环境因素对酸奶菌株自溶的影响

Effect of the Cultivation Conditions on the Autolysis of Yoghurt Strains

摘要:

本论文探究了培养条件对德氏乳杆菌保加利亚亚种KLDS 1.9201和唾液链球菌嗜热亚种KLDS 3.021自溶的影响。结果表明, 随着培养温度(30℃~55℃)、盐浓度(0%~5%)以及酸度值(pH 5.0~7.5)的升高, KLDS 1.9201和KLDS 3.0201不仅自溶度相应增大, 而且在磷酸缓冲液中释放的核酸和蛋白含量也呈递增趋势。高温55℃、pH 7.5和5%乳酸盐浓度的培养环境使KLDS 1.9201和KLDS 3.0201在培养45 h后的自溶度分别达到了55%和36.3%, 显著高于低自溶培养环境下(30℃、pH 5.5和0%乳酸盐) KLDS 1.9201和KLDS 3.0201的自溶度9.96%和8.6% (P<0.05)。透射电镜观察表明高自溶和低自溶培养条件对酸奶菌株菌体形态的影响是截然不同的, 且酸奶菌株自溶时发生的细胞壁降解程度与自溶光密度值相对应。

Abstract:

The influences of cultivated conditions on the autolysis of Lactobacillus delbeueckii subsp.bulgaricus (KLDS 1.9201) and Streptococcus salivarius subsp. thermophilus (KLDS 3.0201) were studied in this paper. The results indicated that temperature shift (from 30℃ to 55℃), pH shift (from pH 5.0 to pH 7.5) and salt concentration shift (from 0% to 5%) not only increased the autolysis rate of KLDS 1.9201 and KLDS 3.0201, but also led to increase nucleic acid and protein released by strains. Extensive autolysis of yoghurt strains occurred when incubated in 5% salt concentration at 55℃and pH 7.5, the extent of autolysis of KLDS 1.9201 and KLDS 3.0201 reached 55% and 36.3% respectively, significantly higher than extent of autolysis of KLDS 1.9201(9.96% lysis) and KLDS 3.0201(8.6% lysis) when incubated in 0% salt concentration at 30℃ and pH 5.5 (P<0.05). As observed by transmission electron microscopy, there were remarkable differences on cell lysis between the optimal and suboptimal culture conditions. The observations revealed that cell-wall degradation occurred concomitantly with cell autolysis and were well correlated to optical density measurements during bacterial cell autolysis.