Bacillus Iicheniformis 7 的細胞外耐熱性澱粉液化酵素

Abstract

中文摘要 由土壤分離出一株能產生對熱穩定之澱粉液化?的細菌，經鑑定並命名為Bacillus licheniformis 7。此一菌株生產澱粉液化?所需條件為50℃培養七天。此菌株在以Starch 2.5%,FeCl3-6H2O 0.05%， peptone 0.35%, yeast extract 0.6%，Na-citrate 0.2%，CaCl2.2H2O 0.008% 作培養基時，可獲得最佳酵素產量，產生之澱粉液化?經四個步驟純化，可純化26倍，回收率為21% ，純化酵素最適作用PH為9.0，最適作用溫度為90℃, PH6~9時很穩定。Hg+, Zn++，Mg++, Ni++, Mn++ 等金屬離子對酵素作用有抑制作用，而Na十，Fe+++, Cu++，Ba++ 則有促進作用，化學藥品K2MnO4之添加有抑制酵素活性之作用，2-Mercaptoethanol則可以促進酵素活性。

ABSTRACT A thermostable alpha-amylase producing bacteria has been isolated from soil and identified as Bacillus licheniformis. 7.Cultural conditions of this strain for alpha-amylase production were studied. The optimum temperature and incubation period for enzyme production were 50°C and 7 days respectively. Starch with a concentration of 2.5% was the best carbon source for enzyme production. Beside the above components, the addition of FeCl3.6H2O 0.05%, yeast extract 0.6%, peptone 0.35%, Na-citrate 0.2% and CaCl2.2HO 0.008% to the incubation medium could produce maximum enzyme activity. The enzyme was purified 26-fold with 21% recovery by a series of four steps. The purified enzyme showed maximal activity at 90℃ and pH9.0.91% of this activity remained at 97℃, even at 110℃, there was still 45% activity remained. The enzyme showed 100% stability at 40°C-70°C. Of the cations, Ba2+ Cu2+ Fe3+ Na+ showed stimulatory effect; whereas Hg2+, Mg2+, Mn2+, Ni2+, Zn2+ were inhibitory. K2MnO4 addition resulted in the complete loss of enzyme activity; whereas 2-Mercaptoethanol afforded protection of the enzyme activity.