应用新型复合保护剂制备高活性直投式干酪乳杆菌发酵剂

Preparation of High-Activity Direct Vat Set Starter of Lactobacillus casei with Novel Cryoprotactants

为应对直投式发酵剂在冷冻干燥处理中较易失活的问题,作者以干酪乳杆菌Lactobacilluscasei Zhang为研究对象,考察了不同冷冻干燥保护剂对菌体细胞生理活性的影响。研究表明,在以脱脂奶粉、山梨醇等传统冷冻干燥保护剂为保护基质的基础上,通过添加5 g/L谷胱甘肽能够将L.casei Zhang细胞的冻干存活率提高至54.5%,活菌数可达6.16×108cfu/mL。进一步分析表明,GSH使冷冻干燥后细胞的膜脂肪酸不饱和度(即U/S值)提高2.02倍,而饱和脂肪酸链长则从对照样本的17.1减少到16.0。此外,透射电镜的研究结果进一步证实,与对照样本相比,GSH能够有效维持冷冻干燥过程中细胞膜结构的完整性。上述研究结果对基于微生物细胞在冷冻干燥过程中的生理状态变化,开拓新型高效的冻干保护剂开辟了新的思路。

To conquer the survival decline of direct vat set(DVS) starter during freeze-drying process,Lactobacillus casei Zhang was used to investigate the effect of different cryoprotectants on physiological activity of cells.The results showed that with the participation of traditional freeze-drying protective agents such as skimmed milk and sorbitol,the survival rate of freeze-dried cells improved to 54.5% by adding 5 g/L glutathione(GSH),and the number of viable cells increased to 6.16 ×10 8 cfu/mL.Further analysis indicated that GSH improved the instauration of cell membrane fatty acids(U/S value) after freeze-drying treatment by 2.02 times compared with the control sample,while it reduced the chain length of saturated fatty acids from 17.1 to 16.0.In addition,the result of transmission electron microscope(TEM) suggested that GSH is able to maintain the integrity of cell membrane structure effectively in freeze-drying process.All of these results provide a constructive way to find novel cryoprotactants based on the understanding of the physiological changes of microbial cells during the freeze-drying process.