Hydrogen ions in microaqueous phase during lipase catalysed esterification in non-aqueous media

Abstract

Lipase catalysed stearoyl lactic acid preparation in non-aqueous media was treated as a model system to study the microaqueous phase containing hydrogen ions arising from dissociation of water soluble lactic acid in it. The thermodynamic factors operating at the microaqueous enzyme-water-solvent phase on the lipase in non-polar solvents were investigated in terms of the water of reaction which constitutes the microaqueous phase, partitioning of acid between water of the microaqueous phase and the organic solvent, dissolution and dissociation of the acid and the resultant number of H⁺ present in the microaqueous phase and the extent of esterification for a given amount of enzyme at various substrate concentrations. Using mass transfer equations, the theoretical number of H⁺ at the microaqueous phase were calculated and expressed as hydrogen ion numbers to generate plots which indicated various thermodynamic processes operating at the microaqueous phase to maintain this concentration to a safe minimum.