Modified β -CD-Cu ion complex and yam mucilage assisted batch foam fractionation for separating puerarin from Ge-gen ( Radix puerariae )

Abstract

Abstract At present, the large scale application of batch foam fractionation is still in confrontation with many problems and difficulties, especially for the enrichment of non-surface-active materials. It is difficult to select a suitable surfactant as the collector when a non-surface-active material can only form a stable association with the expensive surfactants or has not any interactions with the commercially available surfactants. The objective of this work was to investigate the feasibility of batch foam fractionation for recovering such a non-surface-active material, puerarin. Yam mucilage, an abundant byproduct from the manufacture of yam starch, was used to generate a stable foam phase based on its good foamability. According to the properties of puerarin and yam mucilage, β -cyclodextrin ( β -CD) was selected as a basic material to establish an association between them. The results of fluorescence sensitization experiments indicated that puerarin could form an equimolar inclusion complex with β -CD and the inclusion constant was 405.8. Subsequently, β -CD was modified by introducing carbon disulfide and copper (Cu) ion. Then, puerarin could be adsorbed on the gas-liquid interface in the form of ternary complex with modified β -CD-Cu ion complex and glycoprotein molecules (see Fig. 7). Batch foam fractionation was carried out by using the crude extracting solution as the initial feeding solution, in which the concentration of puerarin was as high as 4.6 g/L. Under the suitable conditions of temperature 50 °C, pH 6.0, loading volume of feed solution 400 mL, the pore diameter of gas distributor 0.450 mm, additive volume of yam mucilage 30 mL and volumetric air flow rate 100 mL/min, the enrichment ratio and the percent recovery of puerarin were 4.3 and 82.3%, respectively. This strategy could be generalized to the separation of various non-surface-active materials due to the low cost and the diversiform cavity dimension of cyclodextrins.