Integrated model of the production of soluble microbial products (SMP) and extracellular polymeric substances (EPS) in anaerobic chemostats during transient conditions

A model to predict the accumulation of soluble microbial products (SMP) in anaerobic chemostats during steady-state and transient conditions is presented in this paper. The model incorporates the concept of production and degradation of extracellular polymeric substances (EPS or ECP) as part of SMP, and was used to predict SMP production during hydraulic and organic shock load experiments in anaerobic continuously stirred tank reactors (CSTRs). For most variables the model predicted reasonably well the shock loads, and the best-fit values of the main parameters provided valuable information on the types of SMP that predominate under particular culture conditions. According to the model, during steady-state conditions ∼58% of the SMP are utilization-associated products (UAP) whilst ∼42% are biomass-associated products (BAP) of which ∼7% are soluble EPS (sEPS). During the hydraulic and organic shock loads the importance of BAP and sEPS decreases and the UAP accounts for up to 95% of the SMP.