Production of Antioxidant Exopolysaccharide from Pseudomonas aeruginosa Utilizing Heavy Oil as a Solo Carbon Source

Aim/Background: Pseudomonas aeruginosa is capable of utilizing heavy oil hydrocarbons as a sole carbon source. P. aeruginosa produce exopolysaccharide (EPS) in an inorganic medium in the presence of crude oil. Several environmental factors affect the majority of EPS production. Materials and Methods: Strain of P. aeruginosa were managed under various media (maintenance medium, inoculum, and basal media). Different heavy petroleum oil concentrations (5, 10, 20, and 30 ml/L) were used as solo carbon source to the basal medium. Various conditions of bacterial growth were monitored. The growth of cells was estimated by measuring the absorbance of the mixture of 1 ml of the basal medium diluted with 1 ml of distilled water at 600 nm spectrophotometrically. P. aeruginosa was grown aerobically in a production medium at 37°C and 150 rpm on a rotary shaker. The culture broth was centrifuged to separate the cells. The precipitated polysaccharide was separated by centrifugation and washed with ethanol, acetone, and ether, and then dried under reduced pressure oven at 45°C. The DPPH test was carried out as described by Burits and Bucar to monitor the free radical scavenging activities of the extracts. Results: The preferable culture conditions for EPS production were at 10 ml/L heavy oil, with 0.5 g/L NaNO3 as best N sources at pH 6.0 after 5 days incubation. The net weight of purified EPS production was 0.5 g/L. Conclusion: The obtained polysaccharide showed antioxidant activity that possesses DPPH radical scavenging activity, with an EC₅₀ = 0.201.