Fungal research in Japan: tradition and future
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(2020) 7:14 Takeshita Fungal Biol Biotechnol https://doi.org/10.1186/s40694-020-00104-1
Open Access
EDITORIAL
Fungal research in Japan: tradition and future Norio Takeshita*
“Washoku” means traditional Japanese cuisine and the dietary culture [1, Tokyo]: it was added to UNESCO Intangible Cultural Heritage list in 2013 and attracts increasing attention globally. Shoyu (soy sauce) and miso (soy-bean paste) are used as fundamental seasonings for Japanese dishes. In addition, the traditional Japanese alcoholic beverage sake is primarily paired with Japanese foods. The filamentous fungus Aspergillus oryzae has been used in the production of traditional fermented foods such as shoyu and miso and drinks such as sake for more than 1000 years in Japan, making it the most important filamentous fungus in the country [2] (Fig. 1). A. oryzae has even been heralded as the “national microorganism” of Japan [3, 4]. The utility and safety of A. oryzae are guaranteed by the long history of use in food fermentation industries and modern molecular analyses [5, 6]. Here, this Fungal Biology and Biotechnology special issue collected two reviews and three articles from fungal research in Japan, covering the tradition and future of Japanese fungal biology and biotechnology, using A. oryzae as an example. Amylolytic enzymes play essential roles in the fermentation in A. oryzae. The production of amylolytic enzymes is induced by starch or malto-oligosaccharides, whereas the expression of amylolytic enzymes is repressed by glucose due to carbon catabolite repression. Among amylolytic enzymes, glucoamylases generate glucose from starch. Prof. Gomi at Tohoku University, one of those whom established molecular biology in A. oryzae, has revealed regulatory mechanisms for amylolytic gene expression in A. oryzae. His review focuses on fungal *Correspondence: [email protected] Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tokyo, Japan
research history in Japan and the role of transcription factors in the amylolytic gene expression (in preparation). One of the distinctive features in the use of A. oryzae in the traditional fermentation is the use of solid-state cultivation. “Rice koji” is a solid culture of A. oryzae on steamed rice grains. Multiple parallel fermentations, wherein saccharification of rice by A. oryzae and alcohol fermentation by the budding yeast (Saccharomyces cerevisiae) occur simultaneously, lead to the formation of a variety of ingredients in Japanese sake with its characteristic tastes. Sake quality affected by the metabolite composition depends on the combination of raw materials and sake-making parameters (e.g., rice races, rice polishing ratio, water quality, koji mold, yeast strains, sake mash fermentation methods) used during manufacturing [7]. In sake brewing, the degree of hyphal penetration into the steamed rice highly correlates with its digestibility, since the hyphae growing into the rice secrete amylases and digest t
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