내산성(耐酸性) 아밀라제를 생산하는 Aspergillus niger 균주의 분리

Isolation of Aspergillus niger K-25 Prroducing Acid-stable ${\alpha}-amylase$

내산성 ${\alpha}$-아밀라제를 강력히 생산하는 Aspergillus niger K-25 균주를 토양으로부터 분리하였다. 내산성 아밀라제 효소를 생산하기 위한 균주의 배양조건을 조사하였다. 합성배지 A(soluble starch 3.5%, peptone 2%, $KH_2PO_4$ 0.5%, $MaSO_4{\cdot}7H_2O$ 0.25%, $FeCI_3$ 1.0%, pH 6)에서 배양시 아밀라제 생산이 높았다. 밀기울에 fumaric acid 완충용액(pH3)을 1 : 1(W/V)로 첨가하여 배양했을 때 내산성 ${\alpha}$-아밀라제의 생산력은 완충액 HCI, citric acid과 밀기울만 넣은 배지보다 약 2배가 높았고, 배지 A보다 현저하게 높았다.

One strain of Aspergillus niger K-25 producing an acid-stable ${\alpha}-amylase$ was isolated from the soil. The optimum culture conditions were investigated. The production of the acid-stable ${\alpha}-amylase$ was enhanced when the strain was incubated in a medium containing soluble starch 3.5%, peptone 2%, $KH_2PO_4$ 0.5%, $MaSO_4{\cdot}7H_2O$ 0.25% and $FeCI_3$ 1.0% at pH 3 for 7 days. However, higher activity of acid-stable ${\alpha}-amylase$ was demonstrated on wheat bran culture. Amylase production was doubled when A. niger K-25 was incubated on the wheat bran supplemented with fumaric acid buffer (pH 3).