Affinity partitioning of vancomycin

Abstract

The use of the Flanagan and Barondes model(14) describing affinity partitioning as an aid in designing separation systems is discussed. Experimental studies are described for affinity partitioning of vancomycin, a glycopeptide antibiotic, in a water-methoxypolyethylene glycol-dextran system using methoxypolyethylene glycol-dextran system using methoxypolyethylene glycol bound D-alanyl-Dalanyl-D-alanine or D-alanyl-D-alanine as the reversible affinity ligand. Even for this ideal case of 1:1 binding interaction, the model only qualitatively predicts the affinity effect when all model parameters are measured independently. The discrepancy between measured and predicted values can be attributed to a difference in exposed surface of the free antibiotic and ligand compared to that in the bound state.The effect of experimentally varying model parameters is also described. It was determined that a polymers-ligand which partitions more strongly to the top phase would provide the most significant enhancement to this affinity partitioning system. Such an improvement can be made by increasing the molecular weight of the hydrophobicity of the polymer-ligand. A process for vancomycin recovery from fermentation broth using D--alanyl-D-alanine sepharose as affinity ligand is described.

Partitioning of Vancomycin Using Poly(ethy1ene glycol)‐Coupled Ligands in Aqueous Two‐Phase Systems

“…We measured the binding constant between MPEG-SS-D-Aa-D-Ala and vancomycin to be 7000 f 1000 l/mol in a two-phase system; measurements gave identical results in the two phases within small deviations. These measurements correct the earlier value of 31 000 If: 10 000 l/mol reported by our group (Godbole et al, 1991). The Flanagan and Barondes (1975) model can be used to predict the affinity partitioning of vancomycin with MPEG-SS-D-Ala-D-Ala using model parameters shown in Table 1.…”

“…paper, Godbole et al (1991) demonstrated the use of the Flanagan and Barondes model to describe affinity partitioning by independently measuring all of the model parameters. They found a discrepancy between the measured and predicted values, which was attributed to a difference in the exposed surface of the products and ligand compared to that in the bound state.…”

“…Although affinity partitioning offers excellent potential for bioseparation due to high selectivity and ease of scale-up, very few papers have discussed its theoretical aspects (Flanagan and Barondes, 1975;Cordes et al, 1987;Baskir et al, 1989). In addition, very little work has been done for the experimental verification of the proposed models (Godbole et al, 1991;Cordes et al, 1987). Flanagan and Barondes (1975) presented a thermodynamically based model to explain biomaterial partitioning in the presence of polymer-ligand in two-phase systems.…”

“…The discrepancy between the experimental results obtained by Godbole et al (1991) and the Flanagan model prediction led us to further investigate affinity partitioning with the aim of using Albertsson's and Johansson's modifications to account for the change in surface properties upon complex formation. To provide a clear understanding of various parameters, our objective was to Table 1.…”

Pentachlorophenol Dechlorination in Fluidized-Bed Reactors under Methanogenic Conditions

“…Vancomycin is a glycopeptide antibiotic that binds to D-alanine and thereby prevents bacterial cell wall synthesis, especially for Gram-positive bacteria. Archaea lack D-alanine in their cell walls and so are not affected by this antibiotic (Freedman and Gossett, 1991;Godbole et al, 1991). Perkins et al (1994) reported that vancomycin completely inhibited 246TCP dechlorination in a methanogenic consortium, whereas methanogensis proceeded.…”