Characteristics of phenol biodegradation in saline solutions by monocultures of Pseudomonas aeruginosa and Pseudomonas pseudomallei

Phenol is a highly toxic and carcinogenic compound and its biodegradation is very important to meet the environmental regulations. Two bacterial strains capable of utilizing phenol as a sole source of carbon were isolated from the wastewater of a pharmaceutical industry. On the basis of morphological and biochemical characteristics these strains were identified as Pseudomonas aeruginosa and Pseudomonas pseudomallei. Both of these strains were very efficient for phenol degradation. R pseudomallei degraded phenol at a maximum concentration of 1500 mg L-1 within seven days with a specific growth rate of 0.013 h(-1) and phenol degradation rate of 13.85 mg L-1 h(-1). Maximum initial concentration of phenol utilized by R aeruginosa was 2600 mg L-1 with 0.016 h(-1) specific growth rate and 26.16 mg L-1 h(-1) phenol degradation rate. Moreover, the effect of various salts i.e., NaCl, KCl, Na2SO4 and K2SO4 on the growth of these strains and phenol degradation rate (at 1000 mg L-1) was studied. In the presence of these salts, R aeruginosa showed up to 1.53 and 1.34 times faster phenol degradation rate and specific growth rate, respectively as compared to P. pseudomallei. In addition, P aeruginosa exhibited higher chemical oxygen demand (COD) and biochemical oxygen demand (BOD) reduction rates as compared to the strain R pseudomallei. (C) 2007 Elsevier B.V. All rights reserved.