A phytase characterized by relatively high pH tolerance and thermostability from the shiitake mushroom Lentinus edodes

Improved Thermal Stability of a Novel Acidophilic Phytase

Phytase increases the availability of phosphate and trace elements by hydrolyzing the phosphomonoester bond in phytate present in animal feed. It is also an important enzyme from an environmental perspective because it not only promotes the growth of livestocks but also prevents phosphorus contamination released into the environment. Here we present a novel phytase derived from Turicimonas muris, TmPhy, which has distinctive structure and properties compared to other previously known phytases. TmPhy gene expressed in the Pichia system was confirmed to be 41 kDa in size and was used in purified form to evaluate optimal conditions for maximum activity. TmPhy has a dual optimum pH at pH3 and pH6.8 and exhibited the highest activity at 70°C. However, the heat tolerance of the wildtype was not satisfactory for feed application. Therefore, random mutation, disulfide bond introduction, and N-terminal mutation were performed to improve the thermostability of the TmPhy. Random mutation resulted in TmPhyM with about 45% improvement in stability at 60°C. Through further improvements, a total of three mutants were screened and their heat tolerance was evaluated. As a result, we obtained TmPhyMD1 with 46.5% residual activity, TmPhyMD2 with 74.1%, and TmPhyMD3 with 66.8% at 80°C heat treatment without significant loss of or with increased activity.

Impact of Household Cooking Techniques on African Nightshade and Chinese Cabbage on Phenolic Compounds, Antinutrients, in vitro Antioxidant, and β-Glucosidase Activity

Different household cooking techniques (boiling, steaming, stir frying, and microwave) were tested on the changes of targeted phenolic compounds, antioxidant property (ferric reducing-antioxidant power (FRAP) activity), α-glucosidase activity, antinutritive compounds, and sensory properties in commonly consumed traditional leafy vegetables in Southern Africa, the non-heading Chinese cabbage (Brassica rapa L. subsp. chinensis) and African nightshade (Solanum retroflexum Dun). Stir frying increased kaempferol-3-O-hydroxyferuloyl-trihexoside, kaempferol-dihexoside, sinapoyl malate, rutin, and isorhamnetin-O-dihexoside in Chinese cabbage leaves, followed by steaming. Similarly, stir frying increased kaempferol-3-O-rutinoside, chlorogenic acid, caffeoylmalic acid, and quercetin-3-O-xylosyl-rutinoside in nightshade, followed by steaming. Biomarkers, sinapoyl malate (Chinese cabbage) and caffeoylmalic acid (nightshade), separated the stir frying from the other cooking techniques. Steaming and stir-frying techniques significantly increased the FRAP activity; whereas boiling and microwaving reduced the tannin, oxalate, and phytate contents in both leafy vegetables and steroidal saponins in nightshade. Stir-fried nightshade leaf extract showed the most effective inhibition against α-glucosidase activity, with an IC₅₀ of 26.4 μg ml^-1, which was higher than acarbose, a synthetic compound (positive control; IC₅₀ 69.83 μg ml^-1). Sensory panelists preferred the stir-fried Chinese cabbage and nightshade leaves, followed by steamed, microwaved, and boiled vegetables.

Fungal phytases: from genes to applications

Phytic acid stores 60-90% of the inorganic phosphorus in legumes, oil seeds, and cereals, making it inaccessible for metabolic processes in living systems. In addition, given its negative charge, phytic acid complexes with divalent cations, starch, and proteins. Inorganic phosphorous can be released from phytic acid upon the action of phytases. Phytases are phosphatases produced by animals, plants, and microorganisms, notably Aspergillus niger, and are employed as animal feed additive, in chemical industry and for ethanol production. Given the industrial relevance of phytases produced by filamentous fungi, this work discusses the functional characterization of fungal phytase-coding genes/proteins, highlighting the physicochemical parameters that govern the enzymatic activity, the development of phytase super-producing strains, and key features for industrial applications.

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.

An in vitro chicken gut model for the assessment of phytase producing bacteria

An in vitro simulated chicken gut model was proposed for studying the phytase activity of selected bacteria such as Streptococcus thermophilus, Sporosarcina pasteurii, Sporosarcina globispora, and Sporosarcina psychrophila using known probiotic bacterium, Lactobacillus helveticus as a control. The selected bacteria were viable in the intestinal lumen and produced extracellular phytase at optimal phytate concentration of 6.25 mM when compared to 3.125 mM and 12.5 mM. These bacteria demonstrated significantly higher (p < 0.05) phosphate liberation (up to 387 µM) due to better phytase activity in the production medium, when compared to the growth medium (339 µM). The phytase activity showed a steady increase in phosphate liberation up to 150 min after which it became constant. This trend is observed for the selected bacteria at pH 5, 6 and 7. However, the liberation of phosphates showed no significant difference (p > 0.05) at the tested pH. Among the analyzed bacteria, the members of the genus Sporosarcina showed better phytate degradation when compared to S. thermophilus. The proposed model can be extended to analyze any extracellular enzymes produced by gut microbes.

Strain improvement of Pichia kudriavzevii TY13 for raised phytase production and reduced phosphate repression

In this work, we present the development and characterization of a strain of Pichia kudriavzevii (TY1322), with highly improved phytate‐degrading capacity. The mutant strain TY1322 shows a biomass‐specific phytate degradation of 1.26 mmol g⁻¹ h⁻¹ after 8 h of cultivation in a high‐phosphate medium, which is about 8 times higher compared with the wild‐type strain. Strain TY1322 was able to grow at low pH (pH 2), at high temperature (46°C) and in the presence of ox bile (2% w/v), indicating this strain's ability to survive passage through the gastrointestinal tract. The purified phytase showed two pH optima, at pH 3.5 and 5.5, and one temperature optimum at 55°C. The lower pH optimum of 3.5 matches the reported pH of the pig stomach, meaning that TY1322 and/or its phytase is highly suitable for use in feed production. Furthermore, P. kudriavzeviiTY1322 tolerates ethanol up to 6% (v/v) and shows high osmotic stress tolerance. Owing to the phenotypic characteristics and non‐genetically modified organisms nature of TY1322, this strain show great potential for future uses in (i) cereal fermentations for increased mineral bioavailability, and (ii) feed production to increase the phosphate bioavailability for monogastric animals to reduce the need for artificial phosphate fortification.

Mechanism of Calcium Lactate Facilitating Phytic Acid Degradation in Soybean during Germination

Calcium lactate facilitates the growth and phytic acid degradation of soybean sprouts, but the mechanism is unclear. In this study, calcium lactate (Ca) and calcium lactate with lanthanum chloride (Ca+La) were used to treat soybean sprouts to reveal the relevant mechanism. Results showed that the phytic acid content decreased and the availability of phosphorus increased under Ca treatment. This must be due to the enhancement of enzyme activity related to phytic acid degradation. In addition, the energy metabolism was accelerated by Ca treatment. The energy status and energy metabolism-associated enzyme activity also increased. However, the transmembrane transport of calcium was inhibited by La(3+) and concentrated in intercellular space or between the cell wall and cell membrane; thus, Ca+La treatment showed reverse results compared with those of Ca treatment. Interestingly, gene expression did not vary in accordance with their enzyme activity. These results demonstrated that calcium lactate increased the rate of phytic acid degradation by enhancing growth, phosphorus metabolism, and energy metabolism.

A novel phytase characterized by thermostability and high pH tolerance from rice phyllosphere isolated Bacillus subtilis B.S.46

In this study, an extracellular alkali-thermostable phytase producing bacteria, Bacillus subtilis B.S.46, were isolated and molecularly identified using 16S rRNA sequencing. Response surface methodology was applied to study the interaction effects of assay conditions to obtain optimum value for maximizing phytase activity. The optimization resulted in 137% (4.627 U/mL) increase in phytase activity under optimum condition (56.5 °C, pH 7.30 and 2.05 mM sodium phytate). The enzyme also showed 60-73% of maximum activity at wide ranges of temperature (47-68 °C), pH (6.3-8.0) and phytate concentration (1.40-2.50 mM). The partially purified phytase demonstrated high stability over a wide range of pH (6.0-10.0) after 24 h, retaining 85% of its initial activity at pH 6 and even interestingly, the phytase activity enhanced at pH 8.0-10.0. It also exhibited thermostability, retaining about 60% of its original activity after 2 h at 60 °C. Cations such as Ca(2+) and Li(+) enhanced the phytase activity by 10-46% at 1 mM concentration. The phytase activity was completely inhibited by Cu(2+), Mg(2+), Fe(2+), Zn(2+), Hg(2+) and Mn(2+) and the inhibition was in a dose dependent manner. B. subtilis B.S.46 phytase had interesting characteristics to be considered as animal feed additive, dephytinization of food ingredients, and bioremediation of phosphorous pollution in the environment.