Non-targeted metabolomics unveils metabolic spectrum characteristics and core metabolite interaction networks in water kefir fermentation

Water kefir, a traditional beverage highly valued by consumers, is known for its abundance of probiotics and a wide range of beneficial substances. However, the complex scientific challenges of understanding the interactions among the microbial community in this stable symbiotic drink have not been fully researched. This study aims to fill this gap by using non-targeted metabolomics methodologies, specifically UHPLC-QE-MS and GC-TOF-MS platforms, to explore the metabolomic landscape throughout the fermentation stages of water kefir. This research reveals important metabolic biomarkers, including N-acetyl-l-aspartic acid, β-alanine, and O-acetylserine. These biomarkers are involved in various metabolic pathways such as alanine, aspartate, and glutamate metabolism, as well as cysteine and methionine metabolism, during the fermentation process of water kefir. An important finding is the presence of a positive correlation between amino acids and organic acids within the correlation network. This indicates a synergistic relationship that promotes favorable interactions among these essential components. Furthermore, this study provides a detailed metabolic network depicting the process of water kefir fermentation. This network establishes a solid foundation for further exploration of the intricate metabolic mechanisms governing water kefir fermentation.