Influence of the substitution pattern on the microbial degradation of mono- to tetrachlorinated dibenzo-p-dioxins and dibenzofurans

We have analyzed the influence of the substitution pattern on the microbial degradation of all 210 PCDD/DF congeners. The assays were done with five pure aerobic bacterial strains, whose ability to grow on or to catabolize chlorinated aromatics recommended them for PCDD/DF degradation experiments. Pseudomonas sp. DSM*-No. 6708 and Sphingomonas sp. DSM-No. 7135 showed high potential for isomer-specific degradation of CL1−4DD/DF including the most toxic congener 2,3,7,8-TCDD. Chlorine substitution in 1-, 4-, 6-, or 9- position generally retarded degradation. Significant decrease of penta- and higher chlorinated DD/DF was not observed in a time period up to 84 days. The ability to degrade PCDD/DF depends on the source of carbon and energy used for bacterial growth.