Enzymatic pathway involved in the degradation of fluoranthene by microalgae Chlorella vulgaris

In the present study, the potential of a microalga, Chlorella vulgaris, was assessed for the bioremediation of fluoranthene (FLT), a four ring polycyclic aromatic hydrocarbon (PAH). With an initial cell density of C. vulgaris (OD₆₈₀ = 0.100), 54-58% of 25 μM FLT was removed from the growth medium within 3 days and almost 90-94% after 7 days of incubation. Enzymatic studies confirmed that the enzyme involved in FLT metabolism was catechol 2,3, dioxygenase (C2,3D) which increased almost 2 times in 5 μM FLT and 2.4 times in 25 μM FLT inoculated culture. Activity of dehydrogenase and superoxide dismutase (SOD) was significantly reduced, while peroxidase (POD) activity was induced very prominently in FLT inoculated cultures. Changes in growth, physiological parameters and biochemical compositions of the algae with 5 μM and 25 μM FLT were also analyzed and compared to control. The analysis showed that parameters including growth rate, biomass, chlorophyll, carbohydrate and protein contents, were negatively affected by the higher concentration of FLT, whereas the lipid and carotenoids content significantly increased. To our knowledge, this is the first report to suggest the role of C2,3D pathway for the metabolism of FLT in a eukaryotic algae.