Identification and Characterization of Yeast Species Isolated from Cornus kousa Fruits in Japan

Abstract

The Cornus kousa tree, which is of Asian origin, is often cultivated for ornamental purposes and used in traditional medicine. The tree produces sugar-rich fruits, which are potential habitats for natural yeasts. The identification of new yeast strains has many advantages for the industry and research. This study aimed to isolate and identify yeast species from C. kousa fruits and to understand their microbial ecology. Ripe and rotten fruits, which had fallen on the ground naturally, were collected and soaked in culture media, followed by plate spreading for colony growth. The morphological examination revealed three distinct colony types, including two from the ripe fruits and one from the rotten fruits. The analysis of the internal transcribed spacer 1 region indicated three yeast strains corresponding to the three colony types: Torulaspora delbrueckii and Pichia kluyveri from the ripe fruits and Saccharomyces cerevisiae from the rotten fruits. The metabolic characterizations demonstrated that all three yeasts efficiently consumed glucose and produced alcohol. S. cerevisiae exhibited the strongest fermentation ability and the highest growth rate. These findings showed that Cornus kousa fruit is a source of diverse yeast species, with distinct species associated with different states of fruit decomposition.