Advances in phytase research

Effects of crude protease produced by Bacillus subtilis (MAFIC Y7) on growth performance, immune indices, and anti-inflammatory responses of broilers fed soybean meal- or cottonseed meal-based diets

A strain of Bacillus subtilis (MAFIC Y7) was isolated from the intestine of Tibetan pigs and was able to express high protease activity. The aim of this study was to characterize the proteases produced by MAFIC Y7, and to investigate the effects of protease addition on growth performance, ileal amino acid digestibility, and serum immunoglobulin and immune factors of broilers fed SBM-based diets, or on growth performance, carcass characteristics, and intestinal morphology of broilers fed CSM-based diets. B. subtilis (MAFIC Y7) expressed protease showed its optimal enzyme activity at 50 °C and pH 7.0. The coated crude enzyme (CCE) showed greater stability at pH 3.0 than its uncoated counterpart. Experiment 1 was conducted with six diets based on three levels of crude protein (CP)-CPlow, CPmedium, and CPhigh-with or without CCE. In CPlow, CCE increased gain:feed (G:F) (days 1 to 21, days 1 to 42) by 8%, 3%, respectively, and enhanced apparent ileal digestibility (AID) of crude protein and lysine (on day 42) by 8.8%, 4.6%, respectively, compared with diets containing no CCE (P < 0.05). CCE increased G:F from days 1 to 21 from 0.63 to 0.68, improved G:F and average daily gain (ADG) during days 1 to 42, and enhanced AID of crude protein, lysine, cysteine, and isoleucine on day 42 compared with the unsupplemented treatments (in CPmedium, P < 0.05). CCE increased serum IgA (on day 21), serum IgA and IgG and increased serum IL-10 (on day 42), but decreased serum tumor necrosis factor-α (TNF-α; on day 21), and serum IL-8 and TNF-α (on day 42) compared with unsupplemented treatments. At CPhigh, CCE decreased serum levels of IL-6 and TNF-α (on day 21), and IL-8 and TNF-α (on day 42) compared with unsupplemented treatments (in CPhigh, P < 0.05). In experiment 2, CSM-based diets with two lysine-to-protein ratios (5.2% or 5.5%) with or without CCE. In the high Lys diet (5.5% Lys:protein), CCE increased ADG and G:F, increased carcass, but decreased abdominal fat compared with the unsupplemented treatment (P < 0.05). In the 5.2% Lys:protein dietary treatment, CCE improved duodenal villus height compared with the unsupplemented treatment (P < 0.05). Supplementation of protease produced by MAFIC Y7 was associated with lower inflammatory responses in SBM diets (CPmedium or CPhigh) and improved ADG in broilers fed CPmedium or CPhigh. The proteases improved ADG and the efficiency of CSM use when the ratio of Lys to protein was 5.5%.

Improving phytase production in Pichia pastoris fermentations through de-repression and methanol induction optimization

Pichia pastoris (Komagataella phaffii) is a fast-growing methylotrophic yeast with the ability to assimilate several carbon sources such as methanol, glucose, or glycerol. It has been shown to have outstanding secretion capability with a variety of heterologous proteins. In previous studies, we engineered P. pastoris to co-express Escherichia coli AppA phytase and the HAC1 transcriptional activator using a bidirectional promoter. Phytase production was characterized in shake flasks and did not reflect industrial conditions. In the present study, phytase expression was explored and optimized using instrumented fermenters in continuous and fed-batch modes. First, the production of phytase was investigated under glucose de-repression in continuous culture at three dilution factors, 0.5 d-1 , 1 d-1 , and 1.5 d-1 . The fermenter parameters of these cultures were used to inform a kinetic model in batch and fed-batch modes for growth and phytase production. The kinetic model developed aided to design the glucose-feeding profile of a fed-batch culture. Kinetic model simulations under glucose de-repression and fed-batch conditions identified optimal phytase productivity at the specific growth rate of 0.041 h-1 . Validation of the model simulation with experimental data confirmed the feasibility of the model to predict phytase production in our newly engineered strain. Methanol was used only to induce the expression of phytase at high cell densities. Our results showed that high phytase production required two stages, the first stage used glucose under de-repression conditions to generate biomass while expressing phytase, and stage two used methanol to induce phytase expression. The production of phytase was improved 3.5-fold by methanol induction compared to the expression with glucose alone under de-repression conditions to a final phytase activity of 12.65 MU/L. This final volumetric phytase production represented an approximate 36-fold change compared to the flask fermentations. Finally, the phytase protein produced was assayed to confirm its molecular weight, and pH and temperature profiles. This study highlights the importance of optimizing protein production in P. pastoris when using novel promoters and presents a general approach to performing bioprocess optimization in this important production host.

Thermostability enhancement of Escherichia coli phytase by error-prone polymerase chain reaction (epPCR) and site-directed mutagenesis

Phytase efficiently hydrolyzes phytate to phosphate; thus, it is widely used to increase phosphorus availability in animal feeds and reduce phosphorus pollution through excretion. Phytase is easily inactivated during feed pelleting at high temperature, and sufficient thermostability of phytase is essential for industrial applications. In this study, directed evolution was performed to enhance phytase thermostability. Variants were initially expressed in Escherichia coli BL21 for screening, then in Pichia pastoris for characterization. Over 19,000 clones were generated from an error-prone Polymerase Chain Reaction (epPCR) library; 5 mutants (G10, D7, E3, F8, and F9) were obtained with approximately 9.6%, 10.6%, 11.5%, 11.6%, and 12.2% higher residual activities than the parent after treatment at 99°C for 60 min. Three of these mutants, D7, E3, and F8, exhibited 79.8%, 73.2%, and 92.6% increases in catalytic efficiency (kcat/Km), respectively. In addition, the specific activities of D7, E3, and F8 were 2.33-, 1.98-, and 2.02-fold higher than parental phytase; they were also higher than the activities of all known thermostable phytases. Sequence analysis revealed that all mutants were substituted at residue 75 and was confirmed that the substitution of cysteine at position 75 was the main contribution to the improvement of thermostability of mutants by saturation mutagenesis, indicating that this amino acid is crucial for the stability and catalytic efficiency of phytase. Docking structure analysis revealed that substitution of the C75 residue allowed the mutants to form additional hydrogen bonds in the active pocket, thereby facilitating binding to the substrate. In addition, we confirmed that the intrinsic C77-C108 disulfide bond in E. coli phytase is detrimental to its stability.

Impacts and Industrial Applications of Phytic Acid and Phytase

Phytic acid is an antinutritional compound that chelates P and essential divalent cations such as Fe, Ca, and Zn in cereals and major staple crops such as wheat, maize, rice, and sorghum. As a result, these cations cannot be absorbed by monogastric animals or humans: phytic acid has an inhibitory effect on nutrient uptake and its levels are negatively correlated with protein and starch digestibility. However, phytic acid can be degraded by the action of the enzyme phytase. Phytase plays important roles in the degradation of phytic acid and in increasing the nutritional quality of staple foods. Microbial phytase is a versatile enzyme that is beneficial for humans, animals, the environment, and the industry. In this review, we summarise the interaction of phytic acid with micronutrients, various approaches to enhancing the nutritional profile of staple foods by reducing the phytic acid content, and current knowledge of microbial-based phytase as a potential reducer of phytic acid.

State-of-the-Art Review on Engineering Uses of Calcium Phosphate Compounds: An Eco-Friendly Approach for Soil Improvement

Greenhouse gas emissions are a critical problem nowadays. The cement manufacturing sector alone accounts for 8% of all human-generated emissions, and as the world's population grows and globalization intensifies, this sector will require significantly more resources. In order to fulfill the need of geomaterials for construction and to reduce carbon dioxide emissions into the atmosphere, conventional approaches to soil reinforcement need to be reconsidered. Calcium phosphate compounds (CPCs) are new materials that have only recently found their place in the soil reinforcement field. Its eco-friendly, non-toxic, reaction pathway is highly dependent on the pH of the medium and the concentration of components inside the solution. CPCs has advantages over the two most common environmental methods of soil reinforcement, microbial-induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP); with CPCs, the ammonium problem can be neutralized and thus allowed to be applied in the field. In this review paper, the advantages and disadvantages of the engineering uses of CPCs for soil improvement have been discussed. Additionally, the process of how CPCs perform has been studied and an analysis of existing studies related to soil reinforcement by CPC implementation was conducted.

Thermally stable and acidic pH tolerant mutant phytases with high catalytic efficiency from Yersinia intermedia for potential application in feed industries

Heat- and pH-stable phytase efficiently hydrolyzes phytic acid. In this research, heat- and pH-stable mutant phytases, T⁸³R, L²⁸⁷R, and T⁸³R/L²⁸⁷R were generated by site-directed mutagenesis from Yersinia intermedia. After the induction and expression of recombinant wild-type and mutant phytases in E. coli BL21, the enzymes were purified using nickel sepharose affinity chromatography, and characterized kinetically and thermodynamically using spectroscopy methods. The mutants showed optimum activity at pH 5.15 and 55-61 °C. The catalytic efficiencies of T⁸³R, L²⁸⁷R, T⁸³R/L²⁸⁷R, and wild-type phytases were calculated to be 2941, 29346, 4906, and 6917 mmol/L^-1s^-1, respectively. Moreover, after the incubation of T⁸³R, L²⁸⁷R, wild-type, and T⁸³R/ L²⁸⁷R phytases at 100 °C for 1 h, the enzymes retained 22, 5, 4, and 2% of their initial activities, respectively. In addition, T⁸³R, T⁸³R/L²⁸⁷R, L²⁸⁷R, and wild-type phytases retained 82, 44, 16 as well as 11% of their initial activities after 1 h at pH 5.15, respectively. Among these mutants, T⁸³R mutant showed 18% increase in thermal stability, 71% increase in pH stability, and +0.103 KJ/mole increase in ΔΔG, while the catalytic efficiency and ΔΔG value of L²⁸⁷R mutant increased by 4 times and +0.0903 KJ/mole, respectively. Thus, the mutants have the potential to be used in feed industries to increase the bioavailability of minerals while decreasing soil and water pollution.

Bioinformatic Studies, Experimental Validation of Phytase Production and Optimization of Fermentation Conditions for Enhancing Phytase Enzyme Production by Different Microorganisms under Solid-State Fermentation

Background:

Phytase is an essential enzyme necessary for the digestive process. It is a natural enzyme found in plant materials. It prevents bad effect of phytic acid on protein and energy utilization. Phytase frees the bound minerals such as phosphorus, calcium, zinc, iron, magnesium and manganese from the phytic acid molecule providing essential minerals available for healthy nutrition. This study depends on converting food processing waste into highly valuable products. Optimizing the fermentation conditions for enhancing high phytase production with low cost was the objective of this research.

Methods:

A bibliographical survey was carried out to select the most fungul producers of phytase from fungal species deposited in NCBI database. Phytases of the selected organisms were analyzed in the UNIPROT database and their protein sequences were submitted to multiple sequence alignments using Clustal Omega and visualized using Jalview program. Experimental studies using five fungal strains of Aspergillus.ssp on wheat bran under Solid-State Fermentation carried out. Comparisons were made for phytase production. A. awamori NRC- F18 as the best phytase producer-strain cultured on different types of treated wastes followed by optimizing the fermentation conditions for enhancing phytase production using rice straw as the best substrate, which provides the highest phytase production. Thermostability of crude enzyme was studied. Statistical analyses were performed using SPSS at P < 0.05 or P < 0.01.

Results:

Bioinformatic studies predicted the most producer species and explained the difference in activity of phytases produced from different species, although they have the same function. All phytases of the selected fungal species from the database NCBI have highly conserved amino acid sequences; there are 88 identical positions; 135 similar positions, but the identity percentage was 16.858%. Experimental studies using five fungal strains of Aspergillus ssp. on wheat bran revealed optimum conditions for phytase production by A. awamori NRC- F18, which cultured on different types of treated wastes. A considerably higher phytase production was obtained using rice straw as substrate 424.66± 2.92 IU /g at pH 6 (371.883± 0.822 IU /g), after 144 hrs of incubation at 30°C. The maximum enzyme activity observed when solid: moisture was 1:4; Inoculum concentration 2mg/5g (418.363± 16.709 IU /g) and substrate concentration 4.5% (277.39± 12.05 IU /g). Glucose and Ammonium acetate were the best carbon and nitrogen sources that enhanced phytase production from A. awamori NRC- F18. The obtained phytase was found to be thermostable and the maximum temperature at which phytase still active was 80°C.

Conclusion:

Bioinformatic studies predicted the most producer species. Experimental study revealed that A.awamori NRC- F18 was the best Phytase -producer strain. Solid state fermentation was a good method; pretreatment of agriculture residues as rice straw was useful for less expensive phytase production, which was thermostable. A. awamori NRC- F18 can be used in the industrial production of phytase.

Safety assessment of phytase transgenic maize 11TPY050 in Sprague-Dawley rats by 90-day feeding study

The present study aimed to evaluate the subchronic toxicity of feeding with phytase-transgenic maize line 11TPY050 in Sprague-Dawley (SD) rats. Rats (n = 10/sex/group) were fed with 12.5%, 25% or 50% (w/w) transgenic maize diet, 12.5%, 25% or 50% (w/w) non-transgenic isoline OSL940 maize diet, or 50% (w/w) commercially available Zhengdan958 maize diet for 90 days. Daily clinical observations and weekly measurements of body weights and food consumption were conducted. Blood samples were collected on day 46 and day 91 for hematology and clinical chemistry evaluations. At the end of the study, macroscopic and microscopic examinations were performed. No effects on body weight and food consumption were observed. The results of hematology, clinical chemistry, and absolute and relative organ weights in the transgenic maize group were comparable to those in the parental maize group. Several statistical differences were not dose-related and were not considered to be biologically significant. Furthermore, the terminal necropsy and histopathological examination showed no treatment-related changes among the groups. The results from the present 90-day feeding study of phytase-transgenic maize 11TPY050 indicated no unexpected adverse effects in SD rats. The phytase transgenic maize 11TPY050 has substantial equivalence with non-transgenic maize.

Effects of Microbial Phytase Supplementation on Egg Production and Egg Quality in Hy-line Brown Hens During the Late Laying Period

The objective of this study was to evaluate the effects of microbial phytase on egg production and egg quality in older hens. A total of 216, 63-week-old Hy-line brown laying hens were distributed in a randomized complete design 10-week feeding trial of 3 dietary treatments with 12 replications per treatment and 6 hens per replication. The 3 dietary treatments were corn-soybean meal-based diets supplemented with 0% (CON), 0.06% (TRT1), and 0.12% (TRT2) microbial phytase. Significantly higher hen-day egg production was observed in the TRT1 treatment compared to CON (P<0.05), except during the first two weeks of the experiment. During weeks 3, 4, and 9, TRT2 had a greater hen-day egg production percentage than CON (P<0.05). The damaged egg ratio was not affected. The egg quality parameters (e.g., eggshell color, eggshell strength, albumen height, egg weight, and the Haugh unit) were affected by microbial phytase supplementation (P<0.05). However, there were no significant effects on the eggshell thickness and yolk color. In conclusion, microbial phytase supplementation to the diets of older hens could improve production performance, extend the peak laying period, and alter the egg quality parameters.

Klotho and calciprotein particles as therapeutic targets against accelerated ageing

The klotho gene, named after a Greek goddess who spins the thread of life, was identified as a putative 'ageing-suppressor' gene. Klotho-deficient mice exhibit complex ageing-like phenotypes including hypogonadism, arteriosclerosis (vascular calcification), cardiac hypertrophy, osteopenia, sarcopenia, frailty, and premature death. Klotho protein functions as the obligate co-receptor for fibroblast growth factor-23 (FGF23), a bone-derived hormone that promotes urinary phosphate excretion in response to phosphate intake. Thus, Klotho-deficient mice suffer not only from accelerated ageing but also from phosphate retention due to impaired phosphate excretion. Importantly, restoration of the phosphate balance by placing Klotho-deficient mice on low phosphate diet rescued them from premature ageing, leading us to the notion that phosphate accelerates ageing. Because the extracellular fluid is super-saturated in terms of phosphate and calcium ions, an increase in the phosphate concentration can trigger precipitation of calcium-phosphate. In the blood, calcium-phosphate precipitated upon increase in the blood phosphate concentration is adsorbed by serum protein fetuin-A to form colloidal nanoparticles called calciprotein particles (CPPs). In the urine, CPPs appear in the renal tubular fluid when FGF23 increases phosphate load excreted per nephron. CPPs can induce cell damage, ectopic calcification, and inflammatory responses. CPPs in the blood can induce arteriosclerosis and non-infectious chronic inflammation, whereas CPPs in the urine can induce renal tubular damage and interstitial inflammation/fibrosis. Thus, we propose that CPPs behave like a pathogen that accelerates ageing and should be regarded as a novel therapeutic target against age-related disorders including chronic kidney disease.

Stabilizing enzymes by immobilization on bacterial spores: A review of literature

The ever-increasing applications of enzymes are limited by the relatively poor performance in harsh processing conditions. As a result, there are constant innovations in immobilization protocols for improving biocatalyst activity and stability. Bacterial spores are cheap to generate and highly resistant to environmental stress. The spore core is sheathed by an inner membrane, the germ cell wall, the cortex, outer membrane, spore coat and in some species the exosporium. The spore surface is anion-rich, hydrophobic and contains several reactive groups capable of interacting and stabilizing enzyme molecules through electrostatic forces, hydrophobic interactions and covalent bonding. The probiotic nature of spores obtained from non-toxic bacterial species makes them suitable carriers for the enzyme immobilization, especially food-grade enzymes or those intended for therapeutic use. Immobilization on spores is by direct adsorption, covalent attachment or surface display during the sporulation phase. Hindrances to the immobilization on spore matrix include the production rates, operational instability, and reduced catalytic properties due to conformational changes in enzyme. This paper reviews bacterial spore as a heterofunctional support matrix gives reasons why probiotic bacillus spores are better options and the diverse technologies adopted for spore-enzyme immobilization. It further suggests directions for future use and discusses the commercialization prospects.

Monitoring Phytate Hydrolysis Using Serial Blood Sampling and Feather Myo-Inositol Levels in Broilers

Phytate forms insoluble precipitates with various cations that are recalcitrant to digestion in poultry. Dietary supplementation with exogenous phytase has been shown to improve phytate solubility and digestibility and, in turn, improve animal growth performance. Although the kinetics of phytate hydrolysis by exogenous phytase are well described in vitro, the progression of the reaction in vivo is still not well defined. The aim of the present study was, therefore, to monitor the kinetic variation of myo-inositol (myo-Ins) levels in both circulation and feather following exogenous phytase supplementation. In experiment 1, 4 week-old male broilers were individually housed with ad libitum access to water and a standard commercial diet. Birds were maintained under environmental temperature of 24°C and 30% RH. Birds were cannulated in the cutaneous ulnar vein on the right wing and remained untouched for 3 days. On the day of the experiment, birds were randomly divided into three body weight-matched groups and fed either the control diet, the control diet-supplemented with myo-Ins or Ronozyme HiPhos (0.06%, DSM Nutritional Products, Switzerland) for 10 h. In the experiment 2, birds were fed only HiPhos for 30 h. Growing feathers and blood were collected at baseline and then every 2 h for 10 h (experiment 1) and 30 h (experiment 2) post-prandially. Plasma and feather myo-Ins levels were determined by UHPLC-MS/MS. The relative expression of inositol polyphosphate-1-phosphatase (INPP1), inositol hexakisphosphate kinase 1-3 (IP6K1-3), inositol-3-phosphate synthase (ISYNA), and multiple inositol-polyphosphate phosphatase 1 (MNPP1) genes in blood and feathers was determined by real-time qPCR using 2^–ΔΔCt method. Plasma and feather myo-Ins levels were significantly increased by HiPhos at 6 h to 8 h post-prandial. The mRNA abundances of INPP1, IP6K1, and ISYNA in the circulation were significantly down regulated at all periods compared to the baseline levels. IP6K2, IP6K3, and MINPP1 gene expression, however, was up regulated at 8 h post-prandial and then returned to the baseline levels. In feathers, the expression of INPP1 was induced at 8 h post-prandial and remained higher compared to the baseline. The expression of IP6K2, IP6K3, and MINPP1 was down regulated during the first 10 h and then returned to baseline levels for the rest of the post-prandial period. Taken together, our data show that phytase modulates the expression of genes associated with myo-Ins metabolism and generates release of myo-Ins in both circulation and feather at 6–10 h post-feeding. Feather myo-Ins concentration could be used as a non-invasive method to monitor phytate hydrolysis in practice.

A novel fungal beta-propeller phytase from nematophagous Arthrobotrys oligospora: characterization and potential application in phosphorus and mineral release for feed processing

Phytases are widely utilized in feed industry to increase the utilization of phosphorus, minerals, and amino acids for improvement of animal and human nutrition. At present, all known β-propeller phytases (BPP) have been generated from bacteria, particularly Bacillus. In this work we report for the first time a new fungal-derived BPP phytase. We identified a phytase highly differentially expressed only in the parasitic stage of a nematophagous fungus, Arhtrobotrys oliogospora, during the development of the 3D traps. We found that this phytase was homologous to the known bacterial BPP phytase, thus we referred the new phytase to Aophytase. The heterologous expression of codon-optimized Aophytase gene in Pichia pastoris was successfully investigated to yield recombinant Aophytase (r-Aophytase) with high specific enzyme activity of 74.71 U/mg, much higher than those of recombinant BPP phytases derived bacteria. The kinetic parameters of the r-Aophytase, the optimum pH and temperature, as well as the effects of surfactant, EDTA and different ions on its enzyme activity were further investigated. The potential utilization of r-Aophytase in feed processing was finally explored. We found that the optimal pH value was about 7.5, and the optimal temperature was 50 °C.; r-Aophytase significantly increased the release of inorganic phosphorus from soybean meal, and improved the release of soluble minerals from the durum wheat flour and finger millet flour. The findings indicate its potential utilization in the feed processing to ameliorate nutritional value of cereals and animal feed in the future.

Bioprocess for Production, Characteristics, and Biotechnological Applications of Fungal Phytases

Phytases are a group of enzymes that hydrolyze the phospho-monoester bonds of phytates. Phytates are one of the major forms of phosphorus found in plant tissues. Fungi are mainly used for phytase production. The production of fungal phytases has been achieved under three different fermentation methods including solid-state, semi-solid-state, and submerged fermentation. Agricultural residues and other waste materials have been used as substrates for the evaluation of enzyme production in the fermentation process. Nutrients, physical conditions such as pH and temperature, and protease resistance are important factors for increasing phytase production. Fungal phytases are considered monomeric proteins and generally possess a molecular weight of between 14 and 353 kDa. Fungal phytases display a broad substrate specificity with optimal pH and temperature ranges between 1.3 and 8.0 and 37-67°C, respectively. The crystal structure of phytase has been studied in Aspergillus. Notably, thermostability engineering has been used to improve relevant enzyme properties. Furthermore, fungal phytases are widely used in food and animal feed additives to improve the efficiency of phosphorus intake and reduce the amount of phosphorus in the environment.

Use of Plackett-Burman design for enhanced phytase production by Williopsis saturnus NCIM 3298 for applications in animal feed and ethanol production

Distiller-dried grain solid (DDGS), a co-product of alcohol production, contains cereal grain residues, proteins, and yeast metabolites, which make it suitable in poultry feeding. However, high phytate content of DDGS limits its applicability in poultry feed. In this study, Plackett-Burman design was used to improve cell-bound phytase production by Williopsis saturnus NCIM 3298, and we achieved an enzyme activity of 269 IU/g of dry-wet biomass. The effect of this enhanced phytase-displaying yeast strain on hydrolysis of corn phytate and subsequently on ethanol production and DDGS quality was then investigated. Results of saccharification in the presence of phytase showed that reducing sugar content of liquefied mash increased by 11%, which subsequently improved the ethanol production by 18% (w/v) (p < 0.01) compared with the control. Notably, phytase treatment decreased the phytate content of corn by 70% (p < 0.01) compared with the control, thereby improving the availability of free phosphate in fermentation broth and DDGS. Thus, the results obtained suggest that the addition of W. saturnus NCIM 3298 strain has the potential of providing a new source of phytase that would be useful in the feed and ethanol industries.

Thermostable phytase in feed and fuel industries

Phytase with wide ranging biochemical properties has long been utilized in a multitude of industries, even so, thermostability plays a crucial factor in choosing the right phytase in a few of the sectors. Mesophilic phytases are not considered to be a viable option in the feed industry owing to its limited stability in the required feed processing temperature. In the recent past, inclusion of thermostable phytase in fuel ethanol production from starch based raw material has been demonstrated with economic benefits. Therefore, considerable emphasis has been placed on using complementary approaches such as mining of extremophilic microbial wealth, encapsulation and using enzyme engineering for obtaining stable phytase variants. This article means to give an insight on role of thermostable phytases in feed and fuel industries and methods for its development, highlighting molecular determinants of thermostability.

Characteristics of the First Protein Tyrosine Phosphatase with Phytase Activity from a Soil Metagenome

Protein tyrosine phosphatases (PTPs) fulfil multiple key regulatory functions. Within the group of PTPs, the atypical lipid phosphatases (ALPs) are known for their role as virulence factors associated with human pathogens. Another group of PTPs, which is capable of using inositol-hexakisphosphate (InsP₆) as substrate, are known as phytases. Phytases play major roles in the environmental phosphorus cycle, biotechnology, and pathogenesis. So far, all functionally characterized PTPs, including ALPs and PTP-phytases, have been derived exclusively from isolated microorganisms. In this study, screening of a soil-derived metagenomic library resulted in identification of a gene (pho16B), encoding a PTP, which shares structural characteristics with the ALPs. In addition, the characterization of the gene product (Pho16B) revealed the capability of the protein to use InsP₆ as substrate, and the potential of soil as a source of phytases with so far unknown characteristics. Thus, Pho16B represents the first functional environmentally derived PTP-phytase. The enzyme has a molecular mass of 38 kDa. The enzyme is promiscuous, showing highest activity and affinity toward naphthyl phosphate (K_m 0.966 mM). Pho16B contains the HCXXGKDR[TA]G submotif of PTP-ALPs, and it is structurally related to PtpB of Mycobacterium tuberculosis. This study demonstrates the presence and functionality of an environmental gene codifying a PTP-phytase homologous to enzymes closely associated to bacterial pathogenicity.

Partial purification and characterization of phytase from Aspergillus foetidus MTCC 11682

Phytase is a phosphatase enzyme widely used as feed additive to release inorganic phosphorus from plant phytate and enhance its uptake in monogastric animals. Although engineered fungal phytases are used most, a natural enzyme gives opportunity to understand novel properties, if any. In the current study, a novel fungal strain, Aspergillus foetidus MTCC 11682 was immobilized on poly urethane cubes and used for phytase production, purification and molecular characterization. Phytase produced by this method was partially purified by ammonium sulphate precipitation and Sephacryl S-200HR gel filtration to 23.4-fold (compared to crude extract) with recovery of 13% protein. Electrophoresis analysis revealed that phytase has molecular weight of 90.5 kDa on non-reducing and 129.6 kDa on reducing SDS-PAGE. The purified phytase exhibited a wider pH and temperature stability. Analysis of the cloned sequence showed that the gene has 1176 bp that encodes for a peptide of 391 amino acids of the core catalytic region. It was also found that phytase from A. foetidus has a sequence identity of 99% with the phytase gene of other Aspergillus species at nucleotide level and 100% at protein level in A. niger, A. awamori, A. oryzae. In silico analysis of sequence identified the presence of two consecutive and one non-consecutive intra chain disulfide bonds in the phytase. This probably contributed to the differential migration of phytase on reducing and non-reducing SDS-PAGE. There are predicted 11 O-glycosylation sites and 8 N-glycosylation sites, possibly contributed to an enhanced stability of enzyme produced by this organism. This study opened up a new horizon for exploring the novel properties of phytase for other applications.

Computational-based structural, functional and phylogenetic analysis of Enterobacter phytases

Myo-inositol hexakisphosphate phosphohydrolases (i.e., phytases) are known to be a very important enzyme responsible for solubilization of insoluble phosphates. In the present study, Enterobacter phytases have characterized by different phylogenetic, structural and functional parameters using some standard bio-computational tools. Results showed that majority of the Enterobacter phytases are acidic in nature as most of the isoelectric points were under 7.0. The aliphatic indices predicted for the selected proteins were below 40 indicating their thermostable nature. The average molecular weight of the proteins was 48 kDa. The lower values of GRAVY of the said proteins implied that they have better interactions with water. Secondary structure prediction revealed that alpha-helical content was highest among the other forms such as sheets, coils, etc. Moreover, the predicted 3D structure of Enterobacter phytases divulged that the proteins consisted of four monomeric polypeptide chains i.e., it was a tetrameric protein. The predicted tertiary model of E. aerogenes (A0A0M3HCJ2) was deposited in Protein Model Database (Acc. No.: PM0080561) for further utilization after a thorough quality check from QMEAN and SAVES server. Functional analysis supported their classification as histidine acid phosphatases. Besides, multiple sequence alignment revealed that "DG-DP-LG" was the most highly conserved residues within the Enterobacter phytases. Thus, the present study will be useful in selecting suitable phytase-producing microbe exclusively for using in the animal food industry as a food additive.

Bacterial PhyA protein-tyrosine phosphatase-like myo-inositol phosphatases in complex with the Ins(1,3,4,5)P4 and Ins(1,4,5)P3 second messengers

myo-Inositol phosphates (IPs) are important bioactive molecules that have multiple activities within eukaryotic cells, including well-known roles as second messengers and cofactors that help regulate diverse biochemical processes such as transcription and hormone receptor activity. Despite the typical absence of IPs in prokaryotes, many of these organisms express IPases (or phytases) that dephosphorylate IPs. Functionally, these enzymes participate in phosphate-scavenging pathways and in plant pathogenesis. Here, we determined the X-ray crystallographic structures of two catalytically inactive mutants of protein-tyrosine phosphatase-like myo-inositol phosphatases (PTPLPs) from the non-pathogenic bacteria Selenomonas ruminantium (PhyAsr) and Mitsuokella multacida (PhyAmm) in complex with the known eukaryotic second messengers Ins(1,3,4,5)P₄ and Ins(1,4,5)P₃ Both enzymes bound these less-phosphorylated IPs in a catalytically competent manner, suggesting that IP hydrolysis has a role in plant pathogenesis. The less-phosphorylated IP binding differed in both the myo-inositol ring position and orientation when compared with a previously determined complex structure in the presence of myo-inositol-1,2,3,4,5,6-hexakisphosphate (InsP₆ or phytate). Further, we have demonstrated that PhyAsr and PhyAmm have different specificities for Ins(1,2,4,5,6)P₅, have identified structural features that account for this difference, and have shown that the absence of these features results in a broad specificity toward Ins(1,2,4,5,6)P₅ These features are main-chain conformational differences in loops adjacent to the active site that include the extended loop prior to the penultimate helix, the extended Ω-loop, and a β-hairpin turn of the Phy-specific domain.

Whole genome-wide transcript profiling to identify differentially expressed genes associated with seed field emergence in two soybean low phytate mutants

BACKGROUND

Seed germination is important to soybean (Glycine max) growth and development, ultimately affecting soybean yield. A lower seed field emergence has been the main hindrance for breeding soybeans low in phytate. Although this reduction could be overcome by additional breeding and selection, the mechanisms of seed germination in different low phytate mutants remain unknown. In this study, we performed a comparative transcript analysis of two low phytate soybean mutants (TW-1 and TW-1-M), which have the same mutation, a 2 bp deletion in GmMIPS1, but show a significant difference in seed field emergence, TW-1-M was higher than that of TW-1 .

RESULTS

Numerous genes analyzed by RNA-Seq showed markedly different expression levels between TW-1-M and TW-1 mutants. Approximately 30,000-35,000 read-mapped genes and ~21000-25000 expressed genes were identified for each library. There were ~3900-9200 differentially expressed genes (DEGs) in each contrast library, the number of up-regulated genes was similar with down-regulated genes in the mutant TW-1and TW-1-M. Gene ontology functional categories of DEGs indicated that the ethylene-mediated signaling pathway, the abscisic acid-mediated signaling pathway, response to hormone, ethylene biosynthetic process, ethylene metabolic process, regulation of hormone levels, and oxidation-reduction process, regulation of flavonoid biosynthetic process and regulation of abscisic acid-activated signaling pathway had high correlations with seed germination. In total, 2457 DEGs involved in the above functional categories were identified. Twenty-two genes with 20 biological functions were the most highly up/down- regulated (absolute value Log2FC >5) in the high field emergence mutant TW-1-M and were related to metabolic or signaling pathways. Fifty-seven genes with 36 biological functions had the greatest expression abundance (FRPM >100) in germination-related pathways.

CONCLUSIONS

Seed germination in the soybean low phytate mutants is a very complex process, which involves a series of physiological, morphological and transcriptional changes. Compared with TW-1, TW-1-M had a very different gene expression profile, which included genes related to plant hormones, antioxidation, anti-stress and energy metabolism processes. Our research provides a molecular basis for understanding germination mechanisms, and is also an important resource for the genetic analysis of germination in low phytate crops. Plant hormone- and antioxidation-related genes might strongly contribute to the high germination rate in the TW-1-M mutant.

A Colletotrichum graminicola mutant deficient in the establishment of biotrophy reveals early transcriptional events in the maize anthracnose disease interaction

BACKGROUND

Colletotrichum graminicola is a hemibiotrophic fungal pathogen that causes maize anthracnose disease. It progresses through three recognizable phases of pathogenic development in planta: melanized appressoria on the host surface prior to penetration; biotrophy, characterized by intracellular colonization of living host cells; and necrotrophy, characterized by host cell death and symptom development. A "Mixed Effects" Generalized Linear Model (GLM) was developed and applied to an existing Illumina transcriptome dataset, substantially increasing the statistical power of the analysis of C. graminicola gene expression during infection and colonization. Additionally, the in planta transcriptome of the wild-type was compared with that of a mutant strain impaired in the establishment of biotrophy, allowing detailed dissection of events occurring specifically during penetration, and during early versus late biotrophy.

RESULTS

More than 2000 fungal genes were differentially transcribed during appressorial maturation, penetration, and colonization. Secreted proteins, secondary metabolism genes, and membrane receptors were over-represented among the differentially expressed genes, suggesting that the fungus engages in an intimate and dynamic conversation with the host, beginning prior to penetration. This communication process probably involves reception of plant signals triggering subsequent developmental progress in the fungus, as well as production of signals that induce responses in the host. Later phases of biotrophy were more similar to necrotrophy, with increased production of secreted proteases, inducers of plant cell death, hydrolases, and membrane bound transporters for the uptake and egress of potential toxins, signals, and nutrients.

CONCLUSIONS

This approach revealed, in unprecedented detail, fungal genes specifically expressed during critical phases of host penetration and biotrophic establishment. Many encoded secreted proteins, secondary metabolism enzymes, and receptors that may play roles in host-pathogen communication necessary to promote susceptibility, and thus may provide targets for chemical or biological controls to manage this important disease. The differentially expressed genes could be used as 'landmarks' to more accurately identify developmental progress in compatible versus incompatible interactions involving genetic variants of both host and pathogen.

Candida parapsilosis (sensu lato) isolated from hospitals located in the Southeast of Brazil: Species distribution, antifungal susceptibility and virulence attributes

Candida parapsilosis (sensu lato), which represents a fungal complex composed of three genetically related species - Candida parapsilosis sensu stricto, Candida orthopsilosis and Candida metapsilosis, has emerged as an important yeast causing fungemia worldwide. The goal of the present work was to assess the prevalence, antifungal susceptibility and production of virulence traits in 53 clinical isolates previously identified as C. parapsilosis (sensu lato) obtained from hospitals located in the Southeast of Brazil. Species forming this fungal complex are physiologically/morphologically indistinguishable; however, polymerase chain reaction followed by restriction fragment length polymorphism of FKS1 gene has solved the identification inaccuracy, revealing that 43 (81.1%) isolates were identified as C. parapsilosis sensu stricto and 10 (18.9%) as C. orthopsilosis. No C. metapsilosis was found. The geographic distribution of these Candida species was uniform among the studied Brazilian States (São Paulo, Rio de Janeiro and Espírito Santo). All C. orthopsilosis and almost all C. parapsilosis sensu stricto (95.3%) isolates were susceptible to amphotericin B, fluconazole, itraconazole, voriconazole and caspofungin. Nevertheless, one C. parapsilosis sensu stricto isolate was resistant to fluconazole and another one was resistant to caspofungin. C. parapsilosis sensu stricto isolates exhibited higher MIC mean values to amphotericin B, fluconazole and caspofungin than those of C. orthopsilosis, while C. orthopsilosis isolates displayed higher MIC mean to itraconazole compared to C. parapsilosis sensu stricto. Identical MIC mean values to voriconazole were measured for these Candida species. All the isolates of both species were able to form biofilm on polystyrene surface. Impressively, biofilm-growing cells of C. parapsilosis sensu stricto and C. orthopsilosis exhibited a considerable resistance to all antifungal agents tested. Pseudohyphae were observed in 67.4% and 80% of C. parapsilosis sensu stricto and C. orthopsilosis isolates, respectively. The secretion of phytase (93% versus 100%), aspartic protease (88.4% versus 90%), esterase (20.9% versus 50%) and hemolytic factors (25.6% versus 40%) was detected in C. parapsilosis sensu stricto and C. orthopsilosis isolates, respectively; however, no phospholipase activity was identified. An interesting fact was observed concerning the caseinolytic activity, for which all the producers (53.5%) belonged to C. parapsilosis sensu stricto. Collectively, our results add new data on the epidemiology, antifungal susceptibility and production of potential virulence attributes in clinical isolates of C. parapsilosis complex.

Characteristics and Applicability of Phytase of the Yeast Pichia anomala in Synthesizing Haloperoxidase

The phytase of the yeast Pichia anomala is a histidine acid phosphatase based on signature sequences and catalytic amino acids identified by site-directed mutagenesis. Among modulators, N-bromosuccinimide and butanedione inhibit phytase, while Ca(2+) and Ni(2+) stimulate slightly. Vanadate exhibits competitive inhibition of phytase, making it bifunctional to act as haloperoxidase. Molecular docking supports vanadate to share its binding site with phytate. The T 1/2, activation energy (E a ), temperature quotient (Q 10), activation energy of thermal inactivation (Ed), and enthalpy (ΔH d (0) ) of the enzyme are 4.0 min (80 °C), 27.72 kJ mol(-1), 2.1, 410.62 kJ mol(-1), and ∼407.8 kJ mol(-1) (65-80 °C), respectively. The free energy of the process (ΔG d (o) ) increases from 49.56 to 71.58 kJ mol(-1) with rise in temperature, while entropy of inactivation (ΔS d (0) ) remains constant at ∼1.36 kJ mol(-1) K(-1). The supplementation of whole wheat dough with rPPHY resulted in 72.5 % reduction in phytic acid content of bread. These characteristics confirm that the phytase has adequate thermostability for its applicability as a food and feed additive.

Bacillus phytases: Current status and future prospects

Phytases catalyze the hydrolysis of phytic acid in a stepwise manner to lower inositol phosphates, myo-inositol (having important role in metabolism and signal transduction pathways), and inorganic phosphate. These enzymes have been widely used in animal feed in order to improve phosphorus nutrition and to decrease pollution in animal waste. Compared to previously described phytases, the phytase (PhyL) from Bacillus licheniformis ATCC 14580 has attractive biochemical properties which can increase the profitability of several biotechnological procedures (animal nutrition, humain health…etc). Due to its amino acid sequence with critical substitutions, the PhyL could be a model to enhance other phytases features, in terms of thermal stability and high activity. Otherwise, an engineered PhyL, with low pH optimum, will represent a challenge within the class of β- propeller phytases.

Enhanced Aspergillus ficuum phytase production in fed-batch and continuous fermentations in the presence of talcum microparticles

This study aimed to enhance Aspergillus ficuum phytase production in fed-batch and continuous fermentations with addition of talcum microparticles. Phytase activity almost doubled in fed-batch and continuous fermentations by addition of 15 g/l of talcum compared to the control. Effect of talcum on fungal morphology was also shown that addition of talcum provided smaller fungal pellets and more homogenized fermentation broth compared to the control. Average fungal pellet radius decreased from 500 to 100 µm by addition of 15 g/l of talcum in the bioreactors. Also, 15 g/l talcum addition increased phytase productivity and optimum dilution rate in the continuous fermentations from 0.293 to 0.621 U/ml/h and from 0.09 to 0.1/h, respectively, compared to control.

Microparticle-enhanced Aspergillus ficuum phytase production and evaluation of fungal morphology in submerged fermentation

Phytase can be used in animal's diets to increase the absorption of several divalent ions, amino acids and proteins and to decrease the excessive phosphorus release in manure to prevent negative effects on the environment. This study aimed to enhance the current submerged fungal phytase productions with a novel fermentation technique by evaluating the effect of the various microparticles on Aspergillus ficuum phytase production. It was observed that microparticles prevented bulk fungal pellet growth, decreased average fungal pellet size and significantly increased phytase activity in the submerged fermentation. Microbial structure imaging results showed that the average fungal pellet radius decreased from 800 to 500 and 200 µm by addition of 15 g/L aluminum oxide and talcum, respectively, in shake-flask fermentation. Also, addition of 15 g/L of talcum and aluminum oxide increased phytase activity to 2.01 and 2.93 U/ml, respectively, compared to control (1.02 U/ml) in shake-flask fermentation. Additionally, phytase activity reached 6.49 U/ml within 96 h of fermentation with the addition of 15 g/L of talcum, whereas the maximum phytase activity was only 3.45 U/ml at 120 h of fermentation for the control in the 1-L working volume bioreactors. In conclusion, microparticles significantly increased fungal phytase activity and production yield compared to control fermentation.

Charge-switchable gold nanoparticles for enhanced enzymatic thermostability

Zwitterionic amino acids allow the synthesis of charge-switchable metal nanoparticles, which support efficient immobilization of enzymes on nanoparticles, leading to high thermal stability and enzymatic efficiency.

Preparation, purification, crystallization and preliminary crystallographic analysis of dual-domain β-propeller phytase from Bacillus sp. HJB17

β-Propeller phytases (BPPs) are abundant in nature. Recently, dual-domain BPPs have been found in which the typical BPP domain is responsible for phytate hydrolysis. The dual-domain BPP (PhyH) from Bacillus sp. HJB17 was obtained with an incomplete N-terminal BPP domain (PhyH-DI; residues 41-318) and a typical BPP domain (PhyH-DII; residues 319-644) at the C-terminus. PhyH-DI was found to act synergistically (with a 1.2-2.5-fold increase in phosphate release) with PhyH-DII, other BPPs (PhyP and 168PhyA) and a histidine acid phosphatase. The structure of PhyH was therefore studied with the aim of explaining these functions. PhyH with the secreted signal peptide of the first 40 amino acids deleted (PhyHT) was cloned and expressed in Escherichia coli. Purified and active PhyHT protein was obtained by refolding from the precipitant. PhyHT was crystallized using the vapour-diffusion method. The crystal grew in a condition consisting of 0.2 M sodium acetate trihydrate, 0.1 M Tris-HCl pH 9.5, 25%(w/v) polyethylene glycol 4000 using 1 mg ml(-1) protein solution at 289 K. A complete data set was collected from a crystal to 2.85 Å resolution using synchrotron radiation at 100 K. The crystal belonged to space group P1211, with unit-cell parameters a = 46.82, b = 140.19, c = 81.94 Å, α = 90.00, β = 92.00, γ = 90.00°. The asymmetric unit was estimated to contain one molecule of PhyHT.

Production of Lupin Acid Phosphatase in Transgenic Rice for Use as a Phytate-hydrolyzing Enzyme in Animal Feed

The acid phosphatase gene from lupin was expressed in transgenic rice plants under the control of the maize ubiquitin promoter or rice chlorophyll a/b binding protein (Cab) promoter. Transgenic rice leaves exhibited up to an 18-fold increase in phytate-hydrolyzing activity. Based on the phytate-hydrolyzing activity at pH 5.5, more than 85% this activity was retained after heat-treatment at 80 degrees C for 15 min, and the heterologous enzyme in leaf sections and leaf extracts was relatively stable during storage. A distinct increase in released phosphate was observed when the heterologous enzyme was mixed with the feed extract. These results suggest that the heterologous enzyme in rice plants may maintain its desired characteristics as a phytate-hydrolyzing enzyme when added to animal feed.

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.

Phytase production by Aspergillus niger CFR 335 and Aspergillus ficuum SGA 01 through submerged and solid-state fermentation

Fermentation is one of the industrially important processes for the development of microbial metabolites that has immense applications in various fields. This has prompted to employ fermentation as a major technique in the production of phytase from microbial source. In this study, a comparison was made between submerged (SmF) and solid-state fermentations (SSF) for the production of phytase from Aspergillus niger CFR 335 and Aspergillus ficuum SGA 01. It was found that both the fungi were capable of producing maximum phytase on 5th day of incubation in both submerged and solid-state fermentation media. Aspergillus niger CFR 335 and A. ficuum produced a maximum of 60.6 U/gds and 38 U/gds of the enzyme, respectively, in wheat bran solid substrate medium. Enhancement in the enzyme level (76 and 50.7 U/gds) was found when grown in a combined solid substrate medium comprising wheat bran, rice bran, and groundnut cake in the ratio of 2 : 1 : 1. A maximum of 9.6 and 8.2 U/mL of enzyme activity was observed in SmF by A. niger CFR 335 and A.ficuum, respectively, when grown in potato dextrose broth.