The factors affecting the backward-transfer of Bovine Serum Albumin (BSA) from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micellar solutions

Effect of protein incorporation on the nanostructure of the bicontinuous microemulsion phase of Winsor-III systems: a small-angle neutron scattering study

Small-angle neutron scattering (SANS) analysis using the Teubner-Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oil from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOT's sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. The results of this study demonstrate the importance of ionic strength to modulate protein-surfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.

The influence of particle size on microbial hydrolysis of protein particles in activated sludge

The influence of particle size on hydrolysis rates was evaluated in batch respirometers using protein particles derived from hard-boiled egg whites and activated sludge. It was found that initial hydrolysis rates for large particles were low but increased over time, contradicting commonly used mathematical modeling approaches to describe hydrolysis. A modified mathematical model was proposed based on particle breakup that described the observed hydrolysis kinetics for small and large protein particles. In the particle breakup model, hydrolysis results both in the release of readily biodegradable substrate and, at the same time, breakup of larger aggregates resulting in an increase of the specific surface area available for hydrolysis. Using this model, initial specific hydrolysis rates were calculated for the small and large particles, and ranged from 0.038 to 0.24 d(-1) and 0.19 to 0.98 d(-1) for large and small particles, respectively. The specific hydrolysis rate at the point of maximum overall hydrolysis rate ranged from approximately 2 to 3 d(-1) for all particles.