Separation And Purification Of Maltosyl-?-CD By High-speed Counter-current Chromatography Coupled With Nanofiltration

Maltosyl-?-cyclodextrin(M-?-CD)is a kind of branched cyclodextrin formed by maltose and?-cyclodextrin(?-CD)via?-1,4-glycosidic bond.M-?-CD has many advantages compared with?-CD,such as lower hemolytic activity,higher water solubility,better entrapment property and targeting effect.M-?-CD is difficult to be produced on a large scale because of the high cost of separation.In this study,High-speed Counter-current Chromatography(HSCCC)was investgated to separate and purify M-?-CD.The optimal separation process parameters for membrane separation and the optimal solvent system for HSCCC were optimized and obtained to obtain High purity M-?-CD,which provided a basis for the large-scale application of M-?-CD.Firstly,the mixed solution of maltose and?-CD was used as model solution to investigate the separation ability of the rolled nanofiltration membrane with different pore sizes for impurities in the production of M-?-CD.1000 Da 1812 polyamide nanofiltration membrane was selected to separate and purify M-?-CD.The optimum conditions of membrane separation were determined as follows:operating pressure 0.4 MPa,feed temperature 40°C,material concentration 10%,membrane flux 10.2 L/m² h,maltose and?-CD were the best,the rejection rate of maltose was 35.79%,the rejection rate of?-CD was 95.81%.The results showed that the maltose concentration decreased from 74.95%to 26.91%when the volume factor was 1.3,and the maltose concentration decreased from 74.95%to 26.91%after 4 cycles,the concentration of M-?-CD increased from 9.51%to 31.05%.The results show that nanofiltration can be used to purify M-?-CD,which can improve the preparation efficiency and reduce the cost of pretreatment.Secondly,the separation conditions of PEG-inorganic salt solvent system suitable for HSCCC were studied.The effects of molecular weight and concentration of PEG,kinds and concentration of inorganic salts,p H on the K value of maltose,?-CD and M-?-CD were investigated.It was found that the K value of maltose,?-CD and M-?-CD increased with the increase of PEG molecular weight,and decreased with the increase of PEG concentration.In addition,K₂HPO₄/KH₂PO₄ was selected as the best salt ion type.Under the conditions of PEG400-K₂HPO₄/KH₂PO₄-water(2.5:0.75:0.75:6,w/w/w),the partition coefficients of maltose,?-CD and M-?-CD were 2.65,0.32,1.23,respectively,the purity of M-?-CD was70.64%.Finally,the feasibility and separation conditions of M-?-CD in ethanol-inorganic salt solvent system were studied.Through the determination of the K value of M-?-CD,?-CD and maltose,it was found that when Na H₂PO₄ and acetone were selected as modifiers,the K value of M-?-CD,?-CDand maltose were the most different,and the phase separation time was less than 30s.30%Na H₂PO₄-ethanol-acetone(6:2:1.5,v/v/v)was used as the solvent system,the upper phase was the stationary phase,the lower phase was the mobile phase,the highest purity of M-?-CD was 93.2%,and the retention rate of stationary phase was 60%.The results indicated that HSCCC has potential application value in the separation and purification of M-?-CD.