【摘要】 对一株分离自深海热液口的超嗜热古菌(Thermococcus sp.HJ21)菌株进行了α-淀粉酶发酵条件的优化和酶学性质的研究。该菌株发酵9h后到达产酶高峰,产酶温度范围为60—90℃,其最适产酶温度为80℃。产酶pH范围为5.0—9.0,最适产酶pH为7.5。产酶NaCl浓度范围为0.5%—4.0%,2.5%为最适宜NaCl浓度。糖原、淀粉、麦芽糖、酵母膏和蛋白胨促进产酶。该菌株产生的α-淀粉酶的分子量为51.4kDa,酶的最适作用温度为95℃,在100℃仍有60%的酶活力。酶在90℃的半衰期为5h,在100℃2h仍有40%的残余酶活,酶的热稳定性不依赖Ca2+。酶的最适作用pH为5.0,pH4.5仍有80%的酶活力,pH在5.5—7.0较稳定(80℃4h)。金属离子1mmol/L的Mg2+、Co2+、Sr2+、Ba2+、K+、Na+对酶有激活作用,Cu2+、Pb2+、Hg2+、Zn2+、Al3+对该酶均有抑制作用。更多还原

【Abstract】 The production and characterization of α-amylase from Thermococcus sp.HJ21 are studied.The maximum enzyme production is achieved after 9 h cultivation.The ranges and the best points of α-amylase production are 60—90℃,80℃;5.0—9.0,7.5 in pH;and 0.5%—4.0%,2.5% for NaCl concentration,respectively.The result shows that adding yeast extract,peptone,glycogen,starch,and maltose could enhance the enzyme production,and the strain HJ21 could produce extracellular thermostable and acid-stable α-amylase.In addition,the molecular weight of the enzyme is estimated 51.4 kDa by sodium dode-cyl sulfate-polyacrylamide gel electrophoresis.The maximal activity of α-amylase occurs at 95℃;the half-life of the enzyme is 5 h at 90℃;and over 40% of them remain active 2 h after incubation at 100℃.Meanwhile,no Ca2+ is required for thermostability.The enzyme remain stable in a wide pH range of 5.5 to 7.0(at 80℃ 4 h),and best in 4.5—5.0.Moreover,the enzyme can be activated by Mg2+,Co2+,Sr2+,Ba2+,K +,and Na+,and inhibited by Cu2+,Pb2+,Hg2+,Zn2+,and Al3+.更多还原