Studies On The Chemical Modification Of Phytase From Recombinant Pichia Pastoris E22 & The Effect Of It On Phytase Activity Under Different PH Conditions

The phytic acid and the salts widely exist in nature, they exist in each kind of plant tissue and the grain, and it is essential to maintain the balanced of organism phosphorus. As a kind of single stomach animal's feed additive, the phytase may improve the use of phosphorus and reduce the excretion to the environment pollution of phosphorus. Meanwhile, it can reduce the anti-nutritionfunction of phytic acid.The trace of phytase is discovered from animal, plant and microbe. But only the microbe becomes the main source of selling phytase because it provides many kinds of easy-extracted and large-yield phytase.There is not a perfect product of phytase while tens kind of phytase product came out at present. It's the direction of phytase research in this time to improve the quality and to raise the yield of phytase by mutation and gene enginering.We have gained A 3214, a strain of Aspergillus niger from soil N14, a mutated strain of A 3214, and E22, a recombinant Pichia pastoris with the phytase gene of N14 before.We purified the phytase of E22 and chemical modification on phytase of E22. The results of the research are as follows:1. The purification of phytase from E22We purified the phytase of E22 by precipitation with acetone, molecular sieve chromatography and ion exchange chromatography.2. Chemical modification of phytase from E22The phytase was modified with IAc, thioglycol, TNBS, NBS,PMSF and Phenylglyoxal. The result of the experiment indicated that the activity of IAc,thioglycol and Phenylglyoxal modification's phytase completely vanishedn, but TNBS,NBS and PMSF decorated the phytase along with dressing agent density's enlargement, the enzyme activity reduced gradually when the dressing agent density achieved 5mmol/L,11mmol/L and 6mmol/L respectively, the activity maintained stable.3. The effect of Chemical modification to phytase activity under different pHThe phytase had a two pH optima at 2.5 and 5 in the chemical modification with TNBS. By contrast, the phytase had only one pH optima at 5.5-6 modified with NBS. The phytase had a two pH optima at 3 and 5.5 modified with PMSF.