摘要
从101株低温菌中发现了1株产高温β-半乳糖苷酶菌株G2005,依据形态特征与生理生化反应特性,参照《常见细菌鉴定手册》将其鉴定为乳球菌Lactococcus sp.。该菌株高温β-半乳糖苷酶的最适pH值为6.5,最适作用温度为50℃,65℃相对酶活为总酶活的19%,在30~60℃范围内,具有较好的稳定性。不同金属离子对β-半乳糖苷酶活性的影响为:Mg2+>Na+>K+>Fe2+>Ca2+>Zn2+>Mn2+>Hg2+>Cu2+。Mg2+增强酶活,而Hg2+、Cu2+、Mn2+抑制酶活。经测定该酶Km值为96.8 mmol/L,具高温酶特性。该菌株的最适产酶条件分别为30℃培养48h^60h,培养基初始pH 6.5,培养基乳糖浓度为2%。
A strain No. G2005 producing thermostable lactase was screened from 101 strains of psychrotolerant bacteria. Consistent with these physiological traits, G2005 was phylogenetically related to other Lactococcus genus by the manual of bacteria identify. The enzyme had an optimum pH of 6.5 and an optimum temperature of activity at 42℃, and had 19 percent activity of totall enzyme activity at 65℃, and possessed higher activity and protein stability between 30℃ and 60℃. Lactococcus sp. β-galactosidases is activated by Mg^2＋ （approximately forty percent increase in activity）, whereas Hg^2＋ ,Cu^2＋, Mn^2＋ reduce it significantly （ to 43%-79% of an initial activity）. The Km of emzyme at 50℃ was 96.8 mmol/L, and the Vmax was 133μmol/（s · L） with σ-nitroplenyl β-galactopyranoside. The optimum enzyme synthesis （ lactose as a sufficient inducer） was observed at 30℃ , pH of 6.5 and two percent lactose of culture liquid medium. Key words thermostable β-galactosidase, psychrotolerant, Lactococcus ,characterization of lactase
出处
《食品与发酵工业》
CAS
CSCD
北大核心
2007年第2期56-58,共3页
Food and Fermentation Industries
关键词
Β-半乳糖苷酶
酶学性质
高温酶
低温菌
thermostable β-galactosidase, psychrotolerant, Lactococcus ,characterization of lactase
