Phytase from Aspergillus oryzae SBS50: Biocatalytic reduction of anti-nutritional factor and exhibiting vanadium-dependent haloperoxidase activity

Abstract

Phytases are valuable industrial enzymes widely used in food and feed production for monogastric animals. The purpose of this research is to study the possibility of employing solid-state fermentation (SSF) for phytase production by Aspergillus oryzae SBS50 using mixed substrates. Medium components for improvement of phytase production were optimized using ‘one variable at a time’ method. Optimization resulted in an overall 2.1 times increase in phytase production (506.12 U/g DMR) at 30 °C, pH 5.0 and moisture ratio of 1:4 supplemented with 0.75% ammonium sulphate. There was reduction in phytase production with reduction in water activity. The phytic acid was extracted from flours using hydrochloric acid (HCl) and trichloroacetic acid (TCA). Higher phytic acid content was extracted from wheat flour (3881.6 μg/g), among all the tested flours by HCl extraction method. Fungal phytase was used in the dephytinization of flours. Phytase supplementation enhanced the release of inorganic phosphate, reducing sugars and soluble proteins from all the flours. Treatment of different cereal flours with Aspergillus oryzae phytase resulted in 90–97% reduction in phytic acid content after 24h. A significant amount of inorganic phosphorus was released from wheat flour (10.42 mg/g), pearl millet flour (9.1 mg/g) followed by gram flour (6.2 mg/g) and rice flour (3.9 mg/g). The addition of vanadium resulted in the catalytic conversion of phytase into haloperoxidase, as well as the suppression of phytase activity. This study revealed that phytase from A. oryzae SBS50 can be utilized to improve the nutritional content of cereal-based meals and food products in the food processing sectors. Furthermore, semisynthetic haloperoxidase could be useful in various biotechnological applications.