航天诱变高产酸副干酪乳杆菌A-4-2性质与酶活性研究

Characteristics and Enzyme Activity of Lactobacillus paracasei A-4-2 Produced by Space Mutation

以航天诱变副干酪乳杆菌A-4-2为研究对象,采用扫描电镜、低pH值、荧光定量PCR(聚合酶链式反应)等方法对诱变菌株进行了形态学、耐受性、产胞外多糖含量及β-半乳糖苷酶基因表达量等研究。比较了突变菌株和出发菌株的耐酸、耐胆盐、产胞外多糖、表面疏水性等性能变化和差异以及β-半乳糖苷酶基因表达量的变化。结果表明,突变菌株形态学观察结果与野生菌株无明显差异;在pH值3. 5培养1 h与2 h,突变菌株较野生菌株的存活率显著升高(P <0. 05);发酵7 d后菌株耐酸能力评价结果显示,不同pH值条件下,突变菌株的活菌数均显著高于野生菌株(P <0. 05),且耐胆盐及产胞外多糖的能力均未受到影响,但菌株表面疏水性显著降低;突变菌株β-半乳糖苷酶活性和基因表达量,均显著高于出发菌株(P <0. 05)。同时,证明了β-半乳糖苷酶活性与菌株产酸有密不可分的关系。

The space mutagenesis Lactobacillus paracasei A 4 2 with excellent acid production capability, which was preserved in the laboratory, was selected as the object. The characteristics of A 4 2, including morphology, tolerance, extracellular polysaccharide content and gene expression of β-galactosidase were measured by electron microscopy, low pH value and fluorescence quantitative PCR. The differences of the acid resistance, bile salt, extracellular polysaccharide, surface hydrophobicity and gene expression of β-galactosidase were also evaluated between wild strains and mutant ones. The results showed that there was no significant difference of the morphology between the mutant strain and the wild ones. The survival rate of mutant strain was significantly higher than that of wild one ( P <0.05), which was cultivated for 1 h or 2 h at pH value of 3.5. For the acid capacity evaluation of fermentation strains after 7 d cultivation at different pH values, mutant strain on the number of living bacterium was significantly higher than that of wild one ( P <0.05), however, the ability of acid resistance, bile salt and extracellular polysaccharide was not changed, the surface hydrophobicity showed an significant decrease. The activities of β-galactosidase and gene expression were significantly higher than those of the original strain ( P <0.05). The results indicated that the activity of β-galactosidase was closely related to the acid production capability.