Response surface optimization in biosurfactant production by using a renewable growth substrate

Abstract

The present study investigated the use of blackstrap molasses as renewable carbon source by a <i>Pseudomonas aeruginosa</i> strain to produce rhamnolipid surfactant under shake flask conditions. The process factors considered were total sugar concentration, carbon to nitrogen ratio and incubation period, whereas the responses were utilized total sugar, dry cell biomass, rhamnolipid yield, surface tension and certain kinetic parameters. This is the first report on response surface optimization in biosurfactant production by <i>P. aeruginosa</i> strain grown on molasses. Statistical modeling for all the considered responses was done through desirability, which expressed that the percentage of prediction error was much low. This explains that the prediction performance of the models is quite adequate. The highest dry cell biomass (1.63 g/L) and rhamnolipid (1.46 g/L) yields were observed at 5 d of incubation on 2% total sugars-based molasses amended with sodium nitrate (at C:N, 20:1). The surface tension of this culture medium dropped to 28.0 from 50.0 mN/m.