Abstract:

The effects of initial substrate concentration, temperature and pH on the phenanthrene biodegradation characteristics and enzymatic reaction kinetics were studied by using a strain of gramnegative bacteria J1 that is isolated and purified from the active sludge. The sludge collected from Membrane Bioreactor was cultured and acclimated with phenanthrene. The bacteria cells, in the shape of a short rod, are about 25 μm long and 13 μm wide. The phenanthrene in the aqueous solution was completely degraded in 48 h, however, the biodegradation time prolonged when the initial concentration increased. The temperature had significant effect on the phenanthrene biodegradation by strain J1. The optimum temperature of the biodegradation was 28 ℃. With the same initial concentration of phenanthrene, the biodegradability of phenanthrene was found to be decreased with increasing or decreasing the temperature. 100％ of the phenanthrene was degraded in 48 h for the concentration of 115 mg·L-1 when the temperature was 28 ℃. However, less than 37％ of phenanthrene could be degraded, if the temperature was decreased to 10 ℃. The biodegradation ability of the strain J1 had a certain adaptability with the variety of pH between 6084 and the optimum pH was 72. The experimental outcomes could be fit well with the firstorder biodegradation kinetics model. The high substrate concentration inhibited the enzymatic reaction. The maximum rate constant vm, Michaelis constant Km, substrate inhibition constant kS, and the optimum substrate concentration ［S］opt  of the enzymatic reaction were 117 mg·L-1·h-1, 6170 mg·L-1, 4960 mg·L-1, and 5532 mg·L-1, respectively.

Key words:

phenanthrene; biodegradation characteristics; enzymatic reaction; Michaelis constant; substrate inhibition; kinetics