and anthracnose symptoms, as well as on the initial growth of bean plants. For this, MEs were analyzed using UPLC coupled with a mass spectrometer, allowing the identification of peaks and annotation of potential metabolites. Fungal mycelial growth was assessed seven days after inoculation, and conidial germination was measured 72 h after incubation, using ME concentrations of 0, 0.1, 0.5, and 1.0 mg·mL⁻¹. Bean seeds of the IPR Uirapuru cultivar were sown and treated with 3 mL of extracts at four time points: at sowing and 72 h after each previous treatment. After 11 days of cultivation in a growth chamber, the plants were divided into two groups: one for anthracnose control assessment and the other for evaluating growth promotion by MEs. Plant length as well as fresh and dry weights of shoots and roots were determined, leaf pigments were quantified, and anthracnose severity was assessed using a diagrammatic scale. The UPLC analysis identified 32 compounds in the extracts of the four microalgae, belonging to different chemical and functional groups, with lipids being the most significant fraction. The extracts exhibited variability and diversity in chemical composition depending on the microalgal species. MEs did not affect mycelial growth yet increased the germination of C. lindemuthianum conidia, regardless of the dose or species used. Anthracnose severity was not affected by the microalgae extracts. Regarding growth promotion, the extracts showed varying effects but generally increased shoot and root length, fresh biomass, and leaf pigment content. Full article

Microalgal biotechnology is gaining attention due to its potential to produce pigments, lipids, biofuels, and value-added products. However, challenges persist in terms of the economic viability of microalgal lipid production in photobioreactors due to slow growth rates, expensive media, complex downstream processing, limited product yields, and contamination risks. Recent studies suggest that co-cultivating microalgae with bacteria can enhance the profitability of microalgal bioprocesses. Immobilizing bacteria offers advantages such as protection against shear forces, the prevention of overgrowth, and continuous product secretion. Previous work has shown that biopolymeric immobilization of Paenibacillus polymyxa enhances 2,3-butanediol production. In this study, a novel co-fermentation process was developed by exploiting the chemical crosstalk between a freshwater microalga Scenedesmus obliquus, also known as Tetradesmus obliquus, and an immobilized plant-growth-promoting bacterium, Paenibacillus polymyxa. This co-cultivation resulted in increased metabolite production, with a 1.5-fold increase in the bacterial 2,3-butanediol concentration and a 3-fold increase in the microalgal growth rates compared to these values in free-cell co-cultivation. Moreover, the co-culture with the immobilized bacterium exhibited a 5-fold increase in the photosynthetic pigments and a 3-fold increase in the microalgal lipid concentration compared to these values in free-cell co-cultivation. A fixed bed photobioreactor was further constructed, and the co-cultivation bioprocess was implemented to improve the bacterial 2,3-butanediol and microalgal lipid production. In conclusion, this study provides conclusive evidence for the potential of co-cultivation and biopolymeric immobilization techniques to enhance 2,3-butanediol and lipid production. Full article

Dimethyl sulfoxide (DMSO) is an aprotic solvent widely used in ecotoxicological assays, suitable for solubilizing a wide range of polar and non-polar substances. The aim of this study was to analyze the species-specific biological response of the model organisms Daphnia magna and Ceriodaphnia dubia to 0.5% DMSO, under feeding conditions. Both species were exposed in culture medium, with or without 0.5% DMSO, to the unicellular algae (Raphidocelis subcapitata, Tetradesmus obliquus), either individually or in combination; the algae were pretreated or not pretreated with 0.5% DMSO. The exposure was carried out in acute (24 h and 48 h) and chronic (72 h and 168 h) ecotoxicity tests. The experimental results suggest that a lower DMSO concentration limit (<0.5%) would be appropriate for C. dubia due to its greater sensitivity to the solvent. Finally, considering the ingestion of DMSO-contaminated algae, it can be concluded that, under certain experimental conditions, the solvent ingested through the diet may significantly affect the mortality of both D. magna and C. dubia. Full article

The brewing industry is a major part of the agri-food sector, but its fermentation processes contribute significantly to global CO₂ emissions, exacerbating the greenhouse gas crisis. Achieving net-zero emissions requires innovative solutions, and this study explored one such solution by using microalgae to capture CO₂ from a brewery while simultaneously generating valuable bioproducts. Two microalgae species, Tetradesmus obliquus and Limnospira maxima, were cultivated in a 1000 L raceway and a 400 L tubular photobioreactor, both powered by the brewery’s CO₂ waste gas. The specific growth rates reached 0.3 in the raceway and 0.4–0.5 in the photobioreactor for both species. Notably, L. maxima showed higher productivity, achieving up to 0.80 g L⁻¹ day⁻¹ in the photobioreactor and 0.5 g L⁻¹ day⁻¹ in the raceway. Operating across 300 brewing days per year, a single module (1400 L) of this system could reduce a brewery’s CO₂ emissions by 29%. These low-maintenance systems are modular, allowing for easy scaling and operation. The harvested biomass was nutritionally valuable; L. maxima contained up to 55% protein and 3% phycocyanin, while T. obliquus was rich in carbohydrates (36%) and lipids (12%), levels suitable for feeds and fertilizers. A cost-benefit analysis suggests that coupling CO₂ removal with bioproduct generation supports a sustainable circular economy while offering financial returns. Full article