title: Evaluation of the effect of nutrient ratios on biosurfactant production by Serratia marcescens using a Box-Behnken design.
abstract: The strain SmSA, identified as Serratia marcescens and known as a biosurfactant producer, was isolated from hydrocarbon contaminated soil from Veracruz, México. The interactions among the C/N, C/Mg and C/Fe ratios have not been examined for this microorganism. In this work was evaluated the effect of these nutrients at three levels using a mineral medium with glucose as the carbon source. A Box-Behnken experimental design was utilised to maximise biosurfactant production, which was assessed by oil spreading and surface tension tests. The treatment with C/N=5, C/Fe=26,000 and C/Mg=30 showed the best result since the surface tension was reduced to 30 mN m(-1). The multiple regression and response surface analyses indicated that the interaction between C/N and C/Mg had the utmost effect on the reduction of surface tension and biosurfactant production. The conditions of the best treatment were used to scale up biosurfactant production in a 3L bioreactor giving a yield of 4.1 gL(-1) of pure biosurfactant. It was found that the biosurfactant was mainly produced in the exponential phase and decreased the surface tension to 31 mN m(-1). The contact between the biosurfactant with heavy oil (15° API) increased its displacement from 9.3 to 18 cm.
authors: Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas, Norte 152 Col., San Bartolo Atepehuacan, Del. Gustavo A. Madero, C.P. 07730, México, Distrito Federal, Mexico. troldan@imp.mx
authors: T
authors: T
authors: Roldán-Carrillo
authors: X
authors: X
authors: Martínez-García
authors: I
authors: I
authors: Zapata-Peñasco
authors: G
authors: G
authors: Castorena-Cortés
authors: J
authors: J
authors: Reyes-Avila
authors: M
authors: M
authors: Mayol-Castillo
authors: P
authors: P
authors: Olguín-Lora