Influence of iron and copper nanoparticle powder on the production of lignocellulose degrading enzymes in the fungus Trametes versicolor

Nanotechnology based technological development in biofuel production: Current status and future prospects

Depleting fossil fuels and net carbon emissions associated with their burning have driven the need to find alternative energy sources. Biofuels are near-perfect candidates for alternative energy sources as they are renewable and account for no net CO2 emissions. However, biofuel production must overcome various challenges to compete with conventional fuels. Conventional methods for bioconversion of biomass to biofuel include chemical, thermochemical, and biological processes. Substrate selection and processing, low yield, and total cost of production are some of the main issues associated with biofuel generation. Recently, the uses of nanotechnology and nanoparticles have been explored to improve the biofuel production processes because of their high adsorption, high reactivity, and catalytic properties. The role of these nanoscale particles and nanocatalysts in biomass conversion and their effect on biofuel production processes and yield are discussed in the present article. The applicability of nanotechnology in production processes of biobutanol, bioethanol, biodiesel, biohydrogen, and biogas under biorefinery approach are presented. Different types of nanoparticles, and their function in the bioprocess, such as electron transfer, pretreatment, hydrolysis, microalgae cultivation, lipid extraction, dark and photo fermentation, immobilization, and suppression of inhibitory compounds, are also highlighted. Finally, the current and potential applications of nanotechnology in biorefineries are also discussed.

Nanoscale zero-valent iron changes microbial co-occurrence pattern in pentachlorophenol-contaminated soil

Nanoscale zero-valent iron (nZVI) is a prominent nanomaterial for the remediation of organochlorine-contaminated soil and groundwater. However, a knowledge gap regarding the effects of the coexistence of nZVI and pollutants on soil microorganisms remains. Here, we studied the effects of nZVI on the microbial community structure, co-occurrence network, and keystone taxa in pentachlorophenol (PCP, a typical organochlorine pesticide) contaminated soils. The addition of nZVI (1000 mg/kg) had no obvious recovery effect on the microbial community structure of PCP-contaminated soil, but enhanced the connection and lowered the modularity of the microbial network. These changes were mainly present in the bacterial network rather than in the fungal or archaeal network. Moreover, the addition of nZVI increased the number of keystone taxa in the PCP-contaminated soil from 29 to 76. These keystone taxa are related to the degradation of organochlorine pollutants, carbon metabolism, and nitrogen metabolism and may thus be helpful in recovering soil ecological functions. These findings provide new insights into the interaction among nanomaterials, microorganisms, and pollutants.

Transformation of sulfidized nanoscale zero-valent iron particles and its effects on microbial communities in soil ecosystems

Sulfidized nanoscale zero-valent iron (S-nZVI) is a promising material for in situ soil remediation. However, its transformation (i.e., aging) and effects on the microbial community in soil ecosystems are largely unknown. In this study, S-nZVI having low (S-nZVI (L)) and high sulfur-doping (S-nZVI (H)) were incubated in soil microcosms and bare nZVI was used as a control. Their aged products were characterized using microspectroscopic analyses and the changes in the corresponding soil microbial community were determined using high-throughput sequencing analyses. The results indicate that severe corrosion of both bare and S-nZVI occurred over 56 days of aging with significant morphological and mineral changes. Magnetite, lepidocrocite, and goethite were detected as the main aged products. In addition, sulfate ions, pyrite, and iron polysulfide were formed in the aged products of S-nZVI. Cr(VI) removal test results indicated that S-nZVI(L) achieved the best results after aging, likely because of the optimal FeS arrangement on its nanoparticle surfaces. The presence of nZVI and S-nZVI increased the abundance of some magnetotactic microorganisms and altered bacterial and fungal community structures and compositions. Moreover, the addition of S-nZVI enriched some bacterial and fungal genera related to sulfur cycling because of the presence of sulfide-bearing material. The findings reveal the transformation of S-nZVI during aging and its effects on microbial communities in soil ecosystems, thereby helping to the evaluation of S-nZVI application in soil remediation.

Effects and interactions of metal oxides in microparticle-enhanced cultivation of filamentous microorganisms

Filamentous microorganisms are used as molecular factories in industrial biotechnology. In 2007, a new approach to improve productivity in submerged cultivation was introduced: microparticle-enhanced cultivation (MPEC). Since then, numerous studies have investigated the influence of microparticles on the cultivation. Most studies considered MPEC a morphology engineering approach, in which altered morphology results in increased productivity. But sometimes similar morphological changes lead to decreased productivity, suggesting that this hypothesis is not a sufficient explanation for the effects of microparticles. Effects of surface chemistry on particles were paid little attention, as particles were often considered chemically-inert and bioinert. However, metal oxide particles strongly interact with their environment. This review links morphological, physical, and chemical properties of microparticles with effects on culture broth, filamentous morphology, and molecular biology. More precisely, surface chemistry effects of metal oxide particles lead to ion leaching, adsorption of enzymes, and generation of reactive oxygen species. Therefore, microparticles interfere with gene regulation, metabolism, and activity of enzymes. To enhance the understanding of microparticle-based morphology engineering, further interactions between particles and cells are elaborated. The presented description of phenomena occurring in MPEC eases the targeted choice of microparticles, and thus, contributes to improving the productivity of microbial cultivation technology.

The multidimensional nutritional niche of fungus-cultivar provisioning in free-ranging colonies of a neotropical leafcutter ant

Foraging trails of leafcutter colonies are iconic scenes in the Neotropics, with ants collecting freshly cut plant fragments to provision a fungal food crop. We hypothesised that the fungus‐cultivar's requirements for macronutrients and minerals govern the foraging niche breadth of Atta colombica leafcutter ants. Analyses of plant fragments carried by foragers showed how nutrients from fruits, flowers and leaves combine to maximise cultivar performance. While the most commonly foraged leaves delivered excess protein relative to the cultivar's needs, in vitro experiments showed that the minerals P, Al and Fe may expand the leafcutter foraging niche by enhancing the cultivar's tolerance to protein‐biased substrates. A suite of other minerals reduces cultivar performance in ways that may render plant fragments with optimal macronutrient blends unsuitable for provisioning. Our approach highlights how the nutritional challenges of provisioning a mutualist can govern the multidimensional realised niche available to a generalist insect herbivore.

Influence of saprophytic fungi and inorganic additives on enzyme activities and chemical properties of the biodegradation process of wheat straw for the production of organo-mineral amendments

Cellulose and lignin as main components of crop residues have a significant influence on composting operations and composition of the final products. Both are strongly associated, and lignin can be considered an important barrier during the biodegradation process of lignocellulosic materials. Saprophytic fungi are efficient lignin degraders due to their complex enzymatic system. Therefore, the influence of the inoculation of saprophytic fungi (Coriolopsis rigida, Pleurotus ostreatus, Trichoderma harzianum and Trametes versicolor) and the supply of inorganic additives (Al₂O₃, Fe₂O₃ and allophanic soil) that promote the stabilization of carbon (C), were analyzed in the biodegradation of wheat straw (WS). The activity of Laccase (LAC), manganese peroxidase (MnP) and β-glucosidase and changes in temperature, pH and E₄/E₆ ratio were analyzed in a biodegradation process of 126 days. The activity of LAC, MnP and the E₄/E₆ ratio were significantly influenced and increased (enzymes) by fungi species, inorganic additives, and time of inorganic material addition, as well as their interactions (p < 0.05). The WS inoculated with T. versicolor showed the highest average activities for LAC, MnP and β-glucosidase (2000, 220 UL^-1 and 400 μmol pNP g^-1 h^-1 respectively). Furthermore, the addition of Al₂O₃ and Fe₂O₃ increased all the activities regarded to the decomposition of WS and influenced the changes associated with the stabilization of OM in composted WS. In conclusion, the inoculation of WS with T. versicolor in combination with metal oxides improved the enzyme related to the biodegradation process of WS favorizing its stabilization in the medium time, which is of importance in the composting of residues with high C/N ratio.

Fungal transformation of graphene by white rot fungus Phanerochaete chrysosporium

The wide applications of graphene materials require the thorough investigation on their biosafety and environmental risks. Transformation of graphene materials is a fundamental issue in their environmental risk evaluations. The enzymatic degradation of graphene is widely reported using peroxidases, but the information on the fungal transformation of graphene is still unavailable. Herein, we incubated reduced graphene oxide (RGO) in the white rot fungus Phanerochaete chrysosporium culture system for 4 weeks and investigated the transformation of RGO by multiple techniques. P. chrysosporium efficiently added oxygen to RGO and decreased the its carbon contents accordingly. The I_D/I_G ratios of RGO showed statistically increases upon the transformation by P. chrysosporium according to Raman spectroscopy, suggesting the increase of defects on carbon skeleton. The negatively charged oxygen containing groups exfoliated the graphene sheets as indicated by the larger layer distance according to the X-ray diffraction spectra and the increased roughness under scanning electron microscopy. The transformation was more obvious in the RGO separated from the fungal balls than the precipitates in the culture medium. The mechanism of transformation was attributed to the enzymatic degradation by P. chrysosporium. The environmental implication of the fungal transformation of graphene materials and the potential of using fungi to reduce the environmental risks of graphene materials are discussed.

Prospects of Nanobioremediation in Environmental Cleanup

This century is struggling with the issue of environment friendly management of the pollutants which are contaminating the environment. One of an ecofriendly and economically feasible method is the bioremediation of pollutants using bio nanoparticles. Nanobioremediation is a highly studied and explored area of remediation of contaminants using nanotechnology. Nanoparticles used for bioremediation are biologically synthesized from plant extracts, fungi and bacteria. These biogenic nanoparticles when applied to environmental contaminants had shown very promising results. Based on the various studies the bioremediation of pollutants using biosynthetic nanoparticles is emerging as a very promising and sustainable method of environment cleanup. This review focuses on the synthesis of bio-nanoparticles and their use in cleaning the environment.

Performance and toxicity assessment of nanoscale zero valent iron particles in the remediation of contaminated soil: A review

Nanoscale zero valent iron (nZVI) particles have been studied in recent years as a promising technology for the remediation of contaminated soil. Although the potential benefits of nZVI are considerable, there is a distinct need to identify possible risks after environmental exposure to nZVI. This work firstly introduced the remediation of nZVI for heavy metals and chlorinated organic compounds in contaminated soil. And the corresponding stabilization mechanisms were discussed. We also highlighted the factors affecting nZVI reactivity, including nZVI surface area, nZVI stabilizers, soil pH, soil organic matter and soil types. In addition, this review shows a critical overview of the current understanding of toxicity of nZVI particles to soil bacteria and fungi. The toxicity mechanisms, cellular defenses behaviors and the factors affecting the toxicity of nZVI were summarized. Finally, the remaining barriers to be overcome in materials development for environment application are also discussed.

Toxicity of carbon nanotubes to white rot fungus Phanerochaete chrysosporium

Carbon nanotubes (CNTs) are widely used in diverse areas with increasing annual production, thus the environmental impact of CNTs needs thorough investigation. In this study, we evaluated the effect of pristine multi-walled CNTs (p-MWCNTs) and oxidized multi-walled CNTs (o-MWCNTs) on white rot fungus Phanerochaete chrysosporium, which is the decomposer in carbon cycle and also has many applications in environmental remediation. Both p-MWCNTs and o-MWCNTs had no influence on the dry weight increase of P. chrysosporium and the pH value of culture system. The fibrous structure of P. chrysosporium was disturbed by p-MWCNTs seriously, while o-MWCNTs had litter influence. The ultrastructural changes were more evident for P. chrysosporium exposed to p-MWCNTs and only p-MWCNTs could penetrate into the cell plasma. The chemical composition of P. chrysosporium was nearly unchanged according to the infrared spectra. The laccase activity was suppressed by p-MWCNTs, while o-MWCNTs showed stimulating effect. The decoloration of reactive brilliant red X-3B was not affected by both CNT samples. However, serious inhibition of wood degradation was observed in the p-MWCNTs exposed groups, suggesting the potential threat of CNTs to the decomposition of carbon cycle. The implication to the environmental risks and safe applications of carbon nanomaterials is discussed.

Engineering fungal morphology for enhanced production of hydrolytic enzymes by Aspergillus oryzae SBS50 using microparticles

Effect of microparticles and silver nanoparticles was studied on the production of hydrolytic enzymes by a potent phytase-producing mould, Aspergillus oryzae SBS50. Addition of microparticles, viz. talc powder and aluminum oxide enhanced phytase production from 2894 to 3903 and 2847 to 4204 U/L, cellulase from 2529 to 4931 and 2455 to 3444 U/L, xylanase from 9067 to 9642 and 9994 to 14,783 U/L, amylase from 5880 to 11,000 and 6130 to 13,145 U/L, respectively. Fungal morphology was also engineered by the use of microparticles. Fungal pellet size was significantly reduced (~ 90%) by the addition of microparticles. Fermentation time was reduced from 4 to 3 days after the addition of microparticles, thus increasing the productivity of the enzymes significantly. These results confirmed the importance of microparticles in engineering fungal morphology for enhanced production of hydrolytic enzymes.

Toxicity of Pristine and Chemically Functionalized Fullerenes to White Rot Fungus Phanerochaete chrysosporium

Fullerenes are widely produced and applied carbon nanomaterials that require a thorough investigation into their environmental hazards and risks. In this study, we compared the toxicity of pristine fullerene (C60) and carboxylated fullerene (C60-COOH) to white rot fungus Phanerochaete chrysosporium. The influence of fullerene on the weight increase, fibrous structure, ultrastructure, enzyme activity, and decomposition capability of P. chrysosporium was investigated to reflect the potential toxicity of fullerene. C60 did not change the fresh and dry weights of P. chrysosporium but C60-COOH inhibited the weight gain at high concentrations. Both C60 and C60-COOH destroyed the fibrous structure of the mycelia. The ultrastructure of P. chrysosporium was changed by C60-COOH. Pristine C60 did not affect the enzyme activity of the P. chrysosporium culture system while C60-COOH completely blocked the enzyme activity. Consequently, in the liquid culture, P. chrysosporium lost the decomposition activity at high C60-COOH concentrations. The decreased capability in degrading wood was observed for P. chrysosporium exposed to C60-COOH. Our results collectively indicate that chemical functionalization enhanced the toxicity of fullerene to white rot fungi and induced the loss of decomposition activity. The environmental risks of fullerene and its disturbance to the carbon cycle are discussed.

Environmental behavior, potential phytotoxicity, and accumulation of copper oxide nanoparticles and arsenic in rice plants

Copper oxide nanoparticles (CuO NPs) are widely used in many industries. The increasing release of CuO NPs from both intentional and unintentional sources into the environment may pose risks to rice plants, thereby reducing the quality or quantity of this staple grain in the human diet. Not only has arsenic (As) contamination decreased rice yield, but As accumulation in rice has also been a great human health concern for a few decades. New technologies have succeeded in removing As from water by nanomaterials. By all accounts, few studies have addressed CuO NP phytotoxicity to rice, and the interactions of CuO NPs with As are poorly described. The present study 1) reviews studies about the environmental behavior and phytotoxicity of CuO NPs and As and research about the interaction of CuO NPs with As in the environment, 2) discusses critically the potential mechanisms of CuO NP and As toxicity in plants and their interaction, and 3) proposes future research directions for solving the As problem in rice. Environ Toxicol Chem 2018;37:11-20. © 2017 SETAC.

How do physicochemical properties influence the toxicity of silver nanoparticles on freshwater decomposers of plant litter in streams?

AgNP physicochemical properties may affect AgNP toxicity, but their effects on plant litter decomposition and the species driving this key ecosystem process in freshwaters have been poorly investigated. We assessed the impacts of AgNPs with different size and surface coating (100nm PVP (polyvinylpyrrolidone)-dispersant, 50-60nm and 35nm uncoated) on freshwater decomposers of leaf litter by exposing leaf associated microbial assemblages to increasing concentrations of AgNPs (up to 200mgL^-1) and of AgNO₃ (up to 25mgL^-1). We further conducted a feeding preference experiment with a common invertebrate shredder, Limnephilus sp., which was allowed to feed on microbially-colonized leaves previously exposed to AgNPs and AgNO₃. Leaf decomposition and microbial activity and diversity were inhibited when exposed to increased concentrations of 100nm AgNPs (≥25mgL^-1), while microbial activity was stimulated by exposure to 35nm AgNPs (≥100mgL^-1). Invertebrate shredders preferred leaves exposed to 35nm AgNPs (25mgL^-1) and avoided leaves exposed to AgNO₃ (≥2mgL^-1). Results from the characterization of AgNPs by dynamic light scattering revealed that AgNps with PVP-dispersant were more stable than the uncoated AgNPs. Our results highlight the importance of considering the physicochemical properties of NPs when assessing their toxicity to litter decomposers in freshwaters.

Applications of white rot fungi in bioremediation with nanoparticles and biosynthesis of metallic nanoparticles

White rot fungi (WRF) are important environmental microorganisms that have been widely applied in many fields. To our knowledge, the application performance of WRF in bioremediation can be greatly improved by the combination with nanotechnology. And the preparation of metallic nanoparticles using WRF is an emerging biosynthesis approach. Understanding the interrelation of WRF and nanoparticles is important to further expand their applications. Thus, this mini-review summarizes the currently related reports mainly from the two different point of views. We highlight that nanoparticles as supports or synergistic agents can enhance the stability and bioremediation performance of WRF in wastewater treatment and the biosynthesis process and conditions of several important metallic nanoparticles by WRF. Furthermore, the potential toxicity of nanoparticles on WRF and challenges encountered are also discussed. Herein, we deem that this mini-review will strengthen the basic knowledge and provide valuable insight for the applications of WRF and nanoparticles.

The application of iron-based technologies in uranium remediation: A review

Remediating uranium contamination is of worldwide interest because of the increasing release of uranium from mining and processing, nuclear power leaks, depleted uranium components in weapons production and disposal, and phosphate fertilizer in agriculture activities. Iron-based technologies are attractive because they are highly efficient, inexpensive, and readily available. This paper provides an overview of the current literature that addresses the application of iron-based technologies in the remediation of sites with elevated uranium levels. The application of iron-based materials, the current remediation technologies and mechanisms, and the effectiveness and environmental safety considerations of these approaches were discussed. Because uranium can be reduced and reoxidized in the environment, the review also proposes strategies for long-term in situ remediation of uranium. Unfortunately, iron-based materials (nanoscale zerovalent iron and iron oxides) can be toxic to microorganisms. As such, further studies exploring the links among the fates, ecological impacts, and other environmentally relevant factors are needed to better understand the constraints on using iron-based technologies for remediation.

Mycosynthesis of nanoparticles using edible and medicinal mushrooms

This review distinguishes myco-nanotechnology using metallic nanoparticles (meta-NPs) synthesized from edible mushroom matter. Green chemistry approaches were attempted to myco-synthesize meta-NPs (viz., Ag-NP, Au-NP, Se-NP, CdS-NP, Fe-NP, Pa-NP, and ZnS-NP) via different routes using edible mushrooms and have been tested toward 79% biomedical and 21% industrial applications. Biomaterials were used as biofactors to form metallic NPs. In mushroom science, mycomaterials of mushrooms were used at different percentages to mycosynthesize in an ecofriendly/green way; mycomaterials such as crude extracts of basidocarp (53%), mycelial extract or free cell filtrate (28%), in crude form or in purified form such as polysaccharides at different percentages; 9% (especially glucan), proteins/enzymes (7%) and polysaccharides protein complex (3%) as new research lines. Generally, in this field of mushroom nanoparticles about 84% of mycosynthesized NPs using mushrooms are placed outside the fungal cell (extracellular) and 16% are intracellular in the mushroom hyphae. The knowledge of the performance and influence of meta-NPs in edible mushrooms has developed in the last 10 years. Generally, while

Induction of Laccase, Lignin Peroxidase and Manganese Peroxidase Activities in White-Rot Fungi Using Copper Complexes

Ligninolytic enzymes, such as laccase, lignin peroxidase and manganese peroxidase, are biotechnologically-important enzymes. The ability of five white-rot fungal strains Daedaleopsis confragosa, Fomes fomentarius, Trametes gibbosa, Trametes suaveolens and Trametes versicolor to produce these enzymes has been studied. Three different copper(II) complexes have been prepared ((Him)[Cu(im)₄(H₂O)₂](btc)·3H₂O, where im = imidazole, H₃btc = 1,3,5-benzenetricarboxylic acid, [Cu₃(pmdien)₃(btc)](ClO₄)₃·6H₂O) and [Cu₃(mdpta)₃(btc)](ClO₄)₃·4H₂O, where pmdien = N,N,N′,N′′,N′′-pentamethyl-diethylenetriamine and mdpta = N,N-bis-(3-aminopropyl)methyl- amine), and their potential application for laccase and peroxidases induction have been tested. The enzyme-inducing activities of the complexes were compared with that of copper sulfate, and it has been found that all of the complexes are suitable for the induction of laccase and peroxidase activities in white-rot fungi; however, the newly-synthesized complex M1 showed the greatest potential for the induction. With respect to the different copper inducers, this parameter seems to be important for enzyme activity, which depends also on the fungal strains.

A review of the environmental implications of in situ remediation by nanoscale zero valent iron (nZVI): Behavior, transport and impacts on microbial communities

The increasing use of strategies incorporating nanoscale zero valent iron (nZVI) for soil and groundwater in situ remediation is raising some concerns regarding the potential adverse effects nZVI could have on indigenous microbial communities and ecosystem functioning. This review provides an overview of the current literature pertaining to the impacts of nZVI applications on microbial communities. Toxicity studies suggest that cell membrane disruption and oxidative stress through the generation of Fe(2+) and reactive oxygen species by nZVI are the main mechanisms contributing to nZVI cytotoxicity. In addition, nZVI has been shown to substantially alter the taxonomic and functional composition of indigenous microbial communities. However, because the physico-chemical conditions encountered in situ highly modulate nZVI toxicity, a better understanding of the environmental factors affecting nZVI toxicity and transport in the environment is of primary importance in evaluating the ecological consequences that could result from a more extensive use of nZVI.

Toxicity of graphene oxide to white rot fungus Phanerochaete chrysosporium

With the wide production and applications of graphene and its derivatives, their toxicity to the environment has received much attention nowadays. In this study, we investigated the toxicity of graphene oxide (GO) to white rot fungus (Phanerochaete chrysosporium). GO was prepared by modified Hummers method and well characterized before use. P. chrysosporium was exposed to GO at the concentrations of 0-4 mg/mL for 7 d. The fresh and dry weights, pH values of culture media, structures, ultrastructures, IR spectra and activities of the decomposition of pollutants were measured to reveal the hazards of GO to P. chrysosporium. Our results indicated that low concentrations of GO stimulated the growth of P. chrysosporium. The exposure to GO induced more acidic pH values of the culture media after 7 d. GO induced the disruption of the fiber structure of P. chrysosporium, while at 4 mg/mL some very long and thick fibers were formed. Such changes were reflected in the scanning electron microscopy investigations, where the disruption of fibers was observed. In the ultrastructural investigations, the shape of P. chrysosporium cells changed and more vesicles were found upon the exposure to GO. The infrared spectroscopy analyses suggested that the chemical compositions of mycelia were not changed qualitatively. Beyond the toxicity, GO did not alter the activities of P. chrysosporium at low concentrations, but led to the complete loss of activity at high concentrations. The implication to the ecological safety of graphene is discussed.

Micronized copper wood preservatives: an efficiency and potential health risk assessment for copper-based nanoparticles

Copper (Cu) is an essential biocide for wood protection, but fails to protect wood against Cu-tolerant wood-destroying fungi. Recently Cu particles (size range: 1 nm-25 μm) were introduced to the wood preservation market. The new generation of preservatives with Cu-based nanoparticles (Cu-based NPs) is reputedly more efficient against wood-destroying fungi than conventional formulations. Therefore, it has the potential to become one of the largest end uses for wood products worldwide. However, during decomposition of treated wood Cu-based NPs and/or their derivate may accumulate in the mycelium of Cu-tolerant fungi and end up in their spores that are dispersed into the environment. Inhaled Cu-loaded spores can cause harm and could become a potential risk for human health. We collected evidence and discuss the implications of the release of Cu-based NPs by wood-destroying fungi and highlight the exposure pathways and subsequent magnitude of health impact.

Aggregation, dissolution, and transformation of copper nanoparticles in natural waters

Time-dependent aggregation, sedimentation, dissolution, and transformation of three copper-based engineered nanomaterials (ENMs) of varied properties were measured in eight natural and artificial waters. Nano-Cu and Cu(OH)2 aggregated rapidly to >10(3) nm while the aggregate size of nano-CuO averaged between 250 and 400 nm. Aggregate size for both nano-Cu and nano-CuO showed a positive correlation with ionic strength with a few exceptions. Aggregate size did not correlate well with sedimentation rate, suggesting sedimentation was influenced by other factors. Controlling factors in sedimentation rates varied by particle: Cu(OH)2 particles remained stable in all waters but groundwater, nano-Cu was generally unstable except in waters with high organic content, and nano-CuO was stabilized by the presence of phosphate, which reversed surface charge polarity at concentrations as low as 0.1 mg PO4(3-) L(-1). Dissolution generally correlated with pH, although in saline waters, dissolved copper formed insoluble complexes. Nano-Cu was rapidly oxidized, resulting in dissolution immediately followed by the formation of precipitates. These results suggest factors including phosphate, carbonate, and ENM oxidation state may be key in determining Cu ENM behavior in natural waters.

The effect of silver nanoparticles on seasonal change in arctic tundra bacterial and fungal assemblages

The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages.

Methane oxidation and abundance of methane oxidizers in tropical agricultural soil (vertisol) in response to CuO and ZnO nanoparticles contamination

There is worldwide concern over the increase use of nanoparticles (NPs) and their ecotoxicological effect. It is not known if the annual production of tons of industrial nanoparticles (NPs) has the potential to impact terrestrial microbial communities, which are so necessary for ecosystem functioning. Here, we have examined the consequences of adding the NPs particularly the metal oxide (CuO, ZnO) on CH4 oxidation activity in vertisol and the abundance of heterotrophs, methane oxidizers, and ammonium oxidizers. Soil samples collected from the agricultural field located at Madhya Pradesh, India, were incubated with either CuO and ZnO NPs or ionic heavy metals (CuCl2, ZnCl2) separately at 0, 10, and 20 μg g(-1) soil. CH4 oxidation activity in the soil samples was estimated at 60 and 100 % moisture holding capacity (MHC) in order to link soil moisture regime with impact of NPs. NPs amended to soil were highly toxic for the microbial-mediated CH4 oxidation, compared with the ionic form. The trend of inhibition was Zn 20 > Zn 10 > Cu 20 > Cu 10. NPs delayed the lag phase of CH4 oxidation to a maximum of 4-fold and also decreased the apparent rate constant k up to 50 % over control. ANOVA and Pearson correlation analysis (α = 0.01) revealed significant impact of NPs on the CH4 oxidation activity and microbial abundance (p < 0.0001, and high F statistics). Principal component analysis (PCA) revealed that PC1 (metal concentration) rendered 76.06 % of the total variance, while 18.17 % of variance accounted by second component (MHC). Biplot indicated negative impact of NPs on CH4 oxidation and microbial abundance. Our result also confirmed that higher soil moisture regime alleviates toxicity of NPs and opens new avenues of research to manage ecotoxicity and environmental hazard of NPs.

Physiological responses to nanoCuO in fungi from non-polluted and metal-polluted streams

Nanocopper oxide (nanoCuO) is among the most widely used metal oxide nanoparticles which increases their chance of being released into freshwaters. Fungi are the major microbial decomposers of plant litter in streams. Fungal laccases are multicopper oxidase enzymes that are involved in the degradation of lignin and various xenobiotic compounds. We investigated the effects of nanoCuO (5 levels, ≤ 200 mg L(-1)) on four fungal isolates collected from metal-polluted and non-polluted streams by analyzing biomass production, changes in mycelial morphology, laccase activity, and quantifying copper adsorbed to mycelia, and ionic and nanoparticulate copper in the growth media. The exposure to nanoCuO decreased the biomass produced by all fungi in a concentration- and time-dependent manner. Inhibition of biomass production was stronger in fungi from non-polluted (EC₅₀(10 days) ≤ 31 mg L(-1)) than from metal-polluted streams (EC₅₀(10 days) ≥ 65.2 mg L(-1)). NanoCuO exposure led to cell shrinkage and mycelial degeneration, particularly in fungi collected from non-polluted streams. Adsorption of nanoCuO to fungal mycelia increased with the concentration of nanoCuO in the medium and was higher in fungi from non-polluted streams. Extracellular laccase activity was induced by nanoCuO in two fungal isolates in a concentration-dependent manner, and was highly correlated with adsorbed Cu and/or ionic Cu released by dissolution from nanoCuO. Putative laccase gene fragments were also detected in these fungi. Lack of substantial laccase activity in the other fungal isolates was corroborated by the absence of laccase-like gene fragments.

The impact of zero-valent iron nanoparticles upon soil microbial communities is context dependent

Nanosized zero-valent iron (nZVI) is an effective land remediation tool, but there remains little information regarding its impact upon and interactions with the soil microbial community. nZVI stabilised with sodium carboxymethyl cellulose was applied to soils of three contrasting textures and organic matter contents to determine impacts on soil microbial biomass, phenotypic (phospholipid fatty acid (PLFA)), and functional (multiple substrate-induced respiration (MSIR)) profiles. The nZVI significantly reduced microbial biomass by 29 % but only where soil was amended with 5 % straw. Effects of nZVI on MSIR profiles were only evident in the clay soils and were independent of organic matter content. PLFA profiling indicated that the soil microbial community structure in sandy soils were apparently the most, and clay soils the least, vulnerable to nZVI suggesting a protective effect imparted by clays. Evidence of nZVI bactericidal effects on Gram-negative bacteria and a potential reduction of arbuscular mycorrhizal fungi are presented. Data imply that the impact of nZVI on soil microbial communities is dependent on organic matter content and soil mineral type. Thereby, evaluations of nZVI toxicity on soil microbial communities should consider context. The reduction of AM fungi following nZVI application may have implications for land remediation.

CdTe/CdSe quantum dots improve the binding affinities between α-amylase and polyphenols

People exposed to engineered nanomaterials have potential health risks associated. Human α-amylase is one of the key enzymes in the digestive system. There are few reports about the influence of quantum dots (QDs) on the digestive enzymes and their inhibition system. This work focused on the toxic effect of CdTe/CdSe QDs on the interactions between α-amylase and its natural inhibitors. Thirty-six dietary polyphenols, natural α-amylase inhibitors from food, were studied for their affinities for α-amylase in the absence and presence of CdTe/CdSe QDs by a fluorescence quenching method. The magnitudes of apparent binding constants of polyphenols for α-amylase were almost in the range of 10(5)-10(7) L mol(-1) in the presence of CdTe/CdSe QDs, which were higher than the magnitudes of apparent binding constants in the absence of CdTe/CdSe QDs (10(4)-10(6) L mol(-1)). CdTe/CdSe QDs obviously improved the affinities of dietary polyphenols for α-amylase up to 389.04 times. It is possible that the binding interaction between polyphenols and α-amylase in the presence of CdTe/CdSe QDs was mainly caused by electrostatic interactions. QDs significantly influence the digestive enzymes and their inhibition system.

Influence of a nanoparticle mixture on an arctic soil community

Interest is growing in understanding not only the impact of individual nanoparticles (NPs) on ecosystems but also the effect of NP mixtures. In the present study, the impact of a combination of three different NPs, silver, copper, and silica (all at 0.022%, w/w), on an arctic microbial community was investigated. After adding the NPs, soil microcosms were incubated for 176 d, and subsequent estimates of microbe diversity were obtained using culture-dependent and culture-independent assessments. The treated soil appeared to show a reduction in the ability to use carbohydrate and amino acid substrates and demonstrated an altered pattern of major fatty acid peaks. Polymerase chain reaction-denaturing gradient gel electrophoresis showed consistent differences in the pattern of predominant rRNA gene sequences. Although this is an initial investigation of soil contaminated with mixed NPs, these results demonstrate that even at the relatively modest concentrations used such pollutants have the potential to disrupt microbial communities.

Can metal nanoparticles be a threat to microbial decomposers of plant litter in streams?

The extensive use of nanometal-based products increases the chance of their release into aquatic environments, raising the question whether they can pose a risk to aquatic biota and the associated ecological processes. Aquatic microbes, namely fungi and bacteria, play a key role in forested streams by decomposing plant litter from terrestrial vegetation. Here, we investigated the effects of nanocopper oxide and nanosilver on leaf litter decomposition by aquatic microbes, and the results were compared with the impacts of their ionic precursors. Alder leaves were immersed in a stream of Northwest Portugal to allow microbial colonization before being exposed in microcosms to increased nominal concentrations of nanometals (CuO, 100, 200 and 500 ppm; Ag, 100 and 300 ppm) and ionic metals (Cu(2+) in CuCl(2), 10, 20 and 30 ppm; Ag(+) in AgNO(3), 5 and 20 ppm) for 21 days. Results showed that rates of leaf decomposition decreased with exposure to nano- and ionic metals. Nano- and ionic metals inhibited bacterial biomass (from 68.6% to 96.5% of control) more than fungal biomass (from 28.5% to 82.9% of control). The exposure to increased concentrations of nano- and ionic metals decreased fungal sporulation rates from 91.0% to 99.4%. These effects were accompanied by shifts in the structure of fungal and bacterial communities based on DNA fingerprints and fungal spore morphology. The impacts of metal nanoparticles on leaf decomposition by aquatic microbes were less pronounced compared to their ionic forms, despite metal ions were applied at one order of magnitude lower concentrations. Overall, results indicate that the increased release of nanometals to the environment may affect aquatic microbial communities with impacts on organic matter decomposition in streams.

Perturbation of an arctic soil microbial community by metal nanoparticles

Technological advances allowing routine nanoparticle (NP) manufacture have enabled their use in electronic equipment, foods, clothing and medical devices. Although some NPs have antibacterial activity, little is known about their environmental impact and there is no information on the influence of NPs on soil in the possibly vulnerable ecosystems of polar regions. The potential toxicity of 0.066% silver, copper or silica NPs on a high latitude (>78°N) soil was determined using community level physiological profiles (CLPP), fatty acid methyl ester (FAME) assays and DNA analysis, including sequencing and denaturing gradient gel electrophoresis (DGGE). The results of these different investigations were amalgamated in order to develop a community toxicity indicator, which revealed that of the three NPs examined, silver NPs could be classified as highly toxic to these arctic consortia. Subsequent culture-based studies confirmed that one of the community-identified plant-associating bacteria, Bradyrhizobium canariense, appeared to have a marked sensitivity to silver NPs. Thus, NP contamination of arctic soils particularly by silver NPs is a concern and procedures for mitigation and remediation of such pollution should be a priority for investigation.