Isolation and functional characterization of hydrocarbon emulsifying and solubilizing factors produced by a Pseudomonas species

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Abstract
Pseudomonas PG-1 cultivated on pristane produced in good amount a heat-stable polymeric substance which showed strong hydrocarbon emulsifying and solubilizing properties. The substance was isolated in crude form and contained 34% protein, 16% carbohydrate and 40% lipid. The hydrocarbon solubilizing activity of the isolate was strongly inhibited by EDTA but the chelating agent had no effect on the hydrocarbon emulsifyng activity. Both activities of the isolate were strongly inhibited by chymotrypsin treatment indicating the importance of the protein moiety for its activity. Hydrocarbon solubilization by the isolate showed a certain degree of specificity to pristane in modest agitation generally used in microbial cultivation, but this specificity was lost by vigorous agitation in a Waring blender. It was proposed that in the first case, solubilization was effected by a solubilizing factor specific to pristane, whereas in the latter case, nonspecific solubilization occurred due to the action of the emulsifying factor. The rate of pristane solubilization by heat-treated culture broth under the conditions of agitation used in cultivation (rotary shaker, 120 rpm) was about 750 mg l-1 h-1, which was much larger than the maximal pristane uptake rate of 170 mg l-1 h-1 observed during microbial growth on the substrate. Hydrocarbon solubilization could satisfactorily account for the substrate uptake and growth.