Amorphous calcium carbonate controls avian eggshell mineralization: A new paradigm for understanding rapid eggshell calcification

Translucent eggs of laying hens: a review

Eggshell quality is a significant characteristic that influences consumer preferences. Eggshell translucency is a common defect in the appearance of eggshells, which are characterized by gray spots that are visible to the naked eye under natural light. The presence of various defects resulting from eggshell translucency has caused a decrease in consumer willingness to purchase eggs, leading to considerable economic losses in the egg industry. Although the impact of eggshell translucency on food safety, egg quality, and hatchability has been extensively investigated, the classification and causes of eggshell translucency remain unclear and lack a systematic summary. In recent studies, new interpretations of evaluation methods and causes of eggshell translucency have been proposed, along with numerous innovative solutions. Therefore, this paper aims to provide a comprehensive review of the evaluation methods, classification, causes, effects, and influencing factors of eggshell translucency and to summarize the treatments for translucent eggs. We believe that this review will serve as a valuable reference for researchers involved in the study of translucent eggs.

Effects of dietary free fatty acid content and degree of fat saturation on tibia bone properties of laying hens

Acid oils and fatty acid distillates are fat by-products of the refining process of edible oils and are characterized by their high proportion of free fatty acids (FFA). While lipids are essential in poultry diets, their chemical structure may interfere with calcium absorption. Therefore, this study investigated the effects of dietary FFA content and the degree of fat saturation on bone metabolism in commercial layers. For 15-wk, a total of 144 laying hens (19-wk-old) were randomly assigned to 8 treatments (6 replicates with 3 birds each), which were obtained by gradually replacing crude soybean oil (rich in unsaturated fatty acids [UFA]) with soybean acid oil (rich in UFA and FFA), or crude palm oil (rich in saturated fatty acids [SFA]) with palm fatty acid distillate (rich in SFA and FFA). Following a 2 × 4 factorial design, 4 UFA-rich and 4 SFA-rich diets were created with varying FFA content: 10, 20, 30, and 45%. Tibiae (6 birds/treatment) were collected at the end of the trial for the assessment of mineral composition, morphological properties, and mechanical characteristics. The data were analyzed using a 2-way ANOVA with the GLM procedure. Orthogonal polynomial contrasts were employed to determine the linear effect of increasing %FFA, with statistical significance set at P < 0.05. The degree of saturation was found to negatively impact on calcium and phosphorus bone content, with higher levels found in soybean-based diets (P < 0.001). A significant interaction was observed for medullary bone mineral content, showing a linear decrease as the dietary %FFA increased (P < 0.05) in palm diets. In contrast, morphological and mechanical bone traits, total ash content, and cortical bone mineral composition remained unaffected (P > 0.05). These results suggest that the degree of fat saturation exerts a greater impact than FFA content on bone mineral metabolism, supporting the commercial use of fat by-products rich in FFA in laying hen diets, at least during the early stages of the laying cycle.

The relationship between phosphorus retention and fibroblast growth factor 23 in broiler breeders

Previous studies with broiler breeders indicate a P retention threshold when fed daily dietary levels of non-phytate P (NPP) exceeding 320 mg. Fibroblast growth factor 23 (FGF23) is a hormone secreted by osteocytes which modulates P retention and could be the biological agent which controls the P threshold in breeders. To evaluate the relationship between FGF23 and the P retention threshold, a 4-wk study with 32-wk-old breeders was conducted with 6 dietary treatments with daily NPP intake of 216 to 576 mg/d/h with increments of 80 mg/kg diet. The goals were 1) to elucidate how plasma FGF23 corresponds with the P retention threshold in broiler breeders and 2) to determine the amount of P for optimal egg production and bone health. Results showed that between daily 288 mg and 360 mg dietary NPP intake, P retention decreased from 33 to 26% but FGF23 levels increased from 130 pg/mL to 220 pg/mL with increasing NPP. The elevation of plasma FGF23 between the range of 288 mg to 360 mg dietary NPP/d intake suggests that FGF23 is related to the P retention threshold and may be the major hormone for regulating physiological P levels when intake of daily dietary P levels are increased above 288 mg NPP.

Hydric Environment and Chemical Composition Shape Non-avian Reptile Eggshell Absorption

The amniotic egg fulfils a critical role in reproduction by serving as an interface between the external environment and the embryo. Because non-avian reptiles are rarely incubated, they must be heated by, and absorb water from, the oviposition site for the developing embryo. The mechanisms by which they absorb sufficient, but not excess, water and how these mechanisms vary with local habitat is largely unknown, despite its significance to their evolution. Here, we first performed histology, Fourier-transform infrared spectroscopy and dynamic vapor sorption experiments to elucidate the mechanisms of eggshell absorption for 56 reptile species. Then, we used phylogenetic comparative analysis to test the hypothesis that the absorptive capacity of reptile eggshells increases with aridity of the environment. We found that water absorption increases in the presence of a superficial mucopolysaccharide layer and decreases with increased calcium content. We found that eggs from arid environments have highly absorbent eggshells, but only in species with weakly calcified shells. Our results suggest that reptile eggshells have over evolutionary time tuned absorptive capacity to environmental moisture level. Since these eggs often must sustain conflicting constraints, they may serve as inspirations for new biomimetic materials, such as water filtering membranes or humidity sensors.

3D Printed Eggshell Microparticle-Laden Thermoplastic Scaffolds for Bone Tissue Engineering

Three-dimensional (3D) printing, an additive manufacturing technique, is increasingly used in the field of tissue engineering. The ability to create complex structures with high precision makes the 3D printing of this material a preferred method for constructing personalized and functional materials. However, the challenge lies in developing affordable and accessible materials with the desired physiochemical and biological properties. In this study, we used eggshell microparticles (ESPs), an example of bioceramic and unconventional biomaterials, to reinforce thermoplastic poly(ε-caprolactone) (PCL) scaffolds via extrusion-based 3D printing. The goal was to conceive a sustainable, affordable, and unique personalized medicine approach. The scaffolds were fabricated with varying concentrations of eggshells, ranging from 0 to 50% (w/w) in the PCL scaffolds. To assess the physicochemical properties, we employed scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction analysis. Mechanical properties were evaluated through compression testing, and degradation kinetics were studied through accelerated degradation with the remaining mass ranging between 89.4 and 28.3%. In vitro, we evaluated the characteristics of the scaffolds using the MC3T3-E1 preosteoblasts over a 14 day period. In vitro characterization involved the use of the Alamar blue assay, confocal imaging, and real-time quantitative polymerase chain reaction. The results of this study demonstrate the potential of 3D printed biocomposite scaffolds, consisting of thermoplastic PCL reinforced with ESPs, as a promising alternative for bone-graft applications.

Implications of intracrystalline OC17 on the protection of lattice incorporated proteins

Biogenic CaCO3 formation is regulated by crystallization proteins during crystal growth. Interactions of proteins with nascent mineral surfaces trigger proteins to be incorporated into the crystal lattice. As a result of incorporation, these intracrystalline proteins are protected in the lattice, an example of which is ancient eggshell proteins that have persisted in CaCO3 for thousands of years even under harsh environmental conditions. OC17 is an eggshell protein known to interact with CaCO3 during eggshell formation during which OC17 becomes incorporated into the lattice. Understanding protein incorporation into CaCO3 could offer insights into protein stability inside crystals. Here, we study the protection of OC17 in the CaCO3 lattice. Using thermogravimetric analysis we show that the effect of temperature on intracrystalline proteins of eggshells is negligible below 250 °C. Next, we show that lattice incorporation protects the OC17 structure despite a heat-treatment step that is shown to denature the protein. Because incorporated proteins need to be released from crystals, we verify metal chelation as a safe crystal dissolution method to avoid protein denaturation during reconstitution. Finally, we optimize the recombinant expression of OC17 which could allow engineering OC17 for engineered intracrystalline entrapment studies.

Organic Trace Elements Improve the Eggshell Quality via Eggshell Formation Regulation during the Late Phase of the Laying Cycle

The quality of eggshells is critical to the egg production industry. The addition of trace elements has been shown to be involved in eggshell formation. Organic trace elements have been found to have higher biological availability than inorganic trace elements. However, the effects of organic trace elements additive doses on eggshell quality during the laying period of commercial laying hens required further investigation. This experiment aims to explore the potential mechanisms of different doses of organic trace elements replacing inorganic elements to remodel the eggshell quality of egg-laying hens during the laying period. A total of 360 healthy hens (Lohmann Pink, 45-week-old) were randomly divided into four treatments, with six replications per treatment and 15 birds per replication. The dietary treatments included a basal diet supplemented with inorganic iron, copper, zinc and manganese at commercial levels (CON), a basal diet supplemented with organic iron, copper, zinc and manganese at 20% commercial levels (LOT), a basal diet supplemented with organic iron, copper, zinc and manganese at 30% commercial levels (MOT), and a basal diet supplemented with organic iron, copper, zinc and manganese at 40% commercial levels (HOT). The trial lasted for 8 weeks. The results of the experiment showed that the replacement of organic trace elements did not significantly affect the production performance of laying hens (p > 0.05). Compared with inorganic trace elements, the MOT and HOT groups improved the structure of the eggshells, enhanced the hardness and thickness of the eggshells, increased the Haugh unit of the eggs, reduced the proportion of the mammillary layer in the eggshell, and increased the proportion of the palisade layer (p < 0.05). In addition, the MOT and HOT groups also increased the enzyme activity related to carbonate transport in the blood, the expression of uterine shell gland-related genes (CA2, OC116, and OCX32), and the calcium and phosphorus content in the eggshells (p < 0.05). We also found that the MOT group effectively reduced element discharge in the feces and enhanced the transportation of iron (p < 0.05). In conclusion, dietary supplementation with 30-40% organic micronutrients were able to improve eggshell quality in aged laying hens by modulating the activity of serum carbonate transport-related enzymes and the expression of eggshell deposition-related genes.

Comparative Analysis of the Ultrastructure, Bubble Pores, and Composition of Eggshells of Dwarf Layer-White and Guinea Fowl

The decrease in eggshell quality seriously affects production efficiency. Guinea fowl (GF) eggs possess strong eggshells because of their unique crystal structure, and few systematic studies have compared laying hen and GF eggs. Sixty eggs were collected from both 40-week-old Dwarf Layer-White (DWL-White) laying hens and GF, and the eggshell quality, ultrastructure, bubble pores, and composition were measured. The results showed that the DWL-White eggs had a higher egg weight and a lower eggshell strength, strength per unit weight, thickness, and ratio than the GF eggs (p < 0.01). There were differences in the mammillary layer thickness ratio, the effective layer thickness ratio, the quantity of bubble pores (QBPs), the ratio of the sum of the area of bubble pores to the area of the eggshell in each image (ARBE), and the average area of bubble pores (AABPs) between the DWL-White and GF eggs (p < 0.01). The composition analysis demonstrated that there were differences in the organic matter, inorganic matter, calcium, and phosphorus between the DWL-White and GF eggs (p < 0.01). There were positive associations between the mammillary knob number in the image and the QBPs and ARBE and a negative correlation with the AABPs in the DWL-White eggs (p < 0.01). This study observed distinctions that offer new insights into enhancing eggshell quality.

Effects of 28 h ahemeral light cycle on production performance, egg quality, blood parameters, and uterine characteristics of hens during the late laying period

This study aimed to systematically determined the effect of 28 h ahemeral light cycle on production performance, egg quality, blood parameters, uterine morphological characteristics, and gene expression of hens during the late laying period. At 74 wk, 260 Hy-Line Brown layers were randomly divided into 2 groups of 130 birds each and in duplicates. Both a regular (16L:8D) and an ahemeral light cycle (16L:12D) were provided to the hens. The oviposition pattern in an ahemeral cycle shifted into darkness, with oviposition mostly occurring 3 to 5 h after light out. Production performance was unaffected by light cycle (P > 0.05). Nonetheless, compared to the normal group, the ahemeral group exhibited increased egg weight, eggshell weight, eggshell percentage, yolk percentage, eggshell thickness, and eggshell strength (P < 0.05). There were rhythmic changes in the uterine morphological structure in both cycles, however, the ahemeral group maintained a longer duration and had more uterine folds than the normal group. In the ahemeral cycle, the phases of the CLOCK and PER2 genes were phase-advanced for 3.96 h and 4.54 h compared to the normal cycle. The PHLPP1 gene, which controls clock resetting, exhibited a substantial oscillated rhythm in the ahemeral group (P < 0.05), while the expression of genes presenting biological rhythm, such as CRY2 and FBXL3, was rhythmically oscillated in normal cycle (P < 0.05). The ITPR2 gene, which regulates intracellular Ca2+ transport, displayed a significant oscillated rhythm in ahemeral alone (P < 0.05), while the CA2 gene, which presents biomineralization, rhythmically oscillated in both cycles (P < 0.05). The ahemeral cycle caused 2.5 h phase delays in the CA2 gene compared to the normal cycle. In conclusion, the 28 h ahemeral light cycle preserved the high condition of the uterine folds and changed the uterine rhythms of CLOCK, PER2, ITPR2, and CA2 gene expression to improve ion transport and uterine biomineralization.

Guinea fowl eggshell structural analysis at different scales reveals how organic matrix induces microstructural shifts that enhance its mechanical properties

Guinea fowl eggshells have an unusual structural arrangement that is different from that of most birds, consisting of two distinct layers with different microstructures. This bilayered organization, and distinct microstructural characteristics, provides it with exceptional mechanical properties. The inner layer, constituting about one third of the eggshell thickness, contains columnar calcite crystal units arranged vertically as in most bird shells. However, the thicker outer layer has a more complex microstructural arrangement formed by a switch to smaller calcite domains with diffuse/interlocking boundaries, partly resembling the interfaces seen in mollusk shell nacre. The switching process that leads to this remarkable second-layer microstructure is unknown. Our results indicate that the microstructural switching is triggered by changes in the inter- and intracrystalline organic matrix. During production of the outer microcrystalline layer in the later stages of eggshell formation, the interactions of organic matter with mineral induce an accumulation of defects that increase crystal mosaicity, instill anisotropic lattice distortions in the calcite structure, interrupt epitaxial growth, reduce crystallite size, and induce nucleation events which increase crystal misorientation. These structural changes, together with the transition between the layers and each layer having different microstructures, enhance the overall mechanical strength of the Guinea fowl eggshell. Additionally, our findings provide new insights into how biogenic calcite growth may be regulated to impart unique functional properties. STATEMENT OF SIGNIFICANCE: Avian eggshells are mineralized to protect the embryo and to provide calcium for embryonic chick skeletal development. Their thickness, structure and mechanical properties have evolved to resist external forces throughout brooding, yet ultimately allow them to crack open during chick hatching. One particular eggshell, that of the Guinea fowl, has structural features very different from other galliform birds - it is bilayered, with an inner columnar mineral structure (like in most birds), but it also has an outer layer with a complex microstructure which contributes to its superior mechanical properties. This work provides novel and new fundamental information about the processes and mechanisms that control and change crystal growth during the switch to microcrystalline domains when the second outer layer forms.

Study on Carbonation of Porcine Blood Hydrogel in the Composite Mortar of Ancient Chinese Architectural Painting

In the ancient Chinese recipe for composite mortar used in the construction of ground layers for architectural painting, the mixture of porcine blood and lime water is one of the constituent materials. Herein, according to the traditional recipe, the interaction between porcine blood and lime water was systematically and deeply investigated. The experimental investigation demonstrated that porcine blood mixed with lime water at the ratio found in the recipe can form a hydrogel with a hydrophobic surface. During air-drying, the lime water in porcine blood hydrogel can react with CO2 to form calcium carbonate. The crystal morphology of the formed calcium carbonate depends on the surrounding micro-environment of calcium ions in the porcine blood hydrogel. The formed morphology of calcium carbonate includes small calcite crystallites, small graininess calcite crystals with round features, calcite aggregates with layered ladder-like structures, and amorphous calcium carbonate (ACC). Interestingly, the calcium carbonate formed in the inner part of the porcine blood hydrogel exhibits lamellar distribution due to a Liesegang pattern formation. Based on the findings that the porcine blood hydrogel has surface hydrophobicity and brittleness, it can be predicted that in the preparation process of composite mortar for ancient building color painting base course, porcine blood used in the form of a hydrogel is not only easier to be dispersed in hydrophobic tung oil than in liquid porcine blood but also the affinity between porcine blood gel and tung oil is enhanced. As constituent material dispersed in the composite mortar, the layered distribution of calcium carbonate in the porcine blood hydrogel may presumably be beneficial to reduce the internal stress of the composite mortar material.

TMT-based quantitative proteomic analysis reveals eggshell matrix protein changes correlated with eggshell quality in Jing Tint 6 laying hens of different ages

The decline in eggshell quality resulting from aging hens poses a threat to the financial benefits of the egg industry. The deterioration of eggshell quality with age can be attributed to changes in its ultrastructure and chemical composition. Specific matrix proteins in eggshells have a role in controlling crystal growth and regulating structural organization. However, the variations in ultrastructure and organic matrix of eggshells in aging hens remain poorly understood. This study assessed the physical traits, mechanical quality, chemical content, as well as the microstructural and nanostructural properties of eggs from Jing Tint 6 hens at 38, 58, 78, and 108 wk of age. Subsequently, a quantitative proteomic analysis was conducted to identify differences in protein abundance in eggshells between the ages of 38 and 108 wk. The results indicated a notable decline in shell thickness, breaking strength, index, fracture toughness, and stiffness in the 108-wk-age group compared to the other groups (P < 0.05). The ultrastructure variations primarily involved an increased ratio of the mammillary layer and a reduced thickness of the effective layer of eggshell in the 108-wk-age group (P < 0.05). However, no significant differences in eggshell compositions were observed among the various age groups (P > 0.05). Proteomic analysis revealed the identification of 76 differentially expressed proteins (DEPs) in the eggshells of the 38-wk-age group and 108-wk-age group, which comprised proteins associated with biomineralization, calcium ion binding, immunity, as well as protein synthesis and folding. The downregulation of ovocleidin-116, osteopontin, and calcium-ion-related proteins, together with the upregulation of ovalbumin, lysozyme C, and antimicrobial proteins, has the potential to influence the structural organization of the eggshell. Therefore, the deterioration of eggshell quality with age may be attributed to the alterations in ultrastructure and the abundance of matrix proteins.

Circadian regulation of calcium and phosphorus homeostasis during the oviposition cycle in laying hens

Maintenance of calcium and phosphorus homeostasis in laying hens is crucial for preservation of skeletal integrity and eggshell quality, though physiological regulation of these systems is incompletely defined. To investigate changes in mineral and vitamin D3 homeostasis during the 24-h egg formation cycle, 32-wk-old commercial laying hens were sampled at 1, 3, 4, 6, 7, 8, 12, 15, 18, 21, 23, and 24 h post-oviposition (HPOP; n ≥ 4). Ovum location and egg calcification stage were recorded, and blood chemistry, plasma vitamin D3 metabolites, circulating parathyroid hormone (PTH), and expression of genes mediating uptake and utilization of calcium and phosphorus were evaluated. Elevated levels of renal 25-hydroxylase from 12 to 23 HPOP suggest this tissue might play a role in vitamin D3 25-hydroxylation during eggshell calcification. In shell gland, retinoid-x-receptor gamma upregulation between 6 and 8 HPOP followed by subsequently increased vitamin D receptor indicate that vitamin D3 signaling is important for eggshell calcification. Increased expression of PTH, calcitonin, and fibroblast growth factor 23 (FGF23) receptors in the shell gland between 18 and 24 HPOP suggest elevated sensitivity to these hormones toward the end of eggshell calcification. Shell gland sodium-calcium exchanger 1 was upregulated between 4 and 7 HPOP and plasma membrane calcium ATPase 1 increased throughout eggshell calcification, suggesting the primary calcium transporter may differ according to eggshell calcification stage. Expression in shell gland further indicated that bicarbonate synthesis precedes transport, where genes peaked at 6 to 7 and 12 to 18 HPOP, respectively. Inorganic phosphorus transporter 1 (PiT-1) expression peaked in kidney between 12 and 15 HPOP, likely to excrete excess circulating phosphorus, and in shell gland between 18 and 21 HPOP. Upregulation of FGF23 receptors and PiT-1 during late eggshell calcification suggest shell gland phosphorus uptake is important at this time. Together, these findings identified potentially novel hormonal pathways involved in calcium and phosphorus homeostasis along with associated circadian patterns in gene expression that can be used to devise strategies aimed at improving eggshell and skeletal strength in laying hens.

Zinc Oxide Nanoparticles Significant Role in Poultry and Novel Toxicological Mechanisms

Zinc oxide nanoparticles (ZnO NPs) have involved a lot of consideration owing to their distinctive features. The ZnO NPs can be described as particularly synthesized mineral salts via nanotechnology, varying in size from 1 to 100 nm, while zinc oxide (ZnO), it is an inorganic substrate of zinc (Zn). The Zn is a critical trace element necessary for various biological and physiological processes in the body. Studies have revealed ZnO NPs' efficient immuno-modulatory, growth-promoting, and antimicrobial properties in poultry birds. They offer increased bioavailability as compared to their traditional sources, producing better results in terms of productivity and welfare and consequently reducing ecological harm in the poultry sector. However, they have also been reported for their toxicological effects, which are size, shape, concentration, and exposure route dependent. The investigations done so far have yielded inconsistent results, therefore, a lot of additional studies and research are required to clarify the harmful consequences of ZnO NPs and to bring them to a logical end. This review explores an overview of efficient possible role of ZnO NPs, while comparing them with other nutritional Zn sources, in the poultry industry, primarily as dietary supplements that effect the growth, health, and performance of the birds. In addition to the anti-bacterial mechanisms of ZnO NPs and their promising role as antifungal, and anti-colloidal agent, this paper also covers the toxicological mechanisms of ZnO NPs and their consequent toxicological hazards to vital organs and the reproductive system of poultry birds.

Attaching organic fibers to mineral: The case of the avian eggshell

Bird eggs possess a mineralized eggshell with a soft underlying fibrous membrane. These dissimilar material layers successfully evolved a structural attachment to each other as a conserved avian reproduction strategy essential to avian embryonic development, growth, and hatching of the chick. To understand how organic membrane fibers attach to shell mineral (calcite), 3D multiscale imaging including X-ray and electron tomography coupled with deep learning-based feature segmentation was used to show how membrane fibers are organized and anchored into shell mineral. Whole fibers embed into mineral across the microscale, while fine mineral projections (granules/spikes) insert into fiber surfaces at the nanoscale, all of which provides considerable surface area and multiscale anchorage at the organic-inorganic interface between the fibrous membrane and the shell. Such a reciprocal anchorage system occurring at two different length scales between organic fibers and inorganic mineral provides a secure attachment mechanism for avian eggshell integrity across two dissimilar materials.

Apatite-coated outer layer eggshell membrane: A novel osteoinductive biohybrid composite for guided bone/tissue regeneration

Hybrid biomimetic materials aim to replicate the organic-inorganic constructs of mineralized tissues. During eggshell formation, the outer surface of the eggshell membrane (ESM) promotes calcium carbonate nucleation, while the inner one prevents mineralization toward the egg white and yolk. In the current study, the outer surface of the ESM acted as a heteronucleant in calcium phosphate precipitation by the vapor diffusion sitting drop method, while the inner one remained unmineralized. The aim was to fabricate a 2D biomaterial with dual functions, osteoinductive on one side and protective against cell invasion on the other side. The microstructural, physicochemical, morphological, and mechanical properties of the mineralized ESM were characterized by XRD, TGA, XPS, FTIR/Raman, HR-SEM, and mechanical testing techniques. The cytocompatibility and osteoinductive ability were assessed by biological assays of cell viability, proliferation, and osteogenic differentiation on human mesenchymal stromal cells (hMSCs). Results indicate that the outer surface of the ESM induces the heterogeneous precipitation of carbonate-apatite phase depicting biomimetic features. In addition, the apatite/ESM shows a much higher cytocompatibility than the pristine ESM and promotes the osteogenic differentiation of hMSCs more efficiently. Overall, the apatite/ESM composite exhibits compositional, crystalline, mechanical, and biological properties that resemble those of mineralized tissues, rendering it an approachable and novel material especially useful in guided tissue/bone regeneration.

Effect of Dietary Supplemental Zinc on Laying Performance, Egg Quality, and Plasma Hormone Levels of Breeding Pigeons

This study aimed to evaluate the dietary zinc requirement of parental pigeons for better laying and reproductive performance, egg quality, sex hormones, and mineral content in eggs. A total of 160 pairs of healthy American Silver King pigeons were randomly assigned to five treatments of eight replicate cages each with four pairs of birds per cage, and fed a basal diet without zinc supplementation or the basal diet supplemented with 30, 60, 90, and 120 mg of zinc/kg (ZnSO₄·7H₂O). The experiment lasted for 45 days, including two laying cycles. Results indicated the egg production rate (P = 0.081), egg shape index (P = 0.038), egg eggshell percentage (P = 0.070), and zinc and calcium contents (P < 0.01) tended to be affected or significantly affected by zinc addition. They increased quadratically with dietary zinc levels (P < 0.05). Besides, shell thickness (P = 0.069), plasma testosterone (P = 0.008), LH, and carbonic anhydrase contents (P < 0.05) tended to be affected or significantly affected by zinc addition. They increased linearly as dietary zinc level increased (P < 0.05). Compared with the control, 60 mg/kg zinc addition increased egg production rate, egg shape index, zinc and calcium contents in eggshell, and plasma testosterone concentration in pigeons (P < 0.05), and tended to increase the eggshell percentage (P = 0.07). Besides, supplemental 120 mg/kg zinc had higher shell thickness and LH content than control (P < 0.05), but had no difference with 60 mg/kg zinc addition. In conclusion, the supplementation of zinc at the level of 60 mg/kg to basal diet improved laying performance by increasing eggshell quality and sex hormone levels of breeding pigeons.

Unveiling the secret of ancient Maya masons: Biomimetic lime plasters with plant extracts

Ancient Maya produced some of the most durable lime plasters on Earth, yet how this was achieved remains a secret. Here, we show that ancient Maya plasters from Copan (Honduras) include organics and have a calcite cement with meso-to-nanostructural features matching those of calcite biominerals (e.g., shells). To test the hypothesis that the organics could play a similar toughening role as (bio)macromolecules in calcium carbonate biominerals, we prepared plaster replicas adding polysaccharide-rich bark extracts from Copan's local trees following an ancient Maya building tradition. We show that the replicas display similar features as the organics-containing ancient Maya plasters and demonstrate that, as in biominerals, in both cases, their calcite cement includes inter- and intracrystalline organics that impart a marked plastic behavior and enhanced toughness while increasing weathering resistance. Apparently, the lime technology developed by ancient Maya, and likely other ancient civilizations that used natural organic additives to prepare lime plasters, fortuitously exploited a biomimetic route for improving carbonate binders performance.

Evidence for heterothermic endothermy and reptile-like eggshell mineralization in Troodon, a non-avian maniraptoran theropod

The dinosaur-bird transition involved several anatomical, biomechanical, and physiological modifications of the theropod bauplan. Non-avian maniraptoran theropods, such as Troodon, are key to better understand changes in thermophysiology and reproduction occurring during this transition. Here, we applied dual clumped isotope (Δ47 and Δ48) thermometry, a technique that resolves mineralization temperature and other nonthermal information recorded in carbonates, to eggshells from Troodon, modern reptiles, and modern birds. Troodon eggshells show variable temperatures, namely 42 and 29 ± 2 °C, supporting the hypothesis of an endothermic thermophysiology with a heterothermic strategy for this extinct taxon. Dual clumped isotope data also reveal physiological differences in the reproductive systems between Troodon, reptiles, and birds. Troodon and modern reptiles mineralize their eggshells indistinguishable from dual clumped isotope equilibrium, while birds precipitate eggshells characterized by a positive disequilibrium offset in Δ48. Analyses of inorganic calcites suggest that the observed disequilibrium pattern in birds is linked to an amorphous calcium carbonate (ACC) precursor, a carbonate phase known to accelerate eggshell formation in birds. Lack of disequilibrium patterns in reptile and Troodon eggshells implies these vertebrates had not acquired the fast, ACC-based eggshell calcification process characteristic of birds. Observation that Troodon retained a slow reptile-like calcification suggests that it possessed two functional ovaries and was limited in the number of eggs it could produce; thus its large clutches would have been laid by several females. Dual clumped isotope analysis of eggshells of extinct vertebrates sheds light on physiological information otherwise inaccessible in the fossil record.

Eggshell Membrane as a Biomaterial for Bone Regeneration

The physicochemical features of the avian eggshell membrane play an essential role in the process of calcium carbonate deposition during shell mineralization, giving rise to a porous mineralized tissue with remarkable mechanical properties and biological functions. The membrane could be useful by itself or as a bi-dimensional scaffold to build future bone-regenerative materials. This review focuses on the biological, physical, and mechanical properties of the eggshell membrane that could be useful for that purpose. Due to its low cost and wide availability as a waste byproduct of the egg processing industry, repurposing the eggshell membrane for bone bio-material manufacturing fulfills the principles of a circular economy. In addition, eggshell membrane particles have has the potential to be used as bio-ink for 3D printing of tailored implantable scaffolds. Herein, a literature review was conducted to ascertain the degree to which the properties of the eggshell membrane satisfy the requirements for the development of bone scaffolds. In principle, it is biocompatible and non-cytotoxic, and induces proliferation and differentiation of different cell types. Moreover, when implanted in animal models, it elicits a mild inflammatory response and displays characteristics of stability and biodegradability. Furthermore, the eggshell membrane possesses a mechanical viscoelastic behavior comparable to other collagen-based systems. Overall, the biological, physical, and mechanical features of the eggshell membrane, which can be further tuned and improved, make this natural polymer suitable as a basic component for developing new bone graft materials.

Physiological regulation of calcium and phosphorus utilization in laying hens

Commercial laying hens can produce one egg approximately every 24 h. During this process, regulatory systems that control vitamin D₃ metabolism, calcium and phosphorus homeostasis, and intestinal uptake of these minerals work in concert to deliver components required for eggshell calcification and bone mineralization. Commercial production cycles have been extended in recent years to last through 100 weeks of age, and older hens often exhibit an increased prevalence of skeletal fractures and poor eggshell quality. Issues such as these arise, in part, through imbalances that occur in calcium and phosphorus utilization as hens age. As a result, an in-depth understanding of the mechanisms that drive calcium and phosphorus uptake and utilization is required to develop solutions to these welfare and economic challenges. This paper reviews factors that influence calcium and phosphorus homeostasis in laying hens, including eggshell formation and development and roles of cortical and medullary bone. Metabolism and actions of vitamin D₃ and physiological regulation of calcium and phosphorus homeostasis in key tissues are also discussed. Areas that require further research in avian species, such as the role of fibroblast growth factor 23 in these processes and the metabolism and action of bioactive vitamin D₃, are highlighted and the importance of using emerging technologies and establishing in vitro systems to perform functional and mechanistic studies is emphasized.

Hatched Eggshell Membrane Can Be a Novel Source of Antioxidant Hydrolysates to Protect against H2O2-Induced Oxidative Stress in Human Chondrocytes

Natural antioxidants derived from agricultural by-products have great promise and ecological advantages in the treatment of oxidative stress-related diseases. The eggshell membrane (ESM) from hatched eggs, i.e., the hatched ESM, is a globally abundant agricultural byproduct, and its high-value utilization has been rarely studied compared to the well-studied ESM from fresh eggs. In this research, we systematically characterized the hatched ESM as a novel source of antioxidant hydrolysates and explored their potential role in H2O2-induced human chondrocytes. The results showed that the hatched ESM is a protein-rich fibrous mesh material with a significantly different structure and composition from those of fresh ESM. Enzymatic hydrolysis of hatched ESM can produce antioxidant hydrolysates rich in low molecular weight (MW) peptides, which mainly derived from the Lysyl oxidase homolog by Nano-LC-MS/MS analysis. The peptide fraction with MW < 3 kDa (HEMH-I) exhibited the highest DPPH radical scavenging, Fe2+-chelating, and Fe3+-reducing abilities. In H2O2-induced human SW1353 chondrocytes, HEMH-I treatment significantly increased the cell viability and ameliorated oxidative stress, inflammatory response, and cartilage matrix degradation by reducing the level of ROS, matrix metalloprotease 3 (MMP3), MMP13, and IL-6, and by promoting the expression of SOD and type II collagen, potentially through activating the cellular Keap1/Nrf2/HO-1 pathway. This study provides a theoretical basis for the value-added application of hatched ESM waste to produce antioxidant hydrolysates and indicates their potential as functional food and pharmaceuticals.

Atomic Details of Biomineralization Proteins Inspiring Protein Design and Reengineering for Functional Biominerals

Biominerals are extraordinary materials that provide organisms with a variety of functions to support life. The synthesis of biominerals and organization at the macroscopic level is a consequence of the interactions of these materials with proteins. The association of biominerals and proteins is very ancient and has sparked a wealth of research across biological, medical and material sciences. Calcium carbonate, hydroxyapatite, and silica represent widespread natural biominerals. The atomic details of the interface between macromolecules and these biominerals is very intriguing from a chemical perspective, considering the association of chemical entities that are structurally different. With this review I provide an overview of the available structural studies of biomineralization proteins, explored from the Protein Data Bank (wwPDB) archive and scientific literature, and of how these studies are inspiring the design and engineering of proteins able to synthesize novel biominerals. The progression of this review from classical template proteins to silica polymerization seeks to benefit researchers involved in various interdisciplinary aspects of a biomineralization project, who need background information and a quick update on advances in the field. Lessons learned from structural studies are exemplary and will guide new projects for the imaging of new hybrid biomineral/protein superstructures at the atomic level.

Circadian miR-218-5p targets gene CA2 to regulate uterine carbonic anhydrase activity during egg shell calcification

MicroRNAs (miRNAs) are involved in regulating the circadian clock. In our previous work, miR-218-5p was found to be a circadian miRNA in the chicken uterus, but its role in the eggshell formation process was not clear. In the present study, we found that the expression levels of miR-218-5p and two 2 predicted target genes carbonic anhydrase 2 (CA2) and neuronal PAS domain protein 2 (NPAS2) were oscillated in the chicken uterus. The results of dual-luciferase reporter gene assays in the present study demonstrated that miR-218-5p directly targeted the 3’ untranslated regions of CA2 and NPAS2. miR-218-5p showed an opposite expression profile to CA2 within a 24 h cycle in the chicken uterus. Moreover, over-expression of miR-218-5p reduced the mRNA and protein expression of CA2, while miR-218-5p knockdown increased CA2 mRNA and protein expression. Overexpression of CA2 also significantly increased the activity of carbonic anhydrase Ⅱ (P < 0.05), whereas knockdown of CA2 decreased the activity of carbonic anhydrase Ⅱ. miR-218-5p influenced carbonic anhydrase activity via regulating the expression of CA2. These results demonstrated that clock-controlled miR-218-5p regulates carbonic anhydrase activity in the chicken uterus by targeting CA2 during eggshell formation.

Antimicrobial Proteins and Peptides in Avian Eggshell: Structural Diversity and Potential Roles in Biomineralization

The calcitic avian eggshell provides physical protection for the embryo during its development, but also regulates water and gaseous exchange, and is a calcium source for bone mineralization. The calcified eggshell has been extensively investigated in the chicken. It is characterized by an inventory of more than 900 matrix proteins. In addition to proteins involved in shell mineralization and regulation of its microstructure, the shell also contains numerous antimicrobial proteins and peptides (AMPPs) including lectin-like proteins, Bacterial Permeability Increasing/Lipopolysaccharide Binding Protein/PLUNC family proteins, defensins, antiproteases, and chelators, which contribute to the innate immune protection of the egg. In parallel, some of these proteins are thought to be crucial determinants of the eggshell texture and its resulting mechanical properties. During the progressive solubilization of the inner mineralized eggshell during embryonic development (to provide calcium to the embryo), some antimicrobials may be released simultaneously to reinforce egg defense and protect the egg from contamination by external pathogens, through a weakened eggshell. This review provides a comprehensive overview of the diversity of avian eggshell AMPPs, their three-dimensional structures and their mechanism of antimicrobial activity. The published chicken eggshell proteome databases are integrated for a comprehensive inventory of its AMPPs. Their biochemical features, potential dual function as antimicrobials and as regulators of eggshell biomineralization, and their phylogenetic evolution will be described and discussed with regard to their three-dimensional structural characteristics. Finally, the repertoire of chicken eggshell AMPPs are compared to orthologs identified in other avian and non-avian eggshells. This approach sheds light on the similarities and differences exhibited by AMPPs, depending on bird species, and leads to a better understanding of their sequential or dual role in biomineralization and innate immunity.

Calculations of the Evolution of the Ca L23 Fine Structure in Amorphous Calcium Carbonate

Amorphous calcium carbonate (ACC) has been found in many different organisms. Biogenic ACC is frequently a precursor in the formation of calcite and aragonite. The process of structural transformation is therefore of great interest in the study of crystallization pathways in biomineralization. Changes in the prepeak/main peak (L₂'/L₂) intensity ratio of the Ca L₂₃-edge X-ray absorption spectroscopy (XAS) of Ca-rich particles in skeleton-building cells of sea urchin larva revealed that ACC precipitates through a continuum of states rather than through abrupt phase transitions involving two distinct phases as formerly believed. Using an atomic multiplet code, we show that only a tetragonal or "umbrella-like" distortion of the Ca coordination polyhedron can give rise to the observed continuum of states. We also show on the basis of the structures obtained from previous molecular dynamics simulations of hydrated nanoparticles that the Ca L₂₃-edge is not sensitive to atomic arrangements in the early stages of the transformation process.

Designed nanostructures created via physicochemical switching of the growth mode between single crystals and mesocrystals

Most biominerals are composed of mesocrystals, in which individual nanoparticle building units have a defined long-range order on the atomic scale in at least one direction. Although the crystal size and orientation of the mesostructures are spatially designed in biological architectures, it has been difficult to achieve adequate control of the crystal growth to produce modulated mesostructures in artificial aqueous systems. Here, we propose a simple physicochemical approach for the spatial design of nanostructures using an aqueous solution system. The ordered arrays of oriented fluorapatite (FA) rods similar to tooth enamel are produced on a polymer substrate in a supersaturated solution. We succeeded in reversible switching of the growth mode of FA between single-crystalline rods and mesocrystalline grains through the disturbance of the solution. The primary crystal size was tuned between micrometric rods ∼0.5 μm wide and >5 μm long and nanoscale grains ∼10 nm wide and 50 nm long without a drastic change in the c direction. Hierarchical architectures consisting of iso-oriented FA microrods and nanograins were constructed via temporal control of the crystal growth mode by switching a physicochemical parameter, such as the degree of supersaturation at the growth front.

Biomineralization: Integrating mechanism and evolutionary history

Calcium carbonate (CaCO₃) biomineralizing organisms have played major roles in the history of life and the global carbon cycle during the past 541 Ma. Both marine diversification and mass extinctions reflect physiological responses to environmental changes through time. An integrated understanding of carbonate biomineralization is necessary to illuminate this evolutionary record and to understand how modern organisms will respond to 21st century global change. Biomineralization evolved independently but convergently across phyla, suggesting a unity of mechanism that transcends biological differences. In this review, we combine CaCO₃ skeleton formation mechanisms with constraints from evolutionary history, omics, and a meta-analysis of isotopic data to develop a plausible model for CaCO₃ biomineralization applicable to all phyla. The model provides a framework for understanding the environmental sensitivity of marine calcifiers, past mass extinctions, and resilience in 21st century acidifying oceans. Thus, it frames questions about the past, present, and future of CaCO₃ biomineralizing organisms.

An exceptionally stable and widespread hydrated amorphous calcium carbonate precipitated by the dog vomit slime mold Fuligo septica (Myxogastria)

Biogenic amorphous calcium carbonate (ACC) is typically metastable and can rapidly transform through aging, dehydration, and/or heating to crystalline calcium carbonate. Gaining insight into its structure and properties is typically hampered by its tendency to crystallize over short time periods once isolated from the host organism, and also by the small quantities that are usually available for study. Here we describe an exceptionally stable hydrated ACC (HACC) precipitated by the cosmopolitan slime mold Fuligo septica (L.) F.H. Wigg. (1780). A single slime mold can precipitate up to a gram of HACC over the course of one night. Powder x-ray diffraction (XRD) patterns, transmission electron microscopy images, infrared absorption spectra, together with the lack of optical birefringence are consistent with an amorphous material. XRD simulations, supported by thermogravimetric and evolved gas analysis data, are consistent with an intimate association of organic matter with ~ 1-nm-sized ACC units that have monohydrocalcite- and calcite-like nano-structural properties. It is postulated that this association imparts the extreme stability of the slime mold HACC by inhibiting loss of H₂O and subsequent crystallization. The composition, structure, and thermal behavior of the HACC precipitated by F. septica collected over 8000 km apart and in markedly different environments, suggests a common structure, as well as similar biochemical and biomineralization mechanisms.

Pyrophosphate-stabilised amorphous calcium carbonate for bone substitution: toward a doping-dependent cluster-based model

Multiscale and multitool advanced characterisation of pyrophosphate-stabilised amorphous calcium carbonates allowed building a cluster-based model paving the way for tunable biomaterials.

Tri-ortho-cresyl phosphate exposure leads to low egg production and poor eggshell quality via disrupting follicular development and shell gland function in laying hens

Tri-ortho-cresyl phosphate (TOCP) has been used commercially as a plasticizer and a flame retardant, which has been reported to cause multiple toxicities in humans and other animals. However, the effect of TOCP on female reproductive system is still unclear. The aim of this investigation was to evaluate the reproductive toxicity of TOCP in female avian and investigate its molecular mechanism. In the current study, 50 adult hens were given a single oral dose of TOCP (750 mg/kg). Egg laid by the hens were harvested and counted. Egg quality is assessed by determining the shell strength and thickness. Samples of ovary, shell gland, and serum were collected on day 0, 2, 7, and 21 after the administration. The morphological and pathological changes in tissues were examined. Cell death, follicular development, and steroidogenesis were determined to assess the toxicity of TOCP on laying hens. The results showed that egg production, egg weight, and eggshell strength significantly decreased after TOCP exposure. The calcium levels in serum and eggshell decreased and the expression levels of the eggshell formation-related genes calbindin-D28k (CaBP-D28k) and carbonic anhydrase 2 (CA2) were downregulated. The inhibitory effects of TOCP on follicular development and steroidogenesis were observed with changes in the levels of the related proteins such as forkhead box O1 (FoxO1) and mothers against decapentaplegic homolog 2/3 (Smad2/3). Cell death was identified, which might lead to follicular development disorder. Taken together, TOCP reduced the quantity and quality of the eggs laid by the hens through disrupting follicular development, steroidogenesis, and shell gland function.

Eggshell decalcification and skeletal mineralization during chicken embryonic development: defining candidate genes in the chorioallantoic membrane

During chicken embryonic development, skeleton calcification mainly relies on the eggshell, whose minerals are progressively solubilized and transported to the embryo via the chorioallantoic membrane (CAM). However, the molecular components involved in this process remain undefined. We assessed eggshell demineralization and calcification of the embryo skeleton after 12 and 16 d of incubation, and analyzed the expression of several candidate genes in the CAM: carbonic anhydrases that are likely involved in secretion of protons for eggshell dissolution (CA2, CA4, CA9), ions transporters and regulators (CALB1, SLC4A1, ATP6V1B2, SGK1, SCGN, PKD2) and vitamin-D binding protein (GC).

Our results confirmed that eggshell weight, thickness, and strength decreased during incubation, with a concomitant increase in calcification of embryonic skeletal system. In the CAM, the expression of CA2 increased during incubation while CA4 and CA9 were expressed at similar levels at both stages. SCL4A1 and SCGN were expressed, but not differentially, between the two stages, while the expression of ATP6V1B2 and PKD2 genes decreased. The expression of SGK1 and TRPV6 increased over time, although the expression of the latter gene was barely detectable. In parallel, we analyzed the expression of these candidate genes in the yolk sac (YS), which mediates the transfer of yolk minerals to the embryo during the first half of incubation. In YS, CA2 expression increases during incubation, similar to the CAM, while the expression of the other candidate genes decreases. Moreover, CALB1 and GC genes were found to be expressed during incubation in the YS, in contrast to the CAM where no expression of either was detected.

This study demonstrates that the regulation of genes involved in the mobilization of egg minerals during embryonic development is different between the YS and CAM extraembryonic structures. Identification of the full suite of molecular components involved in the transfer of eggshell calcium to the embryo via the CAM should help to better understand the role of this structure in bone mineralization.

Circadian miR-449c-5p regulates uterine Ca2+ transport during eggshell calcification in chickens

Background

miRNAs regulate circadian patterns by modulating the biological clocks of animals. In our previous study, we found that the clock gene exhibited a cosine expression pattern in the fallopian tube of chicken uterus. Clock-controlled miRNAs are present in mammals and Drosophila; however, whether there are clock-controlled miRNAs in the chicken uterus and, if so, how they regulate egg-laying rhythms is unclear. In this study, we selected 18 layer hens with similar ovipositional rhythmicity (each of three birds were sacrificed for study per 4 h throughout 24 h); their transcriptomes were scanned to identify the circadian miRNAs and to explore regulatory mechanisms within the uterus of chickens.

Results

We identified six circadian miRNAs that are mainly associated with several biological processes including ion trans-membrane transportation, response to calcium ion, and enrichment of calcium signaling pathways. Verification of the experimental results revealed that miR-449c-5p exhibited a cosine expression pattern in the chicken uterus. Ca²⁺-transporting ATPase 4 (ATP2B4) in the plasma membrane is the predicted target gene of circadian miR-449c-5p and is highly enriched in the calcium signaling pathway. We speculated that clock-controlled miR-449c-5p regulated Ca²⁺ transportation during eggshell calcification in the chicken uterus by targeting ATP2B4. ATP2B4 mRNA and protein were rhythmically expressed in the chicken uterus, and dual-luciferase reporter gene assays confirmed that ATP2B4 was directly targeted by miR-449c-5p. The expression of miR-449c-5p showed an opposite trend to that of ATP2B4 within a 24 h cycle in the chicken uterus; it inhibited mRNA and protein expression of ATP2B4 in the uterine tubular gland cells. In addition, overexpression of ATP2B4 significantly decreased intracellular Ca²⁺ concentration (P < 0.05), while knockdown of ATP2B4 accelerated intracellular Ca²⁺ concentrations. We found similar results after ATP2B4 knockdown by miR-449c-5p. Taken together, these results indicate that ATP2B4 promotes uterine Ca²⁺ trans-epithelial transport.

Conclusions

Clock-controlled miR-449c-5p regulates Ca²⁺ transport in the chicken uterus by targeting ATP2B4 during eggshell calcification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08074-3.

How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells, larger clutches and longer lifespans

The avian eggshell is a bio-ceramic structure that protects the embryo. It is composed almost entirely of calcium carbonate and a small amount of organic material. An optimal amount of calcium carbonate in the eggshell is essential for the embryo's development, yet how the ratio of calcium carbonate to organic matter varies between species has not been investigated. Calcium is a limiting resource for most birds, so its investment in their eggs should be optimized for a bird's life history. We measured the relative calcium carbonate content of eggshells in 222 bird species and tested hypotheses for how this trait has evolved with the life-history strategies of these species and other traits of their respective egg physiologies. We found that (i) eggshell calcium carbonate content was positively correlated with species having thinner eggshells and smaller than expected eggs relative to incubating parental mass, (ii) species with small mean clutch sizes had lower calcium carbonate content in their eggshells, and (iii) for species with larger clutch sizes, eggshell calcium carbonate content was negatively correlated with their mean lifespan. The pattern of lower eggshell calcium carbonate in longer lived, larger clutched birds suggests that calcium provision to the eggshell has long-term costs for the individual.

Evolution of the Avian Eggshell Biomineralization Protein Toolkit - New Insights From Multi-Omics

The avian eggshell is a remarkable biomineral, which is essential for avian reproduction; its properties permit embryonic development in the desiccating terrestrial environment, and moreover, are critically important to preserve unfertilized egg quality for human consumption. This calcium carbonate (CaCO₃) bioceramic is made of 95% calcite and 3.5% organic matrix; it protects the egg contents against microbial penetration and mechanical damage, allows gaseous exchange, and provides calcium for development of the embryonic skeleton. In vertebrates, eggshell occurs in the Sauropsida and in a lesser extent in Mammalia taxa; avian eggshell calcification is one of the fastest known CaCO₃ biomineralization processes, and results in a material with excellent mechanical properties. Thus, its study has triggered a strong interest from the researcher community. The investigation of eggshell biomineralization in birds over the past decades has led to detailed characterization of its protein and mineral constituents. Recently, our understanding of this process has been significantly improved using high-throughput technologies (i.e., proteomics, transcriptomics, genomics, and bioinformatics). Presently, more or less complete eggshell proteomes are available for nine birds, and therefore, key proteins that comprise the eggshell biomineralization toolkit are beginning to be identified. In this article, we review current knowledge on organic matrix components from calcified eggshell. We use these data to analyze the evolution of selected matrix proteins and underline their role in the biological toolkit required for eggshell calcification in avian species. Amongst the panel of eggshell-associated proteins, key functional domains are present such as calcium-binding, vesicle-binding and protein-binding. These technical advances, combined with progress in mineral ultrastructure analyses, have opened the way for new hypotheses of mineral nucleation and crystal growth in formation of the avian eggshell, including transfer of amorphous CaCO₃ in vesicles from uterine cells to the eggshell mineralization site. The enrichment of multi-omics datasets for bird species is critical to understand the evolutionary context for development of CaCO₃ biomineralization in metazoans, leading to the acquisition of the robust eggshell in birds (and formerly dinosaurs).

A Promising Solution for Food Waste: Preparing Activated Carbons for Phenol Removal from Water Streams

Phenol and its derivatives are highly toxic chemicals and are widely used in various industrial applications. Therefore, the industrial wastewater streams must be treated to lower the concentration of phenol before discharge. At the same time, food waste has been a major environmental problem globally and the scientific community is eagerly seeking effective management solutions. The objective of this study was to understand the potential of utilizing food waste as a renewable and sustainable resource for the production of activated carbons for the removal of phenol from water streams. The food waste was pyrolyzed and physically activated by steam. The pyrolysis and activation conditions were optimized to obtain activated carbons with high surface area. The activated carbon with the highest surface area, 745 m2 g-1, was derived via activation at 950 °C for 1 h. A detailed characterization of the physicochemical and morphological properties of the activated carbons derived from food waste was performed and a comprehensive adsorption study was conducted to investigate the potential of using the activated carbons for phenol removal from water streams. The effects of pH, contact time, and initial concentration of phenol in water were studied and adsorption models were applied to experimental data to interpret the adsorption process. A remarkable phenol adsorption capacity of 568 mg g-1 was achieved. The results indicated that the pseudo-second-order kinetic model was better over the pseudo-second-order kinetic model to describe the kinetics of adsorption. The intraparticle diffusion model showed multiple regions, suggesting that the intraparticle diffusion was not the sole rate-controlling step of adsorption. The Langmuir isotherm model was the best model out of Freundlich, Temkin, and Dubinin-Radushkevich models to describe the phenol adsorption on activated carbons derived from food waste. This study demonstrated that food waste could be utilized to produce activated carbon and it showed promising capacity on phenol removal.

Synergic Effect of Selected Ingredients and Calcium Chloride on the Technological, Molecular and Microbial Usefulness of Eggshells and Their Impact on Sensory Properties in a Food Model System

Lower levels of calcium in adults increase the risk for osteoporosis, and in children, low calcium levels can impact their potential adult height. The study objective was to analyze the bioavailability and physicochemical properties of a calcium preparation based on chicken eggs. The base calcium preparation was enriched with one of a variety of biologically active substances, inter alia, vitamin D3, vitamin K, lysine, lactose, magnesium chloride and inulin. The newly developed calcium preparations were subjected to structural analysis using X-ray diffraction and scanning electron microscopy, and the hydrodynamic diameter for the molecules was determined using the dynamic light scattering method and their zeta potential. To determine the optimum storage conditions of calcium preparations, their hygroscopicity and bulk density were determined. The calcium preparations were also added to selected food products, such as apple juice with mango, fruit dessert (jelly) and beef meatballs. The enriched food products were subjected to sensory analysis. The study demonstrated the significant influence of additives to calcium preparation in terms of its hygroscopicity and morphology. It was found that all products with the addition of analyzed preparations were characterized by high sensory desirability. The results presented in the study comprise the basis for the development of new food products, enriched with calcium.

Avian eggshell biomineralization: an update on its structure, mineralogy and protein tool kit

BACKGROUND

The avian eggshell is a natural protective envelope that relies on the phenomenon of biomineralization for its formation. The shell is made of calcium carbonate in the form of calcite, which contains hundreds of proteins that interact with the mineral phase controlling its formation and structural organization, and thus determine the mechanical properties of the mature biomaterial. We describe its mineralogy, structure and the regulatory interactions that integrate the mineral and organic constituents during eggshell biomineralization. Main Body. We underline recent evidence for vesicular transfer of amorphous calcium carbonate (ACC), as a new pathway to ensure the active and continuous supply of the ions necessary for shell mineralization. Currently more than 900 proteins and thousands of upregulated transcripts have been identified during chicken eggshell formation. Bioinformatic predictions address their functionality during the biomineralization process. In addition, we describe matrix protein quantification to understand their role during the key spatially- and temporally- regulated events of shell mineralization. Finally, we propose an updated scheme with a global scenario encompassing the mechanisms of avian eggshell mineralization.

CONCLUSION

With this large dataset at hand, it should now be possible to determine specific motifs, domains or proteins and peptide sequences that perform a critical function during avian eggshell biomineralization. The integration of this insight with genomic data (non-synonymous single nucleotide polymorphisms) and precise phenotyping (shell biomechanical parameters) on pure selected lines will lead to consistently better-quality eggshell characteristics for improved food safety. This information will also address the question of how the evolutionary-optimized chicken eggshell matrix proteins affect and regulate calcium carbonate mineralization as a good example of biomimetic and bio-inspired material design.

DNA nanostructures as templates for biomineralization

Nature uses extracellular matrix scaffolds to organize biominerals into hierarchical structures over various length scales. This has inspired the design of biomimetic mineralization scaffolds, with DNA nanostructures being among the most promising. DNA nanotechnology makes use of molecular recognition to controllably give 1D, 2D and 3D nanostructures. The control we have over these structures makes them attractive templates for the synthesis of mineralized tissues, such as bones and teeth. In this Review, we first summarize recent work on the crystallization processes and structural features of biominerals on the nanoscale. We then describe self-assembled DNA nanostructures and come to the intersection of these two themes: recent applications of DNA templates in nanoscale biomineralization, a crucial process to regenerate mineralized tissues.

Morphological study of fibrous aragonite in the skeletal framework of a stony coral

The overall calcareous skeletons, including a low-crystalline core and surrounding fibrous crystals, of juvenile stony corals were characterized to clarify the entire calcic architecture and the contribution of abiotic processes.

Origin of the biphase nature and surface roughness of biogenic calcite secreted by the giant barnacle Austromegabalanus psittacus

The calcite grains forming the wall plates of the giant barnacle Austramegabalanus psittacus have a distinctive surface roughness made of variously sized crystalline nanoprotrusions covered by extremely thin amorphous pellicles. This biphase (crystalline-amorphous) structure also penetrates through the crystal’s interiors, forming a web-like structure. Nanoprotrusions very frequently elongate following directions related to the crystallographic structure of calcite, in particular, the <− 441> directions, which are the strongest periodic bond chains (PBCs) in calcite. We propose that the formation of elongated nanoprotrusions happens during the crystallization of calcite from a precursor amorphous calcium carbonate (ACC). This is because biomolecules integrated within the ACC are expelled from such PBCs due to the force of crystallization, with the consequent formation of uninterrupted crystalline nanorods. Expelled biomolecules accumulate in adjacent regions, thereby stabilizing small pellicle-like volumes of ACC. With growth, such pellicles become occluded within the crystal. In summary, the surface roughness of the biomineral surface reflects the complex shape of the crystallization front, and the biphase structure provides evidence for crystallization from an amorphous precursor. The surface roughness is generally explained as resulting from the attachment of ACC particles to the crystal surface, which later crystallised in concordance with the crystal lattice. If this was the case, the nanoprotrusions do not reflect the size and shape of any precursor particle. Accordingly, the particle attachment model for biomineral formation should seek new evidence.

Avian eggshell formation reveals a new paradigm for vertebrate mineralization via vesicular amorphous calcium carbonate

Amorphous calcium carbonate (ACC) is an unstable mineral phase, which is progressively transformed into aragonite or calcite in biomineralization of marine invertebrate shells or avian eggshells, respectively. We have previously proposed a model of vesicular transport to provide stabilized ACC in chicken uterine fluid where eggshell mineralization takes place. Herein, we report further experimental support for this model. We confirmed the presence of extracellular vesicles (EVs) using transmission EM and showed high levels of mRNA of vesicular markers in the oviduct segments where eggshell mineralization occurs. We also demonstrate that EVs contain ACC in uterine fluid using spectroscopic analysis. Moreover, proteomics and immunofluorescence confirmed the presence of major vesicular, mineralization-specific and eggshell matrix proteins in the uterus and in purified EVs. We propose a comprehensive role for EVs in eggshell mineralization, in which annexins transfer calcium into vesicles and carbonic anhydrase 4 catalyzes the formation of bicarbonate ions (HCO[Formula: see text]), for accumulation of ACC in vesicles. We hypothesize that ACC is stabilized by ovalbumin and/or lysozyme or additional vesicle proteins identified in this study. Finally, EDIL3 and MFGE8 are proposed to serve as guidance molecules to target EVs to the mineralization site. We therefore report for the first-time experimental evidence for the components of vesicular transport to supply ACC in a vertebrate model of biomineralization.

Effect of the level and source of supplementary dietary zinc on egg production, quality, and zinc content and on serum antioxidant parameters and zinc concentration in laying hens

Zinc is vital for proper functioning of an animal. Two sources of zinc are commonly supplemented in animal feed, organic and inorganic zinc, and there are reports that the former is absorbed to a greater extent than the latter. We hypothesized that supplementary zinc would increase zinc content in eggs of laying hens and that organic zinc would be more effective than inorganic zinc. To test these hypotheses, we examined the effect of levels and sources of supplemental dietary zinc on average daily feed intake (ADFI), egg production, and zinc content in eggs and on serum antioxidant capacity and zinc concentration in laying hens. A total of 720 Roman laying hens (21-week-old) were randomly assigned to 5 treatment groups with 6 replicates, with 24 hens in each replicate. Two sources of zinc, organic (zinc amino acid complex) and inorganic (zinc sulfate), each with 2 levels, low (35 mg/kg) and high (70 mg/kg), comprised 4 treatment groups, and a control group without supplementary zinc was the fifth group. Seven days were allowed for adjustment to the conditions, and then measurements were taken over 42 D. There was no difference in ADFI, average egg weight (EW), ADFI-to-EW ratio, and egg quality (P > 0.05) among the 5 treatment groups; supplemental zinc increased serum concentrations of Zn²⁺ and Cu-Zn superoxide dismutase and tended to increase superoxide dismutase content (P = 0.065). Zinc content in eggs increased linearly with supplementary organic zinc (N = 18, R² = 0.363, P = 0.008) and with supplementary inorganic zinc (N = 18, R² = 0.366, P = 0.008) treatment, but there was no difference between the source treatments of zinc. Therefore, our first hypothesis was supported, but our second one was not supported. We concluded that zinc supplementation is effective in enhancing zinc content in eggs and in improving antioxidant capacity in laying hens.

Efficient Removal of Heavy Metals from Aqueous Solutions Using a Bionanocomposite of Eggshell/Ag-Fe

Eggshell and an easily synthesized bionanocomposite of eggshell with Ag-Fe nanoparticles demonstrated to be efficient adsorbent materials for the removal of lead, arsenic, and mercury from water. The natural material and the bionanocomposite were characterized by TEM and XRD. Ag-Fe nanoparticles vary from 1 to 100 nm in size. Equilibrium times of the adsorption systems were achieved between 4 and 8 h. The experimental adsorption data fitted the pseudo-second and Elovich models; therefore, the adsorption of heavy metals ions took place mainly by a chemical process. The adsorption capacity of eggshell in mg/g was 7.01 for As5+, 3.90 for Pb2+, and 1.51 for Hg2+, while the nanocomposite adsorption capacity was 17.7 for As5+, 27.8 for Pb2+ and 15.88 for Hg2+.

Development and characterization of magnetic eggshell membranes for lead removal from wastewater

An increasing concern for natural resources preservation and environmental safety is the removal of heavy metals from contaminated water. It is essential to develop simple procedures that use ecofriendly materials with high removal capacities. In this context, we have synthesized a new hybrid material in which eggshell membranes (ESMs) act as nucleation sites for magnetite nanoparticles (MNPs) precipitation in the presence of an external magnetic field. As a result, ESM was transformed into a magnetic biomaterial (MESM) in order to combine the Pb adsorption abilities of both MNPs and ESM and to facilitate collection of the bioadsorbant using an external magnetic field. This green co-precipitation method produced long strands of bead-like 50 nm superparamagnetic MNPs decorating the ESM fibers. When MESM were incubated in Pb(NO₃)₂ solutions, the hybrid material displayed a 2.5-fold increase in binding constant with respect to that of ESM alone, and a 10-fold increased capacity to remove Pb ions from aqueous solution. The manufactured MESMs present a maximum loading capacity of 0.066 ± 0.009 mg Pb/mg MNPs at 25 °C, which is increased up to 0.15 ± 0.05 mg Pb/mg MNPs at 45 °C. Moreover, the MESM system is very stable, since incubation in 1% HCl solution resulted in rapid Pb desorption, while MNP release from the MESM during the same period was negligible. Altogether, these results suggest that MESM could be utilized as an efficient nanoremediation agent for separation/removal of heavy metal ions or other charged pollutants from contaminated waters, with facile recovery for recycling.

The paradoxical effects of progesterone on the eggshell quality of laying hens

This study demonstrates the effects of progesterone on eggshell quality and ultrastructure by injecting progesterone into laying hens 2 and 5 h post-oviposition, respectively. Progesterone injected 2 h post-oviposition (P₄-2 h) improved eggshell quality with a significant decrease (P < 0.01) in the thickness of the mammillary layer and a significant increase (P < 0.01) in the thickness of the effective layer in the eggshell ultrastructure compared to the control. Progesterone injected 5 h post-oviposition (P₄-5 h) damaged the eggshell quality by significantly reducing (P < 0.01) the effective layer thickness. Progesterone injected delayed obviously (P < 0.01) the following oviposition. Moreover, the concentrations of Thr, Cys, Leu, Lys, and His in the eggshell membranes were significantly higher (P < 0.05) in the P₄-2 h treated hens whereas Val and Lys were significantly lower (P < 0.05) in P₄-5 h treated hens compared to the control. Therefore, progesterone shows paradoxical effects on eggshell quality depending on the injection time-points post-oviposition, which could explain the contradictions in previous related reports. P₄ injected affected the content of amino acids in eggshell membranes, especially lysine which contributed to eggshell quality. In addition, P₄ injected 2 h after oviposition improved eggshell quality by promoting the premature fusion of mammillary knobs. This work contributed to a novel insight to understanding the mechanism of improving eggshell quality.

Effect of age at photostimulation on sexual maturation and egg-laying performance of layer breeders

The objective of this study was to determine the effect of age at photostimulation on sexual maturity and performance of layer breeders. A total of 192 fourteen-wk-old White Leghorn (WL) breeder hens were randomly allocated to 4 treatments of 48 birds each, with 2 replicates per treatment. The birds were photostimulated at 16 (PS16), 18 (PS18), 20 (PS20), and 22 (PS22) wk of age. Four birds per treatment were randomly selected to evaluate sexual organ development at 1 D before photostimulation and 2, 4, and 6 wk after photostimulation. The ovary weight, large yellow follicles number (LYF), oviduct weight, and oviduct length of PS18 increased sharply after photostimulation. Conversely, the increase in PS16 was not observed until 2 wk after photostimulation. There was no difference in age at sexual maturity between treatments (P > 0.05). The PS16 had the longest interval (28 D) from photostimulation to 5% egg production, while PS22 reached 5% egg production 7 D before photostimulation. The PS22 had lower peak production (P = 0.02) and less egg production (P = 0.02) than other treatments. The PS16 had more broken and abnormal eggs (P = 0.01) and lower hatchability (P = 0.04) than other treatments. In conclusion, photostimulation at 16 and 22 wk of age decreases hatchability and egg production, respectively, and photostimulation at 18 wk is appreciated for the WL breeder hens.

Biomacromolecules enabled dendrite-free lithium metal battery and its origin revealed by cryo-electron microscopy

Metallic lithium anodes are highly promising for revolutionizing current rechargeable batteries because of their ultrahigh energy density. However, the application of lithium metal batteries is considerably impeded by lithium dendrite growth. Here, a biomacromolecule matrix obtained from the natural membrane of eggshell is introduced to control lithium growth and the mechanism is motivated by how living organisms regulate the orientation of inorganic crystals in biomineralization. Specifically, cryo-electron microscopy is utilized to probe the structure of lithium at the atomic level. The dendrites growing along the preferred < 111 > crystallographic orientation are greatly suppressed in the presence of the biomacromolecule. Furthermore, the naturally soluble chemical species in the biomacromolecules can participate in the formation of solid electrolyte interphase upon cycling, thus effectively homogenizing the lithium deposition. The lithium anodes employing bioinspired design exhibit enhanced cycling capability. This work sheds light on identifying substantial challenges in lithium anodes for developing advanced batteries.

Inspired by the role of proteins in regulating eggshell mineralization, here Tao, Liu and colleagues apply trifluoroethanol modified eggshell membrane to combat lithium dendrite. Cryo-electron microscopy reveals that the growth along the most favored crystallographic direction is suppressed.

Mineral self-organization on a lifeless planet

It has been experimentally demonstrated that, under alkaline conditions, silica is able to induce the formation of mineral self-assembled inorganic-inorganic composite materials similar in morphology, texture and nanostructure to the hybrid biomineral structures that, millions of years later, life was able to self-organize. These mineral self-organized structures (MISOS) have been also shown to work as effective catalysts for prebiotic chemical reactions and to easily create compartmentalization within the solutions where they form. We reason that, during the very earliest history of this planet, there was a geochemical scenario that inevitably led to the existence of a large-scale factory of simple and complex organic compounds, many of which were relevant to prebiotic chemistry. The factory was built on a silica-rich high-pH ocean and powered by two main factors: a) a quasi-infinite source of simple carbon molecules synthesized abiotically from reactions associated with serpentinization, or transported from meteorites and produced from their impact on that alkaline ocean, and b) the formation of self-organized silica-metal mineral composites that catalyze the condensation of simple molecules in a methane-rich reduced atmosphere. We discuss the plausibility of this geochemical scenario, review the details of the formation of MISOS and its catalytic properties and the transition towards a slightly alkaline to neutral ocean.