In‐vitro and in‐vivo dephosphorylation of rapeseed meal by means of phytate‐degrading enzymes derived from Aspergillus Niger

Abstract

AbstractA meal of ‘double low’ rapeseed (var ‘Jantar’) was subjected to phytate hydrolysis using enzyme preparations derived from a mycelium of Aspergillus niger which contained phytase (EC 3.1.3.8) and acid phosphatase (EC 3.1.3.2) activities. The complete conversion of myo‐inositol hexa‐ and pentaphosphates present in rapeseed meal to lower phosphate esters of myo‐inositol was accomplished at 40°C, a pH value of 4.5, phytase dosage (in phytase units (PhytU)) 0.1 PhytU g−1 accompanied by acid phosphatase activity 37.1 units g−1, in 1 h. Under these conditions, complete dephosphorylation was observed in 4 h. Decreasing the pH value to 3.0 caused a rise in the amount of inorganic phosphorus released, while increasing to 5.5 resulted in substantial reduction in the reaction rate. Purification of phytase to a specific activity 0.375 PhytU mg−1 of protein exhibited a negative influence upon the yield of rapeseed dephosphorylation. The substitution of calcium phosphate for a preparation of phytase in feed containing rapeseed meal did not cause significant differences in the body weight gain or in tibia mineralisation of broilers (Gains galus, ‘Astra B’).