Preliminary Studies On Microbial Conversion Of Isoflavones

Methods for extracting, separating, identifying and quantifying Ge and Da of soybean powder were introduced. Extracting processes included that soybean powder were defatted by hexane(5:1,v/w) and extracted by 70% ethanol(6:l,v/w). After the ethanol in the extraction solution was evaporated and then the ethyl acetate was used to extract the ethanol-free solution three times and then the ethyl acetate extraction of Ge and Da was got. TLC was carried out to separate and identify Ge and Da from ethyl acetate in extraction. The developing solution was toluene-chloroform-acetone (4:1.8:1.8) and Rf values of Ge and Da were 0.63 and 0.50,respectively. The quantity of Ge and Da was evaluated by UV-VIS spectrophotometry. The RSD of the rate of extraction and separation of Da and Ge were 1.40% and 0.87%, respectively. The RSD of the contents of Da and Ge by this quantifying method were 3.69% and 3.52%, respectively. The results indicated that the extraction and separation methods were efficient and stable and quantifying method was exact. Selecting the strain which can effectively hydrolyzed soyaisoflavones currently via evaluating the quantity variety of Ge and Da .It was complicated. The third fluorescent spot was detected during the sample being separated by TLC and its Rf value was 0.82. It was analyzed by HPLC-PDA, MS and color reaction and it was identified as the soyasapogenol. The results of experiment indicated that the hydrolysis degree of soyaisoflavones could be estimated by the fluorescence of the soyasapogenol. One strain of Aspegillus niger, N3, which can hydrolyzed soyaisoflavones was selected .The results of the orthogonal experiment indicated that the optimal condition for Gin hydrolysis was 52 ℃, 12 h ,pH 4.5, 30 mmol · L^-1 Ca²⁺ concentration and the optimal condition for Din hydrolysis was 52 ℃, 12 h ,pH 5.0, 60 mmol ·L^-1 Ca²⁺ concentration. Under the optimal condition the Gin and Din enzymic hydrolysis reached 41.42% and 95.71%, respectively. The p-NPG could be efficiently hydrolyzed by the enzyme. But thegeniposide enzymic hydrolysis only reached 30.82%. The presumable cause of the difference of the enzymic hydrolysis was the structural difference of the different glucosides.