Optimization of Protective Agents and Freeze-Drying Conditions for Lactobacillus casei LT-L614

摘要

In order to improve the way of preserving probiotics so that it will be easier to transfer and preserve, this study focus on developing optimum conditions and protective agents for the freeze-drying of Lactobacillus casei LT-L614. By means of a L_(9)(3~(4)) orthogonaltest, the optimum formula for the protective agents was found as follows: 100 g/L skim milk, 60 g/L mannitol, 15 g/L L-tyrosine, 50 g/L Tween-80. Besides, the optimal freeze-drying conditions were also investigated by taking three factors into consideration and results were: ratio of bacterialsolution and protection agent was 1:7.5, pre-freezing time was 5 h and 10% skimmed milk was used for rehydration. The optimal viable cell count was 9.80 × 10~(11) cfu/g under these conditions. The results also indicated that the freeze-dried cells have a much higher survivalrate compared to the untreated cells. Finally, the tolerance of both the synbiotics and non-lyophilized cells in simulated gastrointestinal fluid was also test. Although the survival rate of the bioconjugate decreased by only 5.37% compared with the non-lyophilized cells. The number of livecells in the digestive juice remained to be 3.27 × 10~(9) cfu/mL.