Effective biodemulsifier components secreted by Bacillus mojavensis XH-1 and analysis of the demulsification process

The purpose of the present study was to investigate the effective components of the demulsifying bacterial strain Bacillus mojavensis XH-1 and its demulsification process. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the shotgun LC-MS/MS method were used to separate and identify proteins with efficient demulsification activity. The zeta potential changes of the emulsion before and after addition of the biodemulsifier were tested, and the relationships between oil-in-water interfacial tension, the demulsification efficiency and the biodemulsifier structure were examined. The study results indicate that the effective biodemulsifier components were extracellular proteins attached to the cells or secreted into the culture solution that presented as a 50-80 kDa band observed by SDS-PAGE. Six of the proteins were unknown or unnamed, and the demulsifying functions of another 14 proteins had not been previously reported. The main demulsification mechanisms were determined to be solubilization and replacement. When the concentration of the biodemulsifier was low, the replacement mechanism dominated, and the demulsification ratio increased with the biodemulsifier concentration. Solubilization dominated when a high concentration of biodemulsifier was provided, and the demulsification ratio decreased as the biodemulsifier concentration increased.