Our Idea

DCMation: decimating DCM pollution Dichloromethane (DCM) is an organic solvent used extensively by the chemical industry. It is a toxic compound that has been demonstrated to cause lung and liver cancer in rodents and is proven to have adverse effects on human health and the environment. Current disposal procedures involve incineration, which leads to further pollution.

Small-scale use of DCM, for example in paint strippers, is even more problematic. Proper disposal procedures are frequently neglected because of the associated expenses and inconvenience, resulting in large amounts of DCM being poured down drains. This is particularly harmful when it accumulates in waters, where it has a half-life of over 700 years.

Our project therefore aims to provide a safe and user-friendly method for small-scale DCM bioremediation. Methylobacterium extorquens DM4 is a bacterium capable of metabolising low concentrations of DCM. This means it takes up the DCM from its surroundings and uses it to grow.

Genetic engineering allows us to make the bacterium produce a coloured compound when the DCM is depleted. Such a chromogenic reporter allows the untrained user to see, unaided, when the solution is free of DCM and safe to pour down the drain.

In order to ensure that the genetically modified bacterium does not pose a contamination threat, it will be placed in a teabag-like envelope that physically contains it. In case this physical barrier ruptures, a kill-switch ensures that the bacterium dies immediately when it is no longer in contact with DCM.

In an effort to make this as user-friendly as possible, we are aiming to develop a kit which does not require specialised equipment for use. This would include the teabag within which the bacteria are contained, a small vial with nutrients for the bacterium and a buffer, as well as a capsule with powder to kill the bacteria after usage. The teabag and nutrient vial are then simply added to a set volume of water and DCM. When the coloured product is observed by eye, either a further aliquot of DCM can be added, or the solution can be poured safely down the drain. In that case, the bacteria are killed by covering the teabag with the supplied powder. An automated dispensing system will also be developed for minimal user intervention. In this design, a photodiode measures the coloured product in the solution and automatically dispenses aliquots of DCM from a larger container.

This model for small-scale bioremediation of DCM could be expanded in two key ways. First, bacteria have been identified capable of metabolising nearly every known pollutant. Adaption of the DCMation system could therefore be used to lessen a wide range of toxic compounds in our environment. Second, redesign of waste disposal centres to accommodate bioremediation systems would allow for large-scale implementation of such systems. Particularly in combination, these expansions have the potential to significantly combat the global problem of environmental pollution.