| On the basis of mutation, a new Aspergilus niger UB52 is obtained. This paper mainly studies the optimal conditions and the kinetic characterization of its producing phytase and the phytase purification, characterization as well. Meantime, the optimal of stabilized phytase was prepared and the digestion of the stabilized phytase was detectedA. niger S306 is mutated with the mutagens of ultra violet ray(UV),ethidium bromide(EB) and the two combined mutagen. After series of treatment, A. niger UB52 is abtained. Its phytase activity in liquid fermentation is 4700 u/ml, and its heredity is stable.The optimal culture medium \ fermentation condition in a flask and 10 L fermentor of submerged fermentation with A. niger UB52 were determined. Under the optimal contion in 10 L fermentor the biomass reached 1.19 g dry weight/100ml fermentation liquid .The activity of phytase is 5800u/ml in fermenting Liquid. The kinetic model of fermentation that can predict liquid-state fermentation was set up.Phytase produced by ,4. niger UB52 was purified with Sephadex G-100 and DEAE-52.The phytase inspected with SDS-PAGE showed: a band, pi 4.5 and the relative molecular weight of phytase 63 KD, Km 0.31 mmol/L. At the same time, the amino acids from purified phytase showed that it consisted of more acidic amino acids and less alkali amino acids, and this can explain the pi of phytase .was acidWith microporous starch as the carrier and fluid-bed as the coating method, the method of stabilization was studied. By the orthogonal experiment the optimal condition of coating was determined to be 5% the sucrose addition of phytase powder, 10% the coating salt of microporous starch , 1.5% coating glutin of microporous starch. The digestion of the stabilized phytase was detected in vitro, and the result showed that the quantity of amino acid, trace element, phosphorus in dialysis liquid of digested corn-soybean meal diet of 21 d broiler with stabilized phytase were higher13.6%, 32.6%, 12.0% than that of the control.
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