New Aspergillus niger Phytase Boosts Mineral Bioavailability and Nutrient Release from Sorghum Flour

Scientists Uncover a Powerful Phytase from Aspergillus niger NT7 to Improve Nutrient Absorption in Plant-Based Foods

A team of Indian researchers has successfully purified and characterized a highly stable and efficient phytase enzyme from Aspergillus niger NT7, revealing its remarkable potential to enhance the nutritional quality of cereal-based foods. The study, published in the World Journal of Microbiology and Biotechnology (2025), details the enzyme’s purification, biochemical traits, and its ability to dephytinize sorghum flour under simulated gastric and intestinal conditions.

Phytate, the major storage form of phosphorus in plants, is known to bind essential minerals like iron, zinc, and calcium, reducing their bioavailability in plant-based diets. This anti-nutrient effect not only limits mineral uptake in humans and monogastric animals but also contributes to environmental phosphate waste. Phytase enzymes can counter this by hydrolyzing phytate into bioavailable forms of phosphate and inositol derivatives, but industrial application has been limited by poor thermal stability and susceptibility to digestive enzymes.

In this new work, A. niger NT7—previously isolated from maize rhizosphere—was used to produce phytase through solid-state fermentation on wheat bran. The enzyme was purified using ammonium sulfate precipitation and DEAE-Sepharose chromatography, achieving an 11.48-fold purification and a specific activity of 34.93 U/mg. The purified phytase had a molecular weight of about 70 kDa, showed optimal activity at pH 5.0 and 50 °C, and demonstrated strong thermotolerance with half-lives of 288.75 min (50 °C), 106.61 min (60 °C), and 52.90 min (70 °C).

Kinetic studies revealed a KM of 1.98 mM and a Vmax of 99 U/mg, confirming the enzyme’s high substrate affinity and catalytic efficiency. The phytase remained resistant to degradation by proteases such as trypsin and pepsin and retained over 90 % activity after one month at 4 °C, indicating excellent storage stability.

Crucially, the enzyme was tested for its dephytinization efficiency in sorghum flour during simulated digestion. Supplementation with A. niger NT7 phytase reduced phytic acid content by approximately 90 %, while significantly increasing the release of inorganic phosphate, reducing sugars, proteins, and free amino acids. ICP-MS analysis further confirmed improved mineral bioaccessibility, particularly for Zn²⁺, Fe²⁺, and Mn²⁺ ions, under both gastric and intestinal conditions.

According to lead author Saurabh Bansal, the robust performance of A. niger NT7 phytase under acidic, thermal, and proteolytic stress makes it an excellent candidate for use in both food and feed industries. Its ability to enhance nutrient absorption in plant-based foods like sorghum offers a sustainable route to combat mineral deficiencies, especially in regions relying on cereal staples.

The enzyme’s strong functional profile—acidic resilience, thermostability, and protease resistance—positions it for commercial exploitation as a functional food additive or feed supplement. Further studies will focus on scaling up production, formulation stability, and in-vivo validation for food fortification applications.

Reference

Kumari, N., Shrivastava, R., Sharma, A., & Bansal, S. (2025). Purification and biochemical characterization of Aspergillus niger NT7 phytase: Evaluation of its dephytinization potential under simulated digestion conditions. World Journal of Microbiology and Biotechnology, 41(10), 406. https://doi.org/10.1007/s11274-025-04572-8