Biomineralization Process Research Articles

Investigation of the effect of urease bioadditives on porosity and water absorption of cement composites

The results of the application of the biomineralization process in concrete to improve concrete properties such as porosity and water absorption are presented. As a result of the research, an assessment of the activity of various bioadditives based on the Bacillus subtilis strain and isolates isolated from samples of chernozem soil of the Yelets district of the Lipetsk region was given.It was found that the immobilized bacteria slightly differ from the native form in terms of urease activity, however, when stored for more than 50 days. they maintain their activity at a high level, and native microorganisms lose their ability to function, reducing urease activity by 10 times practically to minimum values. It was also revealed that when using Portland cement of various types, there is a decrease in water absorption up to 30%, and porosity decreases up to 40%.The use of different types of fine aggregate also affects porosity, so when using the same parts of sand P1 and P2, porosity is lower than with a homogeneous fine aggregate.It was also noted that all samples had increased strength characteristics – compressive strength and bending strength by 15–25%, respectively. Thus, the use of bioadditives is optimal to achieve improved concrete characteristics.

Exploring Biomineralization Processes Using In Situ Liquid Transmission Electron Microscopy: A Review.

Liquid transmission electron microscopy (TEM) is a newly established technique broadly used to study reactions in situ. Since its emergence, complex and multifaceted biomineralization processes have been revealed with real-time resolution, where classical and non-classical mineralization pathways have been dynamically observed primarily for Ca and Fe-based mineral systems in situ. For years, classical crystallization pathways have dominated theories on biomineralization progression despite observations of non-traditional routes involving precursor phases using traditional- and cryo-TEM. The new dynamic lens provided by liquid TEM is a key correlate to techniques limited to time-stamped, static observations - helping shift paradigms in biomineralization toward non-classical theories with dynamic mechanistic visualization. Liquid TEM provides new insights into fundamental biomineralization processes and essential physiological and pathological processes for a wide range of organisms. This review critically reviews a summary of recent in situ liquid TEM research related to the biomineralization field. Key liquid TEM preparation and imaging parameters are provided as a foundation for researchers while technical challenges are discussed. In future, the expansion of liquid TEM research in the biomineralization field will lead to transformative discoveries, providing complementary dynamic insights into biological systems.

Microstructures, crystallography and growth patterns of serpulid tubeworms (Class Polychaeta)

Serpulid polychaetes are marine worms that secrete calcium carbonate tubes in which they live. Despite extensive previous research on their microstructures, there are no crystallographic data and their biomineralization process remains unclear. Here, the microstructures of the tubes of seven serpulid species were studied, including their chemical composition, mineralogy and crystallography, using X-ray diffraction, Raman and Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, focused ion beam, electron backscatter diffraction, and thermogravimetric analysis. Generally, serpulid tubes have a high amount of organic matter (~ 7.5 wt%), consisting of chitin and proteins, and the calcite is always present as medium to high magnesium calcite. Three main microstructures were identified: granular-prismatic and lamello-fibrillar calcite, and fibrous aragonite. They all displayed an axial texture, which is stronger in the lamello-fibrillar calcite, with the c-axis aligned with the elongation axis of the crystals. These findings demonstrate that only some instances of the granular-prismatic and the lamello-fibrillar calcite are biogenic (primary) microstructures. Conversely, other instances of the granular-prismatic calcite and the fibrous aragonite are a consequence of a recrystallization process (i.e. secondary). Replacement may occur on either primary or secondary calcitic microstructures (replaced by aragonite). Secondary microstructures retain remnants of the previously replaced microstructures, such as vestigial crystals or major growth increments. The high-Mg nature of the calcite favors recrystallization. The plywood arrangement of the lamello-fibrillar calcite is hypothesized to result from the ordering of a chitin fibrillar precursor into a cholesteric liquid crystal phase, with the calcite subsequently growing by oriented nucleation onto the organic fibrils.

ISOLATING PURE SILICA FROM SYRIAN CLAY FOR BIOGLASS MANUFACTURING

One material that can be used in bone and soft tissue engineering is bioglass. By adhering to bone tissues and forming an apatite layer that further starts the biomineralization process, it can also encourage skin regeneration and wound healing in addition to playing a significant part in the healing processes of bone fractures.In this research, Syrian clay was used as a cheap silica source for preparation bioglass by melting method. Pure silica was isolated by mixing clay with sodium hydroxide in the following amounts (1:1), (2:1), (3:1), treated at different temperatures (700, 800, 900)˚C, treated with HCl solution, filtrated, dried, the yield reached to 96% with purity of 99% when clay was mixed with NaOH by (2:1) and treated at 800˚C. Bioglass was prepared using isolated silica according to thermal program, the formation of bioglass was confirmed by XRD, IR and biodegradability test, which confirmed formation of hydroxyapatite, on the surface which confirmed the biological effectiveness of the prepared bioglass.

Periosteum-bone inspired hierarchical scaffold with endogenous piezoelectricity for neuro-vascularized bone regeneration

The development of scaffolds for repairing critical-sized bone defects heavily relies on establishing a neuro-vascularized network for proper penetration of nerves and blood vessels. Despite significant advancements in using artificial bone-like scaffolds infused with various agents, challenges remain. Natural bone tissue consists of a porous bone matrix surrounded by a neuro-vascularized periosteum, with unique piezoelectric properties essential for bone growth. Drawing inspiration from this assembly, we developed a periosteum-bone-mimicking bilayer scaffold with piezoelectric properties for regeneration of critical-sized bone defects. The periosteum-like layer of this scaffold features a double network hydrogel composed of chelated alginate, gelatin methacrylate, and sintered whitlockite nanoparticles, emulating the viscoelastic and piezoelectric properties of the natural periosteum. The bone-like layer is composed of a porous structure of chitosan and bioactive hydroxyapatite created through a biomineralization process. Unlike conventional bone-like scaffolds, this bioinspired bilayer scaffold significantly enhances osteogenesis, angiogenesis, and neurogenesis combined with low-intensity pulsed ultrasound-assisted piezoelectric stimulation. Such a scheme enhances neuro-vascularized bone regeneration in vivo. The results suggest that the bilayer scaffold could serve as an effective self-powered electrical stimulator to expedite bone regeneration under dynamic physical stimulation.

Functionalized polyaniline nanofibrils on lamellar structured zirconium for effective bone mineralization

The surface physiology of certain implant material has the ability to promote implant–cell signalling process through which a stable environment is formed. The formation of this favourable environment hastens the process of biomineralization and regeneration. In this context, Zirconium (Zr) when treated with alkali undergoes a surface modification which results in the development of a lamellar structured Zirconium (ATZ). Further, encapsulation of polyaniline (PAni) on ATZ was achieved through the electropolymerization technique which results in an effective and homogeneous electrodeposition of PAni nanofibrils on ATZ surface. A high resolution scanning electron microscope analysis (HR-SEM), phase analysis and functional group analysis were carried out confirming the semi-crystalline PAni nanofibrils braided on the ATZ surface. Potentiodynamic polarization studies of the coated sample exhibited higher Ecorr (−0.060 V) and lower icorr (0.007 µA/cm2) values signifying its better corrosion resistance behaviour in higher potentials coupled with lower electrochemical activity in the SBF medium. The porosity of PAni/ATZ nanofibril was 0.007 % and it provides an effective platform for implant-tissue attachment. The In-vitro biomineralization studies proved the bioactivity of PAni/ATZ which forms well-matured HAp spherules over the surface. Further, hemocompatibility studies of PAni/ATZ expressed a hemolytic rate of ∼0.39 % which denotes it’s biocompatible and non-hemolytic behaviour with the blood cells. Further, the coated sample on gram-positive and gram-negative bacteria causes demise of bacterial cell wall and exhibits higher inhibition percentage. In addition, a standard MTT assay of PAni/ATZ provides an effective support in maintaining cell viability and aids in proliferation of MG-63 cells. Thus, the results demonstrate that the nanoscale surface architecture of PAni/ATZ could serve as a potential and conducive environment for bone-implant interaction on the implant material for better osseointegration.

Bioresorption and Biomineralization of S53P4 Bioactive Glass in Neutral Tris Buffer and Citric Acid Solution.

In this study, S53P4 (53SiO2-23Na2O-20CaO-4P2O5) bioactive glass (BG) were prepared through a melt-milling process, and their bioresorption and biomineralization behavior was evaluated by in vitro dissolution under different solution conditions (neutral and acidic). The particle size of S53P4 BG was controlled by milling, and the in vitro dissolution evaluation was performed in tris buffer and citric acid solution for 21 days at 37 °C according to ISO 10993-14 (biological evaluation of medical devices). During dissolution, the ion release rate of S53P4 BG was confirmed to be three times faster in citric acid solution than that in tris buffer. Among them, the ion concentration of calcium and phosphorus initially increased and then gradually decreased, which is due to the biomineralization process. This process formed a new layer of particles on the surface of S53P4 BG, which was identified as a calcium-phosphate-based compound by X-ray diffraction analysis. Furthermore, the thickness of the layer was observed to be 273 nm in tris buffer and 34 nm in citric acid solution by focused-ion beam scanning electron microscopy, and the morphology of the particles comprising this layer was observed to be thicker and longer in tris buffer than that in citric acid solution. This difference is due to the citrate present in the citric acid solution interacting with the released calcium ions and inhibiting the formation of a new layer. Thus, the ion release of S53P4 BG was faster in citric acid solution than that in tris buffer, but the biomineralization process to form the calcium phosphate-based compound was more effective in tris buffer.

MicroED: Unveiling the Structural Chemistry of Plant Biomineralisation.

Plants are able to produce various types of crystals through metabolic processes, serving functions ranging from herbivore deterrence to photosynthetic efficiency. However, the structural analysis of these crystals has remained challenging due to their small and often imperfect nature, which renders traditional X-ray diffraction techniques unsuitable. This study explores the use of Microcrystal Electron Diffraction (microED) as a novel method for the structural analysis of plant-derived microcrystals, focusing on Armeria maritima (Milld.), a halophytic plant known for its biomineralisation capabilities. In this study, A. maritima plants were cultivated under controlled laboratory conditions with exposure to cadmium and thallium to induce the formation of crystalline deposits on their leaf surfaces. These deposits were analysed using microED, revealing the presence of sodium chloride (halite), sodium sulphate (thénardite), and calcium sulphate dihydrate (gypsum). Our findings highlight the potential of microED as a versatile tool in plant science, capable of providing detailed structural insights into biomineralisation processes, even from minimal and imperfect crystalline samples. The application of microED in this context not only advances the present understanding of A. maritima's adaptation to saline environments but also opens new avenues for exploring the structural chemistry of biomineralisation in other plant species. Our study advocates for the broader adoption of microED in botanical research, especially when dealing with challenging crystallographic problems.

New insights into uranium biomineralization mediated by Pseudomonas sp. WG2-6 in the presence of organic phosphorus: Promoting effect of extracellular polymeric substance and formation of U-P nanominerals

Microbial biomineralization significantly affects the uranium (U) behavior in the environment. However, the mechanism of microbial biomineralization of U is still not fully understood. In this study, a dominant bacterium (Pseudomonas sp. WG2–6) was isolated from U tail mining area. Abiotic precipitation tests demonstrated that U biomineralization was entirely attributed to the mediation of Pseudomonas sp. WG2–6 when the concentration ratio of exogenous β-glycerophosphate (SGP) to U was 10:1. Pseudomonas sp. WG2–6 exhibited strong immobilization ability towards U (97.59 %) according to batch experiments, and acylamide, carbonyls, and phosphate groups were the main functional groups that interacted with U. Besides, U mainly existed in the form of amorphous U-P complexes after biomineralization by Pseudomonas WG2–6, which could be converted into crystalline nano-minerals H2(UO2)2(PO4)2·8H2O in the presence of SGP. In particular, the formation and structural composition changes of extracellular polymeric substance (EPS) as well as the decrease in U4f binding energy were observed during the U biomineralization process of Pseudomonas sp. WG2–6 in the presence of SGP, indicating that EPS provided the nucleation site for the formation of stable biomineralized products. This work provides new insight into the mechanism of U microbial biomineralization and a theoretical basis for the remediation of U contaminated environments through microbial biomineralization.

Nucleus-Spike 3D Hierarchical Superstructures via a Lecithin-Mediated Biomineralization Approach.

3D hierarchical superstructures (3DHSs) are key products of nature's evolution and have raised wide interest. However, the preparation of 3DHSs composed of building blocks with different structures is rarely reported, and regulating their structural parameters is challenging. Herein, a simple lecithin-mediated biomineralization approach is reported for the first time to prepare gold 3DHSs composed of 0D nucleus and 1D protruding dendritic spikes. It is demonstrated that a hydrophobic complex by coordination of disulfiram (DSF) with a share of chloroauric acid is the key to forming the 3DHSs. Under the lecithin mediation, chloroauric acid is first reduced to form the 0D nucleus, followed by the spike growth through the reduction of the hydrophobic complex. The prepared 3DHSs possess well-defined morphology with a spike length of ≈95nm. Notably, the hierarchical spike density is systematically manipulated from 38.9% to 74.3% by controlling DSF concentrations. Moreover, the spike diameter is regulated from 9.2 to 12.9nm by selecting different lecithin concentrations to tune the biomineralization process. Finite-difference time-domain (FDTD) simulations reveal that the spikes form "hot spots". The dense spike structure endows the 3DHSs with sound performance in surface-enhanced Raman scattering (SERS) applications.

Dissolved silicon as a beneficial factor for biomineralization of disordered dolomite by a halophilic cyanobacterium

The genesis of sedimentary dolomite has long been a mystery in Earth science. It has been shown that the formation of low-temperature disordered dolomite, a crucial precursor of sedimentary dolomite, can be catalyzed by various heterotrophic microorganisms through organic mineralization. However, the potential role of cyanobacteria, which are common and cosmopolitan photoautotrophs in sedimentary environments, in the precipitation process of disordered dolomite has been largely underestimated. Moreover, recent emphasis on the beneficial influence of dissolved silicon (Si) in directly enhancing the Mg content in CaMg carbonates under oversaturated conditions has emerged. Nevertheless, the effect of dissolved Si on the formation of microbially-induced disordered dolomite remains poorly understood. To examine the influence and mechanisms of dissolved Si on the biomineralization of CaMg carbonates by cyanobacteria, biomineralization experiments were conducted using a halophilic cyanobacterium (Synechococcus elongatus FACHB-410) in solutions with varying concentrations of dissolved Si (ranging from 0 to 2 mM). Our findings revealed that the presence of dissolved Si resulted in higher Mg levels in the bio-precipitated CaMg carbonates compared to Si-free systems, with disordered dolomite formation observed at 2 mM Si. Importantly, an amorphous Mg-silicate phase formed prior to the crystallization of CaMg carbonates during the biomineralization process, intimately associated with the grains of CaMg carbonates. Subsequent abiotic carbonation experiments demonstrated its catalytic role in the nucleation of CaMg carbonates. These observations suggest that, in addition to the direct catalytic effect of dissolved Si, the positive role of Si in the biomineralization of disordered dolomite by cyanobacteria may also be attributed to the templating role of the neoformed amorphous Mg-silicate. These results have important implications for understanding the co-occurrence of Mg-silicate and dolomite observed in geological records.

INTRATEST TRACE ELEMENT VARIABILITY IN POLAR AND SUBPOLAR PLANKTIC FORAMINIFERA: INSIGHTS INTO VITAL EFFECTS, ONTOGENY, AND BIOMINERALIZATION PROCESSES

ABSTRACT To use planktic foraminiferal tests as paleoproxy substrates, it is necessary to delineate environmental versus biological controls on trace element incorporation. Here we utilize laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to explore interspecies, chamber-to-chamber, and intratest trace element (i.e., Mg, Na, Sr, Ba, Mn, Zn) variability in thickly-calcified specimens of the polar and subpolar planktic foraminifera Neogloboquadrina incompta, N. pachyderma, and Turborotalita quinqueloba collected from plankton tows in the Northern California Current. Among the study taxa, test Mg/Ca, Na/Ca, and Sr/Ca are likely dominantly controlled by depth habitat. The neogloboquadrinids record higher Ba/Ca and Mn/Ca and also show positive covariance between these elements, possibly due to calcifying in an oxygen-depleted marine snow microhabitat. Trace elements are found to be more enriched in the lamellar calcite than the outer chamber wall dominated by gametogenic crust. The data presented herein provide insight into potential vital effects, paleoproxy considerations, ontogeny, and biomineralization processes.

Aerobic bacteria induced biomineralization: effects of nutrient and calcium content on the nanostructure and chemical composition of simulated cement mixture

During the past two decades, aerobic bacteria induced biomineralization has gained popularity for autonomous sealing of cracks in concrete structures due to its environmentally friendly characteristics of carbon retention. However, the mechanism of the biomineralization induced by aerobic bacteria for concrete crack sealing is still unclear due to the complex chemistry of cement matrix. Also, as the main nutrient for bacterial growth, the effect of yeast extract (YE) on biomineralization should be properly evaluated. For the first time, this study investigates the effects of YE and calcium content on the development of nanostructure and chemical composition of cement matrix during the biomineralization process induced by aerobic bacteria Bacillus cohnii. The effects of calcium content were realized by constructing a simulated cement mixture consisting of calcium hydroxide and synthesised C-S-H with different C/S ratios. The effects of YE content were evaluated by the addition of different amounts of YE into simulated cement mixture with different C/S ratios. Results suggest that 10 g/l of YE can cause a high pH value of 10 and an unsuccessful growth of bacteria in simulated cement mixture with C/S ratios 0.6 and 0.8. Upon increasing the YE from 10 g/l to 20 g/l, the pH reduced from 10 to 9 and the bacteria was successfully grown. Higher amounts of bicarbonate ions can cause an enhanced decalcification of synthesised C-S-H rather than calcium hydroxide. The aerobic bacteria Bacillus cohnii showed superior performance on calcium absorption and calcite precipitation, being a promising way for practical concrete crack sealing.

Targeted regulation of autophagy using sorafenib-loaded biomineralization nanoenzyme for enhanced photodynamic therapy of hepatoma

Sorafenib (SF), a multi-targeted tyrosine kinase inhibitor, serves as a primary therapeutic modality for advanced liver cancer. Nonetheless, its clinical efficacy is hindered by various obstacles, such as limited bioavailability and inadequate accumulation. This study introduces a novel biomimetic mineralization enzyme, known as BSA@Pt/Ce6/SF@M (PCFM). The PCFM incorporates platinum (Pt) as a catalytic agent, SF as a molecular-targeted therapeutic agent, and Ce6 as a photosensitizer within liver cancer cell membranes. This strategy enables the combination of various anti-tumor treatments, such as photodynamic therapy (PDT) and autophagy induction, leading to increased bioavailability of SF and achieving a multidimensional synergistic anticancer effect. The PDT effect produced by Ce6 in PCFM greatly enhances SF-induced autophagy, effectively promoting autophagic cell death. Furthermore, Pt dissociates from the biomineralization process, acquiring peroxidase properties through chemokinetic reactions. This facilitates the catalysis of significant oxygen generation, addressing the challenge of hypoxia in the tumor microenvironment and improving the efficacy of PDT. Moreover, the SF further enhances therapeutic efficacy by inducing autophagy in response to energy deprivation, as indicated by the reduced levels of HIF-1α, p62, along with increased levels of ROS and LC3-Ⅱ/Ι. This biomineralization-based nanoenzyme exhibits strong anti-tumor characteristics, offering a novel strategy for overcoming challenges in liver cancer treatment.

Graphene Oxide/Black Phosphorus Functionalized Collagen Scaffolds with Enhanced Near-Infrared Controlled In Situ Biomineralization for Promoting Infectious Bone Defect Repair through PI3K/Akt Pathway.

Infectious bone defects resulting from surgery, infection, or trauma are a prevalent clinical issue. Current treatments commonly used include systemic antibiotics and autografts or allografts. Nevertheless, therapies come with various disadvantages, including multidrug-resistant bacteria, complications arising from the donor site, and immune rejection, which makes artificial implants desirable. However, artificial implants can fail due to bacterial infections and inadequate bone fusion after implantation. Thus, the development of multifunctional bone substitutes that are biocompatible, antibacterial, osteoconductive, and osteoinductive would be of great clinical importance. This study designs and prepares 2D graphene oxide (GO) and black phosphorus (BP) reinforced porous collagen (Col) scaffolds as a viable strategy for treating infectious bone defects. The fabricated Col-GO@BP scaffold exhibited an efficient photothermal antibacterial effect under near-infrared (NIR) irradiation. A further benefit of the NIR-controlled degradation of BP was to promote biomineralization by phosphorus-driven and calcium-extracted phosphorus in situ. The abundant functional groups in GO could synergistically capture the ions and enhance the in situ biomineralization. The Col-GO@BP scaffold facilitated osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSC) by leveraging its mild photothermal effect and biomineralization process, which upregulated heat shock proteins (HSPs) and activated PI3K/Akt pathways. Additionally, systematic in vivo experiments demonstrated that the Col-GO@BP scaffold obviously promotes infectious bone repair through admirable photothermal antibacterial performance and enhanced vascularization. As a result of this study, we provide new insights into the photothermal activity of GO@BP nanosheets, their degradation, and a new biological application for them.

Microbial Mineralization with Lysinibacillus sphaericus for Selective Lithium Nanoparticle Extraction.

Lithium is a critical mineral in a wide range of current technologies, and demand continues to grow with the transition to a green economy. Current lithium mining and extraction practices are often highly ecologically damaging, in part due to the large amount of water and energy they consume. Biomineralization is a natural process that transforms inorganic precursors to minerals. Microbial biomineralization has potential as an ecofriendly alternative to current lithium extraction techniques. This work demonstrates Lysinibacillus sphaericus biomineralization of lithium chloride to lithium hydroxide. Quantitative analysis of biomineralized lithium via the 2-(2-hydroxyphenyl)-benzoxazole fluorescence assay reveals significantly greater recovery with L. sphaericus than without. Furthermore, L. sphaericus biomineralization is specific to lithium over sodium. The nanoparticles produced were further characterized via Fourier transform infrared and transmission electron microscopy analysis as crystalline lithium hydroxide, which is an advanced functional material. Finally, ESI-LC/MS was used to identify several proteins involved in this microbial biomineralization process, including the S-layer protein. Through the isolation of L. sphaericus ghosts, this work shows that the S-layer protein alone plays a critical role in the biomineralization of crystalline lithium hydroxide nanoparticles. Through this study of microbial biomineralization of lithium with L. sphaericus, there is potential to develop innovative and environmentally friendly extraction techniques.

Reconstruction of calcite (10.4) manifests itself in the tip-assisted diffusion of water

Calcite (calcium carbonate) is the most abundant carbonate in the Earth's crust. Due to its omnipresence it plays a prominent role in fields such as geochemistry, biomineralization and industrial processes. Moreover, the interaction of water with the most stable cleavage plane, calcite (10.4), has been studied intensively, elucidating atomic-scale details of water binding and structure formation on this surface. Interestingly, calcite (10.4) reconstructs under ultrahigh vacuum conditions, exhibiting a (2 × 1) surface unit cell. Although first indications of this reconstruction have been presented more than 20 years ago, a clear confirmation of the existence has been provided only very recently. Here, we study the tip-assisted diffusion of water molecules on calcite (10.4) under ultrahigh vacuum conditions. By recording images series using dynamic atomic force microscopy we follow the movement of water molecules on the surface kept at 140 K. Analyzing the change in consecutive images allows for elucidating details of the molecular movement on the surface. Most notably, the analysis reveals that water molecules occupy one type of adsorption position exclusively, while the other type is not adopted. Our analysis thus demonstrates that the (2 × 1) reconstruction manifests itself in the movement of single water molecules on this surface.

Multimodal analysis of renal stones to explore new biomarkers of urolithiasis

Despite advances in minimally invasive surgery, urolithiasis still recurs within the first five years after the first episode in more than 50% of patients. Researchers continue to search for new crystallisation inhibitors, metaphylaxis strategies and laser sources for stone destruction. Therefore, to achieve these goals, it is necessary to study kidney stones not only as the result of an isolated process of pathological biomineralisation in the human body, but also as a biogenic mineral or rock that obeys universal patterns and has certain properties. Consequently, kidney stones need to be studied using methods that are widely used in the geological sciences for the study of minerals, such as computed microtomography and petrological analysis. In this review, the properties of kidney stones studied using various research methods used in geosciences are discussed. These properties are also considered as new biomarkers of urolithiasis. This review discusses how new data from multimodal stone analysis can be used to develop personalised metaphylaxis and treatment strategies for all types of urolithiasis, including the most common idiopathic calcium-oxalate urolithiasis.

Controls on the Barium and Strontium Isotopic Records of Water Chemistry Preserved in Freshwater Bivalve Shells.

Biogenic carbonates, including bivalve shells, record past environmental conditions, but their interpretation requires understanding environmental and biological factors that affect trace metal uptake. We examined stable barium (δ138Ba) and radiogenic strontium (87Sr/86Sr) isotope ratios in the aragonite shells of four native freshwater mussel species and two invasive species in five streams and assessed the effects of species identity, growth rate, and river water chemistry on shell isotopic composition. Shells were robust proxies for Sr, accurately reflecting 87Sr/86Sr ratios of river water, regardless of species or growth rate. In contrast, shell δ138Ba values, apart from invasive Corbicula fluminea, departed widely from those of river water and varied according to species and growth rate. Apparent fractionation between river water and the shell (Δ138Bashell-water) reached -0.86‰, the greatest offset observed for carbonate minerals. The shell deposited during slow growth periods was more enriched in lighter Ba isotopes than the rapidly deposited shell; thus, this phenomenon cannot be explained by aragonite precipitation kinetics. Instead, biological ion transport processes linked to growth rate may be largely responsible for Ba isotope variation. Our results provide information necessary to interpret water chemistry records preserved in shells and provide insights into biomineralization processes and bivalve biochemistry.

Fungal carbonatogenesis process mediates zinc and chromium removal via statistically optimized carbonic anhydrase enzyme

IntroductionWith rapid elevation in population, urbanization and industrialization, the environment is exposed to uncontrolled discharge of effluents filled with broad-spectrum toxicity, persistence and long-distance transmission anthropogenic compounds, among them heavy metals. That put our ecosystem on the verge or at a stake of drastic ecological deterioration, which eventually adversely influence on public health. Therefore, this study employed marine fungal strain Rhodotorula sp. MZ312369 for Zn2+ and Cr6+ remediation using the promising calcium carbonate (CaCO3) bioprecipitation technique, for the first time.ResultsInitially, Plackett–Burman design followed by central composite design were applied to optimize carbonic anhydrase enzyme (CA), which succeeded in enhancing its activity to 154 U/mL with 1.8-fold increase comparing to the basal conditions. The potentiality of our biofactory in remediating Zn2+ (50 ppm) and Cr6+ (400 ppm) was monitored through dynamic study of several parameters including microbial count, CA activity, CaCO3 weight, pH fluctuation, changing the soluble concentrations of Ca2+ along with Zn2+ and Cr6+. The results revealed that 9.23 × 107 ± 2.1 × 106 CFU/mL and 10.88 × 107 ± 2.5 × 106 CFU/mL of cells exhibited their maximum CA activity by 124.84 ± 1.24 and 140 ± 2.5 U/mL at 132 h for Zn2+ and Cr6+, respectively. Simultaneously, with pH increase to 9.5 ± 0.2, a complete removal for both metals was observed at 168 h; Ca2+ removal percentages recorded 78.99% and 85.06% for Zn2+ and Cr6+ remediating experiments, respectively. Further, the identity, elemental composition, functional structure and morphology of bioremediated precipitates were also examined via mineralogical analysis. EDX pattern showed the typical signals of C, O and Ca accompanying with Zn2+ and Cr6+ peaks. SEM micrographs depicted spindle, spherical and cubic shape bioliths with size range of 1.3 ± 0.5–23.7 ± 3.1 µm. Meanwhile, XRD difractigrams unveiled the prevalence of vaterite phase in remediated samples. Besides, FTIR profiles emphasized the presence of vaterite spectral peaks along with metals wavenumbers.ConclusionCA enzyme mediated Zn2+ and Cr6+ immobilization and encapsulation inside potent vaterite trap through microbial biomineralization process, which deemed as surrogate ecofriendly solution to mitigate heavy metals toxicity and restrict their mobility in soil and wastewater.