The effect of various cryoprotective components on the survival of probiotic microorganisms after freeze drying

Abstract

In this study, the influence of various cryoprotectants on the viability of the consortium of probiotic microorganisms Lactobacillus plantarum 8β and Bifidobacterium adolescentis 17-11β after the lyophilic drying. These strains are manufacturing strains and are used for preparing feed additives. A total of 6 different protective environments were tested. The basis of all tested cryoprotector media was skimmed milk in a quantity of 10%, as cryoprotectants also used sucrose, lactose and SiO₂, which were added to the skimmed milk in various combinations. Lyophilic drying was carried out according to standard procedure, with preliminary freezing of samples in cryostat up to minus 72ºC, the lyophilization process lasted 26 hours, during which the vacuum index varied from 40 Pa to 4 Pa, The temperature was raised to 28ºC. The effect of the protective medium on the survival of probiotic microorganisms was determined by planting a series of crops on agar MRS-4, incubation at 37ºC in 48 hours, and then counting the colonies. Crops were produced before the drying procedure (the number of colonies was 100%) and immediately after. The highest survival rates of probiotic bacteria were obtained using a protective medium based on 10% skimmed milk and 10% skimmed milk with 2% SiO₂ added, accounting for 81.84% and 82.48% respectively. The moisture content of the samples after drying was as follows: Medium based on 10% skimmed milk - 4.40%; 10% of skimmed milk plus 2% SiO₂ - 4.93%. This humidity for lyophilic preparations of these bacteria is optimal, and promotes long-term storage of samples with continued viability.