[Preservation of lactic acid bacteria]

Area of Science:

• Microbiology
• Food Science
• Dairy Technology

Background:

• Maintaining the viability of starter cultures is crucial for dairy fermentation.
• Lyophilization (freeze-drying) is a common preservation method for microorganisms.
• Assessing long-term viability and functional activity of preserved cultures is essential.

Purpose of the Study:

• To evaluate the long-term viability of lyophilized lactic acid bacteria (LAB) cultures.
• To assess the stability of specific bacterial strains under different storage conditions.
• To determine the impact of storage on the functional properties of LAB.

Main Methods:

• Lyophilization of Streptococcus lactis, S. cremoris, S. diacetilactis, Lactobacillus bulgaricus, L. casei C10, and L. caucasicus.
• Storage of cultures for up to 4 years under specified conditions.
• Storage of L. casei and S. cremoris strains at -30°C for 3 months and in sterile vaseline oil for 8 months.
• Assay of viable cell counts, lactic acid formation, proteolytic, and lipolytic activities post-storage.

Main Results:

• High numbers of viable cells were observed in lyophilized cultures after 4 years of storage.
• L. casei and S. cremoris strains remained viable after 3 months at -30°C and 8 months in vaseline oil.
• Stored S. cremoris strains exhibited significant lactic acid production, proteolytic, and lipolytic activities.

Conclusions:

• Lyophilization is an effective method for long-term preservation of diverse LAB cultures.
• Specific strains of L. casei and S. cremoris demonstrate excellent stability and functional retention after extended storage.
• Preserved LAB cultures retain crucial metabolic and enzymatic activities necessary for dairy fermentations.