MODELING BIOFILM BIODEGRADATION REQUIRING COSUBSTRATES - THE QUINOLINE EXAMPLE

The aerobic biodegradation of quinoline, a two-ring nitrogen heterocyc le, offers an outstanding example of when structured modeling includin g cosubstrates is required for a biofiln system. In this case, the cos ubstrate is oxygen, which is used as a direct cosubstrate in oxygenase reactions and as a primary electron acceptor in respiration. Quinolin e biodegradation is numerically simulated as occurring in five key ste ps, two of which involve oxygen as a direct cosubstrate. Modeling eval uation of experimental results from a laboratory-scale biofilm column shows that the oxygenation steps are much more sensitive to low oxygen concentrations than are steps in which oxygen only participates throu gh respiration. The result of this differential oxygen sensitivity is that the first intermediate product, 2-hydroxyquinoline, builds up, be cause its degradation through an oxygenase reaction is slowed preferen tially by oxygen depletion.