Biotransformation and recovery of the isoflavones genistein and daidzein from industrial antibiotic fermentations.

The objective of this study was to follow the metabolic fate of isoflavone glucosides from the soybean meal in a model industrial fermentation to determine if commercially useful isoflavones could be harvested as coproducts from the spent broth at the end of the fermentation. The isoflavone aglycones, genistein, and daidzein together make up 0.1-0.2 % of the soybean meal by weight but serve no known function in the manufacturing process. After feeding genistein to washed cells of the erythromycin-producing organism, Saccharopolyspora erythraea, the first biotransformation product (Gbp1) was determined by X-ray crystallography to be genistein-7-O-α-rhamnoside (rhamnosylgenistein). Subsequent feeding of rhamnosylgenistein to growing cells of Saccharopolyspora erythraea led to the production of a second biotransformation product, Gbp2. Chromatographic evidence suggested that Gbp2 accumulated in the spent broth of the erythromycin fermentation. When the spent broth was hydrolyzed with acid or industrial enzyme preparations, the isoflavone biotransformation products were returned back to their parental forms, genistein and daidzein, which were then recovered as coproducts. Desirable features of this method are that it does not require modification of the erythromycin manufacturing process or genetic engineering of the producing organism to be put into practice. A preliminary investigation of five additional antibiotic fermentations of industrial importance also found isoflavone coproduct potential.