The Research On The Microbial Transformation Of Saponins From Dioscorea Zingiberensis C.H. Wright Into Diosgenin With High Efficiency

Diosgenin industry is facing with severe problems of environmental pollution and resource waste. The traditional acid hydrolysis technology has a series of disadvantages of serious pollution and high cost. Therefore, we are in urgent need to develop a new technology meaning to replace the acid hydrolysis technology. The study is based on the new technology of cleaner production of diosgenin utilizing microbial method established in our lab, concentrated liquid of Dioscorea zingiberensis C.H.Wright(DZW) saponinsused in the following research were from this diosgenin producing process. We carried out the research which produces diosgenin of DZW by using of microbial transformation to perfect the whole process and achieve the goal of no acid. The main results are as follows:(1) We established the effective method of detecting saponins of DZW and diosgenin. The test conditions were as follows: the chromatographic column is Agilent C18 column, the mobile phase is acetonitrile(A) and water(B), gradient elution conditions were: 0-10 min:25%?35%A; 10-15 min:35%A; 15-25 min:35%?55%A; 25-42 min:55%A; 42-52 min:55%?100%A; 52-75 min:100%A.The flow rate is 1 ml/min.The detection wavelength is 206 nm,and the column temperature is 25?.The test method has good separating degree, it can simultaneously detect a variety of saponins and saponin.(2) We screened a strain of fungi which could convert saponins of DZW into diosgenin efficiently. It was identified as Aspergillus niger.We named it Aspergillus tubingensis.HG-57.Meanwhile, the optimization of the fermentationprocess conditions ofstrain Aspergillus tubingensis.HG-57 using the saponins of DZW culture medium to produce diosgeninwas conducted.The optimal conditions of fermentation were as follows: the substrate was unsweetened saponins culture medium, inoculums size is 25%(v/v). Under the condition of 37?, 180 r/min and fermentation 1.5 d,we obtained the yield of diosgenin which can reach 1.172 times than the one of traditional acid hydrolysis.(3) The process of saponins transformation by strain Aspergillus tubingensis.HG-57 was studied.We found that four kinds of enzymes were necessary among the 6 kinds of enzymes we detected.The cellulase played a role in initial stage of fermentation, the ?-glucosidase and amylaseplayed a role in the mid- term, the xylanaseplayed a role in the laststage. The strain transformed the multiple-glycosyl saponins into saponins with low number of glycosyl firstly and then transformed into diosgenin during transformation process. As the intermediate products, dioscin,deltonin, trillin, and prosapogenin A of dioscin presented a trend that all of them accumulated firstly and were hydrolysed secondly.In conclusion, on the basis of the diosgenin clean production via microbial technology, we innovated further and completed the whole process without using acid. Series of glycosidases producing microorganism was utilized to transform saponins into diosgenin with higher conversion ratio than that from traditional acid hydrolysis process. Our innovation consolidated the foundation for the new process industrialization of green production of diosgenin.