Continuous two-phase biocatalysis using water-in-oil Pickering emulsions in a membrane reactor: Evaluation of different nanoparticles

The impact of lipases on the rheological behavior of colloidal silica nanoparticle stabilized Pickering emulsions for biocatalytical applications

“…Cyclopentyl methyl ether (CPME) (8465.360, VWR, Germany) was used as the continuous phase since it had already been used for lipase-catalyzed reactions in previous studies [16,24].…”

“…The term rheological behavior is used in this study to describe the group of fluid classifications determined by shear rheology. From previous experiments, the emulsion droplet sizes were expected to be up to 50 µm [16]. To ensure a gap size of at least 10-fold larger than the expected droplet sizes, a plate and plate measurement system (PP50; 49.97 mm diameter) with a gap size of 0.5 mm was used for all experiments.…”

“…Even without stirring the PE, higher yields were achieved for lipasecatalyzed reactions in w/o PEs in batch processes in comparison to batch reactions in stirred dispersions [15]. Furthermore, continuous lipase-catalyzed reactions with a subsequent liquidliquid separation have been recently demonstrated in a fixed-bed reactor or a membrane reactor [14,16]. Particularly in the case of continuous operations, the fluid dynamical design of equipment and operating conditions, e.g., for the latter case membrane modules, the rheological behavior and flow properties of an emulsion are significant characteristics.…”

“…Particularly in the case of continuous operations, the fluid dynamical design of equipment and operating conditions, e.g., for the latter case membrane modules, the rheological behavior and flow properties of an emulsion are significant characteristics. PEs can be stabilized by colloidal silica nanoparticles, which easily adsorb at interfaces [3,[16][17][18] and which can create a thixotropic and shear-thinning rheological behavior [19]. This is due to a particleparticle network formed by hydrogen bonds between residual silanol groups on the surface of the silica nanoparticles.…”

“…Furthermore, the shear-thinning character of an emulsion is more pronounced for fine and monodisperse than for coarse and polydisperse emulsions [21]. It can be expected that the rheological properties of PEs are influenced by interfacially active lipases due to their ability to adsorb to interfaces [22,23] and due to their impact on reducing the droplet sizes and on increasing the monodispersity of w/o PEs [16,24]. However, no literature about the rheology of PEs containing lipases is available yet.…”