title: Prevention of aflatoxin contamination by a soil bacterium of Stenotrophomonas sp. that produces aflatoxin production inhibitors.
abstract: A soil bacterium, designated strain no. 27, was found to produce aflatoxin-production inhibitors. The strain was identified as a species of the genus Stenotrophomonas, and was found to be closely related to Stenotrophomonas rhizophila. Two diketopiperazines, cyclo(L-Ala-L-Pro) and cyclo(L-Val-L-Pro), were isolated from the bacterial culture filtrate as main active components. These compounds inhibited aflatoxin production of Aspergillus parasiticus and Aspergillus flavus in liquid medium at concentrations of several hundred µM without affecting fungal growth. Both inhibitors inhibited production of norsorolinic acid, a biosynthetic intermediate involved in an early step of the aflatoxin biosynthetic pathway, and reduced the mRNA level of aflR, which is a gene encoding a key regulatory protein necessary for the expression of aflatoxin-biosynthetic enzymes. These results indicated that the inhibitors targets are present in early regulatory steps leading to AflR expression. Co-culture of strain no. 27 with aflatoxigenic fungi in liquid medium effectively suppressed aflatoxin production of the fungus without affecting fungal growth. Furthermore, application of the bacterial cells to peanuts in laboratory experiments and at a farmer's warehouse in Thailand by dipping peanuts in the bacterial cell suspension strongly inhibited aflatoxin accumulation. The inhibitory effect was dependent on bacterial cell numbers. These results indicated that strain no. 27 may be a practically effective biocontrol agent for aflatoxin control.
authors: Department of Pharmacology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.|Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Usuma
authors: U
authors: Jermnak
authors: Department of Agriculture, Ministry of Agriculture and Cooperatives, Bangkok 10900, Thailand.
authors: Amara
authors: A
authors: Chinaphuti
authors: Department of Pharmacology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.
authors: Amnart
authors: A
authors: Poapolathep
authors: Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Ryo
authors: R
authors: Kawai
authors: Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Hiromichi
authors: H
authors: Nagasawa
authors: Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Shohei
authors: S
authors: Sakuda
mesh_terms: D000348:Aflatoxins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D001230:Aspergillus / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000187:drug effects; D054659:Diketopiperazines / Q000378:metabolism / Q000494:pharmacology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D008969:Molecular Sequence Data; D012988:Soil Microbiology; D020588:Stenotrophomonas / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000348:Aflatoxins; D054659:Diketopiperazines; D005656:Fungal Proteins