Microbial dynamics in a continuous stirred tank bioreactor exposed to an alternating sequence of organic compounds

Microbial dynamics during aerobic biodegradation of an alternating mixture of organic compounds was investigated experimentally in a continuous stirre d tank bioreactor (CSTB). A mathematical model describing this system was d eveloped and tested using the experimental results. A model microbial cultu re consisting of Pseudomonas sp. JS150, a monochlorobenzene (MCB) degrader, and Xanthobacter autotraphicus GJ10, a 1,2-dichloroethane (DCE) degrader, each with exclusive degradation capabilities, was used. The CSTB was inocul ated with both microbial strains and exposed to an alternating sequence of the two compounds at noninhibitory concentrations. Concentrations of each m icrobial strain, of each organic compound, and of degradation product evolv ed, as well as specific microbial activities via oxygen uptake tests, were monitored. Reduction of the residual DCE discharged from the bioreactor aft er an MCB to DCE transition was successfully achieved by continuously feedi ng a low flow of a concentrated solution of both compounds. (C) 2000 John W iley & Sons, Inc.