Fungal elimination of 2,4,6-trinitrotoluene (TNT) from the soils

Abstract

The analysis of microscopic fungi collection created at theDurmishidze Institute of Biochemistry and Biotechnology revealed 107 strains assimilating 2,4,6-TNT (2,4,6-trinitrotoluene) belonging to the different fungal genera. The strains have been isolated from the polluted areas adjacent to the military grounds and industrial waste waters. It has been shown TNT is degraded most actively by strains belonging to the following genera: Trichoderma, Aspergillus, Mucor and Trichoderma. Optimal cultivation conditions for highly active strains -the destructors of TNT have been revealed. It has been established that the carbon skeleton of TNT being utilized by the mentioned strains undergoes biotransformation. The existence of radioactive intermediates of biotransformation, organic acids (70-90%) and amino acids (10-30%) have been detected in liquid culture. Radioactive label of 1-14C-TNT is mostly found in fumaric acid, which is known as one of the main products of benzene biotransformation and further conversion into succinic acid. Remediation level of TNT-contaminated red and black soils treated by the most active strains Aspergillus nigerN2-2 and Mucor sp. T1-1 have been studied under laboratory and field conditions. Cultivation of the above mentioned strains under laboratory conditions in sterile, black and red soils for 30 days at 30°C allowed decreasing the content of TNT in black soil to the residual, and in red soil - to 15%; cultivation of Aspergillus niger N2-2 decreased the amount of TNT in black soil to 11 and in red soil - to 21%. Under field conditions, TNT degradation level in contaminated soils by naturally existing micro flora during 100 days was equal to 40-50%, and in the case of additional introduction of both fungal strains, TNT-destructors reached 80%.

Keywords

• microscopic fungi
• destructor strains
• organic toxicant
• 2,4,6-trinitrotoluene (tnt)
• bioremediation