TY - JOUR
T1 - Mapping haze-komi on rice koji grains using β-glucuronidase expressing Aspergillus oryzae and mass spectrometry imaging
AU - Wisman, Adinda P.
AU - Tamada, Yoshihiro
AU - Hirohata, Shuji
AU - Gomi, Katsuya
AU - Fukusaki, Eiichiro
AU - Shimma, Shuichi
N1 - Funding Information:
The study represents a portion of the dissertation submitted by AP Wisman to Osaka University in partial fulfillment of the requirement for her doctoral degree. This study was partially supported by the matching fund budget system from Osaka University to S.S. The authors declare that they have no conflicts of interest.
Publisher Copyright:
© 2019 The Society for Biotechnology, Japan
PY - 2020/3
Y1 - 2020/3
N2 - In sake brewing, the quality of rice koji is evaluated by experienced sake brewers based on visual inspection of the haze, which is defined by the extent of fungal hyphae spread on/into the rice grains. There is an increasing interest in understanding the factors that affect the quality of rice koji, which is dependent on its making process. Several studies have focused on the degree of mycelial penetration (haze-komi) and enzyme production during rice koji production. However, there are limited analytical methods available to monitor hyphal growth on a solid surface. Here we used a β-glucuronidase (GUS)-expressing strain of Aspergillus oryzae to visualize and map the fungal growth on rice koji grains. Observation of indigo color revealed that A. oryzae hyphae penetrated the steamed rice grain in the early stage (24 h) of rice koji-making before spreading on the surface during the later stages. Additionally, hyphae penetrated along the endosperm cells and penetrated the cells to form the sou-haze. Furthermore, mass spectrometry imaging (MSI) of glucose demonstrated that the area of mycelial penetration is directly correlated with the spread of glucose during fermentation. This is the first report on utilizing new tools such as GUS-body-mapping of A. oryzae and MSI to monitor fungal growth during rice koji making.
AB - In sake brewing, the quality of rice koji is evaluated by experienced sake brewers based on visual inspection of the haze, which is defined by the extent of fungal hyphae spread on/into the rice grains. There is an increasing interest in understanding the factors that affect the quality of rice koji, which is dependent on its making process. Several studies have focused on the degree of mycelial penetration (haze-komi) and enzyme production during rice koji production. However, there are limited analytical methods available to monitor hyphal growth on a solid surface. Here we used a β-glucuronidase (GUS)-expressing strain of Aspergillus oryzae to visualize and map the fungal growth on rice koji grains. Observation of indigo color revealed that A. oryzae hyphae penetrated the steamed rice grain in the early stage (24 h) of rice koji-making before spreading on the surface during the later stages. Additionally, hyphae penetrated along the endosperm cells and penetrated the cells to form the sou-haze. Furthermore, mass spectrometry imaging (MSI) of glucose demonstrated that the area of mycelial penetration is directly correlated with the spread of glucose during fermentation. This is the first report on utilizing new tools such as GUS-body-mapping of A. oryzae and MSI to monitor fungal growth during rice koji making.
KW - Aspergillus oryzae
KW - Fungal growth
KW - Haze-komi
KW - Mass spectrometry imaging
KW - Rice koji
KW - β-Glucuronidase
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U2 - 10.1016/j.jbiosc.2019.09.016
DO - 10.1016/j.jbiosc.2019.09.016
M3 - Article
C2 - 31623949
AN - SCOPUS:85073557234
VL - 129
SP - 296
EP - 301
JO - Journal of Bioscience and Bioengineering
JF - Journal of Bioscience and Bioengineering
SN - 1389-1723
IS - 3
ER -