Optimizing combination of cryoprotective additives to enhance the viability of probiotic Lactobacillus plantarum

Freeze-drying is widely used to stabilize lactic acid bacteria products for storage and distribution. This lyophilization process damages microbial cells, so improving cell viability during the process is necessary. We evaluated cryoprotective additives to maximize the survival rate of probiotic Lactobacillus plantarum during lyophilization and storage. We used mathematical factorial designs, including Plackett-Burman design (PBD) and central composite design (CCD), to optimize the screening process and types and composition of cryoprotectants. Trehalose, skim milk, and monosodium glutamate (MSG) showed higher protection effects than the other candidates in experiments and PBD. A combination of skim milk (5.1%), trehalose (10.55%), and MSG (4.72%) was predicted as the best composition of the cryoprotectants by employing CCD. The survival rate was determined experimentally and predictively as approximately 80% with this combination, which was 2.67 times higher than the protective effect of 10% skim milk widely used as a cryoprotective additive in laboratories. This study highlights the importance of precise processing for the distribution of probiotics, and suggests a method for selecting proper cryoprotectants to maximize the viability of probiotic bacteria.