Extraction And Purification Of Soy Isoflavones

Isoflavones, belonging to the bioactive substance obtained from soy bean, haveobvious effects in the prevention and therapy of many diseases. In this paper, theextraction, biotransformation and purification process of soy isoflavones were studiedand optimized. The soy protein isolates and oligosaccharides were simultaneouslyobtained from soy bean dregs. So the soybean was utilized comprehensively.The extraction conditions of conventional organic extraction and ultrasonicassisted extraction were investigated through single factor experiments and orthogonalexperiments or response surface methodology. The extraction amount of isoflavonesachieved2099.87μg/g under the optimal extraction conditions of conventional organicextraction (80%ethanol, solid to liquid ratio1:20,70oC,4h) extraction yield ofisoflavones achieved85.16%under the optimal extraction conditions., and theextraction amount of isoflavones of ultrasonic assisted extraction was2104.25μg/gunder the optimal extraction conditions (250w,70%ethanol, solid to liquid ratio1:15,70oC,2h)，extraction yield of isoflavones achieved85.34%. On the basis of aboveresearch, a novel ethanol-alkaline extraction was designed, and the optimal extractionconditions such as pH, temperature, time, ethanol concentration and solid to liquidratio were investigated. A higher extraction amount (2372.25μg/g) of isoflavones wasachieved under the optimal extraction conditions (pH9.0,80oC,70min,80%ethanol,solid to liquid ratio of1:15) a high extraction yield (96.21%) of isoflavones wasachieved under the optimal extraction conditions. The experimental resultsdemonstrated that the ethanol-alkaline extraction was more effective.In the paper, the cellulase (GC-220) was used instead of traditional β-glucosidaseto hydrolyze the glycoside isoflavones into aglycone isoflavones (1398.00μg/g),which gave an excellent conversion of94.80%under the optimal enzymatichydrolysis conditions: pH4.5, temperature50oC, enzyme concentration0.65U/mgglycoside isoflavones, reaction time4h.Finally, the purification process of soy isoflavones were studied and optimized.The aglycone isoflavones were purified by an environmental-friendly procedurecomprised of ethanol-alkaline extraction, enzymatic hydrolysis, ethanol precipitation,ethyl acetate extraction and water rinse. The final amount of aglycone isoflavonesobtained was1280.00μg/g, and the final recovery and purity of aglycone isoflavonescould achieve80.38%and87.25%, respectively. The isoflavones obtained fromultrasonic assisted extraction (glycoside and aglycone) were purified via Ca(OH)2 flocculation, acid precipitation, ethanol precipitation and ethyl acetate extraction. Thefinal amount of isoflavones (glycoside and aglycone) obtained was1838.00μg/g, andthe final recovery and purity of aglycone isoflavones could achieve74.54%and62.09%, respectively. The amount of soy protein isolates and oligosaccharidesobtained from soy bean dregs achieved216.25mg/g and73.75mg/g, respectivelyThere are no toxic solvents used in the whole process and the organic solvents(ethanol and ethyl acetate) could be recovered. There is no waste liquid and solidgenerated from the production.