Stydies On The Screening Isoamylase High-producer Strain And Isoamylase Properties From Aerobacter

In this study, Aerobacter aerogenes was chosen as an original strain and treated repeatedly with various mutagens (UV, EMS) for the purpose of screening high producer of isoamylase. Waxy starch was used to screen target strain and induce enzyme-producing as the sole carbon source. A mutant strain named UV2-10-6 with pretty stable enzyme-producing ability was selected by Iodine vapor method for primary screening and flask fermentation for secondary screening. The enzyme activity was increased from 2.9592U/mL to 17.5812U/mL(It was increased 490%).With the single factor test,FFD,SAE and CCD, the optimal culture media for UV2-10-6 strain producing isoamylase is decided as(g/100ml): corn starch 1.9675, soybeen cake powder3.3176, ammonium acetate0.4829, K₂HPO₄.3H₂O 0.2775, CaCl₂0.005 , FeSO₄.7H₂O 0.005. Under the optimal culture media, the enzyme activity was increased from 17.5812U/mL to 31.8555U/mL.The results from the optimal culture conditions through orthogonal tests indicated that the influence order of various factors were as follows: temperature> medium pH> amount of inoculation> fermentation time. And the optimum culture conditions containing initial medium pH, incubating temperature, amount of inoculation, fermentation time, rotation rate are 6.5, 30℃, 4%, 72h, 200rpm.The properties of the isoamylase were studied and revealed that optimum temperature is 55℃and pH is 5.8, which has an advantage in acid resistance. Addition of Ca²⁺ ,Mg²⁺ will promote the enzyme activity ,whereas Hg²⁺,Cu²⁺,Al³⁺,Fe³⁺ EDTA cause inhibition.The optimum substrate of the isoamylase is waxy cornstarch.