Double Impact Model for Deciphering Substrate Uptake by Bacteria under Controlled Nutrient Release Conditions

Aim: Bacterial growth kinetics under slow nutrient delivery conditions were studied and evaluated on a model basis in order to determine the impact of substrates on bacterial growth dynamics.

Study Design: The study was carried out in a controlled laboratory condition using an agar base slow-release fertilizer formulation, composed of NPK and Urea (in capsular and granular forms).

Place and Duration of Study: The study was carried out at the Environmental Microbiology Laboratory, University of Port Harcourt, Nigeria, for a 35 – day period.

Methodology: A 0.25% concentration of crude oil was used as a hydrocarbon substrate. Three bacterial isolates (Pseudomonas sp., Bacillus sp. and Micrococcus sp.) were employed in this study. The crude oil degradation rate was monitored using oil and grease method while nitrate nitrogen utilization rate was analyzed by the distillation method.

Results: Bacterial growth rate was observed to be limited by the substrate concentration [S] and the substrate saturation constant/affinity (Ks). The substrate saturation constant/affinity (Ks) was evaluated to be 0.25S, while a bacterial growth ratio ( ) was determined to be 0.8.

Conclusion: These findings as well as the developed models could serve as important tools for monitoring the progress of a bioremediation process/strategy. They are therefore recommended for application in the field of environmental biotechnology.