KINETICS OF BENZENE DEGRADATION USING SELECTED BACTERIAL STRAINS

Abstract

Monoaromatic hydrocarbons such as benzene have been found in wastewaters as well as sludge generated from petroleum industries. Benzene is categorized as a carcinogen. Biodegradation has been found to be an important environmental remediation technique for water and soil associated benzene. In this technique, microorganisms utilize pollutant as a source of carbon and energy. The objectives of present work were to study benzene degradation using selected strains along with effects of salinity and pH on degradation efficiency. Three different bacterial strains used for this study which were already isolated from Cannabis sativa and identified on the basis of 16S rRNA sequences. The GenBank accession numbers assigned for Pseudomonas aeruginosa, Bacillus cereus, Acinetobacter junii were KM520129, KM520130, and KM520131. Growth kinetics were observed using batch reactions at different substrate concentrations. The strains were used for degradation using M9 media at 250, 500, 750 and 1000 mg/L benzene concentrations. Bacterial colonies were counted in terms of colony forming units per milliliter (CFU/mL). Biomass was determined using dry weight method. Maximum specific growth rate for Pseudomonas aeruginosa, Bacillus cereus and Acinetobacter junii were found to be 0.177, 0.135 and 0.105 h-1. Significant degradation was observed at 500 mg/L for all bacterial strains. Pseudomonas aeruginosa, Bacillus cereus, and Acinetobacter junii degraded 77, 81, and 74% benzene, respectively. Degradation efficiency was maximum at neutral pH for all the three strains. Results regarding effect of salinity showed that Pseudomonas aeruginosa and Bacillus cereus degraded 47 and 58% respectively at 0.5% salinity while Acinetobacter junii showed 65% degradation efficiency at 3.0% salinity.