Search Results (14)

Microalgae offer a sustainable alternative for wastewater treatment by simultaneously removing pollutants and producing biomass of potential value. This study evaluated five species—Haematococcus pluvialis, Chlorella vulgaris, Chlamydomonas sp., Anabaena variabilis, and Scenedesmus sp.—in three undiluted food and beverage industry effluents from Mexico: nejayote (alkaline wastewater generated during corn nixtamalization for tortilla production), tequila vinasses (from tequila distillation), and cheese whey (from cheese making). Strains were adapted through UV mutagenesis and gradual acclimatization to grow without freshwater dilution. Bioremediation efficiency was assessed via reductions in chemical oxygen demand (COD), total nitrogen (TN), and total phosphates (TPO₄). C. vulgaris achieved complete TN and TPO₄ removal and 90.2% COD reduction in nejayote, while A. variabilis reached 81.7% COD and 79.3% TPO₄ removal in tequila vinasses. In cheese whey, C. vulgaris removed 55.5% COD, 53.0% TN, and 35.3% TPO₄. These results demonstrate the feasibility of microalgae-based systems for treating complex agro-industrial wastewaters, contributing to sustainable and circular wastewater management. Full article

This study concerns the investigation of the sorption and desorption phenomena of the organic dye methylene blue (MB) on three different marine sediments and non-living biomass of the seagrass species Posidonia oceanica. All tested adsorbents were of natural origin and were collected from unpolluted coasts of the North Aegean Sea (Greece). The batch equilibrium technique was applied and MB concentrations were determined by spectrophotochemical analysis (λ = 665 nm). The experimental results showed that all four isotherm models, Freundlich, Langmuir, Henry, and Temkin, could describe the process. The normalized to organic matter content adsorption coefficients (K_OM) ranged between 33.0765 and 34.5279 for the studied sediments. The maximum adsorption capacity (q_max) of sediments was in the range of 0.98 mg g⁻¹ and 6.80 mg g⁻¹, indicating a positive correlation with the adsorbents’ organic matter content, textural analysis of fine fraction (<63 μm), and specific surface area. The bioadsorption of MB on P. oceanica biomass resulted in 13.25 mg g⁻¹ up to 17.86 mg g⁻¹ adsorption efficiency. Desorption studies revealed that the studied dye in most cases was very strongly adsorbed on studied matrices with extremely low quantities of seawater extractable amounts (≤1.62%). According to the experimental findings, phycoremediation by using P. oceanica can be characterized as an efficient method for the bioremediation of dye-polluted wastewater. Full article

The contamination of water by heavy metals is among the main ecological challenges of society due to industrialization and urbanization. To overcome this issue, various treatment processes have been developed. Phycoremediation is considered a promising strategy offering advantages in terms of cost-effectiveness. The present work aims to investigate the cellular responses of an isolated green microalga strain (Chlamydomonas sp.) to chromium (Cr) and copper (Cu) exposure in single and bimetallic systems. At ½ IC₅₀ concentration, the metal removal efficiencies were reported: up to 58.11 ± 0.979% for Cu and 41.4 ± 0.870% for Cr in single systems. When both metals were combined, Cr removal efficiency improved to 57.71 ± 0.832%, whereas Cu removal efficiency showed minimal variation, reaching 58.43 ± 1.059%. Furthermore, Cu and Cr appeared to have a negative effect on cell growth and photosynthetic pigment accumulation. An enhancement in lipid content for microalgae cells after Cu and/or Cr exposure, particularly C14:0, C16:0, C20:0, C18:0, C16:1, C18:1, and C20:1, as well as polysaccharides, was detected, whereas the protein content decreased. FTIR analysis showed that several functional groups could be involved in the phycoremediation process. Full article

Phycoremediation of wastewater with microalgae is a viable option and is considered a process for cleaning up toxic waste using microalgae or macroalgae. Most water is modified by its use and must be treated before discharge. Given this situation, and following the example of other researchers around the world, our study focuses on the filtration method and combines it with the microalgae method to treat domestic wastewater. The aim of our work is to study the effects of using the microalgae system in combination with the decontamination and filtration system to reduce the nutrient content of domestic wastewater. The coupling of the two methods produced very significant results. However, the removal efficiencies for the filtered effluent increased to 86.34%, 100%, and 91.12% for COD, ammonia, and phosphate, respectively. The algae treatment offers an ecologically safe and less expensive system for nutrient removal and eliminates the need for tertiary treatment, which refers to the filtered treatment effluent, allowing us to conclude that the Chlorella vulgaris species has a very interesting influence on dissolved oxygen and that it had a very remarkable effect on COD, with a maximum reduction that reached 80%. The results obtained show that the phosphate content of the treated wastewater was significantly reduced during the cultivation period. In time, a decrease in solids was observed within the microalgae treatment system, influenced by the use of two different types of microalgae and the incorporation of the filtration system, which is based on the use of biosorption of methylene blue by biomass. The parameters analyzed in this study are hydrogen potential (pH), ammonia (NH₃), phosphate ion (PO₄³⁻), chemical oxygen demand (COD), electrical conductivity (EC), total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), nitrates, and dissolved oxygen (DO). Full article

Taking into account the worrying scenario of water scarcity, it is essential to enable more efficient technologies for wastewater treatment. Wastewater may be treated by conventional biological processes that remove pathogenic organisms, particulate and soluble organic compounds, and other components. However, secondary effluents from treatment plants may still contain toxic elements or high concentrations of inorganic nutrients (mainly nitrogen and phosphorus), which enable the growth of photosynthetic microorganisms in water bodies, resulting in eutrophication. In this context, cultivation of photosynthetic microorganisms in secondary wastewater from sewage treatment allows the removal of nutrients from such wastewater, reducing the possibility of eutrophication. Moreover, microalgal biomass, produced in this tertiary wastewater treatment, may be harvested by different methods with the potential for different applications, such as fertilizer and biofuel. Full article

Industrialization, natural processes, and urbanization have potentially accelerated the pace and the level of heavy metals (HMs) in soil and underground water. These HMs may be accumulated in plants and animals when they take up such contaminated water, and then make their way into human food chains. Several remediation technologies have been employed to take up HMs. Diverse conventional means such as ion exchange, electrolytic technologies, and chemical extraction have been employed in the past, but the majority of these techniques are not economical for extensive projects and they need stringent control and continuous monitoring. These technologies also have low efficiency for effective removal of HMs. In this context, algae offer an eco-friendly and sustainable alternative for remediation of HMs from polluted water. The accumulation of HMs by macro and microalgae is advantageous for phycoremediation compared to other approaches that are not economical and not environmentally friendly. So, there is an urgent necessity to refine the chances of accumulation of HMs in algae, employing the techniques of genetic engineering to create transgenic species for over-expressing metallothioneins and phytochelatins, which may form complexes with HMs and store them in vacuoles to make the maximum use of phytoaccumulation while also removing hazardous metals from the aquatic habitats. This review outlines the major sources of HMs, their adverse effects on humans, the potential of algae in phytoremediation (called phycoremediation), and their uptake mechanism of HMs. Full article

Phycoremediation is an eco-friendly treatment for mining wastes. Copper at high concentrations is toxic for microalgae growth (bioremediation). Proteomics is a modern approach that can assist in elucidating, in detail, the highly complex metabolic mechanisms related to phycoremediation. Therefore, this study aimed to evaluate the effect of copper ions (Cu²⁺) on the metabolism of Chlorella protothecoides (UTEX 256), particularly the proteome changes. The WC culture medium supplemented with Cu²⁺ at 0.3, 0.6, and 0.9 mg/L showed a strict correlation to Cu²⁺ removal of 40, 33, and 36% of the initial content, respectively. In addition, Cu²⁺ concentrations did not affect microalgae growth—a very traditional approach to measuring toxicity. However, the proteomics data indicated that when compared to the control, reductions in protein levels were observed, and the 10 most scored proteins were related to the light-harvesting complex. Interestingly, C. protothecoides cultivated at 0.9 mg of Cu²⁺/L biosynthesized the protein Ycf3-interacting chloroplastic isoform X1 to respond to the photooxidative stress and the DNA-directed RNA polymerase III subunit RPC5 was related to the Cu²⁺ binding. Pre-mRNA-processing factor 19 and cytochrome c peroxidase proteins were observed only in the copper-containing treatments indicating the activation of antioxidant mechanisms by reactive oxygen species, which are potential environmental pollutant biomarkers. Full article

Contamination of the biosphere by heavy metals has been rising, due to accelerated anthropogenic activities, and is nowadays, a matter of serious global concern. Removal of such inorganic pollutants from aquatic environments via biological processes has earned great popularity, for its cost-effectiveness and high efficiency, compared to conventional physicochemical methods. Among candidate organisms, microalgae offer several competitive advantages; phycoremediation has even been claimed as the next generation of wastewater treatment technologies. Furthermore, integration of microalgae-mediated wastewater treatment and bioenergy production adds favorably to the economic feasibility of the former process—with energy security coming along with environmental sustainability. However, poor biomass productivity under abiotic stress conditions has hindered the large-scale deployment of microalgae. Recent advances encompassing molecular tools for genome editing, together with the advent of multiomics technologies and computational approaches, have permitted the design of tailor-made microalgal cell factories, which encompass multiple beneficial traits, while circumventing those associated with the bioaccumulation of unfavorable chemicals. Previous studies unfolded several routes through which genetic engineering-mediated improvements appear feasible (encompassing sequestration/uptake capacity and specificity for heavy metals); they can be categorized as metal transportation, chelation, or biotransformation, with regulation of metal- and oxidative stress response, as well as cell surface engineering playing a crucial role therein. This review covers the state-of-the-art metal stress mitigation mechanisms prevalent in microalgae, and discusses putative and tested metabolic engineering approaches, aimed at further improvement of those biological processes. Finally, current research gaps and future prospects arising from use of transgenic microalgae for heavy metal phycoremediation are reviewed. Full article

Colombia is the country with the sixth highest amount of water reserves in the world, and 25% of its territory is covered by wetlands. However, approximately 50% of the country’s water is estimated to exhibit some type of contamination related to anthropic activities. An alternative for the treatment and the recovery of its bodies of water is the use of microalgae, unicellular, and mixotrophic microorganisms, as these bioreactors are highly adaptable to the environment, and their maintenance costs are minimal, because they feed on almost any substrate. In fact, different countries have already reported using microalgae as bioremediators for bodies of water. The use of these microphytes is efficient because they metabolize, degrade, or bioaccumulate heavy metals, pesticides, emerging pollutants, and antibiotics. In general, strategies relying on microalgae to eliminate pollutants are very similar to one another. For example, the first stage often includes a process of bioadsorption, consumption, degradation, and accumulation, wherein the microalgae use molecules generated from their own cellular metabolism. Some pilot studies focusing on the phycoremediation of marshes and other bodies of water have already been conducted in Colombia; however, more studies on process optimization, effectively leveraging the biodiversity of the existing microalgae, and better adapting microalgae to the region are still required. Full article

The pollution of water caused by the excessive presence of organic and inorganic compounds, such as nitrates, phosphates, heavy metals, antibiotics, agrochemicals, etc., is one of the major environmental problems in many countries. Various approaches to remediate wastewater are available, and this review mainly provides the state of the art about the possible adoption of microalgae-based treatments (phycoremediation), which may represent a good alternative to conventional purification methods. Because of its composition, wastewater can provide several nutritional compounds (e.g., carbon, nitrogen, and phosphorus), which represent the essential nutrients for microalgae growth. Microalgae are also attracting the interest of worldwide researchers due to their multipurpose applications; in particular, microalgae cells can represent a useful feedstock for various sectors, among these, the agricultural sector. This review proposes a detailed description of the possible application of microalgae in the process of remediation of wastewaters of different sources, highlighting their possible advantages. Moreover, the review aims to report the application of the microalgae biomasses and their extracts in agriculture, as microalgae-based products can represent a valid alternative to traditional agrochemicals, offering sustainable solutions to improve agricultural technologies. Therefore, since the recently developed wastewater depuration technology based on phycoremediation may directly provide valuable microalgae biomasses, it can be used as a powerful starting means to produce agricultural products able to improve yield and quality of crops (biostimulants, biofertilizers), as well as induce pest and disease resistance (biopesticides). Full article

One of the main concerns in industrialized countries is represented by per- and poly-fluoroalkyl substances (PFAS), persistent contaminants hardly to be dealt with by conventional wastewater treatment processes. Phyco-remediation was proposed as a green alternative method to treat wastewater. Synechocystis sp. PCC6803 is a unicellular photosynthetic organism candidate for bioremediation approaches based on synthetic biology, as it is able to survive in a wide range of polluted waters. In this work, we assessed the possibility of applying Synechocystis in PFAS-enriched waters, which was never reported in the previous literature. Respirometry was applied to evaluate short-term toxicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), which did not affect growth up to 0.5 and 4 mg L⁻¹, respectively. Continuous and batch systems were used to assess the long-term effects, and no toxicity was highlighted for both compounds at quite high concentration (1 mg L⁻¹). A partial removal was observed for PFOS and PFOA, (88% and 37%, with removal rates of about 0.15 and 0.36 mg L⁻¹ d⁻¹, respectively). Measurements in fractionated biomass suggested a role for Synechocystis in the sequestration of PFAS: PFOS is mainly internalized in the cell, while PFOA is somehow transformed by still unknown pathways. A preliminary bioinformatic search gave hints on transporters and enzymes possibly involved in such sequestration/transformation processes, opening the route to metabolic engineering in the perspective application of this cyanobacterium as a new phyco-remediation tool, based on synthetic biology. Full article

The reuse of wastewater has been observed as a viable option to cope with increasing water stress in Africa. The present case studies evaluated the optimization of the process of phycoremediation as an alternative low-cost green treatment technology in two municipality wastewater treatment pond systems that make up the largest number of domestic sewage treatment systems on the African continent. A consortium of specific microalgae (Chlorella vulgaris and Chlorella protothecoides) was used to improve the treatment capacity of domestic wastewater at two operational municipality wastewater pond systems under different environmental conditions in South Africa. Pre- and post-phycoremediation optimization through mass inoculation of a consortium of microalgae, over a period of one year under different environmental conditions, were compared. It was evident that the higher reduction of total phosphates (74.4%) in the effluent, after treatment with a consortium of microalgae at the Motetema pond system, was possibly related to (1) the dominance of the algal taxa C. protothecoides (52%), and to a lesser extent C. vulgaris (36%), (2) more cloudless days, (3) higher air temperature, and (4) a higher domestic wastewater strength. In the case of the Brandwag pond treatment system, the higher reduction of total nitrogen can possibly be related to the dominance of C. vulgaris, different weather conditions, and lower domestic wastewater strength. The nutrient reduction data from the current study clearly presented compelling evidence in terms of the feasibility for use of this technology in developing countries to reduce nutrient loads from domestic wastewater effluent. Full article

The present study aimed to optimize the production of Scenedesmus sp. biomass during the phycoremediation process. The biomass productivity was optimized using face centred central composite design (FCCCD) in response surface methodology (RSM) as a function of two independent variables that included wet market wastewater concentrations (A) with a range of 10% to 75% and aeration rate (B) with a range of 0.02 to 4.0 L/min. The results revealed that the highest biomass productivity (73 mg/L/d) and maximum growth rate (1.19 day⁻¹) was achieved with the 64.26% of (A) and 3.08 L/min of (B). The GC-MS composition analysis of the biomass yield extract revealed that the major compounds are hexadecane (25%), glaucine (16.2%), and phytol (8.33%). The presence of these compounds suggests that WMW has the potential to be used as a production medium for Scenedesmus sp. Biomass, which has several applications in the pharmaceutical and chemical industry. Full article

Microalgae are an excellent source of bioactive compounds for the production of a wide range of vital consumer products in the biofuel, pharmaceutical, food, cosmetics, and agricultural industries, in addition to huge upstream benefits relating to carbon dioxide biosequestration and wastewater treatment. However, energy-efficient, cost-effective, and scalable microalgal technologies for commercial-scale applications are limited, and this has significantly impacted the full-scale implementation of microalgal biosystems for bioproduct development, phycoremediation, and biorefinery applications. Microalgae culture dewatering continues to be a major challenge to large-scale biomass generation, and this is primarily due to the low cell densities of microalgal cultures and the small hydrodynamic size of microalgal cells. With such biophysical characteristics, energy-intensive solid–liquid separation processes such as centrifugation and filtration are generally used for continuous generation of biomass in large-scale settings, making dewatering a major contributor to the microalgae bioprocess economics. This article analyzes the potential of electroflotation as a cost-effective dewatering process that can be integrated into microalgae bioprocesses for continuous biomass production. Electroflotation hinges on the generation of fine bubbles at the surface of an electrode system to entrain microalgal particulates to the surface. A modification of electroflotation, which combines electrocoagulation to catalyze the coalescence of microalgae cells before gaseous entrainment, is also discussed. A technoeconomic appraisal of the prospects of electroflotation compared with other dewatering technologies is presented. Full article