Relationship between thermal inactivation and conformational change of Yarrowia lipolytica lipase and the effect of additives on enzyme stability

The relationship between thermal inactivation and conformational changes of Yarrowia lipolytica lipase has been investigated. The enzyme loses activity over 40 °C, with a half-life of 0.325 h at 50 °C. The thermal inactivation kinetics fits with a first-order expression. The conformational transition from ordered to unfolded structures during thermal denaturation has been studied by fluorescence, circular dichroism (CD), ultraviolet (UV) spectra, and dynamic light-scattering (DLS). The thermal unfolding occurs in three stages where changes in tertiary and secondary structure, are accompanied by molecular aggregation. Additives such as span 85 can prolong the half-life of the lipase by a factor ca. 850 at 50 °C. The increase in denaturation temperature is confirmed by differential scanning calorimetry (DSC).