Biotechnology for producing dry probiotic preparation for feed purposes using lyophilization

The study aimed to develop a biotechnology for creating a new dry probiotic preparation for feed using lyophilisation. A joint culture of Lactobacillus plantarum (7.98×108 CFU/cm 3 ) and Propionibacterium freudenreichii spp. (6.54×108 CFU/cm 3 ) was used. Lyophilisation was performed on an LGJ-6S unit at temperatures of +20 °C and +30 °C and a pressure of 18 Pa. Samples of 50, 100, and 150 ml, frozen at a temperature of -40 °C, were analysed. Viability was determined by plating on selective nutrient media with CFU counting (GOST 10444.11-2013; GOST R 56139-2014). The optimal parameters of lyophilisation were: sample volume of 100 ml, final heating temperature of +30 °C, process duration of 24 h. Residual moisture content for a 100 ml sample was 2.80±0.18 %. The survival rate of L. plantarum reached 27.43 %, P. freudenreichii spp. – 27.97 %. The area of the frozen surface determined the drying rate: in a flat tray, the humidity decreased from 94.7 to 3.85 % (24.6 times) in 8 hours, and in a rectangular pan – to 27.11 % (3.5 times). The technology includes 5 stages: I – freezing at −40 °C (24 h); II – cooling to −45 °C at 100 kPa (1 h); III – initial sublimation at −45 °C and 18 Pa (1 h). IV – sublimation with heating (step 3-5 °C) to +30 °C at 18 Pa (12 h); V – final drying at +30 °C and 18 Pa (10 h). The final titre of L. plantarum in the dry preparation without cryoprotectant was 2.70×109 CFU/g, P. freudenreichii spp. – 2.40×109 CFU/g; with the use of 20 % sucrose solution – 1.18×109 CFU/g and 1.60×109 CFU/g, respectively. The shelf life of L. plantarum and P. freudenreichii spp. for 180 days under freezer conditions remained at least 1.00×108 CFU/g.