The equilibrium uptake of four amino acids (glycine, isoleucine, threonine, tryptophan) of differing physico-chemical properties on two ion exchangers of differing surface chemistries was studied with the aim of assessing the importance of inter-molecular and surface interactions in the ion exchange process. Analysis of data showed that, under the conditions investigated, the ion exchange of amino acids at hydrogen form cation exchangers occurred via the uptake of amino acid zwitterions and subsequent protonation of amino acid molecules within the exchangers. Equilibrium isotherm analysis allowed the determination of the thermodynamic equilibrium constants for each combination of amino acid and ion exchanger. The affinity of the synthetic organic resin (Dowex 50W) for the hydrophobic amion acid (tryptophan) was highest and lowest for the hydrophilic amino acid (threonine). The cellulosic ion exchanger (SE 53) displayed lower selectivity for all the amino acids compared to the Dowex 50W resin. This behaviour is explained by considering the chemical properties of the amino acids and ion exchangers. The heats of exchange of the amino acids at these ion exchangers were obtained by titration microcalorimetry using a Thermometric 2277 Thermal Activity Monitor. An analysis procedure was developed to determine the standard thermodynamic functions (ΔG<SUP>o</SUP>, ΔH<SUP>o</SUP>, ΔS<SUP>o</SUP>) for each ion exchange process. Knowledge of these thermodynamic quantities provided further insight into the interactions that can occur, in addition to the electrostatic interaction, during the ion exchange process. The thermodynamic data indicated the most effective means of manipulating process solution conditions in order to increase the selectivity of an ion exchanger for a particular amino acid and also to maximise the degree of separation between amino acids from a binary mixture. The techniques and data analysis procedures described are likely to be of use in the development of bioseparation processes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638228 |
| Date | January 1995 |
| Creators | Moran, E. B. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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