Biosurfactant production by the hydrocarbon-degrading bacteria (HDB) Serratia marcescens: Optimization using central composite design (CCD)

Abstract

Abstract Based on the nutritional and physiological requirements of a native hydrocarbon-degrading bacterium (HDB), Serratia marcescens, an investigation on the potential biosurfactant production by this bacterial species was conducted. The effects of different carbon sources, nitrogen sources, salinity, pH, temperature, and agitation speeds were extensively studied. The optimal conditions of biosurfactant production and surface tension were determined using central composite design (CCD) by setting glycerol, peptone and ammonium sulphate (NH4)2SO4 in a range of 3–7%, 2–6 g/L and 3–7 g/L, respectively. The results showed that biosurfactant was highly produced at pH 8, a temperature of 30 °C, a salinity of 1% and a speed of 200 rpm after 5 days (120 h) of incubation. The optimal conditions were obtained at 5% glycerol, 4 g/L peptone and 5 g/L (NH4)2SO4 with a maximum biosurfactant production of 1.42 g/L and a minimum surface tension of 28.4 mN/m. Thus, the HDB S. marcescens shows good potential as a biosurfactant-producing bacterium to be used in any environmental application and as an alternative to chemical surfactants.