Modeling recalcitrant intermediate formation during biodegradation

摘要

Complex biological degradation reactions proceed through intermediates. Recalcitrant intermediates sequester carbon and electrons, reducing cell growth and slowing the expected rate of contaminant removal. The distribution of reducing equivalents and energy between catabolic and anabolic processes in the microorganism control the bacterial yield. Bacterialy yields and step-wise stoi-chiometry for a biodegradation pathway can predict the relationships among pri-mary electron-donor and acceptor substrates, degradable and recalcitrant intermediates, and degradation products (e.g., H_2CO_3, NH_4~+, or H~+). The stoi-chiometry of the multi-step degradation pathway is coupled to a kinetic biological reaction model that predicts the rate of substrate removal, cell growth, and the changes to all chemicals affected by the loss of primary substrate and formation and persistence of intermediates. A methodology for bacterial yield predictions and stoichiometric formulations for compounds degraded through intermediates is presented. Degradation of the anthropogenic chelating agent, nitrilotriacetate (NTA), is presented as an example.