Abstract:

The aim of this study was to analyze the diversity and fermentation characteristics of the yeasts in koumiss
collected from Inner Mongolia and Xinjiang. After isolation and purification, the yeasts were identified by 26S rDNA and
ITS sequences. Excellent yeasts were selected according to alcohol yield, acid yield, texture and sensory evaluation. The
results indicated that the number of yeast colonies in koumiss from Inner Mongolia was 105 CFU/mL, while the number of
yeast colonies in koumiss from Xinjiang samples ranged from 105 to 107 CFU/mL. Thirteen species including Kluyveromyces
marxianus, Pichia fermentans, Pichia cactophila and Candida zeylanoides were identified. The compositions of yeast
species in koumiss samples from different regions were different. In Inner Mongolia samples, nine species were identified
with the dominant species being Kluyveromyces marxianus, Pichia cactophila and Pichia fermentans. In Xinjiang samples,
the dominant species were Kluyveromyces marxianus and Candida zeylanoides. Four excellent yeast strains including two
strains of Pichia cactophila, one strain of Kluyveromyces marxianus and one strain of Candida zeylanoides were selected.
They all had excellent fermentation characteristics and could be used in the production of novel fermented dairy products.

Key words: koumiss, yeast, isolation and identification, screening