Chapter 15 - Rhamnolipid Biosurfactants: Solubility and Environmental Issues

Abstract

This chapter focuses on rhamnolipid biosurfactants and their various environmental applications in solubilization and biodegradation, soil and waste treatment (in situ and ex situ), and water treatment. A group of biosurfactants that has been studied extensively is the rhamnolipids from Pseudomonas aeruginosa (P. aeruginosa), which are commercially available and can lower surface tensions of water to 29 mN/m. P. aeruginosa can produce rhamnolipids from a wide variety of substrates including C11 and C12 alkanes, succinate, pyruvate, citrate, fructose, glycerol, olive oil, glucose, and mannitol. The composition and yield depend on the fermentor design, pH, nutrient composition, substrate, and temperature. Rhamnolipid addition can enhance the biodegradation of various pure compounds such as hexadecane, octadecane, n-paraffin, and phenanthrene in liquid systems in addition to hexadecane, tetradecane, pristine, creosote, and hydrocarbon mixtures in soils. It has been demonstrated that a concentration of 300 mg/L of rhamnolipids increases the mineralization of octadecane to 20% in comparison to 5% for the controls. Because of their biodegradability and low toxicity, biosurfactants such as rhamnolipids are very promising for use in remediation technologies. However, further research regarding the prediction of their behavior in the fate and transport of contaminants is required.