Control of the Factors Affecting the Production of Aflatoxin in feed.

点击翻译按钮获取中文摘要

The influences of Rhizopus spp. on aflatoxin B_1(AF) accumulation by several strains of Aspergillus flavus and A. parasiticus in YES broth(2% yeast extracts, 20% saccharose, pH 6.0) were investigated. When inoculated simultaneously with Rhizopus spp., Aspergillus spp. were able to grow, but only negligible amounts of AF were detected at 7days after the inoculation. This result shows the possibility of degradation of AF or inhibition of AF-production. The rates of degradation were confirmed 37-57% in the experiments where Rhizopus spp. were inoculated on the AF-containing YES broth precultured A. flavus. To examine the inhibition of AF-production, Aspergillus spp. were inoculated into the conditioned media ; after the cultivation of Rhizopus spp. in the YES broth for 7days, the media were filtrated, autoclaved, and supplemented with yeast extracts and saccharose. In these cases, the amounts of AF produced by Aspergillus spp. were only 0-61% as compared to pure cultures in YES broth.The metabolites inhibiting AF-production were extracted by ethyl ether from acidified media(pH 2.0) cultured Rhizopus spp. The solution was pH 3.0-4.0 when the extacted substance was dissolved in YES broth. The black-brown precipitation was appeared after the solution was autoclaved. No inhibition activity was observed in the solution removed the precipitation by filtration. On the other hand, the precipitation inhibited AF-production by Aspergillus spp. The precipitation was acidic and lost the inhibition activity when it was dissolved in NaOH solution at pH7.0 and left at room tempreture for 1 week.These results indicate that Rhizopus spp. degradate AF and produce the metabolites inhibiting AF-production which are water soluble acidic substance.