Biodegradation of hydrocarbons in the presence of cyclodextrins

Aliphatic hydrocarbons are one of the main components of oil contamination. Bioremediation is considered to be a cost-effective treatment option among the conventional treatment methods with bioavailability being the limitation. Chemical surfactants could be used to increase the bioavailability of the hydrocarbons but they showed marked toxicity and environmental pollution. Cyclodextrins are cyclic oligosaccharides which can alter the solubility of the hydrocarbons by incorporating suitably sized hydrophobic molecules into their hydrophobic cavities. This paper focuses on studying the degradation of hydrocarbons by Pseudomonas like species named as Vid1 isolated previously from bilge oil contaminated waters in the presence of cyclodextrins. Among the three cyclodextrins (α, β and γ) tested at different concentrations, 2.5 mM of β-cyclodextrin showed higher amount of biodegradation when n-hexadecane was used as a model hydrocarbon compound. The percentage of residual hexadecane remaining in the 2.5 mM β-cyclodextrin supplied medium at 120 h was found to be 15% in comparison with the biotic control which was 43%. In the next experimental setup, degradation of mixture of hydrocarbons (tetradecane, hexadecane and octadecane) by Vid1 (Pseudomonas like species) was studied at a concentration of 2.5 mM β-cyclodextrin. The residual percentage of tetradecane, hexadecane and octadecane at 120 h was found to be 32, 43 and 61% in comparison with the biotic control 50, 58 and 67%, respectively. Our studies show that among a mixture of hydrocarbons (tetradecane, hexadecane and octadecane) in the presence of β-cyclodextrin, the highest concentration of hydrocarbon degradation was found in tetradecane, hexadecane and octadecane, respectively.