Harmful effects of metal(loid) oxide nanoparticles

The incorporation of nanomaterials (NMs), including metal(loid) oxide (MOx) nanoparticles (NPs), in the most diversified consumer products, has grown enormously in recent decades. Consequently, the contact between humans and these materials increased, as well as their presence in the environment. This fact has raised concerns and uncertainties about the possible risks of NMs to human health and the adverse effects on the environment. These concerns underline the need and importance of assessing its nanosecurity. The present review focuses on the main mechanisms underlying the MOx NPs toxicity, illustrated with different biological models: release of toxic ions, cellular uptake of NPs, oxidative stress, shading effect on photosynthetic microorganisms, physical restrain and damage of cell wall. Additionally, the biological models used to evaluate the potential hazardous of nanomaterials are briefly presented, with particular emphasis on the yeast Saccharomyces cerevisiae, as an alternative model in nanotoxicology. An overview containing recent scientific advances on cellular responses (toxic symptoms exhibited by yeasts) resulting from the interaction with MOx NPs (inhibition of cell proliferation, cell wall damage, alteration of function and morphology of organelles, presence of oxidative stress bio-indicators, gene expression changes, genotoxicity and cell dead) is critically presented. The elucidation of the toxic modes of action of MOx NPs in yeast cells can be very useful in providing additional clues about the impact of NPs on the physiology and metabolism of the eukaryotic cell. Current and future trends of MOx NPs toxicity, regarding their possible impacts on the environment and human health, are discussed.This work was supported by National funds through FCT - Foundation for Science and Technology under the scope of the projects UIDB/50006/2020, UID/BIO/04469/2020 unit and BioTecNorte opera tion (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Modulation of siderophore production by Pseudomonas fluorescens through the manipulation of the culture medium composition

Pseudomonas fluorescens has the ability to produce the siderophore pyoverdine, a biotechnologically significant iron chelator, which has a wide range of potential applications, such as in agriculture (iron fertilizers) and medicine (development of antibiotics). The present work aimed to evaluate the influence of culture medium composition on the production of siderophores by P. fluorescens DSM 50090, an industrial relevant strain. It was found that the bacterium grown in minimal medium succinate (MMS) had a higher siderophore production than in King B medium. The replacement of succinate by glycerol or dextrose, in minimal medium, originated lower siderophore production. The increase of succinate concentration, the addition of amino acids or the reduction of phosphate in the culture medium did not improve siderophore production by P. fluorescens. The results obtained strongly suggest that (i) MMS is more appropriate than King B for large-scale production of siderophores; (ii) the modification of the culture medium composition, particularly the type of carbon source, influences the level of siderophore secreted; (iii) the production of siderophore by P. fluorescens seems to be a tightly regulated process; once a maximum siderophore concentration has been reached in the culture medium, the bacterium seems to be unable to produce more compound.João M. Vindeirinho received the grant from the project PTDC-AGR-TEC/0458/2014—POCI-01-0145-FEDER-016681. This work is financed by the FEDER funds through the Operational Competitiveness Factors Program—COMPETE and by national funds through FCT—Foundation for Science and Technology within the scope of the project PTDC-AGR-TEC/0458/2014—POCI-01-0145-FEDER-016681.info:eu-repo/semantics/publishedVersio

Using a flocculent brewer’s yeast strain of Saccharomyces cerevisiae in the removal of heavy metals

Fundação para a Ciência e a Tecnologia (FCT) - POCTI/CTA/47875/2002, (SFRH/BD/31755/2006)Fundo Europeu de Desenvolvimento Regional (FEDER

Removal of heavy metals using cells of Saccharomyces cerevisiae as a green technology

Anthropogenic activities are largely responsible for the release of heavy metals in the environment. Unlike organic pollutants, heavy metals are not degraded and remain indefinitely in the ecosystem, which poses a different kind of challenge for remediation. Municipal sanitary sewers are not designed to treat toxic wastes, such as industrial effluents containing heavy metals. Thus, heavy metals should be removed in a “previous step”, from these metalladen effluents before they are released into the water body or sent to a municipal treatment plant. Conventional physicochemical technologies are not environmental friendly, fully efficient or present very high costs when applied to large volume of wastewaters containing low metal concentration (1- 100 mg/l). The disadvantages of these available “best treatment technologies”, associated with the increase of environmental regulations, have compelled the search for alternative, low-cost and efficient processes for the detoxification of metal-bearing wastewaters. The advantages and the current knowledge of the mechanisms of metal removal by yeast cells of Saccharomyces cerevisiae will be presented. The use of live or dead biomass and the influence of biomass inactivation processes or the modification of the yeast surface on the metal accumulation characteristics will be outlined. The importance of the physico-chemical characteristics of the effluents and the role of chemical speciation as a tool for predicting and optimising metal removal will be highlighted. The use of yeast cells as the only treatment process of real effluents or in a “polishing” step, after the chemical treatment of the raw effluent to remove the bulk of the metal will be presented. The problem of biomass separation, after treatment of the effluents, and the use of flocculent characteristics of yeast cells, as an alternative process of cell-liquid separation, will also be discussed. The convenient management of the contaminated biomass and the advantages of the selective recovery of heavy metals in the development of a closed cycle without residues (green technology) will be presented

Removal of heavy metals from real electroplating effluents using a brewer's yeast strain of Saccharomyces cerevisiae

Background: The release of heavy metals in aquatic systems due to the discharge of industrial wastewaters is a matter of environmental concern. The use of yeast cells has been raised as an alternative to the conventional technologies. Objectives: To evaluate the feasibility of flocculent brewing cells of S. cerevisiae to remove several metals from real electroplating effluents. Methods: Flocculation was assessed using a sedimentation test. The occurrence of structural or molecular changes in the yeast cells during heat treatment (at 45ºC), were evaluated using fluorescence, scanning electron microscopy and infrared spectroscopy. Heavy metals concentrations were determined by atomic absorption spectroscopy with flame atomization. Conclusions: Yeast cells were able to sediment in the presence of most of the heavy metals, as well as in the industrial effluents. Cells inactivated at 45ºC maintained the sedimentation characteristics and showed a higher degree of heavy metal removal than the live cells. Effluents containing Cu, Ni and Zn (effluent A) or Cr, Cu and Ni (effluent B) were used. In both effluents, pH was adjusted to 6.0; in effluent B, Cr(VI) was previously reduced to Cr(III). Subsequently, effluents were treated with a serial batch of heat-inactivated yeast biomass. After the third batch, metal concentrations were lowered to below the legal limits of discharge; removals 89%, were attained for all metals. The usefulness of using heat-inactivated flocculent brewing cells for detoxifying complex industrial effluents loaded with several heavy metals was demonstrated. This approach combines an efficient metal removal with a fast and off-cost yeast separation

Impact of nickel oxide nanoparticles on yeast physiology

[Excerpt] In the recent years, nickel oxide (NiO) nanoparticles (NPs), have been used in different fields, such as in biosensors, catalysis, ceramics, electrochromic film, electronics, conductive and magnetic materials, energy storage devices, fuel cells, printing inks and wastewater treatment [1-2]. Due to the increasing use of these NPs, concerns about their possible toxic effects have been raised. In the present study, the yeast Saccharomyces cerevisiae was used as a cell model to evaluate the possible hazards of NiO NPs. Physicochemical characteristics of NiO in MES buffer, namely NPs agglomeration (examined by dynamic light scattering – DLS), surface charge (determination of zeta potential) and dissolution of the NPs (quantification of Ni2+ released in medium) were evaluated in order to be correlated with their toxicity. [...]info:eu-repo/semantics/publishedVersio

Editorial: Bio-based solutions for sustainable development of agriculture

In summary, this Research Topic comprises a collection of 16 articles that offer new and updated knowledge about biofertilizers, biocontrol and improved resilience to environmental stressors. The information presented can be useful in the future development of bio-based products that are expected to be used, as an alternative to current agrochemicals, in modern and more sustainable agriculture.ES and HS are grateful to the Portuguese Foundation for Science and Technology (FCT) for financial support, funded by national funds through the FCT/MCTES (PIDDAC), under the scope of the strategic funding of UIDB/04469/2020 (Centre of Biological Engineering, University of Minho) and UIDB/50006/2020 (Associated Laboratory for Green Chemistry - Clean Technologies and Processes, LAQV-REQUIMTE) unit, respectively.info:eu-repo/semantics/publishedVersio

Nickel oxide nanoparticles induce toxicity in yeasts via oxidative stress

[Excerpt] The increasing use of nickel oxide (NiO) nanoparticles (NPs) raises concerns about their potential toxicity. In the present study, the yeast Saccharomyces cerevisiae was used, as a cell model, in order to elucidate whether the toxicity of NiO NPs is associated with the oxidative stress (OS). In abiotic conditions (cell free), NiO NPs were unable to induce the generation of reactive oxygen species (ROS), which excludes the possibility of exerting a pro-oxidant effect. However, yeast cells exposed to NiO NPs accumulated intracellularly superoxide anions (assessed with dihydroethidium) and hydrogen peroxide (evaluated with 2′,7′-dichlorodihydrofluorescein diacetate or dihydrorhodamine 123) when incubated in normal (oxygen) atmosphere. Yeast cells exposed to NiO also presented reduced cell viability (measured through a clonogenic assay). Yeasts co-exposed to NiO NPs and the antioxidants L-ascorbic acid (a scavenger of free radicals) or N-tertbutyl-α-phenylnitrone (a spin trapping agent) presented ROS quenching and increased cell viability, which suggests that NiO toxicity is linked to ROS production. [...]info:eu-repo/semantics/publishedVersio

Metal(loid) oxide (Al2O3, Mn3O4, SiO2 and SnO2) nanoparticles cause cytotoxicity in yeast via intracellular generation of reactive oxygen species

In this work, the physicochemical characterization of five (Al2O3, In2O3, Mn3O4, SiO2 and SnO2) nanoparticles (NPs) was carried out. In addition, the evaluation of the possible toxic impacts of these NPs and the respective modes of action were performed using the yeast Saccharomyces cerevisiae. In general, in aqueous suspension, metal(loid) oxide (MOx) NPs displayed an overall negative charge and agglomerated; these NPs were practically insoluble (dissolution <\thinspace8\\%) and did not generate detectable amounts of reactive oxygen species (ROS) under abiotic conditions. Except In2O3 NPs, which did not induce an obvious toxic effect on yeast cells (up to 100 mg/L), the other NPs induced a loss of cell viability in a dose-dependent manner. The comparative analysis of the loss of cell viability induced by the NPs with the ions released by NPs (NPs supernatant) suggested that SiO2 toxicity was mainly caused by the NPs themselves, Al2O3 and SnO2 toxic effects could be attributed to both the NPs and the respective released ions and Mn3O4 harmfulness could be mainly due to the released ions. Al2O3, Mn3O4, SiO2 and SnO2 NPs induced the loss of metabolic activity and the generation of intracellular ROS without permeabilization of plasma membrane. The co-incubation of yeast cells with MOx NPs and a free radical scavenger (ascorbic acid) quenched intracellular ROS and significantly restored cell viability and metabolic activity. These results evidenced that the intracellular generation of ROS constituted the main cause of the cytotoxicity exhibited by yeasts treated with the MOx NPs. This study highlights the importance of a ROS-mediated mechanism in the toxicity induced by MOx NPs.This work was performed in the framework of the financingby Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte and LAQV (UID/QUI/50006/2019)with funding from FCT/MCTES through national funds.info:eu-repo/semantics/publishedVersio

A multi-metal risk assessment strategy for natural freshwater ecosystems based on the additive inhibitory free metal ion concentration index

Scientifically sound risk assessment strategies and derivations of environmental quality standards for metals present in freshwater environments are currently hampered by insufficient chronic toxicity data collected from natural ecosystems, as well as inadequate information on metal speciation. Thus, the aim of the present study was to evaluate the impact of freshwater containing multiple metals (Cd, Cr, Cu, Ni, Pb and Zn) on the chronic toxicity (72h) to the alga Pseudokirchneriella subcapitata and compare the observed toxicity results to the total and free metal concentration of the samples. Based on the information obtained herein, an additive inhibitory free multi-metal ion concentration index, calculated as the sum of the equivalent toxicities to the free metal ion concentration of each sample, was developed. The proposed index was well correlated to the observed chronic toxicity results, indicating that the concentration addition, when expressed as the free-ion activity, can be considered a reliable indicator for the evaluation of ecological risk assessments for natural waters containing multiple metals.This work was performed in the framework of the financing with references LAQV (UID/QUI/50006/2013 - POCI/01/0145/FEDER/007265) and UID/BIO/04469/2013 - POCI-01-0145-FEDER-006684 with financial support from FCT/MEC through national funds and co-financed by FEDER, under the Partnership Agreement PT2020 and Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462)