Phosphate Formation Research Articles

Development of Bacteria biofertilizers using locally isolated rhizosphere populations and agricultural refuse and their impacts on growth of local test crops

Biofertilizers are the preparations of live microorganisms added to the root, seed or soil to promote plant growth. In this study, Plant Growth Promoting Bacteria able to solubilize insoluble phosphate (P) and potassium (K) forms were isolated, characterized and identified. Two isolates that demonstrated excellent solubilization of potassium or phosphate from abundant and bio-available waste biomass (rice husk and cattle bone) were used to produce biofertilizers by solid-state fermentation. The biofertilizers were applied to grow three food security crops, Zea mays, Solanum lycopersicum, and Arachis hypogea, in a screenhouse, and monitored for growth impacts. Treatments A, B, and A + B biofertilizers caused a significant (p < 0.05) increase in plant dry weights. The highest microbial colonization was obtained from treatment A + B (for S. lycopersicum) with a microbial count (log 2.89 (108) cfu/g), whereas treatment with B (for A. hypogea) had the least microbial count (log 2.73 (108) cfu/g). Maximum values of experimental parameters: shoot height, leaf number, plant dry weight and leaf width were obtained with the combined application of both biofertilizers. P and K solubilizing PGPB have shown potential for use as biofertilizers in growing these key crops under the soil conditions and in the environment studied.

Development of an Atmospheric Pressure Plasma Jet Device Using Four-Bore Tubing and Its Applications of In-Liquid Material Decomposition and Solution Plasma Polymerization.

In this study, we describe an atmospheric pressure plasma jet (APPJ) device made of four-bore tubing operable in inhospitable humid environments and introduce two potential applications of liquid material processing: decomposition of aqueous phosphorus compounds and solution-plasma polymerization. A four-bore tube was used as the plasma transfer conduit and two diagonal bores contained metal wires. In the proposed APPJ device, the metal wires serving as electrodes are completely enclosed inside the holes of the multi-bore glass tube. This feature allows the APPJ device to operate both safely and reliably in humid environments or even underwater. Thus, we demonstrate that the proposed electrode-embedded APPJ device can effectively decompose aqueous phosphorus compounds into their phosphate form by directly processing the solution sample. As another application of the proposed APPJ device, we also present the successful synthesis of polypyrrole nanoparticles by solution plasma polymerization in liquid pyrrole.

Cancer in Kidney Transplant Recipients: Latest Findings

Acute renal failure in cancer patients may be due to the existence of tumor cell lysis, in which large amounts of potassium, phosphate, and nucleic acids are released into the bloodstream and cause a cancerous emergency [1]. In addition, it causes metabolic abnormalities that lead to the formation of calcium phosphate, which precipitates into the tissues and some into the kidneys. Metabolic abnormalities increase levels of uric acid, which precipitates in the kidneys. Both situations can lead to End-Stage Renal Failure (ESRF) [2]. The medical solution at this stage is for patients on dialysis or solid organ kidney transplantation.

Two-Step Transesterification of Phosphates, Phosphorothioates, and Phosphonates with a Binaphthyl Group for the Synthesis of P-Chirogenic Phosphates and Phosphonates

AbstractTwo-step transesterification of four-coordinate pentavalent organophosphorus compounds with a binaphthyl group has been studied in detail. The first step involves transfer of the axial chirality of a ­hydroxybinaphthyl group to the central chirality of the phosphorus atom. The second step is the substitution reaction of P-chirogenic compounds with a hydroxybinaphthyl group with lithium alkoxides, leading to the formation of P-chirogenic phosphates and phosphonates with primary and secondary alkoxy groups.

Phosphite treatment can improve root biomass and nutrition use efficiency in wheat.

Phosphite represents a reduced form of phosphate that belongs to a class of crop growth-promoting chemicals termed biostimulants. Previous research has shown that phosphite application can enhance root growth, but its underlying mechanism, especially during environmental stresses, remains elusive. To uncover this, we undertook a series of morphological and physiological analyses under nutrient, water and heat stresses following a foliar application in wheat. Non-invasive 3D imaging of root system architecture directly in soil using X-ray Computed Tomography revealed that phosphite treatment improves root architectural traits and increased root biomass. Biochemical and physiological assays identified that phosphite treatment significantly increases Nitrate Reductase (NR) activity, leaf photosynthesis and stomatal conductance, suggesting improved Nitrogen and Carbon assimilation, respectively. These differences were more pronounced under heat or drought treatment (photosynthesis and photosystem II stability) and nutrient deficiency (root traits and NR). Overall our results suggest that phosphite treatment improves the ability of plants to tolerate abiotic stresses through improved Nitrogen and Carbon assimilation, combined with improved root growth which may improve biomass and yield.

EFFICIENCY OF PLANTING CALCIUM IONS FROM DILUTE AQUEOUS SOLUTIONS IN THE FORM OF PHOSPHATES

The specifics of calcium phosphate formation process during diluted aqueous solutions softening for home or office were researched. Studies have shown that, unlike calcium carbonate, effective precipitation of calcium ions with phosphate is possible even at doses less than stoichiometric. The ratio between concentrations of phosphate ions and calcium ions K = [PO43-, mg-eq] / [Ca2+, mg-eq] is a determining factor. Already at K = 0.5 there is a decrease in the content of calcium ions by more than half. In stoichiometry (K = 1), the residual concentrations of calcium ions in the treated water fall below 1 mg-eq/dm3. At K &gt; 1.5, the content of calcium ions in the treated water stabilizes at the level of 0.2 – 0.1 mg-eq/dm3. Water temperature does not significantly affect the deposition of calcium ions with phosphates. A noticeable decrease in efficiency is recorded only at a temperature of 5 ° C. But even in this case, this decrease is 0.1 – 1.5 mg-eq/dm3, which is quite acceptable for living conditions, since it provides soft and very soft water. The reaction between calcium ions and phosphates is quite complete in the first minutes of contact. The settling of mixed solutions for an hour showed that the reaction of the formation of a solid phase takes place at the time of draining the solutions and over time the residual hardness of the water practically does not change. From the point of view of softening efficiency, phosphate is quite suitable as a reagent for removing calcium ions from hard natural waters. An important aspect of the softening technology is the separation of the precipitate formed from the treated water. To do this, it is necessary to determine the conditions for the formation of a crystalline, most compact and formed precipitate. The clarification of the hard water sample treated with sodium phosphate showed that there was no significant difference in deposition at different initial pH values.

Low-Temperature Formation and Identification of Biphasic Calcium Carbonate Phosphates

Low-Temperature Formation and Identification of Biphasic Calcium Carbonate Phosphates

Influence of Additives Concentration on the Electrical Properties and the Tribological Behaviour of Three Automatic Transmission Fluids

Placing an electric motor (EM) inside the transmission housing of a hybrid electric vehicle (HEV) implies that the automatic transmission fluid (ATF) needs to accomplish additional requirements. Among these requirements, electrical compatibility is of critical significance. This study investigated the influences of the additive concentrations of three commercial ATFs on their electrical compatibilities and tribological performances. Two variations of each ATF with different concentrations of the original additive packages were prepared. The viscosity, electrical conductivity, permittivity, resistivity, dielectric dissipation factor, breakdown voltage, and tribological performance of the nine resulting ATFs were measured. All the ATFs were found to be electrically compatible and showed dissipative performance and sufficiently high breakdown voltage, even at increasing additive concentrations. The tribological performances of the ATFs formulated with the API (American Petroleum Institute) Group III base oils had improved wear reduction at the highest additive concentrations; the better wear performance was related to the formation of iron phosphates and polyphosphates on the worn surface.

Analysis of phosphorus forms on different soil types using heterogeneous isotope exchange reaction

Pot experiments and soil incubation were carried out to follow the processes of added phosphorus (P) fertilizer using radioisotope tracer technique, heterogeneous isotope exchange. Four types of soils were investigated (Dystric Arenosol (Humic), Calcic Vertisol (Gleyic), Rendzic Phaeozem (Hyperhumic), Calcic Gleysol(Arenic, Humic)). The changes of phosphate fractions (water-soluble (Pw), isotopically exchangeable (PIE), ammonium lactate soluble phosphorus (PAL), and tightly sorbed phosphorus (Ptightly)) in soil were determined as a function of P supply, incubation time and the plant culture. The soil samples were incubated at different times (1, 3, 13 weeks) and phosphate quantities. 0, 40, 80, 160, 320 mg P/kg soil doses of P fertilizer were added to the soils. After incubation, perennial ryegrass (Lolium perenne L.) was sown. A significant correlation was found between the sum of Pw and PIE and Puptake of plant proving that these values can be good indicators of plant available phosphorus. During plant culture, the Pw and PIE values always decrease showing that plant directly utilizes these phosphate forms. The transformation of added phosphate to tightly sorbed phosphate is the highest for soils with great humus content.

Thermal stability, pore structure characteristics of char layer and ablation resistance mechanism of new thermal insulation composites based on polyphosphazene polymer

Polyphosphazene (PDPP) composites have emerged as a hot research topic in the field of low-density composite insulation materials because of their good thermal stability and flame retardancy. In this study, the ablative properties and mechanism of PDPP composites reinforced by fiber and functional fillers are studied. The test results show that PDPP composites have good thermal stability and oxidation resistance. The results of the oxyacetylene ablation test show that PDPP composites has strong ablation resistance, and its char layer has high structural strength, as well as high bonding strength with the material matrix. However, the thermal insulation performance of PDPP composites is weak. Based on the physical and chemical analysis of the composite material and the char layer, it is concluded that the excellent ablation resistance is mainly due to the high strength of the char layer, which bnefits from high char yield of polyphosphazene polymer and the formation of silicon phosphate. However, the high thermal conductivity of composite and char layer lead to poor thermal insulation performance.

Functional Characterization of a HAD Phosphatase Involved in Capsular Polysaccharide Biosynthesis in Campylobacter jejuni.

Campylobacter jejuni is a Gram-negative, pathogenic bacterium found in the intestinal tracts of chickens and many other farm animals. C. jejuni infection results in campylobacteriosis, which can cause nausea, diarrhea, fever, cramps, and death. The surface of the bacterium is coated with a thick layer of sugar known as the capsular polysaccharide. This highly modified polysaccharide contains an unusual d-glucuronamide moiety in serotypes HS:2 and HS:19. Previously, we have demonstrated that a phosphorylated glucuronamide intermediate is synthesized in C. jejuni NCTC 11168 (serotype HS:2) by cumulative reactions of three enzymes: Cj1441, Cj1436/Cj1437, and Cj1438. Cj1441 functions as a UDP-d-glucose dehydrogenase to make UDP-d-glucuronate; then Cj1436 or Cj1437 catalyzes the formation of ethanolamine phosphate or S-serinol phosphate, respectively, and finally Cj1438 catalyzes amide bond formation using d-glucuronate and either ethanolamine phosphate or S-serinol phosphate. Here, we investigated the final d-glucuronamide-modifying enzyme, Cj1435. Cj1435 was shown to catalyze the hydrolysis of the phosphate esters from either the d-glucuronamide of ethanolamine phosphate or S-serinol phosphate. Kinetic constants for a range of substrates were determined, and the stereoselectivity of the enzyme for the hydrolysis of glucuronamide of S-serinol phosphate was established using 31P nuclear magnetic resonance spectroscopy. A bioinformatic analysis of Cj1435 reveals it to be a member of the HAD phosphatase superfamily with a unique DXXE catalytic motif.

Experimental Clarification of PRPS-1 Structural Essentials.

Phosphoribosyl pyrophosphate synthetase-1 (PRPS-1; EC 2.7.6.1.) catalyzes the binding of phosphate-group to ribose 5-phosphate, forming the 5-phosphoribosyl-1-pyrophosphate, which is necessary for the salvage pathways of purine and pyrimidine, pyridine nucleotide cofactors - NAD and NADP, the amino acids histidine and tryptophan biosynthesis. We aimed to investigate the impact of the different effectors on the activity of PRPS-1, to check the activity of the enzyme in vitro in a wide range of pHs and investigate some structural essentials of the enzyme, isolated from brain and liver. Molecular docking analyses were used to delineate the essentials of PRPS-1 structure, to find out the existence of enzyme effectors. Previously created by us kit was used for determination of the activity of PRPS-1 based on the formation of the inorganic phosphates (λ = 700 nm, Cary 60, Agilent, USA). Effectors impact on the activity of PRPS-1 was evaluated. In silico results of the effectors were later proven by in vitro experiments. For the first time biochemical essentials, including the existence of the multiple pockets, involvement of the amino acids into the processes of interactions with the effectors, evolutional of the sequence conservation, tissue depended Vmax differences were identified.

Vascular calcification maladaptively participates in acute phosphate homeostasis.

Non-renal extravasation of phosphate from the circulation and transient accumulation into tissues and extracellular fluid is a regulated process of acute phosphate homeostasis that is not well understood. This process is especially relevant in the setting of chronic kidney disease (CKD), where exposure to increased phosphate is prolonged due to inefficient kidney excretion. Furthermore, CKD-associated mineral dysregulation induces pathological accumulation of phosphate causing vascular calcification (VC). Our objective was to determine whether the systemic response to acute phosphate challenges is altered by VC. After bolus phosphate administration, circulating and tissue deposition of this challenge was assessed in two rat models of VC using a radiolabelled phosphate tracer. In an adenine-induced model of CKD (N = 70), animals with VC had a blunted elevation of circulating 33PO4 following oral phosphate administration (P < 0.01), and the discordant deposition could be traced to the calcified arteries (11.4 [7.5-13.1] vs.43.0 [35.5-53.7] pmol/ng tissue, P < 0.001). In a non-CKD model of VC, calcification was induced with 0.5 ug/kg calcitriol and then withdrawn (N = 24). New phosphate uptake by the calcified vasculature correlated to the pre-existing burden of calcification (r = 38, P < 0.001) and was substantially attenuated in the absence of calcification stimulus (P < 0.01). Phosphate accrual was stimulated by the phosphate challenge and not present to the same degree during passive disposition of circulating phosphate. Further, the form of phosphate that deposited to the vasculature was predominately amorphous inorganic phosphate and not that which was bound in matured calciprotein particles. In the process of calcification, arteries acutely deposit substantial amorphous phosphate while blunting the elevation in the circulation, thereby altering the systemic disposition of phosphate and identifying VC as a participatory mineral homeostatic organ. This study demonstrates the negative vascular consequence of acute fluctuations in circulating phosphate, and supports the importance of phosphate bioavailability and diet management in CKD patients as a mediator of cardiovascular risk.

DIAGNOSTIC ACCURACY COMPARISON OF THE QUANTITATIVE POINT-OF-CARE ECO G6PD AND BREWERS TEST FOR ASSESSMENT OF G6PD DEFICIENCY IN INFECTIOUS DISEASES

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked, hereditary condition caused by mutations in the G6PD gene, that results in protein variants with different enzyme activity levels. G6PD provides reducing power to NADPH (reduced form of nicotinamide adenine dinucleotide phosphate). NADPH effect is critical in red blood cells (RBC) due to the absence of a nucleus. Clinical manifestations are usually mild and are induced by an exogenous agent, such as drugs, infections, or dietary (fava beans). The G6PD deficiency diagnosis is crucial in infectious diseases because both infections and treatment can induce acute hemolysis. Rarely, life-threatening cases can require transfusions of RBC and hemodialysis. The gold standard for the measurement of G6PD activity is a quantitative UV spectrophotometric assay, however, it is inaccessible in most cases. Methemoglobin reduction test (Brewer's test) is a qualitative spot test most used for G6PD deficiency screening, but is imprecise, requires a cold chain, some laboratory infrastructure, trained personnel, and is time-costing. Point-of-care (POC) is a simple and fast semi-quantitative test that is becoming increasingly important when a prompt diagnosis is required and in health care of out-of-reach communities. To compare the diagnostic accuracy of the quantitative POC ECO and Brewers test for assessment of G6PD deficiency. A cross-sectional diagnostic accuracy study was enrolled between May 2020 and December 2021 at the Instituto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz. Individuals older than 17 years old with a suspicious diagnosis of an infectious disease were eligible. 125 convenience blood samples were tested to compare concordance analysis between Brewers test and POC STANDARD G6PD. The exclusion criteria were hemoglobin concentration < 7.0 g/dL due to technical device limitations. A total of 125 subjects (38 females and 87 males) were recruited. The median age was 42.0 years (range 18–76) in females and 45.0 years (range 19–78) in males. The median of G6PD activity was 7.1 U/g Hb (0.2-17.5). We observed a trend of concordance between the G6PD status (deficient or normal), with low frequencies of discordances in the screenings. The strength of agreement between G6PD tests was classified as almost perfect in all participants (k = 0.82, IC95% = 0.66,0.97) and in subgroups female (k = 0.83, IC95% = 0.59,1.00) and male (k = 0.81, IC95% = 0.59,1.00). The total concordance percentage (number of concordances/total) was 95% in females, 97% in males, and 96% in all participants. Here, we demonstrate POC ECO G6PD test could be performed during medical consultation, guiding the most appropriate therapy almost immediately. In addition to saving time and having comparable results to Brewer's test, it could be performed even in remote areas and with scarce resources, dispensing minimum laboratory requirements. Our findings will be of value to diagnose conditions that could have life-threatening consequences if not timely recognized, such as before initiating primaquine for the treatment of malaria. Therefore, it can improve healthcare in vulnerable isolated communities. We observed a high concordance result between Brewers test and POC STANDARD G6PD, which is becoming the reference test to diagnose G6PD deficiency worldwide.

Dissection of the response mechanism of alfalfa under phosphite stress based on metabolomic and transcriptomic data

Phosphite, a reduced form of phosphate, inhibits the growth and even has toxic effect on plants. To learn more about the mechanism of alfalfa responses to phosphite, the morphological and physiological characteristics, and the metabolites and transcript levels were comprehensively analyzed following the exposure of alfalfa seedlings to phosphite and phosphate under greenhouse conditions. The results showed that phosphite inhibited seedling growth and photosynthesis. However, the absorption efficiency of phosphite was higher than that of phosphate in roots, which was supported by increased total phosphorus concentration of 16.29% and 52.30% on days 8 and 12. Moreover, phosphite stress affected the synthesis of lipids and carbohydrates, which were reflected in enhanced glycolipid and sulfolipid in roots and amylose in shoots. Phosphite stress resulted in a decrease in indole acetic acid (IAA) in the whole plant and zeatin in the shoots, which could enable alfalfa to adapt to the phosphite environment. Some genes involved in phosphate starvation response included SPX, phosphate response regulator2, and inorganic phosphate transporter 1–4 (PHT1;4) in roots were affected by phosphite stress. In addition, some genes that are involved in stress responses and DNA repair were induced by phosphite stress. These observations together suggest that alfalfa responds to phosphite stress by inhibiting growth, regulating the genes induced by phosphate starvation, improving oxidative protection, promoting DNA repair, and adjusting the IAA and zeatin signaling transductions. Our findings provide novel insights into the molecular response to phosphite stress in alfalfa.

Comparative Response of Fermented and Non-Fermented Animal Manure Combined with Split Dose of Phosphate Fertilizer Enhances Agronomic Performance and Wheat Productivity through Enhanced P Use Efficiency

Low availability of native soil phosphorus (P) is a major constraint limiting sustainable crop production especially in alkaline calcareous soils. Application of organic manure in this regard has gained attention of the scientific community. Yet, the potential of fermented animal manure in improving P use efficiency and subsequent crop yield has not been assessed. This pot experiment was designed to study the performance of wheat under application of non-fermented and fermented animal manure in combination with 0, 45 or 90 kg·ha−1 phosphorus in the form of diammonium phosphate (DAP). Results show that non-fermented animal manure and split dose of phosphorus fertilizer improved plant quantitative attributes including plant growth, yield and nutrient uptake parameters. However, the placement of fermented animal manure combined with the full amount of P (90 kg·ha−1) fertilizer gave the mean highest value of fertile tillers per pot (12) and their grain yield (5.2 g). Moreover, plant physiological parameters were enhanced with fermented animal manure and the recommended rate of P fertilizer compared with the control. Likewise, the biochemical properties of wheat grain such as fat, fiber, ash and protein contents were increased by 1.24, 2.26, 1.47 and 11.2%, respectively, in plants receiving fermented animal manure and P fertilizer (90 kg·ha−1). Furthermore, co-application of fermented animal manure with P (90 kg·ha−1) into soil improved phosphorus uptake from 0.72 to 1.25 g·pot−1, phosphorus usage efficiency from 0.715 to 0.856 mg·pot−1, and soil phosphorus extent from 7.58 to 16.1% over controls. It is thus inferred that this new approach resulted in release of P from fermented manure that not only reduced fixation but also enhanced the growth, yield, physiology and nutrient uptake in wheat.

Aluminium alloy corrosion inhibition by a two-stage modified nanoporous zeolite

ABSTRACT A two-stage synthesis of anti-corrosion pigments based on synthetic zeolites was performed. New pigments retain the zeolite framework structure in the nanopores of which the amorphised phosphate phase is formed. The pigments effectively reduce the aluminium alloy corrosion in sodium chloride solution. The most effective pigment is obtained by mechanochemical modification of zeolite with calcium cations, followed by liquid-phase treatment with zinc nitrate and sodium phosphate. The pigments induce the formation of a protective film of zinc hydroxides on intermetallic inclusions of the alloy. The formation of phosphates is possible on the anode sections. The pigments can become promising inhibitory components of primer paints used for the protection of structures made from aluminium alloys.

An antibacterial porous calcium phosphate bilayer functional coatings on titanium dental implants

BackgroundThe design of biological active and antibacterial implant coating remains a challenging topic to ensure early implant fixation and to prevent peri-implantitis. In this laboratory work, we reported a newly designed antibacterial porous calcium phosphate (CP) bilayer functional coating on titanium implant incorporated with molybdenum trioxide. MethodsThe coating was prepared by using a sol-gel template process. The physicochemical and biological properties of the coatings were investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), in vitro coating degradation, in vitro mineral calcium phosphate formation, cell proliferation and antibacterial tests. Resultsthe porous calcium phosphate bilayer coating enhanced the mineral calcium phosphate formation compared with calcium phosphate coating. Cell proliferation test using MC3T3-E1 osteoblasts showed that the porous calcium phosphate bilayer coating promoted cell growth. Antibacterial test against S. aureus showed that the porous calcium phosphate bilayer coating incorporated with molybdenum oxide exhibited a better antibacterial activity than calcium phosphate coating Conclusionsa combination of porous structure, bilayer coating and doped molybdenum oxide is crucial to improve the performance of calcium phosphate coating.

Metabolic flexibilities and vulnerabilities in the pentose phosphate pathway of the zoonotic pathogen Toxoplasma gondii.

Metabolic pathways underpin the growth and virulence of intracellular parasites and are therefore promising antiparasitic targets. The pentose phosphate pathway (PPP) is vital in most organisms, providing a reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) and ribose sugar for nucleotide synthesis; however, it has not yet been studied in Toxoplasma gondii, a widespread intracellular pathogen and a model protozoan organism. Herein, we show that T. gondii has a functional PPP distributed in the cytoplasm and nucleus of its acutely-infectious tachyzoite stage. We produced eight parasite mutants disrupting seven enzymes of the PPP in T. gondii. Our data show that of the seven PPP proteins, the two glucose-6-phosphate dehydrogenases (TgG6PDH1, TgG6PDH2), one of the two 6-phosphogluconate dehydrogenases (Tg6PGDH1), ribulose-5-phosphate epimerase (TgRuPE) and transaldolase (TgTAL) are dispensable in vitro as well as in vivo, disclosing substantial metabolic plasticity in T. gondii. Among these, TgG6PDH2 plays a vital role in defense against oxidative stress by the pathogen. Further, we show that Tg6PGDH2 and ribulose-5-phosphate isomerase (TgRPI) are critical for tachyzoite growth. The depletion of TgRPI impairs the flux of glucose in central carbon pathways, and causes decreased expression of ribosomal, microneme and rhoptry proteins. In summary, our results demonstrate the physiological need of the PPP in T. gondii while unraveling metabolic flexibility and antiparasitic targets.

Casein phosphopeptide-calcium chelate: Preparation, calcium holding capacity and simulated digestion in vitro

In this work, CPP-Ca chelate was synthesized by chelating casein phosphopeptide (CPP) and calcium and characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The antioxidant activity and calcium holding capacity of CPP-Ca were evaluated and its secondary structure transition was monitored during gastrointestinal digestion by in situ Raman spectroscopy. The results demonstrated that calcium chelating rate reached 40 % and calcium ion was bound to CPP mainly through the interaction of carboxyl and amino groups. The result of calcium holding capacity confirmed the formation of calcium phosphate precipitates could be delayed by 10–15 min with increasing CPP concentration. In vitro simulated digestion revealed CPP-Ca exhibited excellent calcium solubility and its secondary structural changes occurred, especially α-helix and β-sheet content. These findings provided significant insights into enhancing bioavailability of calcium supplements and developing of calcium functional foods for human and animals.