A REVIEW OF CYCLODEXTRINS POTENTIAL IN INCREASING PETROLEUM HYDROCARBONS BIODEGRADATION
Petroleum hydrocarbons are organic pollutants that are released into the environment mainly due to anthropogenic activities and are considered as priority pollutants. The petroleum hydrocarbons degrading microorganisms occur in most environments, where hydrocarbons may serve as organic carbon sources. Bioremediation is based on the use of microorganisms or microbial processes to degrade environmental contaminants, and offers several advantages over the conventional chemical and physical technologies. It can be a cost effective, environmental friendly technology. The intensity of biodegradation is influenced by several environmental factors, such as quality, quantity and activity of the indigenous microbial populations, levels of nutrients, aerobic conditions, pH, temperature, water content and other soil properties. Moreover, low biodegradability and bioavailability of the contaminants / pollutants may limit the biodegradation in a contaminated / polluted site. Cyclodextrins have successfully been used in soil cleaning technologies as solubilisercarrier molecules. These molecules can transfer the insoluble contaminants / pollutants from the soil surface to the aqueous phase by complex formation. In the aqueous phase the microorganisms can degrade the contaminants / pollutants much easier partly because these molecules become available for the microbial cells, partly because the entrapment of contaminants by cyclodextrins reduces their toxicity. The effects of cyclodextrins on the hydrocarbon contaminants in soils (solubilisation, enhancement of desorption from soil, toxicity and bioavailability modulation, catalytic and stabilising effects) have been recently reviewed. Addition of cyclodextrins in aqueous washing solutions has been shown to increase the removal efficiency several times, while being non-toxic agents.