Biodegradation of dichloroacetic acid by entrapped and adsorptive immobilized Xanthobacter autotrophicus GJ10

The degradation of dichloroacetic acid (DCA) by free, Ca-alginate entrapped and adsorptive immobilized cells of Xanthobacter autotrophicus GJ10 has been studied in various experimental systems. Entrapped cells tolerated increasing concentrations of DCA better than free cells. Free and adsorptive immobilized cells degraded DCA most effectively at maximum O₂ supply, 34°C and an initial pH value of 8.0. The degradation of high DCA concentrations led to a decrease in the pH value and to a stagnation of mineralization, particularly with free or entrapped cells. Due to the stabilization of pH, the supplementation of acetate or succinate resulted in a complete degradation of higher DCA concentrations. Higher degradation rates than in shake cultures were achieved in air-bubble and packed-bed fermentors. DCA was mineralized faster by free or entrapped X. autotrophicus GJ10 than by adsorptive immobilized cells, which, however, were able to remove higher DCA concentrations. The results of the recent investigations with immobilized X. autotrophicus GJ10 are an important prerequisite for the application of this bacterium in waste treatment systems.Correspondence to: U. Heinze