Study On The Utilization Of Saponins And Starch Resources Of Dioscorea Composita Hemsl.

Dioscorea composita Hemsl.,native to Mexico,is an important plant material for the production of diosgenin in the Americas.After introduction and planting in China,Dioscorea composita Hemsl has stable saponin component,high saponin and starch content,which has obvious planting advantages and high utilization value.At present,the research on the utilization of Dioscorea composita Hemsl is still in a blank stage.Therefore,its utilization mainly draws on the technology of producing diosgenin from Dioscorea Zingiberensis C.H.Wright..This technology has the disadvantages of single product,backward technology and serious pollution,which restricts industrial development of Dioscorea composita Hemsl.This paper systematically studied the utilization of saponins and starch resources of Dioscorea composita Hemsl from the perspective of efficient use of resources.Among them,steroidal saponins are used to prepare dioscin and diosgenin,while starch resources are used to produce bioethanol;which could improve the efficiency of comprehensive utilization and provide technical and theoretical support for promoting its industrialization.The phytochemical analysis method was used to analyze the steroidal saponin resources in Dioscorea composita Hemsl and the four major steroidal saponins were isolated and identified,which were Dioscin,25-O-Protodioscin,Asperin and pro-asperoside.Due to the low UV response of steroidal saponins,a method of high performance liquid chromatography-evaporative light scattering detector(HPLC-ELSD)was developed for the determination of four steroidal saponins in Dioscorea composita Hemsl.After HPLC-ELSD determination,the total content of four steroidal saponins in the dry matter was 106.4 mg/g.Among them,the contents of Dioscin,25-O-Protodioscin,asperin and pro-asperoside were61.1 mg/g,39.9 mg/g,4.5 mg/g and 0.84 mg/g,respectively.The result showed that the total steroidal saponin content was high,among which dioscin accounted for the highest proportion(57%of total saponins),all this indicated that Dioscorea composita Hemsl is suitable for the production of dioscin.The clean and efficient microwave assisted extraction technology was used to extract the total saponins from Dioscorea composita Hemsl,and the extraction process was optimized by Box-Behnken response surface analysis.The optimal conditions were:power340 W;ratio of material to liquid 1:16,ethanol concentration 70%,and theoretical saponin yield is 8.93 mg/g which is close to the determined extraction yield of 8.82 mg/g±0.04 mg/g.The macroporous resin adsorption method has the advantages of remarkable separation effect and low cost in the enrichment and purification of steroidal saponins,and is used as a method for preparing dioscin from Dioscorea composita Hemsl.AB-8 was selected as the filler and the thermodynamic analysis showed that the adsorption of AB-8 on dioscin was a self-heating process.The kinetics indicated that the adsorption of dioscin from Dioscorea composita Hemsl extract was more consistent with the first-order kinetic equation,and the theoretical value of equilibrium adsorption Q_e for the first-order kinetic equation was closer to the experimental value.Increasing the hydrolysis yield and reducing pollution are the main direction of the current production of diosgenin.The natural fermentation conditions were 48h,temperature45°C and liquid ratio 1:4,the yield of diosgenin was increased to 40.0 mg/g,which was increased by 10%.After pre-hydrolysis of 0.1 mol/L sulfuric acid at 105°C for 5 h,the hydrolysis rate of starch reaches 92.0%.With solid-liquid separation,40%of the solid matter in the raw material can be removed,thereby reducing the acid consumption by 40.0%.The COD per unit of raw material is 215.0 mg/g,which is 74.9%lower than the direct hydrolysis of 828.6 mg/g.The effect of reducing the organic matter content in wastewater was significant for the pre-hydrolysis during the diosgenin production.As a medicinal plant,Dioscorea composita Hemsl contains a variety of biologically active substances,which may have an effect on ethanol fermentation and determine the production process of starch conversion to ethanol.The direct ethanol fermentation by yeast showed that there was an active substance inhibiting yeast fermentation in Dioscorea composita Hemsl.The inhibitory component in Dioscorea composita Hemsl was tracked by Saccharomyces cerevisiae,and was finally determined to be EA30207(1,3-di-(2-hydroxy-4-methoxyphenyl)propane).Saccharomyces cerevisiae C2 is a sensitive yeast strain with an EC₅₀ of 33.2?M/L for EA30207.The inhibition is mainly reflected in the adjustment period of yeast growth and is irreversible.According to the cell cycle analysis,the inhibition mainly occurs in the G1 phase of the yeast cell interval,indicating that EA30207 affects the normal metabolism of the yeast.In order to meet the production needs,the extraction residue of Dioscorea composita Hemsl and the bagasse are mixed,and high-concentration fermentation is carried out.By fed-batch and adding 0.1%(w/v)Tween 80,the solids loading was up to34%and the ethanol concentration was 82.83 g/L.In this paper,the steroidal saponin components in Dioscorea composita Hemsl were analyzed,and the highest content was dioscin.Optimization of microwave-assisted extraction of total saponins from Dioscorea composita Hemsl,and thermodynamic and kinetic analysis of the preparation of dioscin from macroporous resin,provide a theoretical basis for the preparation of dioscin.By pre-hydrolysis treatment,the acid consumption and organic matter emissions during diosgenin production are reduced,which contributes to clean production.The analysis of the inhibition component and its mechanism for fermentation in Dioscorea composita Hemsl provide a basis for further research on direct fermentation to produce ethanol.The high-load mixed fermentation of the extract of Dioscorea opposita L.and sugarcan bagasse can produce high concentration of ethanol,which provides a technical basis for the the production of fuel ethanol by the fermentation of Dioscorea composita Hemsl.In summary,the systematic research on the utilization of saponin resources and biomass resources provides technical and theoretical support for the industrialization of large-scale planting of Dioscorea composita Hemsl.