The 'Nuruk' starter culture has been used for many years in the fermentation of rice wine in Korea. In present study, mycobiota in Nuruk cultures was identified by performing morphological, physiological, and phylogenetical analyses. Mucorales was the most common mycobiota in Nuruk, followed by yeast and Aspergillus. The composition of fungal species in Nuruk was different among samples and did not correlate with the geographical location from where the Nuruk culture was manufactured. For more detailed identification, 174 filamentous fungal strains were isolated from 39 Nuruk samples. Although the morphological and molecular analyses showed that the strains were identical at the genus level, some discordance was identified between species. Of the 174 strains, 160 showed thermotolerance, and the level of thermotolerance matched the clade generated by phylogenetic analysis. Six genera (Lichtheimia, Aspergillus, Rhizopus, Rhizomucor, Mucor, and Syncephalastrum) and 17 fungal species were identified. Among the genera, the genus Syncephalastrum had not been previously identified in Nuruk cultures, and the isolate was identified as Syncephalastrum racemosum. Two genera, Lichtheimia and Aspergillus, comprised approximately 84% of the filamentous fungal isolates from the Nuruk samples, and Lichtheimia ramosa and Aspergillus oryzae were the most commonly found species. The controversy regarding the presence of mycobiota in Nuruk starter cultures was addressed, and results showed that Nuruk contains unique mycobiota not yet found in other Asian starter cultures.

The typical life cycle of filamentous fungi commonly involves asexual sporulation after vegetative growth in response to environmental factors. The production of asexual spores is critical in the life cycle of most filamentous fungi. Normally, conidia are produced from vegetative hyphae (termed mycelia). However, fungal species subjected to stress conditions exhibit an extremely simplified asexual life cycle, in which the conidia that germinate directly generate further conidia, without forming mycelia. This phenomenon has been termed as microcycle conidiation, and to date has been reported in more than 100 fungal species. In this review, first, we present the morphological properties of fungi during microcycle conidiation, and divide microcycle conidiation into four simple categories, even though fungal species exhibit a wide variety of morphological differences during microcycle conidiogenesis. Second, we describe the factors that influence microcycle conidiation in various fungal species, and present recent genetic studies that have identified the genes responsible for this process. Finally, we discuss the biological meaning and application of microcycle conidiation.