Biodegradation of monochloroacetic acid used as a sole carbon and energy source by Xanthobacter autotrophicus GJ10 strain in batch and continuous culture

Abstract

Batch and continuous mode degradation of monochloroacetic acid used as a sole carbon and energy source in the concentration range of 0.9-48.4 mM by pure culture of Xanthobacter autotrophicus GJ10 was investigated. The substrate was completely degraded in each flask in batch system. Partial substrate inhibition occurred at the concentrations exceeding 25.4 mM. Temporary accumulation of glycolic acid in the medium indicated that dehalogenation was undergoing faster than further utilization of glycolate. Three different carbon substrates were used for inoculum preparation--1,2-dichloroethane, tri-sodium citrate and a nutrient broth. The fastest growth on monochloroacetate occurred for 1,2-dichloroethane-grown inoculum. The assays of haloacid dehalogenase in crude extract indicated that the bacteria grown on 1,2-dichloroethane possessed higher level of the enzyme. The response of the GJ10 culture towards spikes of 20 mM monochloroacetate was tested in 2.5-1 continuously stirred tank fermentor. The substrate was readily utilized within 7-8 h. Continuous degradation of monochloroacetate in the fermentor was demonstrated for monochloroacetate concentration of 20 mM and dilution rate 0.016 h(-1). Quantitative agreement between the amount of monochloroacetate introduced and chloride released was found. The results demonstrated that the strain X. autotrophicus GJ10 might be suitable for biodegradation of monochloroacetate contaminated media.