Studies on the Conditions of Extracellular Phytase Production, by Aspergillus niger

Aspergillus niger에 의한 균본외 Phytase 생산조건에 관한 연구

The distribution of acid phosphatase activity was investigated with 141 microorganisms from the type culture collection of Chong Kun Dang laboratory and the 41 strains isolated from natural sources. The phytase activity was detected mainly with fungal strains. A fungus isolated from soil and identified as Aspergillus niger had shown the highest phytase activity. The environmental conditions for the enzyme formation by the isolate and some properties of the enzyme were also studied. The results obtained were as follows: (1) The highest phytase production was observed when the fungus was cultivated at 28$^{\circ}C$ for 5 days in the corn starch based medium using the cells incubated at 34$^{\circ}C$ for 3 days as a seed. (2) The optimal initial pH of the culture medium was found to around 2 for the formation of phytase. (3) Sucrose was proved to be one of the most effective carbon sources tested for the enzyme production. (4) As an inorganic nitrogen source, potassium nitrate was found to give a good result in the production of phytase. (5) Synthesis of phytase was significantly increased by the supplement with 0.2 % corn steep liquor to the basal medium as an organic nitrogen source. (6) At the concentration of 40-80 mg inorganic phosphate per liter of the culture medium, the enzyme formation revealed the highest level. But as the phosphate was increased above this optimum concentration the phytase activity was drastically decreased although the cell density showed to be still increasing

보존균 141주와 토양분리군 41주의 균체 외 phytase 생산능력을 조사한 결과 일반적으로 곰팡이류가 높은 효소활성을 나타내었으며 이중에서 효소활성이 가장 높은 균주를 선별하여 그 형태학적 특성을 조사한 결과 Aspergillus sp. 로 동정되었다. 아울러 분리균주의 효소생산을 위한 배양조건을 연구하여 다음과 같은 결과를 얻었다. 1. 34$^{\circ}C$에서 3일간 전배양한 종균으로 28$^{\circ}C$에서 5 일간 본배양하였을 때 최고의 효소활성을 나타내었다. 2. Phytase생산배지의 초기 최적 pH는 2부근이였다. 3. 탄소원으로서는 일반적으로 galactose를 구성단위로 가진 당류는 비효과적인 반면 glucose를 가진 당류가 더욱 효과적이었다. 특히 sucrose가 가장 양호한 결과를 나타내었다. 4. 무기질소원으로서는 KNO$_3$가 가장 적합하였으며. 무기인산함량이 많은 인산암모늄이 가장 불량하였다. 5. 유기질소원은 0.2%의 corn steep liquor를 첨가했을 때 가장 효과적이었다. 6. KCl, MgSO$_4$, 및 무기인의 최적농도는 각각 0.5g/$\ell$, 0.5g/$\ell$및 40~80mg/$\ell$였다. 한편 고인산배지에서는 균체증식은 현저히 증가되나 효소합성은 현저히 감소됨을 보였다.