Microbial diversity and production of milk spirit using traditional Buryat fermentation and distillation technologies

Distilled fermented milk beverages are rare in food technology, despite the global prevalence of plant-based spirits. Currently, the production of distilled strong alcoholic beverages from fermented milk using traditional technologies is known only among Mongolic-speaking peoples and their Siberian neighbors. This study provides the first interdisciplinary analysis of darasun, a traditional Buryat spirit made from fermented milk beverage khurenge in Southern Siberia. Archival research shows deep historical roots of darasun dating back to the 13th-14th centuries in the period of the Mongol Empire. Low content of fermentable carbohydrates in milk limits the maximum ethanol concentration in the fermented product, which reaches 1.5-2.1%. To increase the beverage's strength, a traditional multi-stage distillation is used, allowing sequential increases in ethanol concentration to 11%, 40%, and 75%. ITS and 16S rRNA gene sequence analysis identified diverse microbial community in khurenge dominated by representatives of Lactobacillus genus among lactic acid bacteria and Trichosporon or Monosporozyma genera among yeasts. Comparison of home-produced and industrially produced khurenge revealed that pasteurization significantly affects microbial composition with non-pasteurized khurenge showing greater microbial diversity and lower ethanol content than pasteurized. Functional analysis showed that pathway composition differed significantly between samples suggesting that final ethanol concentration in fermented milk reflects the balance between competing fermentation and respiration pathways. This study demonstrates that Buryat milk fermentation and distillation represents a unique biotechnological system that exemplifies decentralized, low-input, circular bioeconomy principles adapted to pastoral settings, providing a contrast to industrial whey-to-ethanol processes and contributing to the preservation of endangered cultural heritage.