Aqueous two-phase partitioning of cephalosporin antibiotics: effect of solute chemical nature

The partitioning of certain cephalosporin antibiotics in an aqueous two-phase system of polyethylene glycol phosphate/sulfate salt solution has been investigated. The effect of such parameters as PEG concentration, pH and salt concentration on the portioning behaviour expressed in terms of distribution coefficient of the cephalosporin antibiotics has been evaluated. The experimental results on partitioning behaviour of binary mixture of cephalexin and 7-aminodeacetoxycephalosporanic acid showed reasonably high selectivity for cephalexin indicating good prospects of ATPS as a separation technique for downstream processing in biosynthetic production of cephalexin. The distribution coefficient values for various cephalosporins under otherwise identical optimised conditions have been found to correlate well with their molecular structure expressed in terms of the hydrophobicity values.