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Characterization of phytase produced by Aspergillus niger
J Dvoráková1, O Volfová, J Kopecký
1Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Folia Microbiologica
|January 1, 1997
Summary
Aspergillus niger phytase exhibits high extracellular activity and stability. This enzyme shows broad substrate specificity, with optimal activity at pH 5.0 and 55°C, making it a promising candidate for various applications.
Area of Science:
- Biochemistry
- Enzymology
- Microbiology
Background:
- Phytases are crucial enzymes that catalyze the hydrolysis of phytate, releasing inorganic phosphate.
- Understanding the properties of microbial phytases is essential for their industrial applications, particularly in animal feed and nutrient management.
- Aspergillus niger is a well-known source of industrially relevant enzymes, including phytase.
Purpose of the Study:
- To characterize the extracellular phytase produced by Aspergillus niger.
- To determine the key enzymatic properties, including activity, stability, substrate specificity, and kinetic parameters.
- To investigate the effects of inhibitors and activators on enzyme activity.
Main Methods:
- Cultivation of Aspergillus niger in a laboratory bioreactor to produce extracellular phytase.
- Purification of the enzyme and determination of its molar mass.
- Assays to determine pH optimum, temperature optimum, and thermal/pH stability.
- Enzyme kinetics studies using various phytate substrates and 4-nitrophenyl phosphate.
- Investigation of inhibition and activation by various ions and inorganic phosphate.
Main Results:
- Extracellular phytase activity of 132 nkat/mL was achieved.
- The purified enzyme has a molar mass of approximately 100 kDa, with optimal activity at pH 5.0 and 55°C.
- High stability at elevated temperatures and alkaline pH was observed.
- The enzyme displayed broad substrate specificity with the highest affinity for calcium phytate (Km = 0.45 mmol/L).
- Non-competitive inhibition by inorganic phosphate and divalent metal ions (Cu2+, Zn2+, Hg2+, Sn2+, Cd2+, F-) was noted, while Ca2+, Mg2+, and Mn2+ acted as activators.
Conclusions:
- Aspergillus niger produces a robust extracellular phytase with favorable biochemical properties.
- The enzyme's high activity, stability, and broad substrate specificity, particularly for calcium phytate, highlight its potential for industrial applications.
- Further research into optimizing production and application conditions could enhance its utility in feed and food industries.