Competitive growth kinetics of Sphaerotilus natans and Acinetobacter anitratus

Growth kinetics of Sphaerotilus natans and Acinetobacter anitratus (strain E932) in pure and mixed cultures were analysed. In order to determine mixed cultures biomass composition, a quantitative image analysis technique was developed. Pure culture studies showed that for dilution rates less than 0.188 h(-1), the filamentous micro-organism will predominate leading to bulking phenomena. By using the developed technique to determine biomass composition, mixed culture experiments showed that changes in the dilution rate modify the microbial composition of the biomass determining which micro-organism predominate. The stated equations that predict the predominance of S. natans at low dilution rates agree satisfactorily with the obtained results.