Dual substrate removal by an axenic bacterial culture

A pure bacterial culture capable of utilizing either L-lysine or 2-chlorophenol (2-CP) as sole carbon source was isolated and used in continuous culture experiments to determine its response to dual substrate limitation by those two compounds. Dilution rate and feed composition were each set at three levels in a two factorial experimental design. The total chemical oxygen demand (COD) of the feed was fixed at 225 mg/L and its composition was varied by changing the ratio of lysine to 2-CP. The effects of the two independent variables (dilution rate and feed composition) on the concentrations of cells, lysine, COD, and dissolved organic carbon (DOC) in the reactors were systematic whereas the effects on the 2-CP concentration were less predictable. The concentrations of the two substrates responded to the two independent variables in a complex interactive manner which is not explained by existing models for dual, substitutable substrates. Rather, the results suggested that the prediction of the fate of a single organic component in a reactor receiving a multicomponent feed is a very difficult task.