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The lipase and Triton X-100 mixture is common for stabilization, immobilization and application processes of these kinds of enzymes. The objective of this article was to study the structural behavior and catalytic performance of Thermomyces lanuginose lipase in the presence of Triton X-100 at 25 °C and different pHs. The structural changes were followed by circular dichroism, correlating them with the catalytic performance, which is reported as the initial lipase activity in the hydrolysis of p‑nitro phenyl butyrate at zero time and residual activity after 48 h of incubation in the absence or presence of surfactant, at the selected pHs. Computational simulations allowed to explain the correlations between the physicochemical changes and the formation of surfactant protein complex, leading to the elucidation of the main interactions that drive activity and stability of this lipase in presence of the Triton X-100 surfactant. Main results showed the Triton X-100-enzyme complex modulates the site active geometry, favoring a better substrate-enzyme adjustment, which influences the activity and stability at evaluated pHs. This study contributes to understand the effect of some additives commonly used to improve the biocatalytic performance on several applications for different industrial fields., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Improving the enzyme stability is a challenge for allowing their practical application. The surfactants are stabilizing agents, however, there are still questions about their influence on enzyme properties. The structure-activity/stability relationship for β-galactosidase from Bacillus circulans is studied here by Circular Dichroism and activity measurements, as a function of temperature and pH. The tendency of preserving the β-sheet and α-helix structures at temperatures below 65°C and different pH is the result of the balance between the large- and short-range effects, respecting to the active site. This information is fundamental for explaining the structural changes of this enzyme in the presence of Triton X-100 surfactant and ethanol. The enzyme thermal stabilization in the presence of this surfactant responds to the rearrangement of the secondary structure for having optimal activity/stability. The effect of ethanol is more related with changes in the dielectric properties of the aqueous solution than with protein structural transformations. These results contribute to understand the effects of surfactant-enzyme interactions on the enzyme behavior, from the structural point of view and to rationalize the surfactant-based stabilizing strategies for β-galactosidades., (Copyright © 2016 Elsevier B.V. All rights reserved.)