Correlation between microbial communities, metabolites, and bioactivities in fermented mare’s milk revealed by metagenomics and metabolomics.

Overview

• This study investigates how different fermentation methods of mare’s milk (koumiss)—natural vs. inoculated with specific lactic acid bacteria (LAB)—affect the microbial community, metabolite profiles, and resulting bioactivities such as antioxidant and enzyme inhibitory effects.
• Using metagenomics and metabolomics, the research explains how controlled fermentation with LAB starter cultures enhances the functional properties and metabolite content of fermented mare’s milk compared to natural fermentation.

Background

• Koumiss is traditionally fermented mare’s milk known for antioxidant, hypoglycemic, and antihypertensive benefits.
• Natural fermentation involves complex and uncontrolled microbial communities, leading to fluctuating product quality.
• There is a lack of specialized fermentation agents that can consistently improve and standardize koumiss’ functional qualities.
• The exact mechanisms linking microbes, metabolites, and resulting bioactivities in both natural and inoculated fermentation systems were previously unclear.

Objectives

• To systematically compare the microbial communities, metabolite compositions, and functional bioactivities of mare’s milk under natural fermentation versus inoculated fermentation with mixed LAB cultures.
• To understand how microbial changes influence metabolite levels and bioactivities such as antioxidant capacity and enzyme inhibition.
• To identify candidate fermentation starters that improve the functional qualities of koumiss.

Methods

• Samples of mare’s milk were fermented naturally or inoculated with a known mixture of lactic acid bacteria strains.
• Metagenomic sequencing was used to profile the microbial community composition and diversity.
• Non-targeted metabolomics assessed the types and quantities of metabolites produced during fermentation.
• Bioactivity assays were conducted to measure antioxidant activity, as well as inhibition of α-glucosidase, α-amylase (important in carbohydrate digestion), and angiotensin-converting enzyme (ACE) linked to blood pressure regulation.
• Correlation analyses linked specific microbes, metabolites, and bioactivities to elucidate functional relationships.

Key Findings

• Enhanced bioactivities in inoculated fermentation: Mare’s milk fermented with LAB starter cultures showed significantly increased antioxidant activity, α-glucosidase and α-amylase inhibition, and ACE inhibitory effects compared to natural fermentation.
• Reduced microbial diversity: Inoculated fermentation resulted in a lower diversity of microbes compared to natural fermentation, likely due to dominance by the added LAB strains.
• Metabolite enrichment: Functional metabolites, especially lipids and organic acids like linoleic acid and α-linolenic acid, were more abundant in inoculated fermentation.
• Microbe-metabolite correlations: The abundance of genera Lactiplantibacillus and Limosilactobacillus correlated positively with beneficial metabolites and improved bioactivities.
• Metabolic pathways: Lipid and amino acid metabolic pathways appear central to the observed improvements in bioactivity after inoculated fermentation.

Implications

• This study supports the use of specific lactic acid bacteria starters to standardize and enhance the health-promoting properties of fermented mare’s milk products.
• The identification of metabolic pathways and microbe-metabolite relationships provides a theoretical framework for future product development and optimization.
• Improved control over fermentation could lead to high-value koumiss products with consistent quality and enhanced biological functions, potentially benefiting consumers seeking functional foods with antioxidant, hypoglycemic, and antihypertensive effects.

Conclusion

• The research demonstrates that inoculated fermentation with mixed LAB cultures can significantly improve the functional bioactivities of mare’s milk by altering microbial communities and enriching beneficial metabolites.
• Metagenomic and metabolomic analyses reveal specific microbes and metabolic pathways responsible for these effects, providing technical support for developing improved fermented mare’s milk products.