Microbial Community Variations and Bioconversion Improvements during Soybean-Based Fermentation by Kefir Grains

Area of Science:

• Microbiology
• Food Science
• Biotechnology

Background:

• Soybeans have challenging flavors and poor gastrointestinal absorption.
• Kefir fermentation offers diverse microbial strains and bioactive compounds.
• Fermentation may improve soybean flavor and bioaccessibility.

Purpose of the Study:

• Analyze microbial diversity in milk and soybean kefir grains.
• Evaluate the impact of kefir fermentation on soybean's nutritional and sensory properties.
• Assess isoflavone bioconversion during fermentation and digestion.

Main Methods:

• Third-generation sequencing for microbial diversity analysis.
• Quantification of free amino acids and volatile flavor compounds.
• In vitro digestion model to evaluate isoflavone bioconversion.

Main Results:

• Dominance of *Lactobacillus* bacteria and *Kazachstania* fungi in kefir grains.
• *Lactobacillus kefiranofaciens* and *Lactobacillus kefiri* identified as key species.
• Increased glutamic acid and reduced beany flavors in fermented soybeans.
• Enhanced isoflavone aglycone formation and absorption post-fermentation.

Conclusions:

• Kefir fermentation modifies kefir grain microbial structure.
• Nutritional value and sensory properties of soybean products are improved.
• Fermentation offers a viable strategy for developing enhanced soybean-based foods.