Substrate Versatility Studies on the Aerobic Degradation of BTX Compounds

Abstract

Biodegradation studies were carried out in aerobic batch systems using Benzene, Toluene and Xylene (BTX) as the sole carbon source to evaluate the versatility of a bacterial consortium taken from a domestic sewage treatment plant. This mixed microbial culture was acclimatized using individual BTX compounds and the potential capability of microbes precultured on a single substrate to degrade other compounds was studied over a wide range of BTX concentrations (∼50-500mg/L). The biodegradation pattern and growth rates ascertained experimentally in these versatility studies were compared with results obtained from individual degradation experiments studied earlier. Similar growth pattern was observed for all the substrate with inhibition occurring at higher concentrations (∼200 mg/L for Benzene and Xylene, ∼250mg/L for Toluene). Toluene was degraded more than the other substrates followed by benzene and xylene. Adaptation to a more toxic compound like benzene and xylene improved the utilization of toluene. On the other hand microbes grown on a less toxic compound (toluene), grew at a lower rate in the presence of more toxic compounds. Kinetic parameters such as μ_max, K_I and K_S were determined using the Haldane’s and Levenspiel’s substrate inhibition models. Results from Haldane’s model were more illustrative of the experimental observations and were found to satisfactorily explain the system behavior.