Spectroscopic Investigation of Phosphorus Mineralization as Affected by the Calcite-Water Interfacial Chemistry

The mineralization and bioavailability of phytic acid, the predominant organic phosphorus (OP) species in many soils, have generally been rendered limited due to its interaction with soil minerals. In particularly calcareous and neutral to slightly alkaline soils, phytic acid is known to actively react with calcite, although how this interaction affects phytic acid mineralization is still unknown. This study, therefore, investigated the mechanisms regarding how the calcite-water interface influences phytic acid mineralization by phytase, at pHs 6 and 8 using in situ spectroscopic techniques including solution nuclear magnetic resonance and attenuated total reflection Fourier transform infrared spectroscopy. The findings indicated a pH-specific effect of the calcite-water interface. Inhibited phytase activity and thus impaired phytic acid mineralization were induced by calcite at pH 6, while the opposite effect was observed at pH 8. How the interaction between phytic acid and calcite and between phytase and calcite differed between the two pH values contributed to the pH-specific effect. The results demonstrate the importance of soil pH, enzyme-, and OP-clay mineral interactions in controlling the mineralization and transformation of OP and, consequently, the release of phosphate in soils. The findings can also provide implications for the management of calcite-rich and limed soils.

Investigation into Brazilian Palygorskite for Its Potential Use as Pharmaceutical Excipient: Perspectives and Applications

Palygorskite is an aluminum and magnesium silicate characterized by its fibrous morphology, providing it with great versatility in industrial applications, including pharmaceuticals. Although most of the reserves are in the United States, in recent years occurrences of commercially exploited deposits in Brazil have been recorded, mainly in the country's northeast region. This has motivated this study, which analyzes raw Brazilian palygorskite compared to a commercial sample (Pharmasorb^® colloidal) to demonstrate its pharmaceutical potential. The chemical and mineral composition of the samples were evaluated for surface properties, granulometry, morphology, crystallography, thermal analysis, and spectroscopy. Raw palygorskite presented 67% purity, against 74% for Pharmasorb^® colloidal. The percentage purity relates to the presence of contaminants, mainly carbonates and quartz (harmless under conventional conditions of pharmaceutical use). Furthermore, it was possible to confirm the chemical composition of these phyllosilicates, formed primarily of silicon, aluminum, and magnesium oxides. The crystallographic and spectroscopic profiles were consistent in both samples, showing characteristic peaks for palygorskite (2θ = 8.3°) and bands attributed to fibrous phyllosilicates below 1200 cm^-1, respectively. The thermal analysis allowed the identification of the main events of palygorskite, with slight differences between the evaluated samples: loss of water adsorbed onto the surface (~85 °C), removal of water contained in the channels (~200 °C), coordinated water loss (~475 °C), and, finally, the dehydroxylation (>620 °C). The physicochemical characteristics of raw palygorskite align with pharmacopeial specifications, exhibiting a high specific surface area (122 m²/g), moderately negative charge (-13.1 mV), and compliance with the required limits for heavy metals and arsenic. These favorable technical attributes indicate promising prospects for its use as a pharmaceutical ingredient in the production of medicines and cosmetics.

Effects of Combinations of Toxin Binders with or without Natural Components on Broiler Breeders Exposed to Ochratoxin A

The objective of this study was to investigate the effects of toxin binders on broiler breeders fed an ochratoxin A (OTA)-contaminated diet. A total of 60 45-week-old female Arbor Acres broiler breeder birds with an initial body weight of 3.65 ± 0.35 kg were randomly divided into 6 treatment groups, with 10 replicates per group and 1 bird per replicate. The trial was conducted for 9 weeks (including 1 week of adaptation). Feed additive 1 (FA1) was composed of clay minerals (85% bentonite and 12% clinoptilolite) with 3% charcoal. FA2 was composed of clay minerals (66.1% aluminosilicates) with natural components (0.8% artichoke and rosemary plant extracts), 7% yeast extract, 0.5% beta-glucans, and 25.6% carriers. The dietary treatment groups were as follows: (1) birds fed an OTA-free basal diet (Negative Control; NC); (2) lipopolysaccharide (LPS)-challenged birds fed a diet including OTA (4 mg/kg) (Positive Control, PC); (3) the PC with 0.05% FA1 (Treatment 1, T1); (4) the PC with 0.10% FA1 (Treatment 2, T2); (5) the PC with 0.10% FA2 (Treatment 3, T3); and (6) the PC with 0.20% FA2 (Treatment 4, T4). The LPS challenge (an intramuscular injection of 1 mg E. coli O55:B5 LPS per kg of body weight) was performed on the first day of the experiment. The results of this experiment show that the PC treatment negatively affected (p < 0.05) egg production, hatchability, Haugh unit, bone mineralization, relative organ weight (abdominal fat, liver), the levels of glutamic oxaloacetic transaminase (GOT), high-density lipoprotein (HDL), and total cholesterol in the blood, and OTA accumulation in the liver compared with the NC. However, supplementation with toxin binders mitigated (p < 0.05) the negative effects of the OTA. Specifically, supplementation with 0.10% FA1 and 0.10% FA2 increased (p < 0.05) eggshell strength by week 4, and the Haugh unit and bone mineralization (phosphorous) by week 8, while decreasing (p < 0.05) the relative weight of the liver and the levels of GOT and HDL in the blood. Supplementation with 0.10% FA2 led to greater improvements in various parameters, including laying performance and bone mineralization, than the other treatments. In conclusion, toxin binders with or without natural components can be effective tools in the mitigation of OTA-induced problems due to their synergistic effects.

Nanoclay-Modulated Interfacial Chemical Bond and Internal Electric Field at the Co3 O4 /TiO2 p-n Junction for Efficient Charge Separation

To achieve a high separation efficiency of photogenerated carriers in semiconductors, constructing high-quality heterogeneous interfaces as charge flow highways is critical and challenging. This study successfully demonstrates an interfacial chemical bond and internal electric field (IEF) simultaneously modulated 0D/0D/1D-Co₃ O₄ /TiO₂ /sepiolite composite catalyst by exploiting sepiolite surface-interfacial interactions to adjust the Co²⁺ /Co³⁺ ratio at the Co₃ O₄ /TiO₂ heterointerface. In situ irradiation X-ray photoelectron spectroscopy and density functional theory (DFT) calculations reveal that the interfacial Co²⁺ OTi bond (compared to the Co³⁺ OTi bond) plays a major role as an atomic-level charge transport channel at the p-n junction. Co²⁺ /Co³⁺ ratio increase also enhances the IEF intensity. Therefore, the enhanced IEF cooperates with the interfacial Co²⁺ OTi bond to enhance the photoelectron separation and migration efficiency. A coupled photocatalysis-peroxymonosulfate activation system is used to evaluate the catalytic activity of Co₃ O₄ /TiO₂ /sepiolite. Furthermore, this work demonstrates how efficiently separated photoelectrons facilitate the synergy between photocatalysis and peroxymonosulfate activation to achieve deep pollutant degradation and reduce its ecotoxicity. This study presents a new strategy for constructing high-quality heterogeneous interfaces by consciously modulating interfacial chemical bonds and IEF, and the strategy is expected to extend to this class of spinel-structured semiconductors.

A meta-analysis of the effects of clay mineral supplementation on alkaline phosphatase, broiler health, and performance

The crucial constraint in the broiler production sector is feed efficiency; many feed additives have been widely employed to increase broiler growth. Nonetheless, some of these substances exacerbate health and animal-based food product safety concerns. This meta-analysis examines the effect of clay minerals on alkaline phosphatase (ALP), broiler health, and performance. Metadata was constructed from 369 data items that were harvested from 86 studies. The addition of clay minerals was set as a fixed effect and the difference between experiments was established as a random effect. The metadata were fitted using a linear mixed model. Due to the presence of clay minerals, growth performance as assessed by body weight (BW), average daily gain (ADG), and performance efficiency index (PEI) increased significantly (P < 0.01). In the total period, the increases of BW, ADG, and PEI were 4.12 g, 0.0714 g/d, and 0.648, respectively, per unit of clay minerals added. Clay minerals did not affect blood serum parameters (e.g., ALP and calcium). The IgA and IgM concentrations in the jejunum and ileum were significantly greater (P < 0.01) in the starter phase. Among clay minerals, broilers fed diets with aluminosilicate, halloysite, kaolin, and zeolite consistently exhibited higher (P < 0.05) BW, ADG, PEI, and lower feed conversion ratio (P < 0.05) in the finisher phase. Aluminosilicate was the only clay that increased (P < 0.05) secretory IgA concentration in both jejunum and ileum. In conclusion, clay minerals could be used as a growth promoter, especially during the finisher phase, without adversely affecting feed intake, liver function, and mineral metabolism in broiler chickens. Aluminosilicate was superior in improving the mucosal immunity status of broiler chickens.

Inhibition of Extracellular Enzyme Activity by Reactive Oxygen Species upon Oxygenation of Reduced Iron-Bearing Minerals

The dual roles of minerals in inhibiting and prolonging extracellular enzyme activity in soils and sediments are governed by enzyme adsorption to mineral surfaces. Oxygenation of mineral-bound Fe(II) generates reactive oxygen species (ROS), yet it is unknown whether and how this process alters the activity and functional lifespan of extracellular enzymes. Here, the effect of mineral-bound Fe(II) oxidation on the hydrolytic activity of a cellulose-degrading enzyme β-glucosidase (BG) was studied using two pre-reduced Fe-bearing clay minerals (nontronite and montmorillonite) and one pre-reduced iron oxide (magnetite) at pH 5 and 7. Under anoxic conditions, BG adsorption to mineral surfaces decreased its activity but prolonged its lifespan. Under oxic conditions, ROS was produced, with the amount of •OH, the most abundant ROS, being positively correlated with the extent of structural Fe(II) oxidation in reduced minerals. •OH decreased BG activity and shortened its lifespan via conformational change and structural decomposition of BG. These results suggest that under oxic conditions, the ROS-induced inhibitory role of Fe(II)-bearing minerals outweighed their adsorption-induced protective role in controlling enzyme activity. These results disclose a previously unknown mechanism of extracellular enzyme inactivation, which have pivotal implications for predicting the active enzyme pool in redox-oscillating environments.

Thermally Modified Palygorskite Usage as Adsorbent in Fixed-Bed Reactor for High Concentration NH4+-N Removal and Further Application as N-Fertilizer in Hydroponic Cultivation

Palygorskite sample (Pal) underwent thermal treatment at 400 °C (T-Pal) to be used as adsorbent for the removal of 200 mg NH₄⁺-N/L from artificial solution. After thermal treatment, the sample was characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). For NH₄⁺-N removal, T-Pal was added as a bed matrix in fixed-bed reactor experiments and the effect of flow rate was determined. It was indicated that with the flow rate increase from 10 mL/min to 50 mL/min, fewer liters of the solution were purified, rendering a longer residual time of interactions, which is optimal for NH₄⁺-N removal from T-Pal. The maximum removed amount was calculated at 978 mg NH₄⁺-N (q_total), suggesting T-Pal is a promising ammonium adsorbent. The data of kinetic experiments were applied to Clark, Yoon-Nelson, and Thomas kinetic models, with Clark having the best fit, highlighting a heterogenous adsorption. At the end of kinetic experiments, T-Pal applied in hydroponic cultivations and presented a sufficient release rate, which was found utilizable for saturated T-Pal usage as N fertilizer that satisfactory results were deemed concerning lettuces characteristics and growth.

A Prebiotic Ribosylation of Pyrimidine Nucleobases Enabled by Metal Cations and Clay Minerals

We report a prebiotically relevant solution to the N1-ribosylation of pyrimidine nucleobases, a well-known challenge to the RNA world hypothesis. We found that the presence of metal cations and clay minerals enable the previously unachievable direct ribosylation of uracil. Spectroscopy and chromatography analyses confirmed the formation of ribosylated uracil. The method can be extended to the ribosylation of 2-pyrimidinone. These findings are also compatible with the metal-doped-clay model, developed by our lab for the unified route of the selection of ribose and subsequent syntheses of nucleotide and RNA.

Physico-Chemical Characterization and Antimicrobial Properties of Hybrid Film Based on Saponite and Phloxine B

This research was aimed at the preparation of a hybrid film based on a layered silicate saponite (Sap) with the immobilized photosensitizer phloxine B (PhB). Sap was selected because of its high cation exchange capacity, ability to exfoliate into nanolayers, and to modify different surfaces. The X-ray diffraction of the films confirmed the intercalation of both the surfactant and PhB molecules in the Sap film. The photosensitizer retained its photoactivity in the hybrid films, as shown by fluorescence spectra measurements. The water contact angles and the measurement of surface free energy demonstrated the hydrophilic nature of the hybrid films. Antimicrobial effectiveness, assessed by the photodynamic inactivation on hybrid films, was tested against a standard strain and against methicillin-resistant bacteria of Staphylococcus aureus (MRSA). One group of samples was irradiated (green LED light; 2.5 h) and compared to nonirradiated ones. S. aureus strains manifested a reduction in growth from 1-log10 to over 3-log10 compared to the control samples with Sap only, and defects in S. aureus cells were proven by scanning electron microscopy. The results proved the optimal photo-physical properties and anti-MRSA potential of this newly designed hybrid system that reflects recent progress in the modification of surfaces for various medical applications.

Broad-Spectrum Antimicrobial and Antibiofilm Activity of a Natural Clay Mineral from British Columbia, Canada

Worldwide increases in antibiotic resistance and the dearth of new antibiotics have created a global crisis in the treatment of infectious diseases. These concerns highlight the pressing need for novel antimicrobial agents. Natural clay minerals have a long history of therapeutic and biomedical applications and have lately received specific attention for their potent antimicrobial properties. In particular, Kisameet clay (KC) has strong antibacterial activity against a variety of multidrug-resistant (MDR) bacterial pathogens in vitro Here, we have extended the known spectrum of activity of KC by demonstrating its efficacy against two major fungal pathogens, Candida albicans and Cryptococcus neoformans In addition, KC also exhibits potent activity against the opportunistic bacterial pathogen Mycobacterium marinum, a model organism for M. ulcerans infection. Moreover, aqueous KC leachates (KC-L) exhibited broad-spectrum antibacterial activity, eradicated Gram-negative and Gram-positive biofilms, and prevented their formation. The mechanism(s) underlying KC antibacterial activity appears to be complex. Adjusting KC-L to neutral pH rendered it inactive, indicating a contribution of pH, although low pH alone was insufficient for its antibacterial activity. Treatment of KC minerals with cation-chelating agents such as EDTA, 2,2'-bipyridyl, and deferoxamine reduced the antibacterial activity, while supplementation of KC-L with these chelating agents eliminated the inhibitory activity. Together, the data suggest a positive role for divalent and trivalent cations, including iron and aluminum, in bacterial inhibition by KC. Collectively, these studies demonstrate the range of KC bioactivity and provide a better understanding of the mechanism underlying its antibacterial effects.IMPORTANCE The escalating emergence of multidrug-resistant (MDR) bacteria, together with the paucity of novel antimicrobial agents in antibiotic development, is recognized as a worldwide public health crisis. Kisameet clay (KC), found in British Columbia (BC), Canada, is a clay mineral with a long history of therapeutic applications among people of the First Nations. We previously reported the antibacterial activity of KC against a group of MDR clinical pathogens. Here, we demonstrate its activity against two major human-pathogenic fungal species, as well as against bacterial biofilms, which underlie many recalcitrant bacterial infections. In these studies, we also identified several geochemical characteristics of KC, such as metal ions and low pH, which are involved in its antibacterial activity. These findings provide a better understanding of the components of KC antibacterial activity and a basis for developing defined preparations of this clay mineral for therapeutic applications.

Optimal Synthesis of Environment-Friendly Iron Red Pigment from Natural Nanostructured Clay Minerals

A series of environment-friendly clay minerals-α-Fe₂O₃ iron-red hybrid pigments-were prepared by a simple one-step hydrothermal reaction process using natural nanostructured silicate clay minerals as starting materials. The influence of structure, morphology and composition of different clay minerals on the structure, color properties, and stability of the pigments was studied comparatively by systematic structure characterizations with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmittance electron microscope (TEM), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS) and CIE-L*a*b* Colorimetric analyses. The results showed that the clay minerals act as green precipitants during the hydrothermal reaction to induce in-situ transformation of Fe(III) ions into Fe₂O₃ crystals. Meanwhile, they also act as the "micro-reactor" for forming Fe₂O₃ crystals and the supporter for inhibiting the aggregation of Fe₂O₃ nanoparticles. The color properties of iron-red hybrid pigments are closely related to the surface charges, surface silanol groups, and solid acid sites of clay minerals. The clay minerals with higher surface activity are more suitable to prepare iron-red pigments with better performance. The iron-red hybrid pigment derived from illite (ILL) clay showed the best red color performance with the color values of L* = 31.8, a* = 35.2, b* = 27.1, C* = 44.4 and h° = 37.6, and exhibited excellent stability in different chemical environments such as acid, alkaline, and also in high-temperature conditions.

Kisameet Glacial Clay: an Unexpected Source of Bacterial Diversity

Widespread antibiotic resistance among bacterial pathogens is providing the impetus to explore novel sources of antimicrobial agents. Recently, the potent antibacterial activity of certain clay minerals has stimulated scientific interest in these materials. One such example is Kisameet glacial clay (KC), an antibacterial clay from a deposit on the central coast of British Columbia, Canada. However, our understanding of the active principles of these complex natural substances is incomplete. Like soils, clays may possess complex mixtures of bacterial taxa, including the Actinobacteria, a clade known to be rich in antibiotic-producing organisms. Here, we present the first characterization of both the microbial and geochemical characteristics of a glacial clay deposit. KC harbors surprising bacterial species richness, with at least three distinct community types. We show that the deposit has clines of inorganic elements that can be leached by pH, which may be drivers of community structure. We also note the prevalence of Gallionellaceae in samples recovered near the surface, as well as taxa that include medically or economically important bacteria such as Actinomycetes and Paenibacillus. These results provide insight into the microbial taxa that may be the source of KC antibacterial activity and suggest that natural clays may be rich sources of microbial and molecular diversity.

Identifying and characterizing the resident microbial populations (bacteria, viruses, protozoa, and fungi) is key to understanding the ecology, chemistry, and homeostasis of virtually all sites on Earth. The Kisameet Bay deposit in British Columbia, Canada, holds a novel glacial clay with a history of medicinal use by local indigenous people. We previously showed that it has potent activity against a variety of antibiotic-resistant bacteria, suggesting it could complement our dwindling arsenal of antibiotics. Here, we have characterized the microbiome of this deposit to gain insight into what might make the clay antibacterial. Our analyses suggest that the deposit contains a surprising diversity of bacteria, which live in at least three distinct environments. In addition, the clay harbors bacteria that may have interesting potential as biocontrol/bioremediation agents or producers of novel bioactive compounds.

Rapid exchange between atmospheric CO2 and carbonate anion intercalated within magnesium rich layered double hydroxide

The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2 under ambient conditions. (Ishihara et al., J. Am. Chem. Soc. 2013, 135, 18040-18043). The use of (13)C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2 within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2 can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2 storage and/or separation.

Suppression of humoral immune responses by 2,3,7,8-tetrachlorodibenzo-p-dioxin intercalated in smectite clay

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially.