Isolation, Fermentation Optimization and Performance Studies of a Novel Biosurfactant Producing Strain Bacillus amyloliquefaciens

W. Zhang, X. Zhang and H. Cui

Abstract
In this research, biosurfactant-producing bacteria were isolated from the outlet sludge of a canteen and one promising strain was identified through 16S rDNA sequence as Bacillus amyloliquefaciens. This strain can utilize water-soluble carbon source and the FT-IR analysis indicated the biosurfactant was probably glycolipids. Further factors (fermentation time, temperature, carbon source, nitrogen source, ion concentration) affecting the biosurfactant production were determined. The optimum fermentation conditions and nutrient concentration were as follows: fermentation time 48 h, temperature 30 °C, fermentation pH 6, glucose concentration 30 g L–1, peptone concentration 4 g L–1, total phosphorus concentration 8 g L–1, sodium chloride concentration 2 g L–1, magnesium sulfate concentration 0.25 g L–1, and calcium chloride concentration 0.04 g L–1. In such conditions, the surface tension of the solution was 28 mN m–1. At the same time, the formation of biosurfactant and nano-silica complex system was discussed to improve the biosurfactant performance and provide the basis for expanding the application scope of biosurfactant.

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Keywords
biosurfactant, Bacillus amyloliquefaciens, nano-silica