Fermentation and growth kinetic study of Aeromonas caviae under anaerobic conditions

Although Aeromonas caviae is pathogenic to a broad range of invertebrates including human, frequent in aquatic environments, and potentially vital for acidogenesis in anaerobic digestion, virtually no biokinetic information on its anaerobic growth is at hand. Therefore, this study focused on evaluating its anaerobic growth kinetics on glucose. To provide a set of relevant biokinetic coefficients for modeling, a combination of curve fitting and numerical modeling was used. Microcultivations were performed at eight different initial glucose concentrations of 0.1 to 2.5 g l(-1) to establish a function of specific growth rate versus substrate concentration. A batch anaerobic bioreactor was then operated to collect a data set for the numerical analysis. Kinetic coefficients were estimated from three different biomass growth profiles monitored by optical density, volatile suspended solids (VSS), or DNA measurement, and applied for simulating continuous operations at various hydraulic retention times (HRTs). Assuming the influent glucose concentration is 5,000 mg l(-1), the substrate utilization efficiency predicted to be 77.2% to 92.0% at 17 to 36 h HRTs. For the VSS-model-based simulation, the washout HRT was estimated to be 16.6 h, and similar for the other models. Overall, the anaerobic biokinetic coefficients of A. caviae grown on glucose were successfully estimated and found to follow a substrate inhibition model.