Phytodegradation

Phytodegradation which is also known as phyto-transformation is the breakdown of contaminants taken up by plants through metabolic processes within the plant, or the breakdown of contaminants surrounding the plant through the effect of enzymes produced by the plants. Plants are able to produce enzymes that catalyze and accelerate degradation. Hence, organic pollutants are broken down into simpler molecular forms and are incorporated into plant tissues to aid plant growth.

Enzymes in plant roots break down (degrade) organic contaminants. The fragments are incorporated into new plant material.

[Case Study]

Trinitrotoluene (TNT) is one of the world’s most persistent and dangerous explosives. The use and disposal of TNT has resulted in the contamination of many sites. Furthermore, methods available to clean up such sites are so costly that only a few of them are have been remediated.

There are many plant species that are able to break down TNT in their own tissue. However, this process tremendously affects the plant’s growth and development. Owing to this limiting factor, it prevents their application in large-scale phytodegradation system.

An Entereo cloaca, a soil bacterium was discovered to be able to utilize ester explosive as its source of nitrogen. Enzymes produced by this bacterium are PETN reductase and nitroreductase. Both of these enzymes degrade TNT into less harmless product. The genes expressing the production of these 2 enzymes are introduced into the tobacco plant Tobacco (Nicotiana tabacum).

Subsequently, a study on the transgenic was carried out. The tobacco plant and the wild type plant were both exposed to 0.25mM of TNT. The wild type plant became chlorotic and lost mass, while the transgenic plant continues to grow. The enzymes that were over expressed in the transgenic helped to metabolized TNT at faster rates than the control plants. More importantly, transgenic plant became more resistant to TNT concentration in comparison to non-transformed plants that are greatly affected in their development.