Enzyme activity of horseradish peroxidase in surfactant-free microemulsions

In the present contribution, we investigated the influence of the structuring of surfactant-free microemulsions (SFME) (water/1-propanolilimonene and wateritert-butanolflimonene) on the enzyme activity of horseradish peroxidase (HRP). To this purpose, the oxidation of 2,2'-azino-bis(3-ethylbenzo thiazoline-6-sulfonic acid) diammonium salt (ABTS) with hydrogen peroxide was chosen as a model reaction. Enzymatic activities in SFMEs of varying compositions were investigated by UV-Vis spectroscopy and compared to the enzyme activity in pure buffer solution. Dynamic light, small-angle-X-ray scattering and conductivity measurements were performed in order to obtain structural information on the used SFMEs. Findings presented in this study revealed that the ability of short-chain alcohols to form mesostructures (aqueous aggregates in oil) has a crucial effect on the enzyme activity in SFME5. Mesoscale structuring with 1-propanol (NPA) was found to be more pronounced than for the more hydrophobic tertbutanol (TBA). It was concluded that the most pronounced mesoscale-structured SFMEs lead to the highest enzymatic activities. (C) 2018 Elsevier Inc. All rights reserved.