De-emulsification ability of a microbial compound de-emulsifier

The use of microbial de-emulsifier is limited for its low de-emulsification activity, instability and sensitivity to environmental factors. To solve this problem, two superior strains (Bacillus mojavensis, Bacillus subtilis) were cultured in a mineral salt medium to obtain a microbial compound de-emulsifier with high capability of de-emulsification. The cell culture could demulsify the O/W model emulsion completely in 48 h at room temperature. Comparing with that of the single strain culture, the fermentation process of the mixed culture was shortened more than 6 h. With less addition volume, the mixed culture showed higher de-emulsification activity and stability. The microbial compound de-emulsifier kept high de-emulsification activity in the emulsion with different pH value ranged from 3-7. Thermostability was detected. When the emulsion temperature varied from 20-120°C, changing rate of the oil drain rate was under 15%. After the strains were mixed cultured, the metabolites produced during the fermentation process still took the main function of de-emulsification. The supernatant remained 87% de-emulsification ability of the cell culture while the bacterial cells could hardly break the emulsion. Comparing with the widely used chemical ones, the microbial compound de-emulsifier has almost the same effectiveness in dealing with the oil-bearing waste water from Daqing oilfield. Compounding microbial de-emulsifiers is an effective way to enhance their demulsification abilities.