Production and characterization of biosurfactant by free and immobilized cells from Ochrobactrum intermedium isolated from the soil of southern Algeria with a view to environmental application

In this paper, biosurfactant production by free and immobilized cells of Ochrobactrum intermedium has been studied. This bacterium strain was isolated from an Algerian crude oil-contaminated soil; hexadecane was used for the production as the sole carbon and energy source. The process was monitored by measuring the surface tension and emulsification index E24 for one week at 37 °C and neutral pH. For the production by immobilized cells, the concentrations of sodium alginate, calcium chloride and biomass were optimized. Results showed that O. intermedium entrapped in calcium alginate beads is able to preserve its viability and produce biosurfactants but with an effect on the production kinetics due to diffusional limitations of the alginate beads with greater stability with up to 75%. The product biosurfactant reduced the surface tension below 33 and emulsification index were 68%–93% after 48 and 72 h with free and immobilized cells, respectively. Also, the product belongs to the family of glycolipids and showed stability in a wide range of pH (2–12), temperature (25–120 °C), and to high salinity. Both products by strain O. intermedium, based on spectral features, have a chemical structure identical to that of glycolipids. The production yield of biosurfactant versus concentration of the hexadecane is 1292 g/g. Second, the surfactants are able to promote the solubility of polycyclic aromatic hydrocarbons (PAHs). Results show that the use of biosurfactant, produced by the isolated bacterial strain O. intermedium, obtained a better solubility of naphthalene and phenanthrene