INTRODUCTION

Yeasts are eukaryotic microorganisms that play an important role in fermentation and have been isolated from various natural environments, including food [1]. Since 2000, towing to the global increase in need for research to protect biological resources, studies on wild yeasts isolated from various natural environments have been actively conducted in Korea [2]. Yeasts have various biological activities and are used to produce vitamins and amino acids. Additionally, they have recently been reported as probiotic microorganisms. As a result, industrial applications of yeast are rapidly increasing [3].

However, many yeast species that are widely used in research and industry are not included in the National Species List of Korea (NSLK), an important reference material for claiming rights to biological resources and the importance of which, has increased with the adoption of the Nagoya Protocol [3]. Therefore, this study aimed to analyze the taxonomic, morphological, and physiological characteristics of seven yeast strains not yet included in the NSLK, namely Hyphopichia burtonii, Starmerella sorbosivorans, Cyberlindnera mycetangii, Cutaneotrichosporon oleaginosum, Nakazawaea ernobii, Pichia kudriavzevii, and Schizosaccharomyces japonicus, for their inclusion in the NSLK.

MATERIALS AND METHODS

RESULTS AND DISCUSSION

In this study, we conducted a taxonomic evaluation of seven yeast strains that have not been previously documented in Korea: six ascomycetous yeasts (Hyphopichia burtonii, Starmerella sorbosivorans, Cyberlindnera mycetangii, Nakazawaea ernobii, Pichia kudriavzevii, and Schizosaccharomyces japonicus) and one basidiomycetous yeast (Cutaneotrichosporon oleaginosum). The specific origins of these seven strains are listed in Table 1. Phylogenetic analyses were performed by determining and comparing the D1/ D2-26S rRNA region of the large subunit ribosomal ribonucleic acid (LSU rRNA) gene of the selected strains, which were evaluated and grouped with closely related species obtained from the National Center for Biotechnology Information (NCBI) database.

A yeast strain obtained from Nuruk formed a single clade with the type strain of H. burtonii CBS 2352 (Fig. 1A). Similarly, a strain isolated from Rubus coreanus formed a monophyletic clade with the type strain S. sorbosivorans CBS 8768 (Fig. 2A). A yeast strain isolated from Pinus densiflora bark developed a monophyletic clade with the type strains of Cy. mycetangii NRRL Y-6843 and CBS 8675 (Fig. 3A). A strain isolated from the bark of a deciduous tree in Busan formed a clade distinct from the type strain of Cu. oleaginosum ATCC 20509 (Fig. 4A). Conversely, the strain isolated from Camellia sasanqua was categorized into a single clade with the type strain N. ernobii CBS 1737 (Fig. 5A). A strain isolated from Hydrangea serrata formed a distinct clade with type strains P. kudriavzevii NRRL Y 5396 and CBS 5147 (Fig. 6A). Finally, a strain isolated from the bark of a deciduous tree in Yongin was grouped in a monophyletic clade with the type strain S. japonicus NRRL Y 1361 (Fig. 7A). Further analysis of the cell morphology and physiological characteristics of these strains provided supportive data for including these seven species on the NSLK list.

Table

SPECIES DESCRIPTION