Bacteriophage active against the lactic acid beverage-producing bacterium Lactobacillus casei

Area of Science:

• Microbiology
• Food Science
• Virology

Background:

• Bacteriophages can disrupt lactic acid fermentation in probiotic beverages.
• Maintaining consistent fermentation is crucial for product quality and safety.

Purpose of the Study:

• To isolate and characterize a bacteriophage affecting Lactobacillus casei in Yakult fermentation.
• To understand the phage's properties and growth cycle to explore control strategies.

Main Methods:

• Isolation of bacteriophage from an abnormal fermentation tank.
• Host specificity testing against 18 lactic acid bacteria strains.
• Morphological analysis using electron microscopy.
• Stability tests (pH, UV, heat) and growth experiments.

Main Results:

• Isolated bacteriophage PL-1 exclusively targets Lactobacillus casei S strain.
• PL-1 has a unique "spermatozoon" shape with specific head and tail dimensions.
• Phage is stable at pH 5-8 but sensitive to UV and heat; calcium ions are essential for growth.
• One-step growth revealed an eclipse period of 75 min, latent period of 100 min, and burst size of ~200.

Conclusions:

• Bacteriophage PL-1 can significantly impact Lactobacillus casei fermentation.
• Understanding PL-1's characteristics is key to developing methods to control its development in industrial settings.