Phenol biodegradation by isolated Citrobacter strain under hypersaline conditions

Abstract Phenol is a toxic pollutant in many kinds of hypersaline industrial effluents that should be treated properly before discharged into water bodies. In this work, a halophilic strain which could utilize phenol as the sole source of carbon and energy was isolated. Based on 16S rRNA results, it was identified as a member of Citrobacter. The phenol biodegradation ability and cell growth of the strain was evaluated with the variation of initial phenol concentration and salinity. The effect of temperature and pH on phenol removal was also investigated. The results showed that the strain was capable of withstanding high phenol (up to 1,100 mg L−1) environment with varying salinity conditions (0–10% of NaCl). The optimal initial phenol concentration was 400 mg L−1, at which the average removal rates of phenol peaked at 10.8 mg L−1 h−1. The higher initial concentration of phenol could inhibit the microbial metabolism. The optimal temperature, pH, and salinity were 35 °C, 6.0, and 0%, respectively. Under these conditions, 400 mg L−1 of phenol could be completely degraded within 20 h. The high removal rates of phenol by the strain might provide an alternative for treating phenolic wastewaters containing high salinity.