嗜热链球菌产胞外多糖的研究

以嗜热链球菌为材料,MRS培养基为基础培养基,研究了影响嗜热链球菌菌体生物量及胞外多糖生物合成的因素以及多糖提取的工艺条件.采用单因素法分析了碳源、氮源、初始pH值、温度、时间对嗜热链球菌生物量及胞外多糖生物合成的影响,结果表明嗜热链球菌生长的最佳条件为:葡萄糖20 g/L、大豆蛋白胨5 g/L、胰蛋白胨5 g/L、培养液初始pH 6.5、培养温度为37℃、培养时间24 h时,菌体生物量达5.00×1019个/mL;嗜热链球菌产胞外多糖的最佳条件为:葡萄糖20 g/L、大豆蛋白胨5 g/L、胰蛋白胨5 g/L、培养温度为40℃时、培养时间27 h、培养液初始pH 6.5,胞外多糖产量达到为914.33 mg/L,胞外多糖产量相对于茵体的生长在时间上表现出滞后现象.多糖提取工艺的研究结果表明:以4倍体积的sevag液加入多糖溶液脱蛋白,用三倍体积90%的乙醇于4℃时沉淀12 h,多糖的提取效果最好.

Studies on Exopolysaccharides Produced by Streptococcus Thermophilus

The influencing factors on biomass,exopolysaccharides(EPS) production and EPS extracting conditions were studied with Streptococcus thermophilus cultured on the MRS-based medium. The influencing factors of biomass and exopolysaccharides produced by Streptococcus thermophilus were studied by using single-factor analysis,including carbon,nitrogen,temperature,time and pH. The results showed that the biomass can reach to 5. 0×10~(19)/mL under the optimum conditions,i. e. glucose of 20 g/L,soybeans peptone of 5 g/L,pancreas peptone of 5 g/L, the initial pH of 6. 5 ,the culture temperature of 37 ℃ ,the culture time of 24 h. The optimum conditions of high yield of EPS(914. 33 mg/L) were as follows:glucose of 20 g/L, soybeans peptone of 5 g/L,pancreas peptone of 5 g/L,the initial pH of 6. 5,the culture temperature of 37 ℃ ,the culture time of 27 h. The extracting conditions of EPS were also examined. The results showed that the optimum EPS extracting conditions were:four times volume of sevag to remove protein,then precipitated with 3 times volume of 90% ethanol at 4 ℃ for 12 hours.