Search Results (10)

The kraft pulp process generates liquors with different physicochemical characteristics at each treatment stage. These liquors can accidentally spill into the biological treatment, hindering it and harming ecosystems where the effluents are discharged. Due to the lack of studies on the effects these liquors can have on the aerobic biomass of activated sludges and ecosystems, this investigation aims to assess the toxicity of each liquor spill to the aerobic biomass of an activated sludge, using Selenastrum capricornutum as a bioindicator of water quality. This evaluation used a laboratory-scale activated sludge, which was fed with an effluent with pH 6.62–6.67 and chemical organic demand (COD) of 611–638.5 mg/L. The liquors used had the following parameters: pH = 13 and COD = 1911 mg/L (white); pH = 13 and COD = 141,350 mg/L (black); pH = 13 and 2755 mg/L (green); and pH = 7.5 and COD = 358 mg/L (condensate). White liquor produced the greatest toxicity (EC₂₀ of 17.8 mgCOD/L) and lowest oxygen uptake rate (8.42 mgO₂/L·h with 287.7 mgCOD/L) in the aerobic biomass compared to the other liquors. White liquor presented the greatest inhibition of Selenastrum capricornutum, with 81.7% (48 h) and 98.0% (96 h). Meanwhile, black liquor presented an inhibition of 94.7% (48 h), but a 13% increase in microalga growth at 96 h of culture. The information from this study makes it possible to calculate how much liquor can be fed to an activated sludge system, keeping it optimized to eliminate liquor discharges generated within the kraft mill’s processing units. Full article

This work aimed to characterize the impact of copper (Cu), at environmentally relevant concentrations, using the freshwater microalga Raphidocelis subcapitata. Algae were incubated with 33 or 53 µg/L Cu, in OECD medium, and toxic impacts were evaluated over 72 h, using different cellular and biochemical biomarkers. The exposure to 33 µg/L Cu had an algistatic effect: slowing growth and reducing algal population (53%, at 72 h) without compromising the cell membrane. This Cu concentration promoted a transient reduction in chlorophyll a (chla) content and typical markers of oxidative stress: increased levels of reactive oxygen species (ROS), augmented catalase (CAT) activity, and lipid peroxidation (malondialdehyde, MDA). Algae exposed to 53 µg/L Cu, suffered a severe effect with a 93% reduction in the number of cells, 50% decrease in chla content, and diminished (17%) maximum photochemical quantum yield of PSII (F_v/F_m). This population also presented increased levels of ROS and MDA, 33 and 20 times higher than the control, respectively, at 72 h, augmented CAT activity, and permeabilized cell membrane (5%, at 72 h). These findings provide valuable insights into Cu toxicity in aquatic ecosystems, highlighting the biochemical and physiological impacts at environmentally relevant concentrations. Full article

Ampicillin (AMP) and cefazolin (CZO) are commonly used β-lactam antibiotics which are extensively globally produced. Additionally, AMP and CZO are known to have relatively high ecotoxicity. Notably, the mix of AMP and CZO creates a synergistic effect that is more harmful to the environment, and how exposure to AMP-CZO can induce synergism in algae remains virtually unknown. To yield comprehensive mechanistic insights into chemical toxicity, including dose–response relationships and variations in species sensitivity, the integration of multiple endpoints with de novo transcriptomics analyses were used in this study. We employed Selenastrum capricornutum to investigate its toxicological responses to AMP and CZO at various biological levels, with the aim of elucidating the underlying mechanisms. Our assessment of multiple endpoints revealed a significant growth inhibition in response to AMP at the relevant concentrations. This inhibition was associated with increased levels of reactive oxygen species (ROS) and perturbations in nitrogen metabolism, carbohydrate metabolism, and energy metabolism. Growth inhibition in the presence of CZO and the AMP-CZO combination was linked to reduced viability levels, elevated ROS production, decreased total soluble protein content, inhibited photosynthesis, and disruptions in the key signaling pathways related to starch and sucrose metabolism, ribosome function, amino acid biosynthesis, and the production of secondary metabolites. It was concluded from the physiological level that the synergistic effect of Chlorophyll a (Chla) and Superoxide dismutase (SOD) activity strengthened the growth inhibition of S. capricornutum in the AMP-CZO synergistic group. According to the results of transcriptomic analysis, the simultaneous down-regulation of LHCA4, LHCA1, LHCA5, and sodA destroyed the functions of the photosynthetic system and the antioxidant system, respectively. Such information is invaluable for environmental risk assessments. The results provided critical knowledge for a better understanding of the potential ecological impacts of these antibiotics on non-target organisms. Full article

Antibiotics and pesticides, as well as various emerging contaminants that are present in surface waters, raise significant environmental concerns. Advanced oxidation processes, which are employed to eliminate these substances, have demonstrated remarkable effectiveness. However, during the degradation process, by-products that are not completely mineralized are generated, posing a substantial risk to aquatic ecosystem organisms; therefore, it is crucial to assess effluent ecotoxicity following treatment. This study aimed to assess the toxicity of effluents produced during the removal of amoxicillin and glyphosate with a Fenton-type process using a laminar structure catalyzed with iron (Fe) and copper (Cu). The evaluation included the use of Daphnia magna, Selenastrum capricornutum, and Lactuca sativa, and mutagenicity testing was performed using strains TA98 and TA100 of Salmonella typhimurium. Both treated and untreated effluents exhibited inhibitory effects on root growth in L. sativa, even at low concentrations ranging from 1% to 10% v/v. Similarly, negative impacts on the growth of algal cells of S. capricornutum were observed at concentrations as low as 0.025% v/v, particularly in cases involving amoxicillin–copper (Cu) and glyphosate with copper (Cu) and iron (Fe). Notably, in the case of D. magna, mortality was noticeable even at concentrations of 10% v/v. Additionally, the treatment of amoxicillin with double-layer hydroxides of Fe and Cu resulted in mutagenicity (IM ≥ 2.0), highlighting the necessity to treat the effluent further from the advanced oxidation process to reduce ecological risks. Full article

o-Cresol shows high toxicity and stability. To explore a better degradation method of o-cresol, the degradation of o-cresol by three kinds of microalgae (Selenastrum capricornutum, Scenedesmus obliquus, and Microcystis aeruginosa) was researched in this paper. The growth status and degradation rate were used to reflect the tolerance and degradation effect of microalgae. The effects of the medium’s initial pH, microalgal density, and different exogenous pollutants on the degradation of o-cresol by Selenastrum capricornutum were investigated. The results showed that Selenastrum capricornutum had the best degradation effect on o-cresol. microalgal density increased after adaptation to different concentrations of o-cresol for some time. At pH 7.0 as the initial condition, the microalgal exhibited the best results of degradation. When the microalgal density OD₆₈₀ was 0.20, o-cresol was the first to be completely degraded within 5 days. At higher initial concentrations of o-cresol, the microalgae preferentially degraded glucose to promote the growth of the microalgae under mixotrophic cultivation. Selenastrum capricornutum could degrade phenol and o-cresol at the same time, and the degradation was completed within 8 days when the initial concentration of o-cresol and phenol were 100 and 120 mg/L. It was proven that the degradation of o-cresol by Selenastrum capricornutum is feasible under suitable conditions. Full article

As algae are extremely sensitive to heavy-metal ions and can be critical biological indicators in the heavy-metal toxicity analyses conducted by environmental health researchers, this paper explores the sensitivity to temporal toxicity of three species of green algae: Scenedesmus obliquus, Chlorella pyrenoidosa, and Selenastrum capricornutum. The method of time-dependent microplate toxicity analysis was used to systematically investigate the changes in the toxicities of the three green-algae species induced by different concentrations of cadmium (Cd). The chlorophyll a content, antioxidant enzyme activity, and malondialdehyde (MDA) content in the algae were analyzed to explore the mechanism of Cd toxicity after 96 h of exposure. The results showed that the toxic effects of Cd on the three algae species were time-dependent. By comparing the toxic effect of Cd, indicated by pEC₅₀ (the negative logarithm of EC₅₀), on the algae species at four durations of exposure (24, 48, 72, and 96 h), this study found that the indicator organisms had different sensitivities to Cd. The order of sensitivity was C. pyrenoidosa > S. obliquus > S. capricornutum. Cd exposure had significant effects on the chlorophyll a and MDA content and on the enzyme activity of superoxide dismutase (SOD) and catalase (CAT) in the algae species. The chlorophyll a content in the cells of the algae decreased with increasing Cd concentration. The enzyme activity of CAT and content of MDA increased with increasing Cd concentration, which indicated that Cd had an oxidative stress effect on the three algae species. Full article

The increasing global demand for biofuels for energy security and to reduce the effects of climate change has created an opportunity to explore new sources of biomass, of which, microalgae is the most promising one. The Laboratory of the Biomass Research Centre (CRB, University of Perugia) is equipped with a photobioreactor that is used to cultivate microalgae under batch conditions. Tests were carried out a temperature of 22 °C and a Photosynthetic Photon Flux Density of 140 µE·m⁻²·s⁻¹. Cultures were characterized in terms of biomass produced and lipid fraction distribution. The novelty of this paper is the measure of the fuel properties of Selenastrum capricornutum, a new strain for biodiesel production. In particular, after the microalgae have been collected and oil has been extracted, this has been transesterified using a methanol/NaOH solution. The resulting biodiesel has been analyzed with a high-resolution gas chromatograph to determine the concentration of the different methylesters. Full article

Globally, eutrophication and warming of aquatic ecosystems has increased the frequency and intensity of cyanobacterial blooms and their associated toxins, with the simultaneous detection of multiple cyanotoxins often occurring. Despite the co-occurrence of cyanotoxins such as microcystins and anatoxin-a (ATX) in water bodies, their effects on phytoplankton communities are poorly understood. The individual and combined effects of microcystin-LR (MC-LR) and ATX on the cyanobacteria Microcystis spp., and Anabaena variabilis (a.k.a. Trichormus variabilis), and the chlorophyte, Selenastrum capricornutum were investigated in the present study. Cell density, chlorophyll-a content, and the maximum quantum efficiency of photosystem II (Fv/Fm) of Microcystis cells were generally lowered after exposure to ATX or MC-LR, while the combined treatment with MC-LR and ATX synergistically reduced the chlorophyll-a concentration of Microcystis strain LE-3. Intracellular levels of microcystin in Microcystis LE-3 significantly increased following exposure to MC-LR + ATX. The maximum quantum efficiency of photosystem II of Anabaena strain UTEX B377 declined during exposure to the cyanotoxins. Nitrogen fixation by Anabaena UTEX B377 was significantly inhibited by exposure to ATX, but was unaffected by MC-LR. In contrast, the combination of both cyanotoxins (MC-LR + ATX) caused a synergistic increase in the growth of S. capricornutum. While the toxins caused an increase in the activity of enzymes that scavenge reactive oxygen species in cyanobacteria, enzyme activity was unchanged or decreased in S. capricornutum. Collectively this study demonstrates that MC-LR and ATX can selectively promote and inhibit the growth and performance of green algae and cyanobacteria, respectively, and that the combined effect of these cyanotoxins was often more intense than their individual effects on some strains. This suggests that the release of multiple cyanotoxins in aquatic ecosystems, following the collapse of blooms, may influence the succession of plankton communities. Full article

In this study, a novel 96-well microplate swivel system (M96SS) was built for high-throughput screening of microalgal strains for CO₂ fixation. Cell growth under different CO₂ supply conditions (0.2, 0.4, 0.8, and 1.2 g L⁻¹ d⁻¹), residual nitrate, and pH value of Chlorella sp. SJTU-3, Chlorella pyrenoidosa SJTU-2, and Scenedesmus obliquus SJTU-3 were examined in the M96SS and traditional flask cultures. The dynamic data showed there was a good agreement between the systems. Two critical problems in miniature culture systems (intra-well mixing and evaporation loss) were improved by sealed vertical mixing of the M96SS. A sample screen of six microalgal species (Chlorella sp. SJTU-3, Chlorella pyrenoidosa SJTU-2, Selenastrum capricornutum, Scenedesmus obliquus SJTU-3, Chlamydomonas sajao, Dunaliella primolecta) was carried out in flasks and the M96SS. Chlamydomonas sajao appeared to be a robust performer (highest cell density: 1.437 g L⁻¹) in anaerobic pond water with 0.8, and 1.2 g L⁻¹ d⁻¹ CO₂. The reliability and efficiency of the M96SS were verified through a comparison of traditional flask culture, M96SS, Lukavský’s system, and a microplate shaker. Full article

Nanotechnologies have become a significant priority worldwide. Several manufactured nanoparticles - particles with one dimension less than 100 nm - are increasingly used in consumer products. At nanosize range, the properties of materials differ substantially from bulk materials of the same composition, mostly due to the increased specific surface area and reactivity, which may lead to increased bioavailability and toxicity. Thus, for the assessment of sustainability of nanotechnologies, hazards of manufactured nanoparticles have to be studied. Despite all the above mentioned, the data on the potential environmental effects of nanoparticles are rare. This mini-review is summarizing the emerging information on different aspects of ecotoxicological hazard of metal oxide nanoparticles, focusing on TiO₂, ZnO and CuO. Various biotests that have been successfully used for evaluation of ecotoxic properties of pollutants to invertebrates, algae and bacteria and now increasingly applied for evaluation of hazard of nanoparticles at different levels of the aquatic food-web are discussed. Knowing the benefits and potential drawbacks of these systems, a suite of tests for evaluation of environmental hazard of nanoparticles is proposed. Special attention is paid to the influence of particle solubility and to recombinant metal-sensing bacteria as powerful tools for quantification of metal bioavailability. Using recombinant metal-specific bacterial biosensors and multitrophic ecotoxicity assays in tandem will create new scientific knowledge on the respective role of ionic species and of particles in toxicity of metal oxide nanoparticles. Full article