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

根霉属的影响。研究了几株黄曲霉和寄生曲霉在发酵液(酵母膏2%，蔗糖20%，pH 6.0)中积累黄曲霉毒素B_1(AF)的情况。当与根霉、曲霉同时接种时，根霉、曲霉、根霉分别与根霉、曲霉、根霉和根霉同时接种。都能生长，但在接种后7d只检测到极少量的AF。这一结果表明了降解AF或抑制AF-产生的可能性。在根霉的实验中，降解率为37-57%。接种于预先培养好的黄曲霉含AF的YES肉汤上。研究了曲霉菌对AF产生的抑制作用。接种于条件培养基中；根霉培养后。在YES肉汤中培养7天，过滤，高压灭菌，并添加酵母膏和蔗糖。在这些情况下，曲霉产生的AF量。用乙醚从酸化培养基中(pH 2.0)提取抑制AF产生的代谢物。浸出物溶于YES肉汤时，溶液的pH值为3.0~4.0。溶液经高压灭菌后，出现黑褐色沉淀。经过滤除去沉淀物的溶液未见抑制活性。另一方面，沉淀物对曲霉产AF有抑制作用。沉淀物呈酸性，在pH值为7.0的NaOH溶液中，室温放置1周，即失去抑制活性。降解房颤，产生抑制房颤生成的代谢物，为水溶性酸性物质。

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.