中文摘要：

试验旨在对鼠李糖乳杆菌（Lactobacillus rhamnosus GG，LGG）胞外多糖的提取工艺和合成条件进行优化。采用单因素试验分别研究三氯乙酸浓度、乙醇添加量和乙醇沉淀时间对胞外多糖提取量的影响，利用单因素结合正交试验对碳源、葡萄糖浓度、培养基初始pH值、接种量、培养温度、培养时间等影响胞外多糖合成的条件进行优化。结果表明，胞外多糖合成的最佳条件为：培养基中添加20g/l的葡萄糖，调节其pH值为6．5，在30℃培养20h，在此条件下，胞外多糖的产量为230．2mg/l。胞外多糖最佳提取条件为：用ll％的三氯乙酸除蛋白，4倍体积95％的乙醇沉淀24h，胞外多糖提取效果较佳。

英文摘要：

This study was conducted to opitimize conditions in the extraction and synthesis of exopoly- saccharide （EPS） of Lactobaeillus rhamnosus GG. Single factor and orthogonal experiments were done to optimize the synthesis conditions of EPS. Effects of concentration of trichloroacetic acid, amount of ethanol and precipitation time on EPS production were evaluated in extraction. The maximum yield of EPS （230.2 mg/1） was obtained at pH 6.5, 30 ℃ for 20 h with glucose （20 g/l） as carbon source. The optimal method for the EPS extraction was to use 11% trichloroacetic acid to remove protein and 4 times the volumes of 95% ethanol to precipitate product for 24 h.