[Surfactant production by the Rhodococcus erythropolis sH-5 bacterium grown on various carbon sources]

It has been shown that the Rhodococcus erythropolis sH-5 strain can produce surfactants associated and not associated with the cell wall. Their content depends on medium composition, the nature of the carbon source, and oxygen supply. The highest biosurfactant (bioSF) yield is achieved by growing R. erythropolis sH-5 in medium with 2% kerosene at neutral pH. It has been found that the bioSF yield and emulsification index for various hydrocarbons depend on the kind of the nitrogen source used by the bacterium, increasing with replacement of KNO3 by NaNO3. The yields of biomass and bioSF in R. erythropolis depend on growth temperatures (max at 30 degrees C) but not on water quality (bidistillate, catholyte, or anolyte). It has been found that sH-5 produces more cell-associated bioSF than extracellular species.