Kinetics of biodegradation of petroleum by Pseudomonas sp.

Abstract The biodegradability of two petroleum fractions f1 (180–235°C) and f2 (235–350°C) with different boiling ranges has been studied by using pure cultures of Pseudomonas sp., isolated from the contaminated water of Algiers' port. Experiments were carried out in batch cultures at two temperatures, 15°C and 30°C. Substrate concentrations were 0.4% and 0.8% vol. Growth occurred on both fractions with a very short lag phase. Increasing temperature and concentration enhanced positively bacterial growth on both fractions. Maximal growth and initial growth rate were increased by more than 30%. Limited effects on biodegradation kinetic of oil fraction f1 was observed while for f2 temperature had significant effect at low concentration and a diauxie phenomena at 15°C led to higher overall yield. The rates of growth and biodegradation were higher when using fraction f2 as carbon source. Apparent kinetic parameters of biodegradation reactions were determined. Degradation of f1 followed a mixed order kinetic between 2/3 and 1 with rate constants varying from 0.0174 h −1 (% vol) 1/3 −0.0239 h −1 when the temperature was increased from 15–30°C. While for f2 the order was constant 9/5 and rate constants were 0.0554 and 0.061 h −1 (% vol) − 4/5 respectively. Growth of Pseudomonas sp. on f1 and f2 could be simulated by the Boltzman equation and the adequacy of the equation was proved by X 0.05 (3) test, while a fourth degree polynomial presented well biodegradation as a function of time with high values of sample correlation coefficients ( r * > 0.97). Parameters of both models were determined by least squares method. Finally, a factorial design was used to develop a general model containing four important parameters (time, temperature, substrate nature and concentration) to simulate bacterial growth. High order interactions were observed and only three were insignificant. Linear regression was employed to determine if biodegradation rates were correlated to microbial growth.