Growth kinetics of some subsurface microbial strains using naphthalene as a probe contaminant

The focus of this study is the unravelling of the microbial dynamics of the biodegradation of naphthalene, a polycyclic aromatic hydrocarbon, in an aqueous-sediment matrix. The Pour plate procedure was adopted for the isolation of the microbial colonies, while the sub-culturing of the isolates was based on their cultural (biochemical) and morphological characteristics. Investigations showed that the microbial colonies consisted of the bacterial and fungal strains. The logarithmic growth curve was characterized by an initial lag phase, a rapid and exponential increase in cell biomass, a stationary phase and finally a death phase. Both strains in the presence of naphthalene-impacted basal salt medium demonstrated that the microbial growth results in an almost linear increase in biomass concentration--an indication that mass transfer from the solid phase to the liquid phase (lag phase) is limiting for growth. The kinetics of the utilization of naphthalene expressed as the growth and consumption rates indicated that all the microbial strains isolated from an indigenous soil used in this study exhibited a high metabolic affinity for naphthalene. Optimal performance was demonstrated by the bacterial strains that could use naphthalene as their sole carbon and energy source.