Spirulina enhances the viability of Lactobacillus rhamnosus E/N after freeze-drying in a protective medium of sucrose and lactulose

Aims: Response surface methodology (RSM) was used to optimize a protective medium for enhancing the viability of Lactobacillus rhamnosus E/N cells during lyophilization. Methods and Results: Spirulina, sucrose and lactulose were selected, on the basis of a Plackett‐Burman factorial design, as important protectants having the following protective effects on cell viability: 102·025, 36·885 and ?34·42, respectively. A full‐factorial central composite design was applied to determine optimal levels of three used agents. Conclusion: The optimal protective medium composition was determined to be: Spirulina 1·304% (w/v), lactulose 5·48% (w/v), and sucrose 13·04% (w/v) (Polish Patent P‐393189). The predictive value of cell viability in this medium was 89·619%, and experimental viability obtained during freeze‐drying was 87·5%. Significance and Impact of the Study: In this study, Spirulina was used for the first time as the protective agent in freeze‐drying medium, significantly increasing lactobacilli viability and giving synbiotic character of the final product.