Differential mode of denitrification by Pseudomonas sp. KY1 using molasses as a carbon source

Abstract

A new kinetic model that combines Monod kinetics and a constant denitrification rate is proposed to predict bacterial nitrate removal in groundwater. The model, which was developed with an indigenous bacterium Pseudomonas sp. KY1 isolated from a nitrate-contaminated site using molasses as a carbon source, takes into account the dual-mode substrate utilization pattern depending on the degradability of the compounds that constitute molasses. At the early stage of a batch reactor study with various C/N ratios, the nitrate reduction and molasses degradation was likely to be associated with microbial growth, while at the later stage of the total 48 hr of the study, a significant nitrate reduction occurred without substantial cell growth and molasses degradation. The new model was able to simulate the differential substrate utilization pattern, which could not be explained by either Monod kinetics or a constant denitrification rate model. Although further validation using other types of substrates and inoculums should follow, the new model shows the potential to accurately predict the denitrification kinetics in a heterogeneous carbon substrate system with minimum input parameter determination requirements.