高活性副干酪乳杆菌冻干菌粉的制备及工艺优化

目的:优化副干酪乳杆菌多种冻干保护剂的配比和真空冷冻干燥工艺参数,提高发酵剂的活菌含量,为冻干菌粉的制备提供指导。方法:以存活因子为指标,通过单因素实验筛选大分子保护剂、糖类、聚合物类、抗氧化剂类保护剂,应用正交试验优化保护剂配比,并通过单因素分析冷冻干燥的工艺参数,采用扫描电子显微镜观察冻干菌体形态。结果:副干酪乳杆菌冻干保护剂配方为:脱脂奶粉15%,蔗糖20%,聚乙烯吡咯烷酮(PVP K-30) 7%,谷胱甘肽(GSH)1.3%;真空冷冻干燥的工艺参数为在15℃下预处理2 h,保护剂pH为6.5,菌液和保护剂的比例为1∶1.5 (v/v),冻干厚度为0.5 cm,预冻方式为在液氮(-196℃)下处理15 min。在此条件下,副干酪乳杆菌经真空冷冻干燥后存活因子达(0.998±0.001),活菌数为(2.35±0.02)×1011CFU/g。经电镜观察发现菌体形态饱满,结构完整。结论:研究结果表明优化后的冻干保护剂及冻干工艺参数适用于副干酪乳杆菌菌体的保存,菌体活性保持良好,该工艺具有良好的应用推广前景。

Preparation and Process Optimization of Lyophilized Lactobacillus paracasei Powder with High Activity

Objective: In order to improve the cell viability of Lactobacillus paracasei during freeze-drying,the lyoprotectants and the vacuum freeze-drying operational parameters were optimized.Methods: Using the survival factor as the index,the protective agent was optimized by orthogonal experiment after single factor test.The process parameters of freeze-drying were optimized by single factor tests,and the microscopic morphology of the powder was observed by scanning electron microscope. Results: The formula of lyoprotectant was optimized as follows: Skim milk powder 15%,sucrose 20%,polyvinyl pyrrolidone( PVP K-30)7%,glutathione( GSH) 1.3%. The vacuum freeze-drying operational parameters were obtained as follow: Pre-cooled temperature 15 ℃,pre-cooled time 2 h,the protective agent pH6.5,the ratio of bacteria to protective agent 1∶ 1.5( v/v),the material thickness 0.5 cm,and the pre-freezing temperature-196 ℃,time 15 min.Under these conditions,the survival factor of L.paracasei after freeze-drying could reach( 0.998 ± 0.001) and the number of viable cells was( 2.35 ± 0.02)× 1011 CFU/g.The scanning electron micrograph revealed that the morphology of the cells was integrity.Conductions: The experiment showed that the optimized protective additive and the freeze-drying process would be suitable for the preservation of L. paracasei,and the activity of the bacteria remained well.This freeze-drying technology has great potential in application and development.