OLIVERA nelda Lila
capítulos de libros
BIOSURFACTANTS AND THEIR USES IN THE PETROLEUM INDUSTRY AND HYDROCARBON POLLUTION REMEDIATION
NELDA LILA OLIVERA; MARINA NIEVAS
Detergents: Types, Components and Uses
Nova Science Publishers, Inc.
Lugar: Hauppauge, N.Y.; Año: 2010; p. 1 - 48
Biosurfactants are amphipathic molecules which have the capability to reduce the medium surface tension. At low concentrations, surfactants in aqueous solution exist as monomers. As the surfactant concentration increases, the medium surface tension decreases. Above a threshold concentration known as the critical micelle concentration (CMC), biosurfactant molecules form micelles with a hydrophobic core and a hydrophilic surface. CMC values are characteristic of each biosurfactant, depending on the chemical structure and composition of the biosurfactant as well as the solution conditions (e.g. temperature, ionic strength, additives). There is an important diversity in chemical structures and functions among natural surfactants. A distinction between low and high-molecular-weight biosurfactants is accepted, the former are generally glycolipids or lipopeptides with surface activity, while the latter are exocellular polymeric substances with important emulsifying properties. This chapter focuses on microbial biosurfactants that on the context of degradation of lipophilic compounds, such as hydrocarbons, may enhance their bioavailability to microorganisms, either by increasing the apparent hydrocarbon solubility in the aqueous phase or by increasing the contact surface area due to emulsification. In this regard, different biosurfactants have been applied to enhance the biodegradation of oily residues and to fight against oil pollution. In addition, biosurfactants possess the advantage of being biodegradable molecules which encourages its use in the development of bioremediation strategies. In the petroleum industry, biosurfactants also find application in MEOR (microbial enhanced oil recovery) improving hydrocarbon mobilization and consequently the recovery of crude oil from reservoirs.