Involvement of Bacterial and Fungal Extracellular Products in Transformation of Manganese-Bearing Minerals and Its Environmental Impact.

Manganese oxides are considered an essential component of natural geochemical barriers due to their redox and sorptive reactivity towards essential and potentially toxic trace elements. Despite the perception that they are in a relatively stable phase, microorganisms can actively alter the prevailing conditions in their microenvironment and initiate the dissolution of minerals, a process that is governed by various direct (enzymatic) or indirect mechanisms. Microorganisms are also capable of precipitating the bioavailable manganese ions via redox transformations into biogenic minerals, including manganese oxides (e.g., low-crystalline birnessite) or oxalates. Microbially mediated transformation influences the (bio)geochemistry of manganese and also the environmental chemistry of elements intimately associated with its oxides. Therefore, the biodeterioration of manganese-bearing phases and the subsequent biologically induced precipitation of new biogenic minerals may inevitably and severely impact the environment. This review highlights and discusses the role of microbially induced or catalyzed processes that affect the transformation of manganese oxides in the environment as relevant to the function of geochemical barriers.

Solid-Water Interface Interaction of Selenium with Fe(II)-Bearing Minerals and Aqueous Fe(II) and S(-II) Ions in the Near-Field of the Radioactive Waste Disposal System.

Selenium can be highly toxic in excess for both animals and humans. However, since its mobile forms can be easily adsorbed with ferric minerals, its mobility in the natural oxic environment is generally not an issue. Still, the removal and immobilization of the long-lived radioactive isotope 79Se from the contaminated anoxic waters is currently a significant concern. 79Se can be accessible in the case of radionuclides' leaching from radioactive waste disposals, where anoxic conditions prevail and where ferrous ions and Fe(II)-bearing minerals predominate after corrosion processes (e.g., magnetite). Therefore, reductive and adsorptive immobilizations by Fe(II)-bearing minerals are the primary mechanisms for removing redox-sensitive selenium. Even though the information on the sorptive interactions of selenium and Fe(II)-bearing minerals seems to be well documented, this review focuses specifically on the state of the available information on the effects of the redox properties of Fe(II)-bearing solid phases (e.g., ferrous oxides, hydroxides, sulfides, and carbonates) on selenium speciation via redox transformation and co-occurring coprecipitation.

Mycosynthesis of Metal-Containing Nanoparticles-Fungal Metal Resistance and Mechanisms of Synthesis.

In the 21st century, nanomaterials play an increasingly important role in our lives with applications in many sectors, including agriculture, biomedicine, and biosensors. Over the last two decades, extensive research has been conducted to find ways to synthesise nanoparticles (NPs) via mediation with fungi or fungal extracts. Mycosynthesis can potentially be an energy-efficient, highly adjustable, environmentally benign alternative to conventional physico-chemical procedures. This review investigates the role of metal toxicity in fungi on cell growth and biochemical levels, and how their strategies of resistance, i.e., metal chelation, biomineral formation, biosorption, bioaccumulation, compartmentalisation, and efflux of metals from cells, contribute to the synthesis of metal-containing NPs used in different applications, e.g., biomedical, antimicrobial, catalytic, biosensing, and precision agriculture. The role of different synthesis conditions, including that of fungal biomolecules serving as nucleation centres or templates for NP synthesis, reducing agents, or capping agents in the synthesis process, is also discussed. The authors believe that future studies need to focus on the mechanism of NP synthesis, as well as on the influence of such conditions as pH, temperature, biomass, the concentration of the precursors, and volume of the fungal extracts on the efficiency of the mycosynthesis of NPs.

Mycosynthesis of Metal-Containing Nanoparticles-Synthesis by Ascomycetes and Basidiomycetes and Their Application.

Fungi contain species with a plethora of ways of adapting to life in nature. Consequently, they produce large amounts of diverse biomolecules that can be generated on a large scale and in an affordable manner. This makes fungi an attractive alternative for many biotechnological processes. Ascomycetes and basidiomycetes are the most commonly used fungi for synthesis of metal-containing nanoparticles (NPs). The advantages of NPs created by fungi include the use of non-toxic fungus-produced biochemicals, energy efficiency, ambient temperature, pressure conditions, and the ability to control and tune the crystallinity, shape, and size of the NPs. Furthermore, the presence of biomolecules might serve a dual function as agents in NP formation and also capping that can tailor the (bio)activity of subsequent NPs. This review summarizes and reviews the synthesis of different metal, metal oxide, metal sulfide, and other metal-based NPs mediated by reactive media derived from various species. The phyla ascomycetes and basidiomycetes are presented separately. Moreover, the practical application of NP mycosynthesis, particularly in the fields of biomedicine, catalysis, biosensing, mosquito control, and precision agriculture as nanofertilizers and nanopesticides, has been studied so far. Finally, an outlook is provided, and future recommendations are proposed with an emphasis on the areas where mycosynthesized NPs have greater potential than NPs synthesized using physicochemical approaches. A deeper investigation of the mechanisms of NP formation in fungi-based media is needed, as is a focus on the transfer of NP mycosynthesis from the laboratory to large-scale production and application.

Preconcentration and Separation of Gold Nanoparticles from Environmental Waters Using Extraction Techniques Followed by Spectrometric Quantification.

The quantification of gold nanoparticles (AuNP) in environmental samples at ultratrace concentrations can be accurately performed by sophisticated and pricey analytical methods. This paper aims to challenge the analytical potential and advantages of cheaper and equally reliable alternatives that couple the well-established extraction procedures with common spectrometric methods. We discuss several combinations of techniques that are suitable for separation/preconcentration and quantification of AuNP in complex and challenging aqueous matrices, such as tap, river, lake, brook, mineral, and sea waters, as well as wastewaters. Cloud point extraction (CPE) has been successfully combined with electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICP-MS), chemiluminescence (CL), and total reflection X-ray fluorescence spectrometry (TXRF). The major advantage of this approach is the ability to quantify AuNP of different sizes and coatings in a sample with a volume in the order of milliliters. Small volumes of sample (5 mL), dispersive solvent (50 µL), and extraction agent (70 µL) were reported also for surfactant-assisted dispersive liquid-liquid microextraction (SA-DLLME) coupled with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The limits of detection (LOD) achieved using different combinations of methods as well as enrichment factors (EF) varied greatly, being 0.004-200 ng L-1 and 8-250, respectively.

The Effect of High Selenite and Selenate Concentrations on Ferric Oxyhydroxides Transformation under Alkaline Conditions.

Iron-based nanomaterials have high technological impacts on various pro-environmental applications, including wastewater treatment using the co-precipitation method. The purpose of this research was to identify the changes of iron nanomaterial's structure caused by the presence of selenium, a typical water contaminant, which might affect the removal when the iron co-precipitation method is used. Therefore, we have investigated the maturation of co-precipitated nanosized ferric oxyhydroxides under alkaline conditions and their thermal transformation into hematite in the presence of selenite and selenate with high concentrations. Since the association of selenium with precipitates surfaces has been proven to be weak, the mineralogy of the system was affected insignificantly, and the goethite was identified as an only ferric phase in all treatments. However, the morphology and the crystallinity of ferric oxyhydroxides was slightly altered. Selenium affected the structural order of precipitates, especially at the initial phase of co-precipitation. Still, the crystal integrity and homogeneity increased with time almost constantly, regardless of the treatment. The thermal transformation into well crystalized hematite was more pronounced in the presence of selenite, while selenate-treated and selenium-free samples indicated the presence of highly disordered fraction. This highlights that the aftermath of selenium release does not result in destabilization of ferric phases; however, since weak interactions of selenium are dominant at alkaline conditions with goethite's surfaces, it still poses a high risk for the environment. The findings of this study should be applicable in waters affected by mining and metallurgical operations.

Nanogold Biosynthesis Mediated by Mixed Flower Pollen Grains.

Physical and chemical methods for nanoparticle synthesis are disadvantageous to less energy demanding and more efficient and environmentally friendly biological approaches. Thus, in this paper, we designed simple, bottom-up, in vitro, static experiment under laboratory conditions using suspension of mixed flower pollen grains for nanoparticle synthesis. Pollen grains provided template substrates for gold nanoparticles synthesis from dissolved Au(III). Transmission and scanning electron microscopy along with ultraviolet-visible spectra confirmed the gold nanoparticles formation. The biosynthesized/phytosynthesized gold nanoparticles had relative narrow size distribution (from 3 to 11 nm) with dominant spherical morphology with no aggregated forms. Thus, the gold nanoparticles in pollen dispersion provides excellent stability and dispersity.

Increased Colloidal Stability and Decreased Solubility-Sol-Gel Synthesis of Zinc Oxide Nanoparticles with Humic Acids.

Adding the humic acid coating to the nanoparticles of zinc oxide (ZnO-NP) may improve the properties necessary for their colloidal stability. To show how humic acid coating affects the properties of ZnO-NP, three differently sol-gel synthesized ZnO-NP were synthesized: pristine zinc oxide nanoparticles without coating (p-ZnO-NP) and humic acid coated zinc oxide nanoparticles at two different initial concentrations of 20 mg/L (HA20-ZnO-NP) and 200 mg/L (HA200-ZnO-NP) of humic acids in the starting solution. All ZnO-NP were found to be nanocrystals of mineral zincite exhibiting wurtzite crystal symmetry. Transmission electron microscopy showed that capping by humic acids during synthesis decreased the size of HA20-ZnO-NP and HA200-ZnO-NP compared to p-ZnO-NP nanoparticles. Via experiments, HA20-ZnO-NP were found to dissolve less and have a similar or higher stability than both p-ZnO-NP and HA200-ZnO-NP.

Removal of aluminium from aqueous solution by four wild-type strains of Aspergillus niger.

This paper provides a unique comparison of the performance of four wild-type Aspergillus niger strains in remediation of aluminium(III)-contaminated aqueous solutions. The direct fungal aluminium removal via biosorption and bioaccumulation was compared among all fungal strains, including bioaccumulation efficiency during dynamic and static cultivation. Our results indicate that aluminium bioaccumulation by living biomass outperformed biosorption, although biosorption by non-living biomass is a less time-demanding process. Among others, only one strain significantly differed regarding comparison of dynamic and static bioaccumulation. In this case, a significantly higher removal performance was achieved under dynamic cultivation conditions at initial aluminium(III) concentrations over 2.5 mg L-1. Although the fungal sensitivity towards aluminium(III) differed among selected fungal strains, there was no apparent correlation between the strains' removal performance and their adaptive mechanisms.

Mercury in mercury(II)-spiked soils is highly susceptible to plant bioaccumulation.

Heavy metal phytotoxicity assessments usually use soluble metal compounds in spiked soils to evaluate metal bioaccumulation, growth inhibition and adverse effects on physiological parameters. However, exampling mercury phytotoxicity for barley (Hordeum vulgare) this paper highlights unsuitability of this experimental approach. Mercury(II) in spiked soils is extremely bioavailable, and there experimentally determined bioaccumulation is significantly higher compared to reported mercury bioaccumulation efficiency from soils collected from mercury-polluted areas. Our results indicate this is not affected by soil sorption capacity, thus soil ageing and formation of more stable mercuric complexes with soil fractions is necessary for reasonable metal phytotoxicity assessments.

Bismuth(III) volatilization and immobilization by filamentous fungus Aspergillus clavatus during aerobic incubation.

As with many metals, bismuth can be accumulated or transformed by microorganisms. These interactions affect microbial consortia and bismuth environmental behaviour, mobility, and toxicity. Recent research focused specifically on bismuth anaerobic transformation by bacteria and archaea has inspired the evaluation of the mutual interactions between bismuth and filamentous fungi as presented in this article. The Aspergillus clavatus fungus proved resistant to adverse effects from bismuth contamination in culture medium with up to a concentration of 195 µmol L(-1) during static 15- and 30-day cultivation. The examined resistance mechanism includes biosorption to the fungal surface and biovolatilization. Pelletized fungal biomass has shown high affinity for dissolved bismuth(III). Bismuth biosorption was rapid, reaching equilibrium after 50 min with a 0.35 mmol g(-1) maximum sorption capacity as calculated from the Langmuir isotherm. A. clavatus accumulated ≤70 µmol g(-1) of bismuth after 30 days. Preceding isotherm study implications that most accumulated bismuth binds to cell wall suggests that biosorption is the main detoxification mechanism. Accumulated bismuth was also partly volatilized (≤1 µmol) or sequestrated in the cytosol or vacuoles. Concurrently, ≤1.6 µmol of bismuth remaining in solution was precipitated by fungal activity. These observations indicate that complex mutual interactions between bismuth and filamentous fungi are environmentally significant regarding bismuth mobility and transformation.

Review on Performance of Aspergillus and Penicillium Species in Biodegradation of Organochlorine and Organophosphorus Pesticides.

The use of pesticides in agricultural practices raises concerns considering the toxic effects they generate in the environment; thus, their sustainable application in crop production remains a challenge. One of the frequently addressed issues regarding their application includes the development of a sustainable and ecofriendly approach for their degradation. Since the filamentous fungi can bioremediate various xenobiotics owing to their efficient and versatile enzymatic machinery, this review has addressed their performance in the biodegradation of organochlorine and organophosphorus pesticides. It is focused particularly on fungal strains belonging to the genera Aspergillus and Penicillium, since both are ubiquitous in the environment, and often abundant in soils contaminated with xenobiotics. Most of the recent reviews on microbial biodegradation of pesticides focus primarily on bacteria, and the soil filamentous fungi are mentioned only marginally there. Therefore, in this review, we have attempted to demonstrate and highlight the exceptional potential of aspergilli and penicillia in degrading the organochlorine and organophosphorus pesticides (e.g., endosulfan, lindane, chlorpyrifos, and methyl parathion). These biologically active xenobiotics have been degraded by fungi into various metabolites efficaciously, or these are completely mineralized within a few days. Since they have demonstrated high rates of degradation activity, as well as high tolerance to pesticides, most of the Aspergillus and Penicillium species strains listed in this review are excellent candidates for the remediation of pesticide-contaminated soils.

Prediction of attachment efficiency using machine learning on a comprehensive database and its validation.

Colloidal particles can attach to surfaces during transport, but the attachment depends on particle size, hydrodynamics, solid and water chemistry, and particulate matter. The attachment is quantified in filtration theory by measuring attachment or sticking efficiency (Alpha). A comprehensive Alpha database (2538 records) was built from experiments in the literature and used to develop a machine learning (ML) model to predict Alpha. The training (r-squared: 0.86) was performed using two random forests capable of handling missing data. A holdout dataset was used to validate the training (r-squared: 0.98), and the variable importance was explored for training and validation. Finally, an additional validation dataset was built from quartz crystal microbalance experiments using surface-modified polystyrene, poly (methyl methacrylate), and polyethylene. The experiments were performed in the absence or presence of humic acid. Full database regression (r-squared: 0.90) predicted Alpha for the additional validation with an r-squared of 0.23. Nevertheless, when the original database and the additional validation dataset were combined into a new database, both the training (r-squared: 0.95) and validation (r-squared: 0.70) increased. The developed ML model provides a data-driven prediction of Alpha over a big database and evaluates the significance of 22 input variables.

Evaluation of enzymatic stamp removal strategies on handmade (cellulose-based) and machine-made (lignin-containing) papers.

Two different biocleaning techniques for stamp removal from different paper samples (handmade and machine-made) were investigated. Cellulose is the main component of handmade paper, while higher concentration of lignin is present in machine-made paper. Biocleaning methods included the direct application on paper surfaces of the extracellular enzymatic mixture (EEM) extracted from the yeast Sporidiobolus metaroseus and the recombinant protein CthediskatG of Chaetomium thermophilum var. dissitum. The produced microbial enzymes (EEM or CthediskatG) were also combined with agarose hydrogels. The effectiveness of the cleaning ability of the individual methods was determined using different spectrophotometer measurements based on colorimetric analysis and by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). Some tested samples were also subjected to microstructural and chemical analysis using Scanning Electron Microscope-Energy-Dispersive X-ray spectroscopy (SEM-EDX). The analysis showed that the EEM-based approaches were the most suitable, mainly they are less time-consuming and easy to produce, and moreover slight differences were displayed between EEM and CthediskatG during the removal of the stamp by hydrogel-enzyme approaches. Both EEM applications (direct and hydrogel) speed up the stamp removal process from real paper samples. However, for the complete elimination of the stamp smears a quick N,N-dimethylformamide post-treatment is advised too.

Prospects of Biogenic Xanthan and Gellan in Removal of Heavy Metals from Contaminated Waters.

Biosorption is considered an effective technique for the treatment of heavy-metal-bearing wastewaters. In recent years, various biogenic products, including native and functionalized biopolymers, have been successfully employed in technologies aiming for the environmentally sustainable immobilization and removal of heavy metals at contaminated sites, including two commercially available heteropolysaccharides-xanthan and gellan. As biodegradable and non-toxic fermentation products, xanthan and gellan have been successfully tested in various remediation techniques. Here, to highlight their prospects as green adsorbents for water decontamination, we have reviewed their biosynthesis machinery and chemical properties that are linked to their sorptive interactions, as well as their actual performance in the remediation of heavy metal contaminated waters. Their sorptive performance in native and modified forms is promising; thus, both xanthan and gellan are emerging as new green-based materials for the cost-effective and efficient remediation of heavy metal-contaminated waters.

Current Strategies for Selenium and Iodine Biofortification in Crop Plants.

Selenium and iodine are essential trace elements for both humans and animals. Among other things, they have an essential role in thyroid function and the production of important hormones by the thyroid gland. Unfortunately, in many areas, soils are deficient in selenium and iodine, and their amount is insufficient to produce crops with adequate contents to cover the recommended daily intake; thus, deficiencies have an endemic character. With the introduction of iodized table salt in the food industry, the thyroid status of the population has improved, but several areas remain iodine deficient. Furthermore, due to the strong relationship between iodine and selenium in metabolic processes, selenium deficiency often compromises the desired positive impact of salt iodization efforts. Therefore, a considerable number of studies have looked for alternative methods for the simultaneous supplementation of selenium and iodine in foodstuff. In most cases, the subject of these studies is crops; recently, meat has also been a subject of interest. This paper reviews the most recent strategies in agriculture to fortify selenium and iodine in crop plants, their effect on the quality of the plant species used, and the potential impact of food processing on their stability in fortified crops.

Role of Exopolysaccharides of Pseudomonas in Heavy Metal Removal and Other Remediation Strategies.

Pseudomonas biofilms have been studied intensively for several decades and research outcomes have been successfully implemented in various medical and agricultural applications. Research on biofilm synthesis and composition has also overlapped with the objectives of environmental sciences, since biofilm components show exceptional physicochemical properties applicable to remediation techniques. Especially, exopolysaccharides (ExPs) have been at the center of scientific interest, indicating their potential in solving the environmental issues of heavy metal land and water contamination via sorptive interactions and flocculation. Since exposure to heavy metal via contaminated water or soil poses an imminent risk to the environment and human health, ExPs provide an interesting and viable solution to this issue, alongside other effective and green remedial techniques (e.g., phytostabilization, implementation of biosolids, and biosorption using agricultural wastes) aiming to restore contaminated sites to their natural, pollution-free state, or to ameliorate the negative impact of heavy metals on the environment. Thus, we discuss the plausible role and performance of Pseudomonas ExPs in remediation techniques, aiming to provide the relevant available and comprehensive information on ExPs' biosynthesis and their usage in heavy metal remediation or other environmental applications, such as wastewater treatment via bioflocculation and soil remediation.

Effects of Foliar Application of ZnO Nanoparticles on Lentil Production, Stress Level and Nutritional Seed Quality under Field Conditions.

Nanotechnology offers new opportunities for the development of novel materials and strategies that improve technology and industry. This applies especially to agriculture, and our previous field studies have indicated that zinc oxide nanoparticles provide promising nano-fertilizer dispersion in sustainable agriculture. However, little is known about the precise ZnO-NP effects on legumes. Herein, 1 mg·L-1 ZnO-NP spray was dispersed on lentil plants to establish the direct NP effects on lentil production, seed nutritional quality, and stress response under field conditions. Although ZnO-NP exposure positively affected yield, thousand-seed weight and the number of pods per plant, there was no statistically significant difference in nutrient and anti-nutrient content in treated and untreated plant seeds. In contrast, the lentil water stress level was affected, and the stress response resulted in statistically significant changes in stomatal conductance, crop water stress index, and plant temperature. Foliar application of low ZnO-NP concentrations therefore proved promising in increasing crop production under field conditions, and this confirms ZnO-NP use as a viable strategy for sustainable agriculture.

Removal of arsenic from aqueous environments by native and chemically modified biomass of Aspergillus niger and Neosartorya fischeri.

Arsenic removal from aqueous solutions by biomass of two fungal strains, Aspergillus niger and Neosartorya fischeri, was assessed. The biosorption capacity of fungal biomass was studied within the As(V) concentration range of approximately 0.2 to 5.0 mg L(-1) at two different pH values (pH 5 and 7). With increasing initial arsenic concentration, the biosorption capacity of both fungal strains increased almost linearly and achieved the sorption capacity of 0.317 and 0.124 mg g(-1) for biomass of N. fischeri and A. niger, respectively. The effect of biomass treatment with FeCl3 and HCI on As(III) and As(V) uptake was also studied. The optimum biosorption pH as well as the effect ofbiomass treatment was found to be dependent on the fungal strain used. Treatment with FeCl3 and HCl did not result in any significant increase in arsenic uptake. To the contrary, treatment with ferric oxyhydroxide was found to be very effective and virtually 100% of the arsenic was removed from the samples of contaminated natural water.

Production of Methyl-Iodide in the Environment.

Iodine is an essential micronutrient for most of the living beings, including humans. Besides its indispensable role in animals, it also plays an important role in the environment. It undergoes several chemical and biological transformations resulting in the production of volatile methylated iodides, which play a key role in the iodine's global geochemical cycle. Since it can also mitigate the process of climate change, it is reasonable to study its biogeochemistry. Therefore, the aim of this review is to provide information on its origin, global fluxes and mechanisms of production in the environment.