Efficient separation of phycocyanin of Nostoc commune by multistep diafiltration using ultra-filtration membrane...

Diafiltration (DF) is a separation method used to separate and concentrate macromolecules, such as polysaccharides and proteins. To obtain high-purity target molecules by DF, appropriate conditions should be used. In this study, a mathematical model was developed to suggest appropriate ultra-filtration (UF) membrane modules for the separation of phycocyanin (PC) by multistep DF. PC is a protein produced by microalgae. The contribution of each UF membrane module to PC productivity and purity at each stage of the multistep DF process was quantified by the proposed model. The parameters required as model inputs (k, F_α1, and F_α2) were experimentally determined by permeating PC-containing solution through UF membrane modules (150, 30, and 10 kDa cutoffs). The resulting analytical solutions and those predicted by the model were in close agreement. The PC purity increased from 0.20 to 0.30 when a 10 kDa UF membrane module was used in two-step DF. An orthogonal table was used to determine the combination of UF membrane modules needed to achieve higher purity of PC. The model predicted that the 30 kDa UF membrane module would have the highest contribution to PC productivity and purity at any position in a three-step DF. The developed model can help identify appropriate conditions for separating macromolecules by DF.