Exploring core microbiota responsible for the production of volatile flavor compounds during the traditional fermentation of Koumiss

This study aimed to explore the core microbiota involved in the production of volatile flavor compounds during the fermentation of traditional Koumiss. Microbiological analysis based on high-throughput sequencing (HTS) demonstrated that Lactobacillus, Lactococcus, Acetobacter, Streptococcus, Serratia, and Leuconostoc bacteria as well as Kazachstania, Kluyveromyces, Trichosporonaceae, Pichia, and Candida fungus were the predominant genera during the traditional fermentation process. A total of 112 volatile compounds were identified in fresh mare's milk and during the simulation of the traditional brewing process. Heatmaps and Cluster Analysis revealed that the flavor formation of Koumiss is largely determined by the types and contents of acids, esters, and alcohols. Furthermore, the correlations between microbiota succession and volatile flavor dynamics were explored through bidirectional orthogonal partial least squares (O2PLS) based correlation analysis. Four bacterial genera (Lactobacillus, Acetobacter, Lactococcus, Pseudomonas), and two fungal genera (Kazachstania, and Candida) were determined as the core microbiota for production of the main volatile flavor compounds of Koumiss. The information provided in this study is beneficial in understanding the fermentation mechanism of traditional Koumiss, and to provide a theoretical basis and quality control guidance for the semi-industrial or industrial production of Koumiss.