Kinetics studies of p-cresol biodegradation by using Pseudomonas putida in batch reactor and in continuous bioreactor packed with calcium alginate beads

Present study deals with the biodegradation of p-cresol by using Pseudomonas putida in a batch reactor and a continuous bioreactor packed with calcium alginate beads. The maximum specific growth rate of 0.8121 h⁻¹ was obtained at 200 mg L⁻¹ concentration of p-cresol in batch reactor. The maximum p-cresol degradation rate was obtained 6.598 mg L⁻¹ h⁻¹ at S_o=200 mg L⁻¹ and 62.8 mg L⁻¹ h⁻¹ at S_o=500 mg L⁻¹ for batch reactor and a continuous bioreactor, respectively. The p-cresol degradation rate of continuous bioreactor was 9 to 10-fold higher than those of the batch reactor. It shows that the continuous bioreactor could tolerate a higher concentration of p-cresol. A Haldane model was also used for p-cresol inhibition in batch reactor and a modified equation similar to Haldane model for continuous bioreactor. The Haldane parameters were obtained as μ_max 0.3398 h⁻¹, K_s 110.9574 mg L⁻¹, and K_I 497.6169 mg L⁻¹ in batch reactor. The parameters used in continuous bioreactor were obtained as D_max 91.801 mg L⁻¹ h⁻¹, K_s 131.292 mg L⁻¹, and K_I 1217.7 mg L⁻¹. The value K_I of continuous bioreactor is approximately 2.5 times higher than the batch reactor. Higher K_I value of continuous bioreactor indicates P. putida can grow at high range of p-cresol concentration. The ability of tolerance of higher p-cresol concentrations may be one reason for biofilm attachment on the packed bed in the continuous operation.