耐热乳酸菌的筛选及其β-半乳糖苷酶性质分析

Screening of heat tolerable lactic acid bacteria and characterization of their β-galactosidases

摘要: 本研究从鸡粪样品中分离高产β-半乳糖苷酶的耐热乳酸菌,经16S r RNA序列鉴定,分离得到的6株菌株均为罗伊氏乳杆菌（Lactobacillus reuteri）。初步分析分离菌株所产β-半乳糖苷酶,其最适p H均为6.5。热稳定性实验发现,菌株MF1567产生的β-半乳糖苷酶在55℃温育1 h,仍保持51.2%的酶活力。分析菌株MF1567的β-半乳糖苷酶氨基酸序列和蛋白质结构,发现该菌株中β-半乳糖苷酶Lac Z存在22个氨基酸替代,其二级结构α-螺旋的比例较高（26.5%）。结果显示,蛋白质一级和二级结构的改变可能是该酶具有较好耐热性的原因。

Abstract: In this study,heat tolerable LAB strains producing high level β-galactosidase were isolated from chicken feces samples. With 16 S r RNA gene sequence analysis,6 isolated strains were all identified as Lactobacillus reuteri. All β-galactosidases from the isolated L. reuteri strains had the same optimum p H of 6.5.After incubating for 1 h at 55 ℃,51.2% of β-galactosidase of strain MF1567 activity was retained. The amino acid sequence analysis showed that 22 amino acid residues of β-galactosidase Lac Z were substituted. The secondary protein structure was further predicted and Lac Z had a relatively higher degree of α-helix(26.5%),which might contribute to the heat stability of β-galactosidase Lac Z from L. reuteri MF1567.