Potentials for use of biosurfactants in oil spills cleanup and oil bioremediation

Biosurfactant are environmental friendly, effective and stable compounds with many advantages over synthetic surfactants. Their use is gaining prominence in several industrial applications due to their broad capabilities which includes emulsification, wetting, foaming, solubilisation and viscosity reduction. Their main types are glycolipids in which carbohydrates are attached to a long-chain aliphatic acids. Other more complex types such as lipopeptides, lipoproteins and heteropolysaccharides also exist. The use of biosurfactants for oil spills cleanup or enhanced oil recovery involves a reduction of the oil-water interfacial tension leading to its emulsification. Stable emulsions are formed because biosurfactants lowers interfacial tension between interfaces and oil. Such an effect can be achieved through the direct addition of active microbial cells to the contaminated environments or augmentation with the biosurfactant compounds. Laboratory studies have shown that the addition of biosurfactant mixtures alone may be useful for stimulating biodegradation of hydrocarbon contaminants in the environment. Biosurfactants are also useful in solubilisation and removal of oil from sand and sludge in oil storage tanks. In ecological terms, the use of biosurfactants is obvious in closed systems but remains speculative in the open environment. The precise mechanism of enhanced oil recovery in situ however, remains unclear and mainly economically unfeasible. Both product characterisation and production process optimisation are expected to facilitate biosurfactants' future applications particularly in oil-related industries and environmental protection and by cleaning-up agencies. This article reviews the state of the art in potential uses in biosurfactants in oil bioremediation.