为促进国产乳品发酵剂自主研发，从内蒙传统发酵乳中分离鉴定一株嗜热链球菌菌株 H2 (Streptococcus thermophilus)，通过响应面法优化培养基组成，采用体外分析法对菌株 H2 进行益生特性评价。结果表明，培养基氮源为 45. 25 g/L 酵母提取物、生长因子为 169. 5mg/L 半胱氨酸、缓冲体系补充物为 0. 705g/L 碳酸钙且培养条件控制为温度 40℃、初始 pH 值 5.5、接种量 3. 5% 时，培养液中活菌数达 4. 20 ×10⁹ CFU/mL，是优化前的 37. 8 倍。体外益生特性评价实验证明，H2 在 pH =3 时存活率为 49. 65%，胆盐质量分数为 0. 3% 时存活率可达 99. 62%。H2 的发酵上清液经高效液相色谱(HPLC) 法检测，分别检测到 L-乳酸、甲酸、乙酸、丙酸、异丁酸、异戊酸等多种发酵代谢产物，其中 L-乳酸浓度达到最大，为 12.64mmol/L，且未检到 D-乳酸。H2 的发酵上清液对 3 种自由基均有清除作用，其中对 1，1-二苯基-2-三硝基苯肼 (DPPH) 的清除率最高，为 94. 06%。

To promote the independent research and development of domestic dairy starter，Streptococcus ther-mophilus H2 was isolated from Inner Mongolia traditional fermented milk． The composition of culture medium was optimized by response surface methodology，and the probiotic characteristics in vitro of strain H2 were evaluated by in vitro analysis． The results show that，the number of viable bacteria can reach 4. 20 ×10⁹ CFU/mL，37. 8 times larger than that before optimization，when the nitrogen source is 45.25g/L yeast extract，growth factor is 169. 5mg/L cysteine，buffer system supplement is 0. 705 g/L calcium carbonate，and the culture temperature is 40 ℃，initial pH value is 5. 5，inoculum size is 3. 5%． Evaluation of the probiotic characteristics in vitro show that the survival rate of Streptococcus thermophilus H2 is 49. 65% when pH is 3 and 99. 62% when bile salt is 0. 3%． Many kinds of fermentation metabolites，such as L-lactate，formic acid，acetic acid，propionic acid，isobutyric acid and isovaleric acid，were detected by high performance liquid chromatography (HPLC) in fermentation supernatant of H2． The concentration of L-lactate is up to 12. 64mmol/L，and D-lactate is not detected． The supernatant of H2 has scaven-ging effect on three free radicals，of which the scavenging rate of 1，1-diphenyl-2-trinitrophenylhydrazine (DPPH) was the highest，reaching 94. 06%．