Soluble Phytate Research Articles

Effects of nitrogen on the distribution and chemical speciation of iron and zinc in pearling fractions of wheat grain.

Increasing nitrogen supply can increase Fe and Zn concentrations in wheat grain, but the underlying mechanisms remain unclear. Size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry was used to determine Fe and Zn speciation in the soluble extracts of grain pearling fractions of two wheat cultivars grown at two N rates (100 and 350 kg of N ha(-1)). Increasing N supply increased the concentrations of total Fe and Zn and the portions of Fe and Zn unextractable with a Tris-HCl buffer and decreased the concentrations of Tris-HCl-extractable (soluble) Fe and Zn. Within the soluble fraction, Fe and Zn bound to low molecular weight compounds, likely to be Fe-nicotianamine and Fe-deoxymugineic acid or Zn-nicotianamine, were decreased by 5-12% and 4-37%, respectively, by the high N treatment, whereas Fe and Zn bound to soluble high molecular weight or soluble phytate fractions were less affected. The positive effect of N on grain Fe and Zn concentrations was attributed to an increased sink in the grain, probably in the form of water-insoluble proteins.

Assessing Potential Effects of Inulin and Probiotic Bacteria on Fe Availability from Common Beans (Phaseolus vulgaris L.) to Caco‐2 Cells

Inulin, a prebiotic, may enhance intestinal Fe absorption. Our objective was to assess the effects of supplemental inulin and 2 probiotic bacteria (B. infantis and L. acidophillus) on Fe availability to Caco-2 cells from common white and red beans (Phaseolus vulgaris L.). Cooked beans were mixed or not with supplemental inulin (4%, w/w), and then subjected to simulated gastrointestinal digestion (pepsin, pH 2; pancreatin, pH 7.2). Subsequently, the digests were incubated overnight with and without B. infantis or L. acidophilus. Ferritin formation in Caco-2 cells was used to evaluate Fe uptake. Total soluble phenols (Folin-Ciocalteau) and phytate (HPLC-electrochemical detection) were quantified, and the flavonoids profile (HPLC-PDA/UV detection) was monitored in the digests. Supplemental inulin did not affect Fe uptake from white nor red beans. Incubation with B. infantis increased total soluble phenols (TSP) in the digests and decreased Fe uptake. Incubation with L. acidophilus decreased TSP in the digest and increased Fe uptake. Variations in Fe uptake were not associated with soluble phytate concentrations in the digests. The largest change in flavonoids profile were found in the digests incubated with L. acidophilus, which decreased the soluble concentration of astragalin (kaempferol-3-O-glucoside). These results suggest that certain probiotics could increase Fe uptake from common beans.

Peniophora lycii phytase is stabile and degrades phytate and solubilises minerals in vitro during simulation of gastrointestinal digestion in the pig

Microbial phytases (EC 3.1.3) are widely used in diets for monogastric animals to hydrolyse phytate present in the feed and thereby increase phosphorus and mineral availability. Previous work has shown that phytate solubility is strongly affected by calcium in the feed and by pH in the gastrointestinal (GI) tract, which may have an effect on phytase efficacy. An in vitro model simulating the GI tract of pigs was used to study the survival of Peniophora lycii phytase and the effect of the phytase on phytate degradation, inositol phosphate formation and mineral solubilisation during in vitro digestion of a 30:70 soybean meal/maize meal blend with different calcium levels. The phytase retained 76 and 80% of its initial activity throughout the gastric in vitro digestion. Total phytate hydrolysis by P. lycii phytase was in the same range at total calcium levels of 1.2 and 6.2 mg g(-1) dry matter (DM), despite very large differences in phytate solubility at these calcium levels. However, at 11.2 and 21.2 mg Ca g(-1) DM, phytate hydrolysis was significantly lower. The amount of soluble mineral was generally increased by P. lycii phytase. Stability of P. lycii phytase during gastric digestion was not found to be critical for phytate hydrolysis. Furthermore, original phytate solubility was not an absolute requirement for phytate degradation; phytate solubility seemed to be in a steady state, allowing insoluble phytate to solubilise as soluble phytate was degraded. This is new and interesting knowledge that adds to the current understanding of phytate-phytase interaction. Copyright © 2007 Society of Chemical Industry.

Interaction of phytate with protein and minerals in a soybean–maize meal blend depends on pH and calcium addition

AbstractIn order to investigate possible interactions of phytate with protein and minerals in simplified animal diets, studies were conducted on the solubility of endogenous phytate, protein and essential minerals in a soybean–maize meal blend within a physiological relevant pH range. The blend was mixed with water for 10 min and then allowed to incubate at 40 °C (30 min) after adjustment of the pH. Finally, soluble phytate, protein, zinc, manganese and iron were determined. Phytate and mineral solubility was highly influenced by pH whereas protein solubility was less affected. Addition of 5 g Ca2+ kg−1 drastically reduced the solubility of phytate, zinc, manganese and iron at pH above 4.4, indicating that the formation of insoluble phytate–mineral complexes is increased in the presence of calcium. The action of pepsin increased the solubility of protein and phytate at pH below 4, indicating that insoluble phytate–protein complexes are present at low pH. Calcium had the same solubilising effect as pepsin at pH 2–4 but to a lesser degree. Copyright © 2007 Society of Chemical Industry

Assimilation of Phytate-phosphorus by the Extracellular Phytase Activity of Tobacco (Nicotiana tabacum) is Affected by the Availability of Soluble Phytate

Phytate, the major organic phosphorus in soil, is not readily available to plants as a source of phosphorus (P). It is either complexed with cations or adsorbed to various soil components. The present study was carried out to investigate the extracellular phytase activities of tobacco (Nicotiana tabacum variety GeXin No.1) and its ability to assimilate external phytate-P. Whereas phytase activities in roots, shoots and growth media of Pi-fed 14-day-old seedlings were only 1.3–4.9% of total acid phosphatase (APase) activities, P starvation triggered an increase in phytase secretion up to 914.9 mU mg−1 protein, equivalent to 18.2% of total APase activities. Much of the extracellular phytase activities were found to be root-associated than root-released. The plants were not able to utilize phytate adsorbed to sand, except when insoluble phytate salts were preformed with Mg2+ and Ca2+ ions for supplementation. Tobacco grew better in sand supplemented with Mg-phytate salts (31.9 mg dry weight plant−1; 0.68% w/w P concentration) than that with Ca-phytate salts (9.5 mg plant−1; 0.42%), presumably due to its higher solubility. We conclude that insolubility of soil phytate is the major constrain for its assimilation. Improving solubility of soil phytate, for example, by enhancement of citrate secretion, may be a feasible approach to improve soil phytate assimilation.

Monitoring the stepwise phytate degradation in the upper gastrointestinal tract of pigs

AbstractThe degradation and formation of inositol phosphates as affected by microbial phytase and gastrointestinal enzyme activities during the passage of phytate through the stomach and small intestine were studied in two experiments with four barrows and three collection periods. The degradation and formation of inositol phosphates were measured at the duodenal and ileal sites using Cr‐NDR, TiO2and Co‐EDTA as indigestible markers. In experiment 1, the effect of graded doses ofAspergillus nigerphytase (0, 150 and 900 FTU Natuphos®kg−1), added to a maize–soybean meal‐based diet with very low intrinsic phytase activity on the degradation of phytate and the formation of inositol phosphates during digestion in the stomach and small intestine was investigated. In experiment 2, three different mixtures of inositol phosphates, produced byAspergillus nigerphytase, containing mainly high, intermediate and low phosphorylated inositol phosphates, were added to the same maize–soybean meal‐based diet as used in experiment I. The fate of the inositol phosphates during digestion in the stomach and small intestine was studied. Experiment 1 showed that the extent of phytate degradation was dependent of the graded dietary phytase activities. At high phytase activity (900 FTU kg−1of diet), strong phytate degradation occurred and the once hydrolysed phytate was rapidly dephosphorylated to lower inositol phosphates (mainly inositol di‐ and triphosphates). Intermediate inositol phosphates, such as inositol tetraphosphates, were quantitatively unimportant in duodenal and ileal digesta. At a phytase activity of 150 FTU kg−1of diet, a broader spectrum of intermediate inositol phosphates was determined, which was probably due to a slower breakdown of phytate. Experiment 2 showed as a predominant result that lower inositol phosphates such InsP4and InsP3were degraded, whereas InsP2accumulated in the duodenal and ileal digesta. No substantial disappearance of phytate from the stomach and small intestine was found when high concentrations of soluble phytate were added to the diet, which indicates that no substantial phytate absorption occurs in the upper part of the pig gut. Copyright © 2005 Society of Chemical Industry

Hydrolysis of precipitated phytate by three distinct families of phytases

While genetically modified plants that secrete histidine acid phosphatases (HAPs), β-propeller phytases (BPPs) and purple acid phosphatases (PAPs) have been shown to assimilate soluble phytate, little is known about whether these plants have the ability to hydrolyze precipitated phytate. In this study, the ability of representative members of these three classes of phytases to hydrolyze metal-phytate salts and to hydrolyze phytate adsorbed to aluminum precipitates was compared. All three phytases were able to hydrolyze Ca 2+-, Mg 2+-, and Mn 2+-phytates, but were unable to hydrolyze Al 3+-, Fe 2+-, Fe 3+-, Cu 2+-, and Zn 2+-phytates. When these ions were present, the hydrolysis of Ca 2+-phytate was prevented. Citrate was more potent than malate and oxalate in solubilizing some of these phytate salts for enzyme hydrolysis. Phytate adsorbed to aluminum precipitates was resistant to all three enzymes, except when organic acids were added (citrate>oxalate>malate). While increasing concentrations of organic acids were inhibitory to enzyme activity (oxalate >citrate>malate), PAP was more resistant to citrate than HAP. As desorption of phytate from a solid surface by organic acids is essential for phytase activity, the genetic engineering of plants that enhances the secretion of both citrate and phytases from the root may be a feasible approach to improving soil phytate assimilation.

The use of inositol hexaphosphate as a phosphorus source by mycorrhizal and non‐mycorrhizal Scots Pine (Pinus sylvestris)

1. The external mycelia of the ectomycorrhizal fungi Thelephora terrestris and Suillus luteus, associated with Pinus sylvestris roots, exhibited a substantial extracellular acid phosphatase activity. The activity was positively correlated with the ergosterol concentration in the growth substratum and decreased with an increasing P nutrition. 2. The pioneer species T. terrestris grew best at a high Pi nutrition level whereas S. luteus, a ‘late‐stage’ mycobiont, produced more active biomass at a low Pi nutrition level. 3. The phytase activity of the external mycelia could not be detected; at the root surface a phytase activity was observed. Mycorrhizas had significantly higher activities than uninfected roots. 4. The addition of a relatively high concentration of a soluble phytate to the growth substratum resulted in an increased relative growth rate (RGR) in both mycorrhizal and non‐mycorrhizal plants. The influence of the mycorrhizal fungi on the use of the phytate‐P was small, despite the phytase activity of the mycorrhizal feeder roots. 5. The addition of phytate fixed on a HPLC resin did not result in an increase of the RGR and P uptake neither in the non‐mycorrhizal nor in the mycorrhizal Pines. The experiment did not support the hypothesis that phytate, which has a low solubility in soils, is a useful P source for ectomycorrhizal plants.

Effect of Varying Concentrations of Phytate, Calcium, and Zinc on the Solubility of Protein, Calcium, Zinc, and Phytate in Soy Protein Concentrate

The phytate x Ca:Zn millimolar ratio was varied in a number of soy protein concentrates and subjected to a sequential pH treatment to simulate gastrointestinal conditions. In two independent studies, calcium was either decreased incrementally from 4.94 to 0.25 mmol or zinc was increased from 0.0036 to 0.55 mmol. At the lowest level of calcium, a significant increase (P < 0.01) in soluble zinc and soluble phytate was Observed at pH 5.5, due to the possible formation of a soluble calcium-phytate-zinc complex. Soluble zinc significantly increased (P < 0.01) only when the level of zinc was raised to 0.55 mmol. Neither soluble calcium nor soluble phytate was altered at this level.

Growth characteristics of Laccaria laccata and Paxillus involutus in liquid culture media with inorganic and organic phosphorus sources

Two ectomycorrhizal species, Laccaria laccata (Scop, ex Fr.) Berk &amp; Br. and Paxillus involutus (Batch, ex Fr.) Fr., were grown aseptically in liquid media to determine their ability to use soluble phytate as a sole source of phosphorus. Efficiency of glucose utilization and rates of acid production were also determined. Both species grew well with phytate as the sole source of phosphorus and released large amounts of inorganic phosphorus to the medium. However, L. laccata hydrolysed the phytate during exponential growth, whereas P. involutus cultures showed accumulation of inorganic phosphate during the senescence stage, suggesting that hydrolysis was occurring after release of intracellular phosphatases from lysing cells in the latter case and by surface-active enzymes in the former. Paxillus involutus had a lower glucose utilization efficiency per unit biomass than L. laccata. Paxillus involutus also acidified the growing medium more strongly than L. laccata and it released large amounts of pigmented substances into the medium.

Effects of Ca(II) ions on Cu(II) ion-phytic acid interactions

In vitro interactions among phytic acid (PA), Cu(II) ions, and Ca(II) ions were examined as functions of PA:Cu(II):Ca(II) molar ratios and pH. Ca(II) ions competed with Cu(II) ions for binding by the soluble phytate species for PA:Cu(II) molar ratios ranging from 10:1 to 1:6 and pH values in the 2.4–5.9 range. At pH values where precipitation occurred, Ca(II) ions potentiated Cu(II) ion binding by the precipitated phytate species for PA:Cu(II) molar ratios of 10:1 to 1:3. At lower PA:Cu(II) molar ratios, Ca(II) ions competed with Cu(II) ions for binding by the precipitated phytate species. Compositions of the precipitated copper-calcium phytates are reported.

Comparative toxicity of arsenite and arsenate to rice seedling under various levels of phosphate supply

Abstract Toxic effects of arsenite and arsenate on the elongation of rice radicle or plumule were compared under various levels of phosphate application. The toxicity of arsenite was almost independent of added phosphate and the lethal concentration was found to tend to be 10-4.0, M, whereas that of arsenate was antagonistically reduced by phosphate appIied in the range from a little lower than 10-4.5 to 10-2.5 M without supply of the other nutrients and to 10-2.0 M with it, though at 10-5.5 M of phosphate the growth response to arsenate was similar to that without phosphate and the antagonism seemed to be no longer brought about. The application of soluble phytate did not show such an effect as the phosphate. The above lethal concentration of arsenite was found to be equal to that of arsenate in the middle range of 10-6.5 and 10-3.5 m of phosphate irrespective of the co-existence of other nutrients. Below this phosphate level, therefore, arsenate came to exceed arsenite in toxicity to rice seedling. These observations lead to the tentative eonclusion that the common view that arsenite is more toxic than arsenate without regard to the status of co-existing phosphate is questionable.

Availability to Rats of Zinc from Soybean Seeds as Affected by Maturity of Seed, Source of Dietary Protein, and Soluble Phytate

Male rats were used to assess the availability of zinc in soybean seeds (Glycine max, var. ‘Amsoy’) as affected by maturity of seed, dietary protein source, and exogenous dietary sodium phytate. Seeds were harvested from either 84-(immature) or 120-day-old (mature) plants grown in 65Zn-labeled nutrient solutions that contained either 0.066 or 0.262 ppm zinc as zinc sulfate. Increased zinc supply to plants increased the zinc content of seeds; immature seeds had higher concentrations of zinc than mature seeds. Phytic acid concentration averaged about 0.6 and 1.7% dry weight in immature and mature seeds, respectively. Seeds of each type were incorporated into fed to zinc-depleted rats. In experiment 1, rats fed mature, high-phytate seeds absorbed about 60% of the 65Zn in the seeds, whereas rats fed immature, low-phytate seeds absorbed about 89% of the 65Zn (P < 0.05). In experiment 2, the source of dietary protein (egg albumen or soy protein) did not markedly affect 65Zn absorption by rats fed mature soybean seeds. In experiment 3, dietary sodium phytate (1.76% of diet as phytic acid) depressed (P < 0.05) 65Zn absorption by about 16 and 44% from mature soybean seeds and zinc suflate, respectively. Zinc in soybean seeds apparently was as readily available to rats as that reported for other legume and cereal seeds. Moreover, the nutritional quality of soybean seeds with respect to zinc apparently can be increased by increasing zinc supplies to plants.zinc zinc availability phytic acid Phytin soybeans