Abstract:

The formulation of protectant for lyophilized Lactobacillus plantarum was optimized by means of response surface methodology. First, based on the single factor experiments, Plackett-Burman design was used to evaluate the importance of ingredients of compound protectant formula affecting cell viability of Lactobacillus plantarum. Second, steepest ascend method was used to obtain the maximum response regions of the most important ingredients. Finally, central composite design combined with response surface methodology was employed to investigate the optimal compound protectant formula. Results indicated that the most important ingredients included skimmed milk, glycerol and vitamin C, and their optimal amounts in 100 mL of protectant formula were skimmed milk 13.68 g, glycerol 1.97 g and vitamin C 0.20 g. The optimal cell survival rate was observed to be 85.01% using the optimal compound protectant, which was very close to the expected value (84.85%) and also exhibited an increase of 63.48% compared with using a single protectant, and the number of living Lactobacillus plantarum was 4.98 × 1010 CFU/g.

Key words: Lactobacillus plantarum, lyophilization, protectant, response surface methodology