Investigation of biosurfactant production by Bacillus pumilus 1529 and Bacillus subtilis WPI

Biosurfactants are unique amphipathic molecules with extensive application in removing organic and metal contaminants. The purpose of this study was to investigate production of biosurfactant and determine optimal conditions to produce biosurfactant by Bacillus pumilus 1529 and Bacillus subtilis WPI.
In this study, effect of carbon source, temperature and incubation time on biosurfactant production was evaluated. Hemolytic activity, emulsification activity, oil spreading, drop collapse, cell hydrophobicity and measurement of surface tension were used to detect biosurfactant production. Then, according to the results, the optimal conditions for biosurfactant production by and Bacillus subtilis WPI was determined.
In this study, both bacteria were able to produce biosurfactant at an acceptable level. Glucose, kerosene, sugarcane molasses and phenanthrene used as a sole carbon source and energy for the mentioned bacteria. Bacillus subtilis WPI produced maximum biosurfactant in the medium containing kerosene and reduced surface tension of the medium to 33.1 mN/m after 156 hours of the cultivation at 37°C. Also, the highest surface tension reduction by Bacillus pumilus 1529 occurred in the medium containing sugarcane molasses and reduce the surface tension of culture medium after 156 hours at 37°C from 50.4 to 28.83 mN/m.
Discussion and Bacillus pumilus 1529 and Bacillus subtilis WPI had high potential in production of biosurfactant and degradation of petroleum hydrocarbons and Phenanthrene. Therefore, it could be said that these bacteria had a great potential for applications in bioremediation and other environmental process.