Macrogenomic-Based Exploration of the Relationship Between Microbial Diversity and Volatile Characteristic Flavor Substances in Xinjiang Kazakh Traditional Fermented Koumiss and Functional Gene Analysis

Abstract

The quality and flavor development of fermented koumiss are intricately connected to metabolic processes in microbial communities. This study utilized a combination of macrogenome sequencing technology and gas chromatography–mass spectrometry to explore variations in bacterial and fungal communities, flavor compounds, and environmental factors and mine their associated functional genes in traditional Kazakh fermented koumiss from Altay, Tacheng, and Ili Kazakh Autonomous Prefecture in Xinjiang. A total of 87 volatile flavor compounds were successfully identified. Flavor compounds exhibited a close correlation with Lactobacillus, which was identified as a potential core functional microbial group in koumiss fermentation on the basis of its abundance and hypothesized flavor contributions. The analysis of environmental factors revealed the significant influence of geographical location on the distribution of microbial communities. The microbial flavor network highlighted the significance of Lactobacillus and Kluyveromyces as pivotal microbial groups with crucial contributions to the formation of flavor-active substances. Kluyveromyces and Acetobacter followed these genera in importance. Moreover, the types and concentrations of acids, esters, and alcohols had a substantial effect on the formation of koumiss flavor. Furthermore, metagenomic data were annotated and analyzed by using Kyoto Encyclopedia of Genes and Genomes and evolutionary genealogy of genes: Nonsupervised Orthologous Groups databases. Microorganisms in koumiss possessed prominent functions in carbohydrate and amino acid degradation pathways. Annotation with the Carbohydrate-Active enZYmes Database revealed that glycoside hydrolases constituted the highest proportion. The enzymatic features corresponding to genes in bacteria with high abundance were also characterized. The findings of this research offer valuable insights for screening and applying aroma-producing microorganisms in fermented koumiss. They facilitate the targeted isolation of functional microbes, which are ideally suited for koumiss fermentation processes.