| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 101 === Soy isoflavones are the components responsible for estrogenic responses observed in vitro and in experimental animals. The beneficial effects of isoflavones include: the reduction of serum lipids, increase of bone mineral density, relief of menopausal symptoms, and chemoprevention of mammary and prostate cancer. A number of studies have revealed that the biological effects of isoflavones mainly attributed to their aglyconic forms rather than the glycosidic forms. However, many studies reported that aglycones show low bioavailability to humans because of their poor water-solubility.
In the previous work of our lab, a Bacillus subtilis strain designated as Bacillus subtilis FC-10 showed the capability on the biotransformation of daidzein and genistein into daidzein-7-O-phosphate and genistein-7-O-phosphate. The objective of this thesis is develop a procedure for recovering D7-P and G7-P from the culture broth of biotransformation, including exploring some factors on biotransformations for recovering D7-P and G7-P. Moreover, we investigate the feasibility of using soybean powder as the substrate for the transformation to produce D7-P and G7-P. The results indicated that B. subtilis FC-10 was inoculated into the initial culture medium containing the biotransformation substrate isoflavone showed the highest bioconversion rates were 95.7% for D7-P and 94.4% for G7-P. EtOAc is an efficient solvent for the extraction of D7-P and G7-P from culture broth. The purity and the recovery of the products through this operation by the extraction of 1.2 fold EtoAc for 4 times were 37.9% and 97.5%, respectively. Furthermore, the products containing D7-P and G7-P were purified by adding various ratios of n-hexane to EtOAc extract and the products were recovered from the precipitation. The purity and the recovery of D7-P and G7-P in the precipitate of 88.9% n-hexane were 47.6% and 97.2%, respectively. Then the precipitate was dissolved with little amount of deionized water and was passed through HP-20 resin column. The fraction containing the most D7-P and G7-P was collected from 15% and 30% MeOH eluates of the HP-20 resin adsorpted fraction. The purity and recovery of products containing D7-P and G7-P were 83.1% and 94.6%, respectively. Moreover, soybean powder was a feasible for D7-P and G7-P production. However, pretreatment processes of soybean substrate would seriously affected the conversion rate of D7-P and G7-P. Autoclaved treatment with 85.6% conversion rate seemed to be a better choice where as the conversion rate for soybean was only 37.0%.
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