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Β- galactosidase produced by the filamentous fungus Aspergillus oryzae (Aspergillus oryzae) conducted a systematic study , including strain selection and optimization of fermentation conditions of β- galactosidase enzyme extraction and purification and enzymatic properties analysis . A Aspergillus oryzae strain after N ion implantation , breeding to a β- galactosidase producing strains - Aspergillus oryzae A-UN518, the liquid enzyme fermentation broth achieve 700U / L, compared with the original strain enzyme activity increased by 40% . Through single factor and uniform design to determine the best medium for Aspergillus oryzae A-UN518 liquid fermentation production of β- galactosidase : 3% Gupi water , lactose , 0.5 % , (NH 4 < / sub>) 2 SO 4 0.5%, KH 2 PO 4 1%, MnSO 4 1mmol / L, pH5.5; optimum fermentation conditions : seed culture 11h, inoculum 10% , set the rotary shaker , 30 ° C , 180r/min , cultured 96h . A-UN518 optimized fermentation broth in the enzyme activity of 800U / L, compared with the original strain enzyme activity increased by 60% . Purification steps of the A-UN518 Aspergillus oryzae produced β- galactosidase by the centrifugal sterilization body , ammonium sulfate precipitation, carboxymethyl cellulose column chromatography, etc. , to be purified 40 times, than the activity reached 84.0U/mg The final yield was 45.6% . The purified β- galactosidase after polyacrylamide gel electrophoresis showed only a coloring area band , indicating that the β- galactosidase has reached electrophoresis pure . The enzymatic properties of the purified β- galactosidase enzyme activity analysis showed that the enzyme and the optimum pH is 5.0 , and the optimum temperature was 60 ° C ; high thermal stability of the enzyme , 60 ℃ 30min , basic without loss ; the refined enzyme solution kept for three months in the refrigerator at 4 ℃ , enzyme activity residual rate is still more than 90% ; Zn 2 , Hg 2 , Cu < sup > 2 , iodoacetic acid , galactose on the activity of certain inhibitory ; ONPG and lactose enzyme hydrolysis kinetic parameters were 7.08mmol / L and 24.8mmol / L ; refined solution in milk and whey the the powder solution adding β- galactosidase to the 6U/mL , 40 ° C reaction 72h, the degree of hydrolysis of lactose , respectively, 80% and 60% .
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