Optimization of phenol degradation by Antarctic bacterium<i>Rhodococcus</i>sp.
Tengku Athirrah Tengku-Mazuki, Kavilasni Subramaniam, Nur Nadhirah Zakaria, Peter Convey, Khalilah Abdul Khalil, Gillian Li Yin Lee, Azham Zulkharnain, Noor Azmi Shaharuddin, Siti Aqlima Ahmad
Abstract
Abstract This study focused on the ability of the Antarctic bacterium Rhodococcus sp. strain AQ5-14 to survive exposure to and to degrade high concentrations of phenol at 0.5 g l -1 . After initial evaluation of phenol-degrading performance, the effects of salinity, pH and temperature on the rate of phenol degradation were examined. The optimum conditions for phenol degradation were pH 7 and 0.4 g l -1 NaCl at a temperature of 25°C (83.90%). An analysis using response surface methodology (RSM) and the Plackett-Burman design identified salinity, pH and temperature as three statistically significant factors influencing phenol degradation. The maximum bacterial growth was observed (optical density at 600 nm = 0.455), with medium conditions of pH 6.5, 22.5°C and 0.47 g l -1 NaCl in the central composite design of the RSM experiments enhancing phenol degradation to 99.10%. A central composite design was then used to examine the interactions among these three variables and to determine their optimal levels. There was excellent agreement ( R 2 = 0.9785) between experimental and predicted values, with less strong but still good agreement ( R 2 = 0.8376) between the predicted model values and those obtained experimentally under optimized conditions. Rhodococcus sp. strain AQ5-14 has excellent potential for the bioremediation of phenol.