5485
Asmaa Ibrahim Mohamed El-Shazly
Microbiological And Biochemical Studies On The Production Of Isoflavones
fementation, soy isojlavanes, bacilluslchentons
In this study, ten bacterial and thirteen fungal isolates were screened for their capabilities to transform soy glycosides to their aglycone forms with higher titer of antioxidant activity in comparison with unfermented soy flour. According to extracellular β-glucosidase activity, it was ranged from 1.22 to 11.56 mU/mL and from 0.3 to 534.3 U/mL for bacterial and fungal isolates, respectively. Bacterial cell-bound β-glucosidase was ranged from 44.72 to 128.89 mU/mL. Most of the bacterial isolates showed higher amounts of daidzein than that of genistein. After fermentation of soybean flour using bacterial and fungal isolates, the content of isoflavone aglycones was varied greatly from 0.0 to 431.89 µg/g in comparing to unfermented autoclaved soybean flour. Most of the bacterial isolates were efficiently transformed daidzin and genistin than fungal isolates. Among the tested bacterial isolates, the most potent one was selected, characterized according to the morphological and molecular analysis and identified as Bacillus licheniformis NRC24 Total aglycones content (daidzein and genistein) of soy flour was increased by fermentation using B. licheniformis NRC24 from 26.98 to 431.89 µg/g. The results of one-factor-at-a-time optimization of transformation of soy daidzin and genistin using B. licheniformis NRC24 showed that of different defatted soybean flour concentrations, 80 g/L recorded maximum glucosides transformation. Maximum level of transformed aglycones using B. licheniformis NRC24 was achieved with optimum fermentation time of 16 hr., fermentation temperature 370C, initial pH value of 7, inoculum volume of 5% a cell suspension (6x107 CFU/mL), and with a culture volume of 50 mL in 250 mL Erlenmeyer flask under shaking conditions of 100 rpm. Addition of (1% w/v) cellobiose to soy flour medium showed a notably greater increase in the total aglycones content in comparing to plain fermented soybean flour. As a result of applying one-factor-at-a-time optimization, the total aglycone content of fermented soy flour using B. licheniformis NRC24 was increased from 431.89 to 887.00 µg/g, as it was folded 2.05 times. Further optimization of culture parameters by applying Box-Behnken design, the transformation of daidzin and genistin was increased by 1.11-fold. As a consequence, applying the two optimization steps was able to increase total aglycones content of fermented soy flour using B. licheniformis NRC24 from 431.89 to 985.581 µg/g, as it was folded 2.28 times. Fermented and unfermented soybean flour extracts showed antiviral activity against (H5N1) Influenza virus A/chicken/ Egypt/ M7217B/1/2013, herpes simplex virus type 1 and rotavirus. Additionally, MTT cytotoxicity assay of both extracts using MDCK, Vero and MA104 cell lines showed that fermentation of soybean flour by B. licheniformis NRC24 reduced the cytotoxicity against MDCK and MA104 cell lines more than the unfermented soybean flour extract. Fermented soybean flour extract showed also antifungal activity against Fusarium solani whilst both unfermented and fermented extracts had no antibacterial activity toward the tested pathogenic bacterial strains. Fermented soy flour extract showed higher cytotoxicity against HCT116 colon cancer cells, MCF-7 breast cancer cells and PC3 prostate cancer cells than the unfermented soy extract.
2018
Ph.d
Ain Shams
Science