Lipase action on a monoolein/sodium oleate aqueous cubic liquid crystalline phase - a NMR and X-ray diffraction study

The effect of adding Thermomyces (formerly Humicola) lanuginosa lipase (TLL) to a monoolein (MO)/sodium oleate (NaO) aqueous cubic liquid crystalline phase has been studied. H-1-NMR, C-13-NMR, H-1-PGSE (Pulsed-magnetic field Gradient Spin-Echo) self-diffusion measurements, and Small Angle X-ray Diffraction were used to follow the degradation of the cubic phase. The reaction sequence in terms of phase transitions follows the order bicontinuous cubic --> reverse hexagonal --> micellar cubic --> micellar phase and corresponds to the previously determined phase diagrams. These changes correlate with changes in the lipid composition observed by C-13-NMR and confirmed by HPLC analysis. The initial decrease of the diffusion coefficients of water and lipid can be related to the transformation of the bicontinuous cubic phase to a reverse hexagonal structure. (C) 2002 Elsevier Science B.V. All rights reserved