Effect of two lyoprotectants on the survival rate and storage stability of freeze-dried probiotic lactic acid bacterial strains

Abstract

Lactic acid bacteria are very important for biotechnology, pharmaceutical and food industry, and are extensively used as probiotic products and starter cultures. Freeze-drying is a widely used and effective process for preservation of lactic acid bacteria in a dried form. To ensure stability and maintain biological activity of lactic acid bacteria, suitable protective media formulations should be used during the freeze-drying process. Twelve oral strains with functional and probiotic properties were subjected to freeze-drying and assessed for viability after the process and after long-term storage. Two lyoprotective media with different composition were used and the freeze-drying process was performed, where retained stability of the studied strains in both lyoprotectors was reported. Viability after four and eight months of storage was assessed, showing that the strains maintained high viability. The two lyoprotective media ensured the obtaining of freeze-dried samples with preserved viability for all studied strains of lactic acid bacteria. Four of the tested strains, L. fermentum N 2 and TC 3-11, L. delbrueckii subsp. lactis VG 2, and W. confusa NN 1 showed well preserved stability and viability after freeze-drying and long-term storage and, prepared in freezedried formulations, are suitable to be included in the  omposition of probiotic products for oral healthcare.