PRODUCTION AND CHARACTERIZATION OF AN Aspergillus niger GS1S6 PHYTASE CULTIVATED IN PHYTIC ACID-RICH AGRICULTURAL SUBSTRATES
PRODUCTION AND CHARACTERIZATION OF A FUNGAL PHYTASE
Keywords:Phytic acid, Phytase characterisation, Aspergillus niger, Submerged fermentation, Agro-based polymeric substrates
In animal farming, improvement of growth performance through successful nutrient uptake and digestibility is critical. Phytases hydrolyze the anti-nutritive phytic acid present in grains to lesser derivatives and release the phosphorus trapped therein. Twenty-eight fungi obtained from poultry droppings, cereal-rich soils and garden soils were screened for phosphate solubilization and phytase production using Pikovskaya agar and phytase screening medium. Out of the fungi, 61% were positive for phytase producing abilities and the most proficient, isolate GS1S6 with a solubilization index of 121%, was identified as Aspergillus niger GS1S6. Optimum phytase production was achieved at a fermentation period of 120 h, pH 5.5, glucose, (NH4)2SO4 using 72 hour old fungal inoculum. Mineral supplementation of natural agricultural substrates enhanced phytase production (1000U/L) the most in milled sesame seed medium. The ~31-38 KDa partially purified and characterized enzyme demonstrated optimum activities at 55oC and pH 6.0, while cationic inclusions reduced phytase activities. The Km and Vmax were low (1.308 mM and 0.077 mM/mL/min) from Linear-weaver plot with increasing substrate concentration implying that A. niger GS1S6 phytase may efficiently mineralize phytic acid and therefore hold great prospect for its commercialization.
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