Cloning of the thermostable phytase gene (phy) from Bacillus sp. DS11 and its overexpression in Escherichia coli

Prospects for Using Phosphate-Solubilizing Microorganisms as Natural Fertilizers in Agriculture

Phosphates are known to be essential for plant growth and development, with phosphorus compounds being involved in various physiological and biochemical reactions. Phosphates are known as one of the most important factors limiting crop yields. The problem of phosphorus deficiency in the soil has traditionally been solved by applying phosphate fertilizers. However, chemical phosphate fertilizers are considered ineffective compared to the organic fertilizers manure and compost. Therefore, increasing the bioavailability of phosphates for plants is one of the primary goals of sustainable agriculture. Phosphate-solubilizing soil microorganisms can make soil-insoluble phosphate bioavailable for plants through solubilization and mineralization. These microorganisms are currently in the focus of interest due to their advantages, such as environmental friendliness, low cost, and high biological efficiency. In this regard, the solubilization of phosphates by soil microorganisms holds strong potential in research, and inoculation of soils or crops with phosphate-solubilizing bacteria is a promising strategy to improve plant phosphate uptake. In this review, we analyze all the species of phosphate-solubilizing bacteria described in the literature to date. We discuss key mechanisms of solubilization of mineral phosphates and mineralization of organic phosphate-containing compounds: organic acids secreted by bacteria for the mobilization of insoluble inorganic phosphates, and the enzymes hydrolyzing phosphorus-containing organic compounds. We demonstrate that phosphate-solubilizing microorganisms have enormous potency as biofertilizers since they increase phosphorus bioavailability for the plant, promote sustainable agriculture, improve soil fertility, and raise crop yields. The use of phosphate-solubilizing microbes is regarded as a new frontier in increasing plant productivity.

Research status of Bacillus phytase

Phytic acid is abundant in seeds, roots and stems of plants, it acts as an anti-nutrient in food and feed industry, since it affects the absorption of nutrients by humans and monogastric animals. Furthermore, phosphorus produced through its decomposition by microorganisms can cause environmental pollution. Phytase degrades phytic acid generating precursors of inositol that can be used in clinical practice; in addition, phytase treatment can minimize the anti-nutritional effect of phytic acid. The use of phytase synthesized from Bacillus is more advantageous due to its high activity. Additionally, its good heat resistance under neutral conditions greatly fills the gap of commercial utilization of acid phytase. In this review, we summarize the latest research results on Bacillus phytase, including its physiological and biochemical characteristics, molecular structure information, calcium effects on its catalytic activity and stability, its catalytic mechanism and molecular modification.

Identification of two novel bacterial phosphatase-encoding genes in Pseudomonas putida strain P13

AIMS

Isolation and identification of genes encoding putative phosphatases from Pseudomonas putida strain P13 DSM 23335.

METHODS AND RESULTS

By functional screening of a P. putida P13 genomic library, a number of Pho⁺ clones were identified. Two genes were identified that encoded proteins exhibiting both phytase and sugar phosphatase activities. The proteins were 249 and 462 amino acids, with molecular masses of 26 and 50 kDa respectively. Sequence alignments revealed no significant similarities to representatives of known phosphatase or phytase gene families. However, the genes were found to have a high similarity to members of the major facilitator superfamily (MFS). Both genes were overexpressed in Escherichia coli and the corresponding partially purified recombinant enzymes were found to have significant phytate-dephosphorylating activity. The protein designated P. putida phytase 1 (Ppp1) displayed the highest activity among potential substrates studied on Na phytate, whereas Ppp2 more likely represents a sugar phosphatase than a phytase. The optimal conditions for phytate dephosphorylation were determined as 60°C and pH 4·5 (Ppp1) or pH 5·0 (Ppp2).

CONCLUSIONS

Two novel bacterial phosphatase-encoding genes, named ppp1 and ppp2, were isolated from P. putida P13 DSM 23335 by a functional screening procedure.

SIGNIFICANCE AND IMPACT OF THE STUDY

Phosphatase-encoding genes are of great importance for industrial applications, particularly in agriculture. The identified phosphatase genes represent a new class of acid phosphatases.

Screening and Characterization of Phytases from Bacteria Isolated from Chilean Hydrothermal Environments

Phytases are enzymes involved in organic phosphorus cycling in nature and widely used as feed additives in animal diets. Thermal tolerance is a desired property of phytases. The objectives of this study were to screen and characterize bacterial phytases from Chilean hydrothermal environments. In this study, 60% (30 of 63) of screened thermophilic (60 °C) isolates showed phytase activity in crude protein extracts. The characterization of phytase from two selected isolates (9B and 15C) revealed that both isolates produce phytases with a pH optimum at 5.0. The temperature optimum for phytate dephosphorylation was determined to be 60 and 50 °C for the phytases from the isolates 9B and 15C, respectively. Interestingly, the phytase from the isolate 15C showed a residual activity of 46% after incubation at 90 °C for 20 min. The stepwise dephosphorylation of phytate by protein extracts of the isolates 9B and 15C was verified by HLPC analysis. Finally, the isolates 9B and 15C were identified by partial sequencing of the 16S rRNA gene as members of the genera Bacillus and Geobacillus, respectively.

β-Propeller phytases: Diversity, catalytic attributes, current developments and potential biotechnological applications

Phytases are phosphatases which stepwise remove phosphates from phytic acid or its salts. β-Propeller phytase (BPPhy) belongs to a special class of microbial phytases that is regarded as most diverse, isolated and characterized from different microbes, mainly from Bacillus spp. BPPhy class is unique for its Ca²⁺-dependent catalytic activity, strict substrate specificity, active at neutral to alkaline pH and high thermostability. Numerous sequence and structure based studies have revealed unique attributes and catalytic properties of this class, as compared to other classes of phytases. Recent studies including cloning and expression and genetic engineering approaches have led to improvements in BPPhy which provide an opportunity for extended utilization of this class of phytases in improving animal nutrition, human health, plant growth promotion, and environmental protection, etc. This review describes the sources and diversity of BPPhy genes, biochemical properties, Ca²⁺ dependence, current developments in structural elucidation, heterogeneous expression and catalytic improvements, and multifarious applications of BPPhy.

Cloning, Codon Optimization, and Expression of Yersinia intermedia Phytase Gene in E. coli

BACKGROUND

Phytate is an anti-nutritional factor in plants, which catches the most phosphorus contents and some vital minerals. Therefore, Phytase is added mainly as an additive to the monogastric animals' foods to hydrolyze phytate and increase absorption of phosphorus.

OBJECTIVES

Y. intermedia phytase is a new phytase with special characteristics such as high specific activity, pH stability, and thermostability. Our aim was to clone, express, and characterizea codon optimized Y. intermedia phytase gene in E. coli .

MATERIALS AND METHODS

The Y. intermedia phytase gene was optimized according to the codon usage in E. coli. The sequence was synthesized and sub-cloned in pET-22b (+) vector and transformed into E. coli Bl21 (DE3). The protein was expressed in the presence of IPTG at a final concentration of 1 mM at 30°C. The purification of recombinant protein was performed by Ni2+ affinity chromatography. Phytase activity and stability were determined in various pH and temperatures.

RESULTS

The codon optimized Y. intermedia phytase gene was sub-cloned successfully.The expression was confirmed by SDS-PAGE and Western blot analysis. The recombinant enzyme (approximately 45 kDa) was purified. Specific activity of enzyme was 3849 (U.mg-1) with optimal pH 5 and optimal temperature of 55°C. Thermostability (80°C for 15 min) and pH stability (3-6) of the enzyme were 56 and more than 80%, respectively.

CONCLUSIONS

The results of the expression and enzyme characterization revealed that the optimized Y. intermedia phytase gene has a good potential to be produced commercially andto be applied in animals' foodsindustry.

Novel Glucose-1-Phosphatase with High Phytase Activity and Unusual Metal Ion Activation from Soil Bacterium Pantoea sp. Strain 3.5.1

Phosphorus is an important macronutrient, but its availability in soil is limited. Many soil microorganisms improve the bioavailability of phosphate by releasing it from various organic compounds, including phytate. To investigate the diversity of phytate-hydrolyzing bacteria in soil, we sampled soils of various ecological habitats, including forest, private homesteads, large agricultural complexes, and urban landscapes. Bacterial isolate Pantoea sp. strain 3.5.1 with the highest level of phytase activity was isolated from forest soil and investigated further. The Pantoea sp. 3.5.1 agpP gene encoding a novel glucose-1-phosphatase with high phytase activity was identified, and the corresponding protein was purified to apparent homogeneity, sequenced by mass spectroscopy, and biochemically characterized. The AgpP enzyme exhibits maximum activity and stability at pH 4.5 and at 37°C. The enzyme belongs to a group of histidine acid phosphatases and has the lowest Km values toward phytate, glucose-6-phosphate, and glucose-1-phosphate. Unexpectedly, stimulation of enzymatic activity by several divalent metal ions was observed for the AgpP enzyme. High-performance liquid chromatography (HPLC) and high-performance ion chromatography (HPIC) analyses of phytate hydrolysis products identify dl-myo-inositol 1,2,4,5,6-pentakisphosphate as the final product of the reaction, indicating that the Pantoea sp. AgpP glucose-1-phosphatase can be classified as a 3-phytase. The identification of the Pantoea sp. AgpP phytase and its unusual regulation by metal ions highlight the remarkable diversity of phosphorus metabolism regulation in soil bacteria. Furthermore, our data indicate that natural forest soils harbor rich reservoirs of novel phytate-hydrolyzing enzymes with unique biochemical features.

Mining the phytomicrobiome to understand how bacterial coinoculations enhance plant growth

In previous work, we showed that coinoculating Rhizobium leguminosarum bv. viciae 128C53 and Bacillus simplex 30N-5 onto Pisum sativum L. roots resulted in better nodulation and increased plant growth. We now expand this research to include another alpha-rhizobial species as well as a beta-rhizobium, Burkholderia tuberum STM678. We first determined whether the rhizobia were compatible with B. simplex 30N-5 by cross-streaking experiments, and then Medicago truncatula and Melilotus alba were coinoculated with B. simplex 30N-5 and Sinorhizobium (Ensifer) meliloti to determine the effects on plant growth. Similarly, B. simplex 30N-5 and Bu. tuberum STM678 were coinoculated onto Macroptilium atropurpureum. The exact mechanisms whereby coinoculation results in increased plant growth are incompletely understood, but the synthesis of phytohormones and siderophores, the improved solubilization of inorganic nutrients, and the production of antimicrobial compounds are likely possibilities. Because B. simplex 30N-5 is not widely recognized as a Plant Growth Promoting Bacterial (PGPB) species, after sequencing its genome, we searched for genes proposed to promote plant growth, and then compared these sequences with those from several well studied PGPB species. In addition to genes involved in phytohormone synthesis, we detected genes important for the production of volatiles, polyamines, and antimicrobial peptides as well as genes for such plant growth-promoting traits as phosphate solubilization and siderophore production. Experimental evidence is presented to show that some of these traits, such as polyamine synthesis, are functional in B. simplex 30N-5, whereas others, e.g., auxin production, are not.

Metabolite changes during natural and lactic acid bacteria fermentations in pastes of soybeans and soybean-maize blends

The effect of natural and lactic acid bacteria (LAB) fermentation processes on metabolite changes in pastes of soybeans and soybean-maize blends was studied. Pastes composed of 100% soybeans, 90% soybeans and 10% maize, and 75% soybeans and 25% maize were naturally fermented (NFP), and were fermented by lactic acid bacteria (LFP). LAB fermentation processes were facilitated through back-slopping using a traditional fermented gruel, thobwa as an inoculum. Naturally fermented pastes were designated 100S, 90S, and 75S, while LFP were designated 100SBS, 90SBS, and 75SBS. All samples, except 75SBS, showed highest increase in soluble protein content at 48 h and this was highest in 100S (49%) followed by 90SBS (15%), while increases in 100SBS, 90S, and 75S were about 12%. Significant (P < 0.05) increases in total amino acids throughout fermentation were attributed to cysteine in 100S and 90S; and methionine in 100S and 90SBS. A 3.2% increase in sum of total amino acids was observed in 75SBS at 72 h, while decreases up to 7.4% in 100SBS at 48 and 72 h, 6.8% in 100S at 48 h and 4.7% in 75S at 72 h were observed. Increases in free amino acids throughout fermentation were observed in glutamate (NFP and 75SBS), GABA and alanine (LFP). Lactic acid was 2.5- to 3.5-fold higher in LFP than in NFP, and other organic acids detected were acetate and succinate. Maltose levels were the highest among the reducing sugars and were two to four times higher in LFP than in NFP at the beginning of the fermentation, but at 72 h, only fructose levels were significantly (P < 0.05) higher in LFP than in NFP. Enzyme activities were higher in LFP at 0 h, but at 72 h, the enzyme activities were higher in NFP. Both fermentation processes improved nutritional quality through increased protein and amino acid solubility and degradation of phytic acid (85% in NFP and 49% in LFP by 72 h).

Overexpression and functional characterization of an Aspergillus niger phytase in the fat body of transgenic silkworm, Bombyx mori

In a previous study, we isolated 1,119 bp of upstream promoter sequence from Bmlp3, a gene encoding a member of the silkworm 30 K storage protein family, and demonstrated that it was sufficient to direct fat body-specific expression of a reporter gene in a transgenic silkworm, thus highlighting the potential use of this promoter for both functional genomics research and biotechnology applications. To test whether the Bmlp3 promoter can be used to produce recombinant proteins in the fat body of silkworm pupae, we generated a transgenic line of Bombyx mori which harbors a codon-optimized Aspergillus niger phytase gene (phyA) under the control of the Bmlp3 promoter. Here we show that the Bmlp3 promoter drives high levels of phyA expression in the fat body, and that the recombinant phyA protein is highly active (99.05 and 54.80 U/g in fat body extracts and fresh pupa, respectively). We also show that the recombinant phyA has two optimum pH ranges (1.5-2.0 and 5.5-6.0), and two optimum temperatures (55 and 37 °C). The activity of recombinant phyA was lost after high-temperature drying, but treating with boiling water was less harmful, its residual activity was approximately 84% of the level observed in untreated samples. These results offer an opportunity not only for better utilization of large amounts of silkworm pupae generated during silk production, but also provide a novel method for mass production of low-cost recombinant phytase using transgenic silkworms.

Overexpression of Escherichia coli phytase in Pichia pastoris and its biochemical properties

To obtain a Pichia pastoris mutant with an Escherichia coli phytase gene, which was synthesized according to P. pastoris codon preference, a mature phytase cDNA of E. coli being altered according to the codons usage preference of P. pastoris was artificially synthesized and cloned into an expression vector of pGAPZαC. The final extracellular phytase activity was 112.5 U/mL after 72 h of cultivation. The phytase, with a molecular mass of 46 kDa, was purified to electrophoretical homogeneity after Ni Sepharose 6 Fast Flow chromatography. The yield, purification fold, and specific activity were 63.97%, 26.17, and 1.57 kU/mg, respectively. It had an optimal pH and temperature of 4.0-6.0 and 50 °C, respectively, and was stable at pH 3.0-8.0 and 25-40 °C. The purified recombinant phytase was resistant to trypsin, highly inhibited by Cu(2+), Zn(2+), Hg(2+), Fe(2+), Fe(3+), phenylmethylsulfonyl fluoride, and N-tosyl-l-lysine chloromethyl ketone, but activated by Mg(2+), Ca(2+), Sr(2+), Ba(2+), glutathione, ethylenediaminetetraacetic acid, and N-ethylmaleimide. It revealed higher affinity to calcium phytate than to other phosphate conjugates.

Expression of food-grade phytase in Lactococcus lactis from optimized conditions in milk broth

The major objective of this study was to engineer lactic acid bacteria to produce the enzyme phytase from a gene native to Bacillus subtilis GYPB04. The phytase gene (phyC) of B. subtilis GYPB04 was cloned into the plasmid pMG36e for expression in Lactococcus lactis. The enzyme activity in L. lactis cultured in GM17 broth was 20.25 U/mL at 36°C. The expressed phytase was characterized as active in a pH range of 2.0-9.0 at a temperature range of 20-80°C, with an optimum pH of 5.5-6.5 and temperature of 60°C. When cultured in food-grade milk broth, the transformed L. lactis grew to an OD(600 nm) value of 1.05 and had a phytase yield of 13.58 U/mL. In same broth under optimized conditions for cell growth and phytase production, the transformant reached an OD(600 nm) value of 1.68 and a phytase yield of 42.12 U/mL, representing approximately 1.6-fold and 3.1-fold increases, respectively, compared to growth in natural milk broth. Fermentation was scaled to 5 L under optimized conditions, and product analysis revealed a final OD(600 nm) value of 1.89 and an extracellular enzyme activity of 24.23 U/mL. The results of this study may be used in the dairy fermentation industry for the development of functional, healthy yogurts and other fermented dairy foods that provide both active phytase and viable probiotics to the consumer.

PCR-RFLP analysis of the diversity of phytate-degrading bacteria in the Tibetan Plateau

Phytases play a very important role in increasing phytate digestion and reducing phosphorus pollution in the environment, and phytate-degrading bacteria have a ubiquitous distribution in the environment. Due to its extremely harsh environment, the Tibetan Plateau breeds possibly abundant, extreme microorganisms. In this research, 67 phytate-degrading bacteria were isolated from different habitats in the Tibetan Plateau. Among all isolates, 40.3% were screened from farmland, 25.3% from wetland, 4.5% from saline-alkaline soil, 7.5% from hot springs, and 22.4% from lawns, which showed that the distribution of the phytate-degrading bacteria varied with habitats. By the PCR-RFLP method, 16 different species were identified and named, 4 of which are reported for the first time as phytate-degrading bacteria, that is, Uncultured Enterococcus sp. GYPB01, Bacillaceae bacterium strain GYPB05, Endophytic bacterium strain GYPB16, and Shigella dysenteria strain GYPB22. Through the assay of phytase activity of 16 strains, Klebsiella sp. strain GYPB15 displayed the highest capability of phytase production. Through analysis of the optimum pH, the optimum temperature, and the thermal stability of enzyme from 16 strains, some especial phytate-degrading bacteria were obtained. Our findings clearly indicate a good relation between the composition of the soils from the different environments in the Tibetan Plateau and populations of cultivable phytate-degrading bacteria. Moreover, extreme harsh soils are logically the best soils in which to find some strains of phytate-degrading bacteria for exploiting in the fields of biotechnology and industry.

β-propeller phytase hydrolyzes insoluble Ca(2+)-phytate salts and completely abrogates the ability of phytate to chelate metal ions

Phytate is an antinutritional factor that influences the bioavailability of essential minerals by forming complexes with them and converting them into insoluble salts. To further our understanding of the chemistry of phytate's binding interactions with biologically important metal cations, we determined the stoichiometry, affinity, and thermodynamics of these interactions by isothermal titration calorimetry. The results suggest that phytate has multiple Ca(2+)-binding sites and forms insoluble tricalcium- or tetracalcium-phytate salts over a wide pH range (pH 3.0-9.0). We overexpressed the β-propeller phytase from Hahella chejuensis (HcBPP) that hydrolyzes insoluble Ca(2+)-phytate salts. Structure-based sequence alignments indicated that the active site of HcBPP may contain multiple calcium-binding sites that provide a favorable electrostatic environment for the binding of Ca(2+)-phytate salts. Biochemical and kinetic studies further confirmed that HcBPP preferentially recognizes its substrate and selectively hydrolyzes insoluble Ca(2+)-phytate salts at three phosphate group sites, yielding the final product, myo-inositol 2,4,6-trisphosphate. More importantly, ITC analysis of this final product with several cations revealed that HcBPP efficiently eliminates the ability of phytate to chelate several divalent cations strongly and thereby provides free minerals and phosphate ions as nutrients for the growth of bacteria. Collectively, our results provide significant new insights into the potential application of HcBPP in enhancing the bioavailability and absorption of divalent cations.

A new method for gene synthesis and its high-level expression

An optimized Citrobacter braakii phytase gene, appA-c, was chemically synthesized by oligonucleotides synthesis and over-lap PCR method. The appA-c gene encoding 423 amino acids was cloned into expression vector pPIC9 and transformed into methylotropic yeast Pichia pastoris. From about 2000 transformants, 400 transformants exhibiting phytase activity were obtained. One transformant showing the strongest phytase activity was selected for detailed analyses in 5 L bioreactor. Under control of the highly-inducible alcohol oxidase gene (AOX1) promoter, the transformant was able to secrete 3.85 mg/ml protein to the culture supernatant in about 110 h methanol induction, which comprises of 12,116 U ml(-1) phytase activity. Further characterization of the recombinant phytase was conducted. The optimal pH and temperature for this recombinant phytase was about 4.0 and 50 degrees C, respectively. Fe3+, Zn2+ and Cu2+ could significantly inhibit the recombinant phytase enzyme activity. The specific activity of this recombinant enzyme was 3147 U mg(-1). The K(m) and V(max) values for sodium phytate were determined to be 0.5 mM and 3085 U/mg, respectively. To our knowledge, this is the first report of a chemically synthesized C. braakii appA gene heterologous expression with the highest expression level and highest phytase activity achieved. The novel gene optimization and synthesis method can be applied to other related researches.

Gene cloning, expression, and characterization of a novel phytase from Dickeya paradisiaca

A novel phytase gene, appA, was isolated by degenerate polymerase chain reaction (PCR) and thermal asymmetric interlaced PCR from Dickeya paradisiaca. The full-length appA comprises 1278 bp and encodes 425 amino acid residues, including a 23-residue putative N-terminal signal peptide. The deduced amino acid sequence of appA reveals the conserved motifs RHGXRXP and HD, which are typical of histidine acid phosphatases; significantly, APPA shows maximum identity (49%) to a phytase from Klebsiella pneumoniae. To characterize the properties of APPA, appA was expressed in Escherichia coli and purified. The purified recombinant APPA has two pH optima at pH 4.5 and 5.5, optimum temperature at 55 degrees C, specific activity of 769 U/mg, and good pH stability. The K(m) value for the substrate sodium phytate is 0.399 mM with a Vmax of 666 U/mg. To our knowledge, this is the first report of a phytase or phytase gene isolated from Dickeya.

Expression, purification and characterization of a phyA(m)-phyCs fusion phytase

The phyA(m) gene encoding acid phytase and optimized neutral phytase phyCs gene were inserted into expression vector pPIC9K in correct orientation and transformed into Pichia pastoris in order to expand the pH profile of phytase and decrease the cost of production. The fusion phytase phyA(m)-phyCs gene was successfully overexpressed in P. pastoris as an active and extracellular phytase. The yield of total extracellular fusion phytase activity is (25.4+/-0.53) U/ml at the flask scale and (159.1+/-2.92) U/ml for high cell-density fermentation, respectively. Purified fusion phytase exhibits an optimal temperature at 55 degrees C and an optimal pH at 5.5~6.0 and its relative activity remains at a relatively high level of above 70% in the range of pH 2.0 to 7.0. About 51% to 63% of its original activity remains after incubation at 75 degrees C to 95 degrees C for 10 min. Due to heavy glycosylation, the expressed fusion phytase shows a broad and diffuse band in SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). After deglycosylation by endoglycosidase H (EndoH(f)), the enzyme has an apparent molecular size of 95 kDa. The characterization of the fusion phytase was compared with those of phyCs and phyA(m).

Gene cloning and characterization of a thermostable phytase from Bacillus subtilis US417 and assessment of its potential as a feed additive in comparison with a commercial enzyme

An extracellular phytase from Bacillus subtilis US417 (PHY US417) was purified and characterized. The purified enzyme of 41 kDa was calcium-dependent and optimally active at pH 7.5 and 55 degrees C. The thermal stability of PHY US417 was drastically improved by calcium. Indeed, it recovered 77% of its original activity after denaturation for 10 min at 75 degrees C in the presence of 5 mM CaCl2, while it retained only 22% of activity when incubated for 10 min at 60 degrees C without calcium. In addition, PHY US417 was found to be highly specific for phytate and exhibited pH stability similar to Phyzyme, a commercial phytase with optimal activity at pH 5.5 and 60 degrees C. The phytase gene was cloned by PCR from Bacillus subtilis US417. Sequence analysis of the encoded polypeptide revealed one residue difference from PhyC of Bacillus subtilis VTTE-68013 (substitution of arginine in position 257 by proline in PHY US417) which was reported to exhibit lower thermostability especially in the absence of calcium. With its neutral pH optimum as well as its great pH and thermal stability, the PHY US417 enzyme presumed to be predominantly active in the intestine has a high potential for use as feed additive.

Phytase from antarctic yeast strain Cryptococcus laurentii AL27

Cryptococcus laurentii strain AL27 demonstrating significant potential for intracellular phytase production was selected by 2-step screening of Antarctic yeasts. The strain showed increased phytase activity in a culture medium with 40 g/L sucrose, KH2PO4 providing 5 mg/L phosphorus, and cultivation temperature of 24 degrees C, which relates it to psychrotrophic microorganisms. The enzyme kinetic characteristics according to sodium phytate were Km = 0.98 mmol/L, vlim = 33.3 micromol g(-1) min(-1). The enzyme had maximum activity at 40 degrees C and acted within a wide pH range: from 2.0 to 5.5, which is of positive significance for its direct inclusion into the feed of monogastric animals.

Phytate-degrading enzyme production by bacteria isolated from Malaysian soil

Over two hundred bacteria were isolated from the halosphere, rhizosphere and endophyte of Malaysian maize plantation and screened for phytases activity. Thirty isolates with high detectable phytase activity were chosen for media optimization study and species identification. Ten types of bacterial phytase producers have been discovered in this study, which provides opportunity for characterization of new phytase(s) and various commercial and environmental applications. The majority of the bacterial isolates with high detectable phytase activity were of endophyte origin and 1.6% of the total isolates showed phytase activity of more than 1 U/ml. Most of the strains produced extra-cellular phytase and Staphylococcus lentus ASUIA 279 showed the highest phytase activity of 1.913 U/ml. All 30 species used in media optimization study exhibit favorable enzyme production when 1% rice bran was included in the growth media.

Design and expression of a synthetic phyC gene encoding the neutral phytase in Pichia pastoris

The 1074-bp phyCs gene (optimized phyC gene) encoding neutral phytase was designed and synthesized according to the methylotrophic yeast Pichia pastoris codon usage bias without altering the protein sequence. The expression vector, pP9K-phyCs, was linearized and transformed in P. pastoris. The yield of total extracellular phytase activity was 17.6 U/ml induced in Buffered Methanol-complex Medium (BMMY) and 18.5 U/ml in Wheat Bran Extract Induction (WBEI) medium at the flask scale, respectively, improving over 90 folds compared with the wild-type isolate. Purified enzyme showed temperature optimum of 70 degrees and pH optimum of 7.5. The enzyme activity retained 97% of the relative activity after incubation at 80 degrees for 5 min. Because of the heavy glycosylation the expressed phytase had a molecular size of approximately 51 kDa. After deglycosylation by endoglycosylase H (EndoH(f)), the enzyme had an apparent molecular size of 42 kDa. Its property and thermostability was affected by the glycosylation.

Dual role of the PhoP approximately P response regulator: Bacillus amyloliquefaciens FZB45 phytase gene transcription is directed by positive and negative interactions with the phyC promoter

Several Bacillus strains secrete phytase, an enzyme catalyzing dephosphorylation of myo-inositol hexakisphosphate (phytate). We identified the phyC (phytase) gene from environmental Bacillus amyloliquefaciens FZB45 as a member of the phosphate starvation-inducible PhoPR regulon. In vivo and in vitro assays revealed that PhoP approximately P is essential for phyC transcription. The transcriptional start site was identified downstream of a sigmaA-like promoter region located 27 bp upstream of the probable translation ATG start codon. Inspection of the phyC promoter sequence revealed an unusual structure. The -35 and -10 regions are separated by a window of 21 bp. A pair of tandemly repeated PhoP TT(T/A/C)ACA binding boxes was located within and upstream of the -35 consensus promoter region. A single PhoP box was found within the -10 consensus promoter region. DNase I footprinting experiments performed with isolated PhoP confirmed that PhoP approximately P binds at two sites overlapping with the phyC -35 and -10 consensus promoter region. While binding of dimeric PhoP approximately P at -35 is essential for activation of the phyC promoter, binding of PhoP approximately P at -10 suppresses promoter activity. A sixfold enhancement of phyC gene expression was registered after T:G substitution of nucleotide -13 (mutant MUT13), which eliminates PhoP binding at the single PhoP box without impairing the -10 consensus sequence. Moreover, MUT13 also expressed phyC during phosphate-replete growth, suggesting that the repressing effect due to binding of PhoP approximately P at -10 was abolished. A model is presented in which transcription initiation of phyC is positively and negatively affected by the actual concentration of the PhoP approximately P response regulator.

Alkaline phytase from Lilium longiflorum: Purification and structural characterization

Phytases catalyze the hydrolysis of phytic acid (myo-inositol hexakisphosphate), the most abundant inositol phosphate in cells. Phytases are of great commercial importance because their use as food and animal feed supplement has been approved by many countries to alleviate environmental and nutritional problems. Although acid phytases have been extensively studied, information regarding alkaline phytases is limited. Alkaline phytases with unique catalytic properties have been identified in plants, however, there is no report on the purification or structural properties. In this paper, we describe the purification of alkaline phytase from plant tissue. The purification was challenging because of contamination from non-specific phosphatases and acid phytases and low endogenous concentration. The purification of alkaline phytase from pollen grains of Lilium longiflorum involved selective precipitation by heat and ammonium sulfate followed by anion exchange and chromatofocusing chromatography and, finally, gel electrophoresis. Alkaline phytase was purified approximately 3000-fold with an overall recovery of 4.2%. The native molecular mass was estimated to be in the range of 118+/-7 kDa by Ferguson plot analysis and Mr of denatured protein in the range of 52-55 kDa by SDS-PAGE suggesting that the enzyme is a homodimer. Separation by 2-D gel and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometric analysis of separated proteins indicates the presence of multiple mass and charge isoforms with pI values between 7.3 and 8.3. To our knowledge, this is the first alkaline phytase to be purified from plant sources. The unique properties suggest that the enzyme has the potential to be useful as a feed and food supplement.

Beta-propeller phytases in the aquatic environment

Phytate, which is one of the dominant organic phosphorus compounds in nature, is very stable in soils. Although a substantial amount of phytate is carried from terrestrial to aquatic systems, it is a minor component of organic phosphorus in coastal sediments. The ephemeral nature of phytate implies the rapid hydrolysis of phytate under aquatic conditions. Among the four classes of known phytases that have been identified in terrestrial organisms, only beta-propeller phytase-like sequences have been identified in the aquatic environment. A novel beta-propeller phytase gene (phyS), cloned from Shewanella oneidensis MR-1, was found to encode a protein with two beta-propeller phytase domains. The characterization of recombinant full-length PhyS and its domains demonstrated that Domain II was the catalytic domain responsible for phytate hydrolysis. The full-length PhyS displayed a K(m) of 83 microM with a kcat of 175.9 min(-1) and the Domain II displayed a K(m) of 474 microM with a kcat of 10.6 min(-1). These results confirm that the phyS gene encodes a functional beta-propeller phytase, which is expressed in S. oneidensis under phosphorus deficient condition. The presence of multiple sequences with a high similarity to phyS in aquatic environmental samples and the widespread occurrence of the Shewanella species in nature suggest that the beta-propeller phytase family is the major class of phytases in the aquatic environment, and that it may play an important role in the recycling of phosphorus.

Molecular Cloning of the Phytase Gene from Citrobacter braakii and its Expression in Saccharomyces cerevisiae

The gene, appA, encoding phytase was cloned from a size-selected genomic library of Citrobacter braakii YH-15 by Southern hybridization using a degenerate probe based on the N-terminal amino acid sequence of the phytase. The deduced amino acid sequence of appA contained the N-terminal RHGXRXP motif and the C-terminal HD motif, which are common in histidine acid phosphatases. It also had significant homology (60% identity) with phytase from Escherichia coli, while the physical mapping analysis of appA revealed that gene organization near appA in C. braakii was similar to that in Salmonella typhimurium genome. C. braakii AppA contained five putative N-glycosylation sites. The recombinant phytases, rAppAEc and rAppASc, were produced in E. coli and Saccharomyces cerevisiae, respectively, with both being fused with C-terminal His-tag. After purification, rAppASc was shown to be hyperglycosylated by Endo-H treatment. It had greater thermostability than the wild type phytase and rAppAEc.

Alkaline phytase from lily pollen: Investigation of biochemical properties

Phytases catalyze the hydrolysis of phytic acid (InsP6, myo-inositol hexakisphosphate), the most abundant inositol phosphate in cells. In cereal grains and legumes, it constitutes 3-5% of the dry weight of seeds. The inability of humans and monogastric animals such as swine and poultry to absorb complexed InsP6 has led to nutritional and environmental problems. The efficacy of supplemental phytases to address these issues is well established; thus, there is a need for phytases with a range of biochemical and biophysical properties for numerous applications. An alkaline phytase that shows unique catalytic properties was isolated from plant tissues. In this paper, we report on the biochemical properties of an alkaline phytase from pollen grains of Lilium longiflorum. The enzyme exhibits narrow substrate specificity, it hydrolyzed InsP6 and para-nitrophenyl phosphate (pNPP). Alkaline phytase followed Michaelis-Menten kinetics with a K(m) of 81 microM and V(max) of 217 nmol Pi/min/mg with InsP6 and a K(m) of 372 microM and V(max) of 1272 nmol Pi/min/mg with pNPP. The pH optimum was 8.0 with InsP6 as the substrate and 7.0 with pNPP. Alkaline phytase was activated by calcium and inactivated by ethylenediaminetetraacetic acid; however, the enzyme retained a low level of activity even in Ca2+-free medium. Fluoride as well as myo-inositol hexasulfate did not have any inhibitory affect, whereas vanadate inhibited the enzyme. The enzyme was activated by sodium chloride and potassium chloride and inactivated by magnesium chloride; the activation by salts followed the Hofmeister series. The temperature optimum for hydrolysis is 55 degrees C; the enzyme was stable at 55 degrees C for about 30 min. The enzyme has unique properties that suggest the potential to be useful as a feed supplement.

Molecular cloning of a phytase gene (phy M) from Pseudomonas syringae MOK1

A phytase gene (phy M) was cloned from Pseudomonas syringae MOK1 by two steps of degenerate PCR and inverse PCR. This gene consists of 1,287 nucleotides and encodes a polypeptide of 428 amino acids with a deduced molecular mass of 46,652 kDa. Based on its amino acid sequence, the Phy M shares the active site RHGXRXP and HD sequence motifs, typically characterized by histidine acid phosphatases familly. Each phy M gene fragment encoding mature Phy M with its own signal sequence (pEPSS) and without (pEPSM) was subcloned into the E. coli BL21 (DE3) expression vector, pET22b (+). The enzyme activity in crude extracts of clone pEPSM was 2.514 Umg(-1) of protein, and about 10-fold higher than that of clone pEPSS.