Faculty Members

Faculty of Environmental and Information Sciences

Department of Applied Chemistry and Food Science

Key words
Food safety, aflatoxin, biosynthesis, detection method of aflatoxigenic fungi, microorganisms, secondary metabolism

Ph.D. / Professor

Kimiko Yabe


Ochanomizu University, Faculty of Science, Department of Biology
The University of Tokyo, Graduate School of Science, Biochemistry, Master course & Doctor course University of Tsukuba, Department of Medicine, Ph.D. researcher

Professional Background

Research Associate, The Institute of Medical Science, The University of Tokyo; Senior Researcher, National Institute of Animal Health, MAFF; Guest Researcher, UCSF; Director of Laboratory, National Food Research Institute, National Agriculture and Food Research Organization (NARO); Research Manager, NARO Headquarters; Director of Division, National Food Research Institute, NARO

Consultations, Lectures, and Collaborative Research Themes

Joint research on detection techniques and biochemical research on the problem of mold poison contamination in agriculture; Detection and metabolism of mold bacteria related to food safety; Lectures about food hazards and Food Safety

Main research themes and their characteristics

「Clarification of aflatoxin biosynthetic mechanism」

 Aflatoxins (AFs) are highly toxic and carcinogenic secondary metabolites produced by fungi, mainly Aspergillus flavus and Aspergillus parasiticus. Since AFs are stable substances, detoxification of AFs contaminated in crops is practically impossible. Therefore, prevention of aflatoxin contamination in crops in agricultural fields or at postharvest are thought to be the most useful method to solve this severe problem. To develop a useful regulation method of the aflatoxin contamination, clarification of aflatoxin biosynthetic mechanism is important. We have investigated most of all enzyme steps involved in aflatoxin biosynthesis for more than 30 years. We also clarified the biosynthetic pathways of all 8 kinds of AFs. Now, it is well known that AFs are produced from acetic acid through complicated pathway composed of more than 25 enzymatic reactions. These reactions are catalyzed by various membrane enzymes and cytosol enzymes and most of them require cofactors such as NADPH, NADH, NAD or S-adenosyl methionine. We also clarified functions of some genes in the aflatoxin gene cluster in the fungal genome.

「Development of dichlorvos-ammonia (DV-AM) method for visible detection of aflatoxigenic fungi and distribution of aflatoxigenic fungi」

 To prevent aflatoxin contamination in crops, precise monitoring of aflatoxigenic fungi in environments such as agriculture fields or crop storage place after harvest is of primary importance. We recently developed a sensitive and simple visual detection method, dichlorvos-ammonia (DV-AM) method, for detection of aflatoxigenic fungi. In this method, fungi are cultured on AF-inducible agar medium supplemented with dichlorvos (DV) for 2–6 d, and then treated by ammonia (AM) vapor to cause mycelial color changes from yellow to brilliant purple-red (2). Monitoring this color change makes us to easily find aflatoxigenic fungi while those of non-aflatoxigenic do not change. We further developed a semi-selection medium for aflatoxigenic fungi, which contained yeast extract, sucrose, Na-deoxycholate, chloramphenicol and agar. We confirmed that combination of this selection medium and the DV-AM method are practically useful for detection of aflatoxigenic fungi in environmental samples such as soils and plants.
 We already isolated some aflatoxigenic fungi from soils in various non-agricultural fields in Japan by using the semi-selection medium together with the DV-AM method. We also succeeded is isolation of aflatoxigenic fungi in imported raw nuts such as peanuts from South Africa and macadamia nuts from Australia. We are aiming to improve food safety by clarifying the localization and dynamics of the toxic fungi in environments and food using this method.

「Future perspective」

 The DV-AM method using the improved medium is a promising method for clarification of distribution and movement of aflatoxigenic fungi in various environments. We are doing screening of aflatoxigenic fungi in soils of various agricultural fields and imported food. We are also searching for microorganisms inhibitory to AF production by the fungi. We hope that some practical prevention method to aflatoxin contamination in crops will be developed for world agriculture by using the DV-AM method soon.

Major academic publications

Yabe, K.; Chihaya, N.; Hamamatsu, S.; Sakuno, E.; Hamasaki, T.; Nakajima, H.; Bennett, J.W. "Enzymatic conversion of averufin to hydroxyversicolorone and elucidation of a novel metabolic grid involved in aflatoxin biosynthesis" Appl. Environ. Microbiol. 2003, 69, 66–73.
Yan, P.; Song, Y.; Sakuno, E.; Nakajima, H.: Nakagawa H.; Yabe, K "Cycle (l-Leucyl-l-Prolyl) produced by Achromobacter xylosoxidans inhibits aflatoxin production by Aspergillus parasiticus" Appl. Environ. Microbiol. 2004, 70, 7466–7473.
Yabe, K.; Yan, P.S.; Song, Y.; Ichinomiya, M.; Nakagawa, H.; Shima, Y.; Ando, Y.; Sakuno, E.; Nakajima, H. "Isolation of microorganisms and substances inhibitory to aflatoxin production" Food Addit. Contam. Part A Chem. Anal. Control. Expo. Risk Assess. 2008, 25, 1111–1117.
Yabe, K.; Hatabayashi, H.; Ikehata, A.; Zheng, Y.; Kushiro, M. "Development of the dichlorvos-ammonia (DV-AM) method for the visual detection of aflatoxigenic fungi" Appl. Microbiol. Biotechnol. 2015, 99, 10681–10694.
Yabe, K. Ozaki, H. Maruyama, T. Hayashi, K. Mato, Y. Ishizaka, M. Makita, T. Noma, S.-Y. Fujiwara, K. Kushiro.M. "Improvement of the Culture Medium for the Dichlorvos-Ammonia (DV-AM) Method to Selectively Detect Aflatoxigenic Fungi in Soil" Toxins 10(12):519 2018.
Yabe, K.; Yushita, M.; Yamamoto, Y.; Kushiro, M. "Detection of aflatoxigenic fungi in imported raw nuts using the dichlorvos-ammonia(DV-AM) method" JSM Mycotoxins 2020 Volume 70:7-13