Preservation of Lactic Acid Bacteria on Anhydrous Silica Gel for Three Years

This study, which covers three years of storage. analyzes the application of silica gel preservation methods to lactic acid bacteria widely used in yogurt and cheese fermentation. Strains of Streptococcus lactis , Streptococcus lactis subsp. diacetylactis , Streptococcus cremoris , Streptococcus thermophilus . Lactobacillus bulgaricus , Lactobacillus helveticus and a yogurt culture were adsorbed on anhydrous silica gel in screw-cap tubes or in ordinary test tubes which were subsequently flame-sealed under vacuum. During 3 years. the bacteria were tested for viability by incubation in sterile milk. All of the bacteria retained their acidifying activity, with the exception of the yogurt culture. Extending preservation for more than 2 years had a negative effect on the activity of the yogurt culture. Results obtained support the use of screw-cap tubes which, in general, were suitable to preserve suspensions of lactic acid bacteria adsorbed on anhydrous silica gel.