*2.1. Microorganism and the Production of the Biosurfactant*

The bacterium *Bacillus cereus* UCP 1615 obtained from the culture bank of the Catholic University of Pernambuco was used as the biosurfactant-producing microorganism. This strain was previously isolated from environmental samples of water contaminated with petroleum byproducts spilled from ships (port area) in the Atlantic Ocean in the state of Pernambuco, Brazil. As described by Durval et al. [15], the bacterium was cultured by adding a 2% cell suspension (optical density of 0.7 at a wavelength of 600 nm corresponding to a 24 h inoculum of 10<sup>7</sup> colony-forming units/L) to a 500 mL flask containing 100 mL of a mineral salt medium (0.087% K2HPO4, 0.65% trisaminomethane, 0.02% KCl, 0.06% MgSO4·7H2O, 0.01% NaCl and 0.005% yeast extract) supplemented with 2% waste frying soybean oil and 0.12% peptone with the pH adjusted to 7.0 ± 0.2. After culturing for 48 h at 28 ◦C and 250 rpm, the samples were withdrawn to determine the concentration of the biosurfactant.
