Basic Study On Enzymatic Extraction Of Isoflavone From Pueraria Root Residue

The pueraria root residue (PRS) from pueraria starch manufactory still contains some isoflavone which is a kind of phytoestrogen with important physiological effects. Cellulose and hemicellulose lead to the compactness of the cell wall of PRS, which makes isoflavone hard to be fully extracted by ethanol. Methods of enzymatic pretreatment together with direct ethanol extract were used to obtain isoflavone from PRS in this study, and extract of isoflavone would be purified through macroporous resins afterwards. The major research work and achievements were as follows:Cellulase and xylanase were used to pretareat PRS before ethanol extract and the working condition was optimized. The total yield of isoflavone of direct ethanol extract was 0.84%. By pretreating PRS with 10FPIU/g cellulase for 12h, total yield of isoflavone could reach 1.14%. When xylanase was used for pretreatment of PRS, the optimal xylanase dosage was 300 IU/g and the treating time was 6 h, then total yield of isoflavone could reach 1.28%. Cellulase and xylanase could cooperate with each other to enhance the extracting efficiency: When the PRS was pretreated by both xylanase (300IU/g) and a small quantity of cellulase for 6h, the total yield of isoflavone could be even higher, and it could reach 1.38% when the added cellulase dosage was 7.5FPIU/g.PRS was used as the main material for solid-state fermentation. Enzyme produced by A. niger ZU-01 strain could hydrolyze the cell wall's fiber of PRS, thus improving the yield of isolavone. Optimized parameters of solid-state fermentation were ratio of PRS to wheat bran 7:3 and water content ratio 70%. After 120 hours' fermentation at the temperature of 30°C, the yield of total isoflavone could be 1.53%. HPLC showed that the content of daidzein decreased while the content of glucoside isoflavones increased after fermentation. The content of puerarin was 70% higher comparing to that of direct ethanol extract.Another strain A. niger ZU-02 was also studied by solid-state fermentation. The compose of culture medium was the same as that of A. niger ZU-01. After 144 hours'fermentation at the temperature of 30°C, the yield of total isoflavone could reach 1.47%. HPLC showed that content of daidzin, daidzein, genistin and genistein all increased to different extents except for content of puerarin after fermentation.Macroporous resins were used to purify isoflavone from PRS. HZ801 was selected from six kinds of resins for its relatively better separating efficiency through static adsorption. Research of dynamic adsorption was conducted with resin HZ801 afterwards. HZ801 had the best separating efficiency when the concentration of the work solution was 0.5mg/mL, flow rate lmL/min, volum 6BV (volum of resin bed) with pH value 4, and the volume of 95% ethanol as eluant 4BV with flow rate 2.5mL/min. As a result, the purity of isoflavone could reach about 85%.Production of high quality could be obtained through enzymatic extraction of isoflavone from PRS with mild working condition. Still, it could turn waste into valuable things, alleviate the pollution and protect the environment, so it was meaningful both in theoretical research and practical application.