Predicting the accumulation of harmful metabolic byproducts during the treatment of VOC emissions in suspended growth bioreactors.

A predicting model is proposed to evaluate metabolic byproducts accumulation and process performance in suspended growth reactors treating air emissions contaminated with volatile organic compounds (VOCs). The model presented integrates a multistep kinetic model and a general mechanistic model describing bioreactor operation. This integrated model is based on general equations modeling, both mass transport and the mechanisms underlying pollutant biotransformation and byproducts accumulation, and can be applied to a wide range of operating conditions (VOC substrate, O-2, and nutrients limitation) The model was tested for predicting benzyl alcohol (BA) accumulation in a chemostat reactor treating toluene. BA accumulates in Pseudomonas putida F1 cultures degrading toluene as a result of methyl monooxygenation reaction parallel to the main TOD degradation pathway. The operational conditions leading to BA accumulation are evaluated through simulations assays. Simulation results indicate that BA accumulation occurs when other substrates rather than toluene are limiting. Therefore, operation under toluene limitation is highly recommended to ensure not only the detoxification goals but also to avoid potential mutagenic effects of BA over the microbial culture.