摘要
用聚乙烯醇凝胶包埋具有高活力天冬氨酸酶的大肠杆菌（Escherichia coli）No.1 细胞。该酶的表现活力高达163800u/g 湿细胞,酶活力的回收率为97.5%。固定化细胞和游离细胞天冬氨酸酶的最适 pH 均为8.0,最适温度分别为40—45℃和40—55℃。二价金属离子Mn2+、Mg2+、Ca2+和Fe2+对热钝化的天冬氨酸酶活力具有保护作用。在37—45℃下,两种细胞的热稳定性相同。二者在 pH6.0的柠檬酸缓冲液中比较稳定。固定化细胞在1mol/L、pH8.0的底物溶液(内含 Mn2+1mmol/L)中于4℃冰箱保存6个月,天冬氨酸酶的活力保持不变。用固定化细胞柱连续生产 L-天冬氨酸,底物转化为产物的转化率达95%以上;产物的总收率为91.1%。固定化细胞柱连续运转40天,天冬氨酸酶活力仍保持最初酶活力的90%。
The immobilized cells of Escherichia coli No.1 with high activity of aspartase was pre-pared by entrapping bacterial cells in 12.5% polyvinyl alcohol gel.The aspartase activity was163.800u/g.h.The yield of aspartase activity was 97.5%.The enzymatic properties of immobilized E.coli No.1 cells were studied comparatively withthose of free cells.The effect of pH on the reaction rate of both immobilized and free cells werethe same.The optimal temperature of immobilized cells was found to be 40—45℃,while thatof free cells was 40—45℃.The thermostability of both immobilized and free cells were thesame at 37—45℃ and can be protected by bivalent metal ions such as Mn^(2+),Mg^(2+),Ca^(2+),Fe^(2+)against thermal inactivation.These two kinds of cells were stable at pH 6.0 citrate buffer.Theaspartase activity remained constant during 6 months of storation at 4℃.When the immobilizedcells were packed in the column and fed continuously with 1 mol/L ammonium fumarate in thepresence of Mn^(2+) at 37℃ and pH (?).0,the aspartase activity retained 90.7% of the initial acti-vity after 40 days.
出处
《微生物学报》
CAS
CSCD
北大核心
1992年第4期266-271,共6页
Acta Microbiologica Sinica
关键词
大肠杆菌
天冬氨酸酶
固定化细胞
Escherichia coli
Aspartase
Polyvinyl alcohol
Immobilized cells
