Synergistic interaction of a consortium of the brown-rot fungus Fomitopsis pinicola and the bacterium Ralstonia pickettii for DDT biodegradation

1,1,1-Trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) is a toxic and recalcitrant pesticide that has been greatly used to eradicate malaria mosquitos since the 1940s. However, the US Environmental Protection Agency banned and classified DDT as priority pollutants due to its negative impact on wildlife and human health. Considering its negative effects, it is necessary to develop effective methods of DDT degradation. A synergistic interaction of a consortium consisting of the brown-rot fungus <i>Fomitopsis pinicola</i> and the bacterium <i>Ralstonia pickettii</i> was adopted to degrade DDT. For the microbial consortia, <i>F. pinicola</i> was mixed with <i>R. pickettii</i> at 1, 3, 5, 7 and 10 ml (1 ml ≈ 1.44 × 10¹³ CFU) in a potato dextrose broth (PDB) medium to degrade DDT throughout the seven days incubation period. The degradation of DDT by only the fungus <i>F. pinicola</i> was roughly 42%, while by only <i>R. pickettii</i> was 31%. The addition of 3 ml of <i>R. pickettii</i> into <i>F. pinicola</i> culture presented appropriate optimization for efficient DDT degradation at roughly 61%. The DDT transformation pathway by co-inoculation of <i>F. pinicola</i> and <i>R. pickettii</i> showed that DDT was converted to 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (DDD), further transformed to 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE), and then ultimately transformed to 1-chloro-2,2-bis(4-chlorophenyl) ethylene (DDMU). These metabolites are less toxic than DDT. This research showed that <i>R. picketti</i> synergistically interacts with <i>F. pinicola</i> by enhancing DDT degradation.