AUTHOR=Engelskirchen Sandra , Wellert Stefan , Holderer Olaf , Frielinghaus Henrich , Laupheimer Michaela , Richter Sven , Nestl Bettina , Nebel Bernd , Hauer Bernhard TITLE=Surfactant Monolayer Bending Elasticity in Lipase Containing Bicontinuous Microemulsions JOURNAL=Frontiers in Chemistry VOLUME=8 YEAR=2021 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.613388 DOI=10.3389/fchem.2020.613388 ISSN=2296-2646 ABSTRACT=

Lipase-catalyzed reactions offer many advantages among which a high degree of selectivity combined with the possibility to convert even non-natural substrates are of particular interest. A major drawback in the applicability of lipases in the conversion of synthetically interesting, non-natural substrates is the substantial insolubility of such substrates in water. The conversion of substrates, natural or non-natural, by lipases generally involves the presence of a water–oil interface. In the present paper, we exploit the fact that the presence of lipases, in particular the lipase from Candida antarctica B (CalB), changes the bending elastic properties of a surfactant monolayer in a bicontinuous microemulsion consisting of D2O/NaCl -n-(d)-octane-pentaethylene glycol monodecyl ether (C10E5) in a similar manner as previously observed for amphiphilic block-copolymers. To determine the bending elastic constant, we have used two approaches, small angle neutron scattering (SANS) and neutron spin echo (NSE) spectroscopy. The time-averaged structure from SANS showed a slight decrease in bending elasticity, while on nanosecond time scales as probed with NSE, a stiffening has been observed, which was attributed to adsorption/desorption mechanisms of CalB at the surfactant monolayer. The results allow to derive further information on the influence of CalB on the composition and bending elasticity of the surfactant monolayer itself as well as the underlying adsorption/desorption mechanism.