A Halotolerant, Thermotolerant, and Facultative Biosurfactant Producer: Identification and Molecular Characterization of a Bacterium and Evolution of Emulsifier Stability of a Lipopeptide Biosurfactant

A halotolerant, thermotolerant, and facultative biosurfactant producing bacterium was identified as a strain of Bacillus mojavensis based on the phenotypic data, a phylogenetic analysis, and DNA-DNA relatedness with closely-related species. This strain grew at temperatures and salinities up to 55 degrees C and 0 similar to 10% (w/v) NaCl, respectively, and under anaerobic conditions. A batch fermentation showed that this strain secreted a lipopeptide biosurfactant that can reduce surface tension to 27 mN/m while growing on mineral medium. The emulsifying activity of the cell-free supernatant and stability of the formed emulsions were studied at various temperatures and salinities. The results showed that the ability to significantly reduce surface tension was not sufficient to form stable emulsions. The ability of this strain to grow and reduce surface tension under a wide range of salinities and temperatures gives it an advantage for many applications.