First Report of Dothiora infuscans as a Spoilage Organism in Nuruk Fermentation in Korea

The Nuruk starter culture has long been used during fermentation to prepare rice wine in Korea. They host several microorganisms that inhabit them and multiply naturally. In the present study, we report the occurrence of the yeast-like fungus Dothiora, in Nuruk samples and on the outer wall of a Nuruk fermentation room in Namwon-si, Jeollabuk-do, South Korea. The strain was designated as KACC 410160, and its growth was observed ranging from temperatures 5°C to 40°C, with optimum growth at 25°C. The colonies were slimy, yeast-like, and spread with characteristic dark (brown to black) velvety textures observed on malt extract agar, potato dextrose agar, oatmeal agar, glucose peptone yeast extract agar, and yeast malt peptone agar. The strain formed brown, septate hyphae on malt extract agar, undergo vegetative reproduction by budding, and produce conidia by conidiogenous cells. A maximum-likelihood phylogenetic tree based on the combined internal transcribed spacer (ITS) and large subunit (LSU) sequences revealed that the strain clustered with D. infuscans FMR 16326T with a bootstrap value of 100%. Based on its morphological, physiological, and molecular characteristics, strain KACC 410160 was identified as D. infuscans. To our knowledge, this is the first report of Dothiora species inhabiting Nuruk in Korea.