Russian Kefir Grains Microbial Composition and Its Changes during Production Process

Area of Science:

• Microbiology
• Food Science
• Fermentation Technology

Background:

• Kefir, a fermented dairy product, relies on a complex microbial community for its unique characteristics.
• Understanding the microbial dynamics within kefir grains and the final product is crucial for quality control and production.

Purpose of the Study:

• To characterize the microbial composition of kefir grains, starter, and the final kefir drink from Central Russia.
• To isolate and identify pure cultures of microorganisms involved in kefir fermentation.
• To investigate the potential for reconstructing kefir grains from isolated cultures.

Main Methods:

• Denaturing Gradient Gel Electrophoresis Polymerase Chain Reaction (DGGE-PCR) for microbial community analysis.
• Classical microbiological techniques for isolation and identification of pure cultures.
• Light and electron microscopy for morphological observations.

Main Results:

• Kefir microbial communities include Lactobacillus, Leuconostoc, Lactococcus bacteria, and Saccharomyces, Kazachstania, Gibellulopsis yeasts.
• Fifteen prokaryotic and four eukaryotic pure cultures were isolated and identified from kefir grains.
• Lactobacillus species were predominant in kefir grains, while Leuconostoc pseudomesenteroides and Lactococcus lactis dominated the kefir drink.
• Yeasts, initially present in low numbers in grains, significantly increased in the kefir drink during fermentation.

Conclusions:

• The study identified key bacterial and yeast species responsible for kefir fermentation in Central Russia.
• The dominance shifts from Lactobacillus in grains to Leuconostoc and Lactococcus in the final product.
• Reconstruction of kefir grains from isolated cultures remains challenging, with full formation not yet achieved after 1.5 years.