以甘肃藏区牦牛乳中分离出的嗜热链球菌为研究对象,通过紫外线(UV)和硫酸二乙酯(DES)的单一诱变和复合诱变,筛选出Q4F8高产胞外多糖突变株,该菌株具有良好的遗传稳定性.此外,脱脂乳培养基中的胞外多糖与粘度具有一定的相关性,这为今后筛选胞外多糖产生菌提供有效的途径.结果表明:单独诱变的效率低于复合诱变的效率,胞外多糖最高可达150.33mg/L,比初始菌株提高了80.95％.%The Streptococcus thermophilus isolated from yak yogurt samples in Tibetan areas of Gansu province was test in this study. The high yield EPS mutant Q4 F8, has good genetic stability, was selected by choosing Streptococcus thermophilus Q4 as initial strain and UV irradiation and diethyl sulfate (DES) as mutagens. In addition, the mutagenized strain of the viscosity were related with the extracellular polysaccharide in the skimmed milk cultures, which was beneficial to improve the efficient way for screening extracellular polysaccharides in the future. The results showed that the efficiency of compound mutagenesis much higher than ingle mutagenesis, and the highest production of polysaccharide was up to 150.33 mg/mL which was 80.95％ higher than that of the initial. In addition, the mutagenized strain of the viscosity were related with the extracellular polysaccharide in the skimmed milk cultures, which was beneficial to improve the efficient way for screening extracellular polysaccharides in the future.
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