Screening, characterization and optimization for synergistic interaction of potential dichlorodiphenyltrichloroethane degrading fungi isolated from agro-industrial effluent and farm soil

Abstract

Dichlorodiphenyltrichloroethane (DDT) is a recalcitrant synthetic chemical that threatens the environment. Despite being banned in most industrialized nations, DDT is still used as a pesticide to fight malaria and agricultural pests. The main objective of this study is to screen, characterize, and evaluate potential DDT-degrading fungi and their synergetic interaction effects for mycoremediation purpose. The soil and effluent samples were collected from Ziway, Koka, and Addis Ababa. Fungal isolation and screening were performed using a serial dilution on potato dextrose agar growth media. Matrix-Assisted Laser Desorption, Ionization, and Time of Flight Mass Spectrometry technology was used for fungal identification and the selected isolates AS1 and T1 were identified as Aspergillus niger and Trichoderma koningii. Fungal biomass production and sporulation capacity were examined and optimized using a Box-Behnken experimental design. The potential DDT-tolerant fungi were studied based on growth factor optimization. The optimization results revealed that the co-inoculated isolates AS1T1 had a maximum biomass (1.01 ± 0.16g) and spore count (5.74 ± 0.37 log spore/mL) and were selected as possible DDT-degrading fungi. Gas Chromatograph-Electron Capture Detector technology was used for the DDT degradation study. Its analysis confirmed that fungal-co-cultured Aspergillus niger and Trichoderma koningii in DDT-amended liquid medium were able to degrade DDT into its metabolites (DDE and DDD). The results also revealed that 99.5–99.99% of DDT and its metabolites degraded from initial concentrations of 1750, 3500, 5250, and 7000 ppm. The co-inoculated fungi Aspergillus niger and Trichoderma koningii are promising candidates for the removal of DDT and its metabolites from polluted environments.