Aspergillus flavus and related fungi were isolated from sugarcane field soil samples from three areas located along Nansei Shoto; Amami-Ohshima, Hateruma, and Okinawa islands in Southern Japan. Aspergillus species were isolated by dilution plate technique on Aspergillus Flavus/Parasiticus Agar (AFPA) and by plating plant debris on two different selective media, PCNB/2-aminobutane medium and Demosan/PCNB/Streptomycin medium. Among 60 Aspergillus isolates obtained from the soil samples, 17 were A. flavus, of which 12 were potential aflatoxin-producing strains, and 43 were A. parasiticus, all detecting aflatoxin production.
Aspergillus flavus var. parvisclerotigenus var. nov., for some isolates from soils in maize fields in Thailand, is described and illustrated. It is characterized by the formation of abundant sclerotia smaller than those of A. flavus var. flavus. All of the isolates were identified with the remarkable producers of aflatoxins.
The production of aflatoxins (AFs) by Aspergillus parasiticus NRRL 2999 attained maximum 144 hr after inoculation and the incubation time was used for subsequent experiment. AF producibility of 34 strains belonging to A . oryzae and A. sojae were inspected by enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography (HPLC). All 34 strains did not produce AFs. On the other hand, the presence of AFs-like material was confirmed by HPLC, and its retention time was similar to but different from that of AF B2. The AFs-like material was not detected by ELISA.
A simple and rapid method is described for the determination of aflatoxin (AF) B1 in mixed feeds. AF B1 is extracted with a mixture of chloroform-0.1 N hydrochloric acid. The extract is cleaned up by using a Sep-Pak Florisil cartridge. AF B1 is determined by high performance liquid chromatography (HPLC), using a μPorasil column, a fluorescence detector, and a mobile phase of toluene-ethyl acetate-formic acid-methanol (89+7.5+2+1.5). The mean recoveries of AF B1 spiked at levels from 10 to 40 ng/g in mixed feeds are in the range of 94.2∼102.9%.
A total of 72 strains of bacteria, isolated from commercial “Kimchi”, both retailed in Seoul (Korea) and Koriyama (Japan), were assayed for their antifungal activity against three mycotoxin-producing fungi: Aspergillus flavus, Fusarium nivale and Penicillium islandicum. As a result, the 55 strains showed the antifungal activity, and they were classified into two types: one was shown as inhibition for mycelial growth of the three fungi, and another as inhibition for sporulation of A. flavus.