Assessment of Genistein and Daidzein Production By Some Local Fungal and Bacterial Isolates

Abstract

Twenty-three different bacterial and fungal isolates were grown and screened for their capability to transform soy glycosides to their aglycone forms with higher titer of antioxidant activity compared to unfermented soy flour. Most of the bacterial isolates showed higher amounts of daidzein than of genistein, which are the aglycone products of daidzin and genistin. After fermentation of soybean flour using bacterial and fungal isolates, the content of isoflavone aglycones varied from 0.0 to 431.89 µg/g compared to unfermented autoclaved soybean flour. Extracellular β-glucosidase activity was ranged from 1.22 to 11.56 mU/mL and 0.3-534.3 U/mL for bacterial and fungal isolates, respectively, while, bacterial cell-bound β-glucosidase ranged from 44.72 to 128.89 mU/mL. Most of the bacterial isolates more efficiently transformed daidzin and genistin into the aglycones than fungal isolates. Among the tested bacterial isolates, the most potent one was selected, characterized according to the morphological and 16S rDNA sequence analysis and identified as Bacillus licheniformis NRC24.