Invited Review |
Genomics of Aspergillus oryzae: Learning from the History of Koji Mold and Exploration of Its Future
1 Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Central 6, 1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan
2 National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan
3 Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi 981-8555, Japan
Received 14 June 2008 ; accepted 1 August 2008.
At a time when the notion of microorganisms did not exist, our ancestors empirically established methods for the production of various fermentation foods: miso (bean curd seasoning) and shoyu (soy sauce), both of which have been widely used and are essential for Japanese cooking, and sake, a magical alcoholic drink consumed at a variety of ritual occasions, are typical examples. A filamentous fungus, Aspergillus oryzae, is the key organism in the production of all these traditional foods, and its solid-state cultivation (SSC) has been confirmed to be the secret for the high productivity of secretory hydrolases vital for the fermentation process. Indeed, our genome comparison and transcriptome analysis uncovered mechanisms for effective degradation of raw materials in SSC: the extracellular hydrolase genes that have been found only in the A. oryzae genome but not in A. fumigatus are highly induced during SSC but not in liquid cultivation. Also, the temperature reduction process empirically adopted in the traditional soy-sauce fermentation processes has been found to be important to keep strong expression of the A. oryzae-specific extracellular hydrolases. One of the prominent potentials of A. oryzae is that it has been successfully applied to effective degradation of biodegradable plastic. Both cutinase, responsible for the degradation of plastic, and hydrophobin, which recruits cutinase on the hydrophobic surface to enhance degradation, have been discovered in A. oryzae. Genomic analysis in concert with traditional knowledge and technology will continue to be powerful tools in the future exploration of A. oryzae.
Key words: Aspergillus oryzae; genome sequence; solid-state culture; secretory hydrolase; non-syntenic block; comparative genomics
* To whom correspondence should be addressed. Tel. +81 298-61-6164. Fax. +81 298-61-6174. E-mail: m.machida{at}aist.go.jp