Separation Technique Of Rhamnose From Acidolysis Liquor Of Dioscorea Nipponica Makino Dioscin

Rhamnose is a byproduct in the process of extracting diosgenin from the Dioscorea nipponica,existing in the waste liquid after hydrolyzing. In the present production process of saponin,rhamnose as part of the wastewater is discharged,which not only pollutes the environment,but also brings about an unnecessary waste. At present,glucose had been extracted from the wastewater. In fact,L-rhamnose is much more expensive than glucose.Extracting rhamnose from the acid waste water can not only dispose wastewater, but also get high-value product. By improving technique,rhamnose can be obtained at a lower consumption. The fare for sewage treatment can be used to extract rhamnose from the wastewater,which can achieve low-effluent or zero-effluent discharge,and produce rhamnose at the same time.The process for extracting rhamnose was studied. First get acidolysis wastewater after pretreating Dioscorea nipponica,and then dispose the acid wastewater by neutralization, decolorization,yeast for glucose removal,filtration,concentration,crystallization and, ultimately,rhamnose crystals can be got.The fiber,water-soluble matter and starch were removed after grinding,filtrating,centrifuging,precipitating and alcohol-extracting so that total dioscin can be obtained. Then the total dioscin was hydrolyzed,filtrating,neutralizing,decoloring and eliminating the glucose in the filtration liquid with yeast. At last, the rhamnose was obtained.The optimal conditions for the isolation of rhamnose were:under 0.14 Mpa with 0.5 mol/L sulfuric acid for 1 h,not add nutrition during yeast fermentation,not less than 17 h fermentation time. In this way,the yield rate of rhamnose was 0.196%. DNS method was accurate and convenient to measure the content of rhamnose in the fermentation liquid.The TLC analysis indicated that the product obtained was rhamnose.At the same time,the pollution problems of the traditional diosgenin production were briefly discussed.In order to solve these problems,a new technique for extracting diosgenin from Dioscorea nipponica Makino was introduced and the pollution caused by the new technique was studied.Firstly,the solid wastes were weighted and their contents were 35.6%,24.4%,3.4% respectively.The wastewater concentrations were measured by Chinese standards. The first wastewater COD_Cr was 27876mg/L,BOD₅ 19791 mg/L,NH₃-N 86 mg/L, total phosphorus 157 mg/L,SS 466 mg/L. The second wastewater CODCr was 21412 mg/L, BOD₅ 14642 mg/L,NH₃-N 84 mg/l,total phosphorus 28 mg/L,SS 374 mg/L. In addition,the wastewater pollution comparison was made between the new technique and the traditional one. The couclusion was as follows:total phosphorus and colority were decreased by about 50%;the water amount,COD_Cr and SS by more than 70%;NH₃-N and acid usage by 83% and 85% respectively;wastewater's biochemical ability was increased and became easy for biological treatment.Finally,some utilization measures were proposed to solve the solid waste pollution and the reasons for the wastewater pollution reduction were analyzed.