Study of laccase activity and stability in the presence of ionic and non-ionic surfactants and the bioconversion of indole in laccase-TX-100 system

Abstract

The aim of this study was to characterize the stability and activity of laccase from Trametes versicolor in the presence of three different surfactants, namely sodium di-2-ethylhexylsulfosuccinate (AOT), Triton X-100 (TX-100), and cetyltrimethylammonium bromide (CTAB). The kinetic parameters (such as Km, kcat, kcat/Km ratio), optimal pH and temperature and the thermostability of the enzyme at different temperatures were determined and compared in the absence and presence of the three surfactants. Results revealed that the catalytic activity of the enzyme was greatly improved in the presence of low concentrations of AOT, whereas the activity declined in the presence of TX-100 and CTAB inactivated it almost completely. Results also depicted that, in general, the presence of the surfactants affected the enzyme optimum pH and temperature. In terms of stability, TX-100-induced stabilization and AOT and CTAB-mediated destabilization of the enzyme were observed. Laccase-mediated bioconversion of indole to 2,2-bis(3′-indolyl)-indoxyl in the presence of TX-100 as the effective stabilizing surfactant and TEMPO as the enzyme mediator was also investigated.