INVESTIGATION ON AFLATOXIN B_1 PRODUCING SPECIES OF ASPERGILLUS FLAVUS GROUP
黄曲霉群菌种产生黄曲霉毒素B1的调查研究

In this paper, Aflatoxin B_1-producing ability of the randomly selected 82 strains of Aspergillus flavus group (including 9 taxa anl 2 unknown species) was assayed. The strains were isolated from various substrates from different localities in China, and supplied by Laboratory of Culture Collection of the Institute of Microbiology, the Chinese Acadefy of Sciences and other organizations. It has been proved that Aflatoxin B_1 is produced only by the strains of A. parasiticus and A. flavus among the 9 taxa known, and 2 unknown species are also Aflatoxin B_1 producers. Within the strains of A. flavus tested, the positive rate of Aflatoxin B_1 producers approximate to 30% (28.3%). The highest amount of Aflatoxin B_1 produced in GAN (Glucose Ammonium Nitrate) anl rice media are 133,333.3 and 160,000.0 ppb respectively, roughly reflecting the present situation of Aflatoxin B_1 producers growth on general substrates in China. In the course of the experiment, the yield of Aflatoxin B_1 and the number of Aliatoxin B_1 producers of A. flavus group in GAN and rice media are also compared. As a result, the yield of Aflatoxin B_1 produced in rice is higher than that in GAN. Within the Aflatoxin B_1 producers of A. flavus (15 strains), some of the strains tested were found to be Aflatoxin B_1 negative in GAN or rice medium. However, Aflatoxin B_1 was found to be positive in one of them. Apparently, Aflatoxin B_1 producers would be missed if only one of the two media is used.