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. P. 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 P. 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, Na(2)SO(4) and K(2)SO(4) on the growth of these strains and phenol degradation rate (at 1000 mg L(-1)) was studied. In the presence of these salts, P. 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 P. pseudomallei.