Search Results (7)

Drug removal from urban wastewater (UW) is a topic of growing interest. The new European Directive addresses this problem by introducing quaternary treatment by 2045, as part of the “Zero Pollution” plan from a One Health perspective. In this context, the role of microalgae remains very promising in achieving clean and safe effluents, although its cost–benefit ratio needs to be carefully evaluated. The purpose of this review is to disclose the latest approaches to drug removal and energy recovery from UWs adopting different algae (Chlorella spp., Galdieria spp., and Scenedesmus spp.), to provide a detailed background for further research towards the development of new effective strategies on UW remediation while producing clean energy. We examined the most recent studies, considering most drugs found in wastewater, their management, as well as strategies used to recover energy while being mindful of a circular economy. There is growing interest in algae-based systems. The latest findings on algae–bacteria consortia show that it could be a better alternative to suspended biomass and represent a way to manage drug waste. This finding suggests that large-scale experiments should be conducted to confirm the potential benefits of such waste treatments. Full article

Although biogas is a renewable energy source alternative to natural gas, it contains approximately 40 vol% CO₂ and, hence, a low calorific value. The sequestration of CO₂ from biogas is, therefore, essential before its widespread use. As CO₂ can be easily solubilized as carbonate and bicarbonate in alkaline water, in this study, we isolated and characterized alkaliphilic wild microalgae that grow under high-level CO₂ conditions and evaluated their application potential in CO₂-removal from biogas. For this purpose, freshwater samples were enriched with 10 vol% CO₂ and an alkaline culture medium (pH 9.0), wherein almost free CO₂ was converted to carbonate and bicarbonate to yield alkaliphilic and high-level CO₂-tolerant microalgae. Ten microalgal strains of Micractinium, Chlorella, Scenedesmus/Tetradesmus, or Desmodesmus spp. were isolated, some of which demonstrated good growth even under conditions of >pH 10 and >30 vol% CO₂. All algal strains grew well through fixing biogas-derived CO₂ in a vial-scale biogas upgrading experiment, which reduced the CO₂ level in biogas to an undetectable level. These strains yielded antioxidant carotenoids, including lutein, astaxanthin, zeaxanthin, and β-carotene, particularly rich in lutein (up to 7.3 mg/g dry cells). In addition, these strains contained essential amino acids, accounting for 42.9 mol% of the total amino acids on average, and they were rich in unsaturated fatty acids (comprising 62.2 wt% of total fatty acids). The present study identified strains that can contribute to biogas upgrading technology, and the present findings suggest that their biomass can serve as useful raw material across the food, nutraceutical, and feed industries. Full article

East Asia leads the global chemical industry, but environmental chemical risk in these countries is an emerging concern. Despite this, only a few native species that are representative of East Asian environments are listed as test species in international guidelines compared with those native to Europe and America. This review suggests that Zacco platypus, Misgurnus anguillicaudatus, Hydrilla verticillata, Neocaridina denticulata spp., and Scenedesmus obliquus, all resident to East Asia, are promising test species for ecotoxicity tests. The utility of these five species in environmental risk assessment (ERA) varies depending on their individual traits and the state of ecotoxicity research, indicating a need for different applications of each species according to ERA objectives. Furthermore, the traits of these five species can complement each other when assessing chemical effects under diverse exposure scenarios, suggesting they can form a versatile battery for ERA. This review also analyzes recent trends in ecotoxicity studies and proposes emerging research issues, such as the application of alternative test methods, comparative studies using model species, the identification of specific markers for test species, and performance of toxicity tests under environmentally relevant conditions. The information provided on the utility of the five species and alternative issues in toxicity tests could assist in selecting test species suited to study objectives for more effective ERA. Full article

Conventional biological wastewater treatment systems have a low pathogen removal capacity. Microalgae-based systems are sustainable and low-cost alternatives for wastewater treatment and are capable of removing pathogens from domestic effluents. Other microorganisms have been identified as alternative indicators of disinfection since they have greater resistance than Escherichia coli, either because of the formation of spores or because of other mechanisms of protection, and because they spread in wastewater treatment plants; the most important are Clostridium perfringens and Staphylococcus spp. This study assessed the influence of microalgal strains (e.g., Chlorella vulgaris and Scenedesmus acutus Meyen) and the addition of CO₂ and O₂ on the removal of C. perfringens and Staphylococcus spp. from domestic wastewater in microalgal–bacterial systems. The removal of C. perfringens (2.5 to 3.2 log units) and Staphylococcus sp. (1.8 to 2.0 log units) was higher when using Chlorella sp. inoculum. The addition of CO₂ and O₂ did not have a significant effect on the removal of pathogenic bacteria. The main mechanism of C. perfringens removal was by means of toxins and bactericidal substances produced by the microalgae, while Staphylococcus spp. removal also occurred through photooxidative processes. Full article

Algae are considered pigment-producing organisms. The function of these compounds in algae is to carry out photosynthesis. They have a great variety of pigments, which can be classified into three large groups: chlorophylls, carotenoids, and phycobilins. Within the carotenoids are xanthophylls. Xanthophylls (fucoxanthin, astaxanthin, lutein, zeaxanthin, and β-cryptoxanthin) are a type of carotenoids with anti-tumor and anti-inflammatory activities, due to their chemical structure rich in double bonds that provides them with antioxidant properties. In this context, xanthophylls can protect other molecules from oxidative stress by turning off singlet oxygen damage through various mechanisms. Based on clinical studies, this review shows the available information concerning the bioactivity and biological effects of the main xanthophylls present in algae. In addition, the algae with the highest production rate of the different compounds of interest were studied. It was observed that fucoxanthin is obtained mainly from the brown seaweeds Laminaria japonica, Undaria pinnatifida, Hizikia fusiformis, Sargassum spp., and Fucus spp. The main sources of astaxanthin are the microalgae Haematococcus pluvialis, Chlorella zofingiensis, and Chlorococcum sp. Lutein and zeaxanthin are mainly found in algal species such as Scenedesmus spp., Chlorella spp., Rhodophyta spp., or Spirulina spp. However, the extraction and purification processes of xanthophylls from algae need to be standardized to facilitate their commercialization. Finally, we assessed factors that determine the bioavailability and bioaccesibility of these molecules. We also suggested techniques that increase xanthophyll’s bioavailability. Full article

Milk whey processing wastewaters (MWPWs) are characterized by high COD and organic nitrogen content; the concentrations of phosphorus are also relevant. A microalgal-based process was tested at lab scale in order to assess the feasibility of treating MWPW without any dilution or pre-treatment. Different microalgal strains and populations were tested. Based on the obtained results, Scenedesmus acuminatus (SA) and a mixed population (PM) chiefly made of Chlorella, Scenedesmus, and Chlamydomonas spp. were grown in duplicate for 70 days in Plexiglas column photobioreactors (PBRs), fed continuously (2.5 L culture volume, 7 days hydraulic retention time). Nutrient removal, microalgae growth, photosynthetic efficiency, and the composition of microalgal populations in the columns were monitored. At steady state, the microalgal growth was similar for SA and PM. The average removal efficiencies for the main pollutants were: 93% (SA), 94% (PM) for COD; 88% (SA) and 90% (PM) for total N; and 69% (SA) and 73% (PM) for total P. The residual pollution levels in the effluent from the PBRs were low enough to allow their discharge into surface waters; such good results were achieved thanks to the synergy between the microalgae and bacteria in the CO₂ and oxygen production/consumption and in the nitrogen mineralization. Full article

Nano-based products are widespread in several sectors, including textiles, medical-products, cosmetics, paints and plastics. Nanosafety and safe-by-design are driving nanoparticle (NP) production and applications through NP functionalization (@NPs). Indeed, @NPs frequently present biological effects that differ from the parent material. This paper reviews the impact of quantum dots (QDs), gold nanoparticles (AuNPs), and polystyrene-cored NPs (PSNPs), evidencing the role of NP functionalization in toxicity definition. Key biological models were taken into consideration for NP evaluation: Saccharomyces cerevisiae, fresh- (F) and saltwater (S) microalgae (Raphidocelis subcapitata (F), Scenedesmus obliquus (F) and Chlorella spp. (F), and Phaeodactylum tricornutum (S)), Daphnia magna, and Xenopus laevis. QDs are quite widespread in technological devices, and they are known to induce genotoxicity and oxidative stress that can drastically change according to the coating employed. For example, AuNPs are frequently functionalized with antimicrobial peptides, which is shown to both increase their activity and decrease the relative environmental toxicity. P-NPs are frequently coated with NH₂⁻ for cationic and COOH⁻ for anionic surfaces, but when positively charged toxicity effects can be observed. Careful assessment of functionalized and non-functionalized NPs is compulsory to also understand their potential direct and indirect effects when the coating is removed or degraded. Full article