The functional emulsifying component of SL-bioemulsifier is an SDR family oxidoreductase protein

Abstract

HypothesisBioemulsifiers play an important role in microbial enhanced oil recovery (MEOR) due to their excellent emulsion stability. Different from biosurfactants, bioemulsifiers cannot significantly reduce the oil-water interfacial tension, and the mechanism through which they improve oil recovery remains poorly understood. It is helpful to study the mechanism by analyzing its functional emulsifying components of bioemulsifier. ExperimentsIn our previous work, the thermophilic strain Aeribacillus pallidus SL-1 efficiently degraded crude oil and insoluble polycyclic aromatic hydrocarbons (naphthalene and phenanthrene) with the help of a bioemulsifier. In this study, the glycoprotein SL-bioemulsifier was studied. FindingsThe main functional emulsifying component was identified as a 26 kDa SDR family oxidoreductase protein, called E26. The recombinant E26 protein exhibited excellent emulsifying activity with different hydrophobic substrates, and stabilized the emulsions for a long time even at extreme pH, high salt concentrations and high temperatures. Notably, the emulsion formed by E26 protein was found to have a gel-like structure, facilitating the formation of an oil-water barrier to stabilize the emulsion. In addition, E26 protein effectively improved the surface wettability of calcite minerals in the oil-water system at a low concentration, which may play a role in the enhancement of oil recovery by bioemulsifiers.