对搭载神舟十一号返回式飞船的嗜热链球菌菌株进行分离纯化，得到10株突变株。对野生株G2与突变株生长曲线、滴定酸度、黏度和胞外多糖含量等各指标进行测定，并对菌株进行扫描电镜(scanning electron microscope, SEM)和透射电镜(transmission electron microscopy, TEM)测试。结果表明，10株突变菌中有2株B2-1、B2-4的OD600值(2.073±0.15、2.06±0.11)、滴定酸度(106±0.23)°T、(98.5±0.25)°T、黏度(3.27±0.04 )Pa·s、(2.94±0.01) Pa·s及胞外多糖含量(409.35±1.38) mg/L、(398.80±5.38) mg/L均高于或者显著高于野生株G2的OD600值(2.051±0.11)、滴定酸度(92±0.16)°T、黏度(2.66±0.07) Pa·s及胞外多糖含量(385.11±3.074) mg/L。最终得到2株具有优良性状的嗜热链球菌(B2-1和B2-4)。因此，航天诱变育种有可能改变嗜热链球菌发酵性能,从而得到具有优良发酵性能的嗜热链球菌菌株，为乳制品开发利用提供理论基础。

In this experiment, 10 strains of Streptococcus thermophilus strain from Shenzhou-11 return spacecraft was isolated and purified. The growth curve, titration acidity, viscosity and extracellular polysaccharide content of wild strain G2 and test strains were measured, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) tests were performed. The results showed that OD600 value of two strains B2-1 and B2-4 (2.073±0.15, 2.06±0.11), titration acidity (106±0.23) °T, (98.5±0.25)°T, viscosity (3.27±0.04) Pa·s, (2.94±0.01)Pa·s, and Extracellular polysaccharides (409.35±1.38) mg/L, (398.80±5.38) mg/L were all higher or significantly higher than those of wild strain G2 with OD600 of (2.051±0.11 ), Titration acidity of (92±0.16) °T, viscosity of (2.66±0.07 )Pa·s and extracellular polysaccharide content of (385.11±3.074) mg/L. Finally, two strains of Streptococcus thermophilus with excellent characters of B2-1 and B2-4 were obtained. Therefore, space mutation breeding may change the Streptococcus thermophilus fermentation performance.