Purification of phytase produced from a local fungal isolate and its applications in food systems

الملخص EN

Phytase produced from local isolate of Aspergillus tubingnesis SKA was purified to homogeneity by three steps including 80% ammonium sulphate precipitation, followed by ion exchange chromatography by using DEAE-Cellulose and gel filtration with a Sephacryl S-200, the purified enzyme was obtained with 9.18 fold of purification and a yield of 25.92%.

The purified phytase showed an optimal pH and temperature for its activity with about 5.0 and 40 °C respectively.

The purified phytase was used to produce high quality (low phytate) soy protein concentrate (SPC) and soy protein isolate (SPI) from defatted soy flour (DSF).

Enzymatic treatment increased the protein content and the yield from 52.00% and 40.32% to 55.00% and 46.58% in the untreated and treated SPC respectively, meanwhile for SPI the protein content and the yield increased from 72.00% and 50.00% to 87.00% and 63.91% respectively.

On the other hand a significant decrease were seen in phytate content from 0.94% (untreated) to 0.42% (treated) SPC, and for SPI phytate content decreased from 1.10% to 0.39% respectively.

Purified phytase enzyme was successfully capable to fractionate soybean globulins (glycinin and β-conglycinin), as phytate content decreased from 1.30% in defatted soymilk (DSM) to 0.33% and 0.37% in soymilk treated with A.

tubingensis SKA phytase and wheat phytase respectively, protein content of soy globulins fractions (glycinin and β-conglycinin) was increased to (14.27 and 12.05%), (13.44 and 11.80%) respectively.

Comparing to the treatment of buffer and reducing agent, protein content was (12.57 and 10.39%) and no change was observed on phytate content by this method.