Microbial Phytases and Phytate: Exploring Opportunities for Sustainable Phosphorus Management in Agriculture

Myo-inositol phosphates (phytates) are important biological molecules produced largely by plants to store phosphorus. Phytate is very abundant in many different soils making up a large portion of all soil phosphorus. This review assesses current phytase science from the perspective of its substrate, phytate, by examining the intricate relationship between the phytate-hydrolyzing enzymes and phytate as their substrate. Specifically, we examine available data on phytate’s structural features, distribution in nature and functional roles. The role of phytases and their localization in soil and plant tissues are evaluated. We provide a summary of the current biotechnological advances in using industrial or recombinant phytases to improve plant growth and animal nutrition. The prospects of future discovery of novel phytases with improved biochemical properties and bioengineering of existing enzymes are also discussed. Two alternative but complementary directions to increase phosphorus bioavailability through the more efficient utilization of soil phytate are currently being developed. These approaches take advantage of microbial phytases secreted into rhizosphere either by phytase-producing microbes (biofertilizers) or by genetically engineered plants. More research on phytate metabolism in soils and plants is needed to promote environmentally friendly, more productive and sustainable agriculture.

Combining Phytate/Ca^(2+) Fractionation with Trichloroacetic Acid/Acetone Precipitation Improved Separation of Low-Abundant Proteins of Wheat (Triticum aestivum L.) Leaf for Proteomic Analysis

Proteomic assessment of low-abundance leaf proteins is hindered by the large quantity of ribulose-1,5-bisphosphate carboxylase/oxygenase （Rubisco） present within plant leaf tissues. In the present study, total proteins were extracted from wheat （Triticum aestivum L.） leaves by a conventional trichloroacetic acid （TCA）/acetone method and a protocol first developed in this work. Phytate/Ca2＋ fractionation and TCA/acetone precipitation were combined to design an improved TCA/acetone method. The extracted proteins were analysed by two-dimensional gel electrophoresis （2-DE）. The resulting 2-DE images were compared to reveal major differences. The results showed that large quantities of Rubisco were deleted from wheat leaf proteins prepared by the improved method. As many as （758±4） protein spots were detected from 2-DE images of protein extracts obtained by the improved method, 130 more than those detected by the TCA/acetone method. Further analysis indicated that more protein spots could be detected at regions of pI 4.00-4.99 and 6.50-7.00 in the improved method-based 2-DE images. Our findings indicated that the improved method is an efficient protein preparation protocol for separating low-abundance proteins in wheat leaf tissues by 2-DE analysis. The proposed protocol is simple, fast, inexpensive and also applicable to protein preparations of other plants.

Association of Phytate Formation with Grain Filling in Rice

The grain-filling characteristics of six rice varieties (combinations) and the relationships between their relative biochemistry composition during phytate synthesizing and grain plumpness were studied. Regarding results for ISHR1, ISHR2, R198 and JW21, with good grain plumpness, the two-step-filling in superior spikelets and inferior spikelets was not clear, while for ISHR3 and 559, with poor grain plumpness, it was very clear. From booting stage to flowering stage, the contents of phytate and inositol in varieties with good grain plumpness was obviously higher than those in varieties with poor grain plumpness. While at grain filling stage, the content of inorganic phosphorus in varieties with poor grain plumpness was obviously higher than that in varieties with good grain plumpness. The contents of phytate and inositol from booting stage to flowering stage was highly significantly correlated with the initial filling power (R_0), the mean filling rate (R_M) and grain filling percentage (P_(GF)), and the content of inorganic phosphorus at grain filling stage was negatively significantly correlated with R_0, F_M and P_(GF). Furthermore, effective approach to improving grain filling was put forward.

Effect of phytate on the amylosynthetase activity and rice grain quality

Phytate of three concentrations was sprayed on the leaves of an indica rice Yuanfengzao in heading stage, full heading stage, filling stage and wax ripeness stage respectively. The effects of phytate on the enzyme activity in endosperm and rice grain quality were determinated. Plants sprayed with distilled water were used as control. It was showed that spraying solutions in full heading stage had the most manifest effect. The activity of amylosynthetase between the 100mg/kg and 150mg/kg phytate treatment was identical, which was 7.4% higher than that of 50mg/kg treatment. On the other hand, amylase activity on the 50mg/kg treatment was 12.5% and 8.7% lower than those

Amino acid and mineral digestibility,bone ash,and plasma inositol is increased by including microbial phytase in diets for growing pigs

Background The effect of microbial phytase on amino acid and energy digestibility is not consistent in pigs,which may be related to the phytase dosage or the adaptation length to the diet.Therefore,an experiment was conducted to test the hypotheses that increasing dietary phytase after an 18-day adaptation period:1)increases nutrient and energy digestibility;2)increases plasma P,plasma inositol,and bone ash of young pigs;and 3)demonstrates that maximum phytate degradation requires more phytase than maximum P digestibility.Results Data indicated that increasing inclusion of phytase[0,250,500,1,000,2,000,and 4,000 phytase units(FTU)/kg feed]in corn-soybean meal-based diets increased apparent ileal digestibility(AID)of Trp(quadratic;P<0.05),and of Lys and Thr(linear;P<0.05),and tended to increase AID of Met(linear;P<0.10).Increasing dietary phytase also increased AID and apparent total tract digestibility(ATTD)of Ca and P(quadratic;P<0.05)and increased ATTD of K and Na(linear;P<0.05),but phytase did not influence the ATTD of Mg or gross energy.Concentrations of plasma P and bone ash increased(quadratic;P<0.05),and plasma inositol also increased(linear;P<0.05)with increasing inclusion of phytase.Reduced concentrations of inositol phosphate(IP)6 and IP5(quadratic;P<0.05),reduced IP4 and IP3(linear;P<0.05),but increased inositol concentrations(linear;P<0.05)were observed in ileal digesta as dietary phytase increased.The ATTD of P was maximized if at least 1,200 FTU/kg were used,whereas more than 4,000 FTU/kg were needed to maximize inositol release.Conclusions Increasing dietary levels of phytase after an 18-day adaptation period increased phytate and IP ester degradation and inositol release in the small intestine.Consequently,increasing dietary phytase resulted in improved digestibility of Ca,P,K,Na,and the first 4 limiting amino acids,and in increased concentrations of bone ash and plasma P and inositol.In a corn-soybean meal diet,maximum inositol release requires approximately 3,200 FTU/kg more phytase than that required for maximum P digestibility.

Effect of Soybean Cultivars on the Nutrients and Consumer Acceptance of Soymilk

Soymilk is one of the most available beverages, an alternative to dairy milk and is recognized for its nutritional value. The nutritional quality, the presence of anti-nutritional factors, isoflavones and sensory acceptability of soymilk depended on the soybean variety as well as the processing conditions. The soymilks from conventional and specialty Brazilian soybean cultivars were compared regarding the composition and consumer acceptance. There were significant differences on the protein, oil, sugars, isoflavones, presence of anti-nutritional factors (phytate and trypsin inhibitor activity) and NSI (nitrogen solubility index) among cultivars and soymilks and for sensory acceptance of soymilks. The preference mapping and cluster analysis identified three different segments of consumers. The soymilk from the conventional cultivar BRS284 achieved higher and similar acceptance score for the three consumer’s segments while the lipoxygenase free cultivars (BRS213 and BRS257) and specialty cultivar BRS216 showed higher score for two segments of consumers. The sensory evaluation of soymilk from different soybean cultivars could improve consumer uptake.

Phytate-Coordination Triggered Enrichment of Surface NiOOH Species on Nickel Foam for Efficient Urea Electrooxidation

Nickel(Ni)-based materials are promising electrocatalysts for the urea electrooxidation reaction, as the in situ formed NiOOH species on their surface during operation are catalytically active sites. In this work, phytate-coordinated Ni foam(PA-NF)is shown to deliver a high catalytic performance, with a potential as low as 1.38 V at 10m A/cm2, a Tafel slope as low as 64.1 mV/dec, and superior catalytic stability. Characterizations revealed that such a high performance was ascribed to the kinetic acceleration of surface reconstruction and the enriched NiOOH active species on the PA-NF surface owing to PA-coordination induced upshift of d-band center of Ni sites.Overall, a novel and simple strategy is provided for designing the efficient as well as universal Ni-based catalyst for the electrooxidation of urea, which can also be extended to other transition-metal-based systems.

Phytate and phosphorus utilization by broiler chickens and laying hens fed maize-based diets

Maize grain is primarily used as an energy source for poultry and other animals.Maize has relatively high phytate-P content and very low intrinsic phytase activity.Given that feed phosphates are produced from finite rock phosphate resources,a reduction in the use of feed phosphates in maize-based diets by increasing the utilization of plant P sources by animals is necessary to make poultry meat and egg production more sustainable.The utilization of P by poultry is affected by two intrinsic characteristics of maize:the concentration of inositol phosphates and the activity of the intrinsic phytase of the grain in the digestive tract.The objective of this review is to present data on the variation that exists in composition of maize relevant for P use and to address factors that influence P utilization in maize-based diets of poultry.Broiler chickens and laying hens have the potential to degrade phytate in the gastrointestinal tract,but this is depressed by high dietary Ca and P concentrations.Published values of phytate degradation in broilers are overall higher than those in laying hens.Differences also exist between broiler chickens and growing turkeys and Pekin ducks.The exogenous supplementation of microbial phytases and the introduction of transgenic high phytase maize in poultry diets are efficient not only for the improvement of phytate-P digestibility,production performance,egg quality and bone mineralization,but also for the reduction of P excreta to control environmental impact.

Effect of feeding broilers diets differing in susceptible phytate content

Measurements of total phytate phosphorus content of diets may be deceptive as they do not indicate substrate availability for phytase; it may be that measurements of phytate susceptible to phytase effects are a more accurate measure of phosphorus(P) availability to the bird. To verify this hypothesis, an experiment was conducted to compare diets formulated to contain either high or low susceptible phytate, supplemented with either 0 or 500 FTU/kg phytase. Susceptible phytate was determined by exposing the feed samples to conditions that mimicked the average pH of the proximal gastrointestinal tract(pH 4.5) and the optimum temperature for phytase activity(37℃) and then measuring phytate dissolved. Ross 308 birds(n = 240) were fed one of 4 dietary treatments in a 2 x 2 factorial design; 2 diets with high(8.54 g/kg, 57.90% of total phytate) or low(5.77 g/kg, 46.33% of total phytate) susceptible phytate, containing 0 or 500 FTU/kg phytase. Diets were fed to broilers(12 replicate pens of 5 birds per pen) from d 0 to 28 post hatch. Birds fed diets high in susceptible phytate had greater phytate hydrolysis in the gizzard(P < 0.001), jejunum(P < 0.001) and ileum(P < 0.001) and resulting greater body weight gain(BWG)(P = 0.015) and lower FCR(P = 0.003) than birds fed the low susceptible phytate diets,irrespective of phytase presence. Birds fed the high susceptible diets also had greater P solubility in the gizzard and Ca and P solubility in the jejunum and ileum(P < 0.05) and resulting greater tibia and femur Ca and P(P < 0.05) content than those fed the low susceptible diets. All the susceptible phytate was fully degraded in the tract in the absence of added phytase, suggesting the assay used in this study was able to successfully estimate the amount of total dietary phytate that was susceptible to the effects of phytase when used at standard levels. No interactions were observed between susceptible phytate and phytase on phytate hydrolysis. Hydrolysis of phytate was greater(P < 0.05) in the gizzard of birds fed the diets supplemented with phytase, regardless of the concentration of susceptible phytate in the diet. Phytase supplementation resulted in improved BWG(P < 0.001) and FCR(P = 0.001), increased P solubility(P < 0.001) in the gizzard, Ca and P solubility(P < 0.001) in the jejunum and ileum and Ca and P concentration(P < 0.001) and strength(P < 0.001) in the tibia and femur. Pepsin activity was higher in birds fed the diets supplemented with phytase(P < 0.001) and was greater(P = 0.031) in birds fed the high susceptible phytate diets compared with the low susceptible phytate diets. Findings from this study suggest that there may be a measure more meaningful to animal nutritionists than measurements of total phytate.

A novel microcosm to identify inherently competitive microorganisms with the ability to mineralize phytate in solum

Fertilizer phosphorus(P)is a finite resource,necessitating the development of innovative solutions for P fertilizer efficiency in agricultural systems.Myo-inositol hexakisphosphate(phytate)constitutes the majority of identified organic P in many soil types and is poorly available to plants.Incorporating phytase-producing biofertilizers into soil presents a viable and environmentally acceptable way of utilizing P from phytate,while reducing the need for mineral P application.A deeper understanding of the microbial ecology in relation to degradation of phytate under natural soil conditions is however needed to obtain successful biofertilizer candidates able to compete in complex soil environments.Here we present the development of a microcosm for studying microbial communities able to colonize and utilize Ca-phytate hotspots in solum.Our results provide evidence that the recruited microbial population mineralizes Ca-phytate.Furthermore,quantification of bacterial genes associated with organic P cycling in alkaline soils indicated that the phosphatases PhoX and PhoD may play a larger role in phytate mineralization in soil than previously recognized.Amplicon sequencing and BioLog®catabolism studies show that hotspots containing Ca-phytate,recruited a different set of microorganisms when compared to those containing an addition of C source alone,with the genus Streptomyces specifically enriched.We propose that Streptomyces represents an hitherto unexplored resource as P biofertilizer with competitive advantage for utilizing CaPhy in an inherently competitive soil environment.We further conclude that the use of our newly designed microcosm presents an innovative approach for isolating soil microorganisms with the potential to degrade precipitated phytate in solum.

Effect of dephytinization on bioavailability of iron,calcium and zinc from infant cereals assessed in the Caco-2 cell model

AIM： To test the effect of the dephytinization of three different commercial infant cereals on iron, calcium, and zinc bioavailability by estimating the uptake, retention, and transport by Caco-2 cells. METHODS： Both dephytinized （by adding an exogenous phytase） and non-dephytinized infant cereals were digested using an in vitro digestion protocol adapted to the gastrointestinal conditions of infants younger than 6 too. Mineral cell retention, transport, and uptake from infant cereals were measured using the soluble fraction of the simulated digestion and the Caco-2 cells. RESULTS： Dephytinization of infant cereals significantly increased （P 〈 0.05） the cell uptake efficiency （from 0.66%-6.05% to 3.93%-13%）, retention （from 6.04%-16.68% to 14.75%-20.14%） and transport efficiency （from 0.14%-2.21% to 1.47%-6.02%）, of iron, and the uptake efficiency （from 5.0%-35.4% to 7.3%-41.6%） and retention （from 4.05%-20.53% to 14.45%-61.3%） of zinc, whereas calcium only cell uptake showed a significant increase （P 〈 0.05） after removing phytate from most of the samples analyzed. A positive relationship （P 〈 0.05） between mineral solubility and the cell uptake and transport efficiencies was observed. CONCLUSION： Removing phytate from infant cereals had a beneficial effect on iron and zinc bioavailability when infant cereals were reconstituted with water. Since in developing countries cereal-based complementary foods for infants are usually consumed mixed with water, exogenous phytase additions could improve the nutritional value of this weaning food.

Hollow Bio-derived Polymer Nanospheres with Ordered Mesopores for Sodium-Ion Battery

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials.However,the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure.Here,we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy,using phytic acid-based natural compounds as an example,for the spatially controlled fabrication of metal coordination bio-derived polymers.The resultant ferric phytate polymer nanospheres feature hollow architecture,ordered meso-channels of^12 nm,high surface area of 401 m2 g−1,and large pore volume of 0.53 cm3 g−1.As an advanced anode material,this bio-derivative polymer delivers a remarkable reversible capacity of 540 mAh g−1 at 50 mA g−1,good rate capability,and cycling stability for sodium-ion batteries.This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.

Treatment of zinc deficiency without zinc fortification

Zinc(Zn) deficiency in animals became of interest until the 1950s.In this paper,progresses in researches on physiology of Zn deficiency in animals,phytate effect on bioavailability of Zn,and role of phytase in healing Zn deficiency of animals were reviewed.Several studies demonstrated that Zn is recycled via the pancreas;the problem of Zn deficiency was controlled by Zn homeostasis.The endogenous secretion of Zn is considered as an important factor influencing Zn deficiency,and the critical molar ratio is 10.Phytate(inositol hexaphosphate) constituted up to 90% of the organically bound phosphorus in seeds.Great improvement has been made in recent years on isolating and measuring phytate,and its structure is clear.Phytate is considered to reduce Zn bioavailability in animal.Phytase is the enzyme that hydrolyzes phytate and is present in yeast,rye bran,wheat bran,barley,triticale,and many bacteria and fungi.Zinc nutrition and bioavailability can be enhanced by addition of phytase to animal feeds.Therefore,using phytase as supplements,the most prevalent Zn deficiency in animals may be effectively corrected without the mining and smelting of several tons of zinc daily needed to correct this deficiency by fortification worldwide.

Soy Consumption and Obesity

Obesity is now present worldwide, including China, India and developing countries. It now seems no longer acceptable to argue that obesity can simply be explained in terms of caloric consumption only using simple concept of energy in and energy out. There may be specific causes of altered metabolism that produce nutritional imbalances. Individual variation in response to food intake may also be considered. Specific substances in the food chain can influence meta-bolism towards an increase in fat deposits. Xenoestrogens have been suggested to have such an influence. Soy contains phytoestrogens plus phytates, protease inhibitors and other anti-nutrients which block or compromise the body’s uptake of essential vitamins and minerals. This may contribute to nutritional anomalies. We analyzed data from WHO and FAO for 167 countries. These contained percentage of obese individuals (BMI > 30 kg/m2), GDP, caloric consump-tion per capita, and sugar and soy consumption per capita. Regressions and partial correlations were used. Soy con-sumption correlates significantly with levels of obesity, irrespective of GDP and caloric intake. For instance, poor Latin America with soy consumption of 28.9 kg/person/year has more obesity (18.4%) than better off European Union (14.1%) consuming 16.1 kg/person/year of soy. Soy consumption seems to contribute approximately 10% - 21% to the worldwide variation in obesity, depending on the method of statistical analysis. The ubiquitous presence of unfermented soy products in mass produced foods seems to be an important contributor to the obesity epidemic.

Effect of Indigenous Phytase-Producing Yeast Cultures on Growth Performance, Digestion and Health of Rabbits (Oryctolagus cuniculus)

This study investigated the effects of dietary supplementation of indigenous phytase producing live yeast cultures on growth performance, phytate degradation and blood biochemical parameters of weanling rabbits. Fifty-six rabbits (28 males and 28 females) were allotted randomly into four groups containing a control and three groups administrated each with the yeasts Saccharomyces cerevisiae ADR1B1, Hanseniaspora jakobsenii ADR3E1, Hanseniaspora guilliermondii RD31 during 8 weeks. The results showed that the administration of the three yeast strains accelerated the weight gain and improved rabbits growth performance in comparison to the control group, but did not affect the serum biochemical and hematological parameters. The highest weight gain (1715.95 ± 236 g), and phytate degradation rate (73.82% ± 0.92%) and the lowest biochemical parameters (triglycerides, cholesterol, HDL and LDL) were observed on rabbits fed with the yeast Hanseniaspora jakobsenii ADR3E1. This indigenous yeast species, which is used for the first time in animal feeding provided the best beneficial effects in rabbit breeding. Therefore, based on this finding, Hanseniaspora jakobsenii ADR3E1 can be recommended to supplement rabbit diets for growth performance and profitability enhancement.

Secretive expression of Aspergillus fumigatus phytase in tobacco improves phosphorus nutrition in plant

To generate transgenic plants capable of utilizing exogenous phytate, an Aspersgillus fumigatus phytase gene （fphyA） was constitutively expressed in tobacco and recombinant enzyme was secreted from plant roots into the rhizosphere using the signal sequence from tobacco calreticulin. After 40 days of plant growth in hydroponic media, phytase activities in leaves, stems, roots and growth media of transgenic plants were 8.6-fold, 7.4-fold, 12.6-fold and 14.3-fold higher than those of wild-type plants. Signifi- cant improvements in plant growth and phosphorus （P） utilization were observed in the transgenic plants. When phytate was supplied as the sole P source, 45-day-old transgenic tobaccos accumulated 1.0-fold and 0.5-fold more shoot and root biomass than wild-type tobaccos, with a concomitant of l. 7-fold increase in total P concentration. These results indicate that secretive expression of the A. fumigatus phytase improves acquisition and use of P from phytate in plants.

Nutritional Status of Patients with Cutaneous Leishmaniasis from a Tropical Area of Bolivia, and Implications for Zinc Bioavailability

Macro and micronutrient deficiencies are a significant problem among people in rural areas in developing countries. Deficiencies may lead to an impaired immune system making the organism vulnerable to infections and diseases. In this paper, the dietary intake, anthropometric measurements, zinc and copper levels in serum, of patients with cutaneous leishmaniasis (CL) are compared with a group of healthy controls and reference values. Results showed no significant differences in most nutrient intake or anthropometrics between patients and controls. However, serum zinc level of patients (80 μg/dl) was significantly lower (P 0.001) than in controls (85 μg/dl), likely explained by the presence of leishmaniasis. The median serum zinc level in both groups was below the reference values, even though their median zinc intake met the zinc recommendations from WHO. Consequently, besides the presence of leishmaniasis, serum zinc levels may be compromised by inhibitory components in their diet, such as phytates, as it is shown by the molar ratio phytate:zinc (Phy:Zn) that was between 11 and 19, while 15 is the level said to compromise zinc status. There were significant (P 0.05) negative correlations between serum zinc and Phy:Zn, for patients (r = - 0.413) and controls (r = - 0.410). In conclusion this study shows that patients with CL in Chapare, Bolivia had low serum zinc levels due to the leishmaniasis per se and the decreased zinc bioavailability in their diet. CL infection was not in direct association with the nutritional status indicated by the anthropometric or dietary assessments. However, dietary intake showed 5 essential nutrients below the nutrient recommendation in both groups.

Fermentation Effect on the Nutrient and Antinutrient Composition of <i>Senegalia macrostachya</i>and <i>Parkia biglobosa</i>Seeds: A Comparative Study

This study aimed to evaluate the effect of the fermentation on the nutrient and antinutrient composition of Senegalia macrostachya and Parkia biglobosa seeds. For condiments production, the raw seeds were cleaned, cooked, drained, washed, cooked, drained and fermented. Results show that the pH increased (from 6.09 to 7.76 and from 6.99 to 7.92) from the onset of the fermentation till 48 h during fermentation of Senegalia macrostachya and Parkia biglobosa seeds respectively. Biochemical analyses revealed a slight increase in water content, ashes, lipids, minerals and a decrease in total carbohydrate for the two products. The fermentation of Senegalia macrostachya and Parkia biglobosa seeds reduced the initial phytates content by 38.21% and 41.37% respectively. Fermented seeds of Senegalia macrostachya are rich in protein (59.59 ± 0.74 g/100g DM), potassium and magnesium (1076.74 ± 37.49 mg/100g DM and 111.63 ± 06 mg/100g DM respectively) with an appreciable iron content (26.27 ± 0.06 mg/100g DM). Given its nutritional composition, fermented seeds of Senegalia macrostachya could be used as an alternative to soumbala in areas where it is not available.

Nutritional Status of Children with Intestinal Parasites from a Tropical Area of Bolivia,Emphasis on Zinc and Iron Status

Malnutrition and parasitic diseases are within the major issues in rural areas in developing countries. In this study, the nutritional status, dietary intake including mineral absorption inhibitor (phytate), hematological indicators and trace element status (zinc, iron) were evaluated and associated to the presence of intestinal parasites in a group of children from a rural area of Bolivia. The results showed that 96% of the children had intestinal parasites;7 types of parasites (Ascaris lumbricoides, Giardia lamblia, Ancylostoma duodenale, Entamoeba histolytica, Entamoeba coli, Trichuris trichiura, Strongyloides stercolaris) were identified. Anthropometric measurements indicated that 37% of the children were stunted and 17% were underweight. Iron and zinc intake showed that 34% and 30% of children had inadequate intake of these nutrients respectively. Phytate: zinc molar ratios were between 6.5 and 21, and from 6.2 to 15 for phytate: iron, indicating that the absorption of zinc and iron might be compromised by the level of phytate in the diet. The serum zinc was below the lower cut-off in 87% of the children, indicating zinc deficiency. Moreover, a multiple regression model showed the significant effect of the presence of the parasite Giardia lamblia and phytate intake on the serum zinc levels. Regarding the iron status, 30% of the children presented with anemia and about 66% had iron deficiency;a simple linear regression model showed the significant negative effect of the presence of the parasite Ancylostoma duodenale on iron status. In conclusion, the levels of zinc and iron, which were low in this child population, were greatly affected by the presence of intestinal parasites;in addition, the consumption of plant-based diets with high levels of phytate also impaired the zinc absorption.

Applied and Environmental Chemistry of Animal Manure:A Review

Animal manure consists of predominantly urine and feces, but also may contain bedding materials, dropped feed, scurf, and other farming wastes. Manure is typically applied to soils as fertilizer for agricultural production. The estimated amount of manure produced in 12 major livestock-producing countries is 9 × 10^9 Mg of manure annually. Manure is rich in plant nutrients. However, manure is also considered as an environmental pollutant when it is over-applied to cropland or following runoff into surface water. Manure can also influence global climate change via emissions of methane （CH4） and nitrous oxide （N2O）. Thus, increased and updated knowledge of applied and environmental chemistry of animal manure is needed to shed light on the research and development of animal manure utilization and minimization of its adverse environmental concerns. The advances in basic and applied studies of manure major components, organic matter, phosphorus, and nitrogen, primarily related to US livestock production are summarized in this review. Detailed focus was placed on three notable challenges for future manure research： 1） soil application of animal manure, 2） manure phytate phosphorus, and 3） manure nitrogen availability. This review may contribute to the global effort in sustainable and environmentally sound agriculture by stimulating new ideas and directions in animal manure research, and promoting application of knowledge and insight derived from manure research into improved manure management strategies.