Study On Protectants Of Probiotics

Microbial cells are intensely affected by freezing and drying when being lyophilized.Damages are strongly alleviated and avoided by suitable protective measures when cells underwent freeze-drying. Protective materials play a fairly role in protecting. This thesis discusses the freeze-drying protective material and the protective mechanism of Streptococcus thermophillus, Lactobacillus bulgaricus and Lactobacillus acidophilus. Then make the experimental results use of pilot production, and investigate the probiotic powder.First, use of different substances to inspect the cell protective effect in experimental design and selected effective protective agent; then determined single factor experiments which factors affect the cell viability of freeze-dried process; then use the response surface methods for Box Behnken Design Test. Use the Design Expert7.0as experimental design and data analysis software.Results indicated that the most important ingredients that contribute to the survival of the cells after cryodesiccation included skimmed milk, trehalose, maltodextrin, inulin and sodium glutamate. Then the formulation of protectants was optimized by means of response surface methodology. Design Expert7.0design is used to evaluate the freeze-drying protective effect of skimmed milk, trehalose, maltodextrin and inulin, and their optimal amounts in100mL of protectant formula were skimmed milk5.94g, trehalose7.75g,inulin8.39g and maltodextrin9.04g.The optimal L.bulgaricus cell survival rate was observed to be90.46%.The optimum cryoprotectants formula for S. thermophilus was deterined as: skimmed milk6.46g, trehalose5.61g,inulin6.2g; using the optimal compound protectant, the survive ratio of S. thermophilus was98.68%. And the optimal cryoprotectants formula for L.acidophilus was deterined as:skimmed milk6.19g, trehalose5.15g, sodium glutamate1.01g; using the optimal compound protectant, the survive ratio of L. acidophilus was90.72%. The number of viable cells after freeze-drying were109cfu/g.Then develop the probiotic powder and use the best protection formula of L.bulgaricus to200L fermentation’s pilot production, the highest number of viable cell can reach4.59×10cfu/g after freeze-dried, and the company can reduce materials cost1.7yuan per kilogram.