乳酸菌冻干特性的研究

Studies on characteristics of freeze-dried of lactic acid bacteria

对乳酸菌冻干存活率的影响因素及质粒稳定性进行研究。结果表明,乳酸菌冷冻干燥过程中,残余水分质量分数在2％～3％,菌体的相对存活率较高;悬浮液中菌体密度降低,存活率降低;在冷冻干燥过程中,存在两个最大冰晶生成带,即:0～-3.7℃和-30～37.4℃。快速通过最大冰晶生成带可以减小菌体的冷冻损伤。复水介质中营养组分对菌株的存活性影响不显著（P>0.05）。LDB菌株在冻干前后质粒保持了很好的稳定性。液态发酵剂、冻干发酵剂、冻藏发酵剂的生长迟滞期分别为0.61,1.26,0.84h;对数生长末期每小时pH值分别为0.5992,0.3968,0.5159。冻藏发酵剂比冻干发酵剂更利于保持菌体活力。

The factors influencing survival rate of LAB and plasmid stability during lyophilization were systematically studied. The results showed that LAB survived well in the frozen-dried process when residual water content in the suspended medium was 2% - 3% , Survival rate decreased when the density of bacteria dropped. Two maximal ice crystal production area were founded in the frozen-dried process: 0 - - 3. 7 ℃ and - 30 --37. 4℃. Quick pass of the ice crystal production area could decrease freeze damage of LAB. Nutrients in the rehy dration medium did little to survival of LAB (P>0. 05). Plasmid of LDB was stable before and after frozen-dried process. The lag periods of liquid, frozen-dried, frozen cultures were 0.61 h, 1.26 h and 0. 84 h; The acid production rates at the logarithmic period were 0. 599 2 ,0. 396 8 and 0. 515 9 pH/h respectively. Frozen cultures kept higher activities than frozen-dried ones.