Purification and characterisation of an extracellular phytase from Aspergillus niger 11T53A9

Strategies of organic phosphorus recycling by soil bacteria: acquisition, metabolism, and regulation

Critical to meeting cellular phosphorus (P) demand, soil bacteria deploy a number of strategies to overcome limitation in inorganic P (P_i ) in soils. As a significant contributor to P recycling, soil bacteria secrete extracellular enzymes to degrade organic P (P_o ) in soils into the readily bioavailable P_i . In addition, several P_o compounds can be transported directly via specific transporters and subsequently enter intracellular metabolic pathways. In this review, we highlight the strategies that soil bacteria employ to recycle P_o from the soil environment. We discuss the diversity of extracellular phosphatases in soils, the selectivity of these enzymes towards various P_o biomolecules and the influence of the soil environmental conditions on the enzyme's activities. Moreover, we outline the intracellular metabolic pathways for P_o biosynthesis and transporter-assisted P_o and P_i uptake at different P_i availabilities. We further highlight the regulatory mechanisms that govern the production of phosphatases, the expression of P_o transporters and the key metabolic changes in P metabolism in response to environmental P_i availability. Due to the depletion of natural resources for P_i , we propose future studies needed to leverage bacteria-mediated P recycling from the large pools of P_o in soils or organic wastes to benefit agricultural productivity.

Recovery and purification of Aspergillus niger phytase from crude extract using AOT / isooctane reversed micelles

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The application of the reverse micelles resulted in purification of A. niger phytase.

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It was possible purify phytase from A. niger by reversed micelles in short period time.

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Reversed micelles proved to be a viable alternative for phytase purification.

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Phytase remained active after extraction using AOT/isooctane reversed micelles.

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The phytase purity and activity were confirmed by SDS-PAGE and zymogram analyzes.

This work describes the successful extraction of Aspergillus niger phytase from a crude extract (CE) obtained from solid-state fermentation by reversed micelle system using anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane achieved in two simple steps: forward and backward extractions. The effects of potassium chloride (KCl) concentration, pH of the aqueous solution, and AOT concentration that affect the system were examined. The best result for the forward extraction was obtained with the CE solution at pH 4.0, 50 mM KCl, and 100 mM AOT, while for the backward extraction the best result was achieved with a stripping aqueous solution at pH 5.5 containing 200 mM KCl, achieving a purification factor of 4.03, 1.15 times higher than that reported for the conventional purification process. Phytase purity was demonstrated by SDS-PAGE (89 kDa) and its activity by zymogram, confirming the efficiency of the process with low time consumption (∼40 min).

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.

Phytases from Enterobacter and Serratia species with desirable characteristics for food and feed applications

Phytases are enzymes of great industrial importance with wide range of applications in animal and human nutrition. These catalyze the hydrolysis of phosphomonoester bonds in phytate, thereby releasing lower forms of myo-inositol phosphates and inorganic phosphate. Addition of phytase to plant-based foods can improve its nutritional value and increase mineral bioavailability by decreasing nutritional effect of phytate. In the present investigation, 43 phytase positive bacteria on PSM plates were isolated from different sources and characterized for phytase activity. On the basis of phytase activity and zone of hydrolysis, two bacterial isolates (PSB-15 and PSB-45) were selected for further characterization studies, i.e., pH and temperature optima and stability, kinetic properties and effect of modulators. The phytases from both isolates were optimally active at the pH value from 3 to 8 and in the temperature range of 50-70 °C. Further, the stability of isolates was good in the pH range of 3.0-8.0. Much variation was observed in temperature and storage stability, responses of phytases to metal ions and modulators. The K m and V max values for PSB-15 phytase were 0.48 mM and 0.157 μM/min, while for PSB-45 these were 1.25 mM and 0.140 μM/min, respectively. Based on 16S rDNA gene sequence, the isolates were identified as Serratia sp. PSB-15 (GenBank Accession No. KR133277) and Enterobacter cloacae strain PSB-45 (GenBank Accession No. KR133282). The novel phytases from these isolates have multiple characteristics of high thermostability and good phytase activity at desirable range of pH and temperature for their efficient use in food and feed to facilitate hydrolysis of phytate-metal ion complex and in turn, increased bioavailability of important metal ions to monogastric animals.

Performance of Seven Commercial Phytases in an in Vitro Simulation of Poultry Digestive Tract

The aim of this study was to compare the biochemical properties of seven commercially available phytase products as well as their catalytic performance in an in vitro simulation of the digestive tract of poultry. Their enzymatic properties relevant with respect to phytate dephosphorylation in the digestive tract of birds were determined under identical assay conditions. All phytase products included in the study showed an acid pH optimum of activity and were capable of releasing the organically bound phosphate from phytate during the in vitro simulation. However, their overall biochemical properties and relative catalytic performances were remarkably different. The in vitro degradation system was considered as a simple and useful tool to evaluate the suitability of a phytase to be used as a feed supplement. Although relevant factors such as dietary P levels, intestinal phytase, and P absorption are not implemented in the system, this approach might help to reduce the number of feeding trials necessary in the search for a better suited phytase for animal feeding application.

Isolation of a thermostable acid phytase from Aspergillus niger UFV-1 with strong proteolysis resistance

An Aspergillus niger UFV-1 phytase was characterized and made available for industrial application. The enzyme was purified via ultrafiltration followed by acid precipitation, ion exchange and gel filtration chromatography. This protein exhibited a molecular mass of 161 kDa in gel filtration and 81 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), indicating that it may be a dimer. It presented an optimum temperature of 60 °C and optimum pH of 2.0. The K M for sodium phytate hydrolysis was 30.9 mM, while the k cat and k cat / K M were 1.46 ×10 (5) s (-1) and 4.7 × 10 (6) s (-1) .M (-1) , respectively. The purified phytase exhibited broad specificity on a range of phosphorylated compounds, presenting activity on sodium phytate, p-NPP, 2- naphthylphosphate, 1- naphthylphosphate, ATP, phenyl-phosphate, glucose-6-phosphate, calcium phytate and other substrates. Enzymatic activity was slightly inhibited by Mg (2+) , Cd (2+) , K (+) and Ca (2+) , and it was drastically inhibited by F (-) . The enzyme displayed high thermostability, retaining more than 90% activity at 60 °C during 120 h and displayed a t 1/2 of 94.5 h and 6.2 h at 70 °C and 80 °C, respectively. The enzyme demonstrated strong resistance toward pepsin and trypsin, and it retained more than 90% residual activity for both enzymes after 1 h treatment. Additionally, the enzyme efficiently hydrolyzed phytate in livestock feed, liberating 15.3 μmol phosphate/mL after 2.5 h of treatment.

Hydrolysis of phytate and formation of inositol phosphate isomers without or with supplemented phytases in different segments of the digestive tract of broilers

The objective was to characterise degradation of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP₆) and formation of inositol phosphate (InsP) isomers in different segments of the broiler digestive tract. Influence of an Aspergillus niger (PhyA) and two Escherichia coli-derived (PhyE1 and PhyE2) phytases was also investigated. A total of 600 16-d-old broilers were allocated to forty floor pens (ten pens per treatment). Low-P (5·2 g/kg DM) maize–soyabean meal-based diets were fed without (basal diet; BD) or with a phytase added. On day 25, digesta from different digestive tract segments were pooled per segment on a pen-basis, freeze-dried and analysed for P, InsP isomers and the marker TiO₂. InsP₆ degradation until the lower ileum (74 %) in BD-fed birds showed a high potential of broilers and their gut microbiota to hydrolyse InsP₆ in low-P diets. Different InsP patterns in different gut segments suggested the involvement of phosphatases of different origin. Supplemented phytases increased InsP₆ hydrolysis in the crop (P < 0·01) but not in the lower ileum. Measurements in the crop and proventriculus/gizzard confirmed published in vitro degradation pathways of 3- and 6-phytases for the first time. In the intestinal segments, specifically formed InsP_4–5 isomers of supplemented phytases were still present, indicating further activity of these enzymes. Myo-inositol tetrakisphosphate (InsP₄) accumulation differed between PhyE1 and PhyE2 compared with PhyA in the anterior segments of the gut (P < 0·01). Thus, the hydrolytic cleavage of the first phosphate group is not the only limiting step in phytate degradation in broilers.