Polycyclic aromatic hydrocarbons (PAHs) are produced by various activities, from grilling meat to coal gasification, and are potent carcinogens. Our project aims to degrade PAHs in industrial waste. The current waste handling method for PAHs is simply to deposit them in landfills where they leak into the environment. The bacterial cells we use need to detect the PAHs for the degradation. However, the molecules do not readily pass through the membrane.

We solved this predicament by using one of the smaller PAHs as an indicator to degrade the larger, more dangerous PAHs. The degradation of this small PAH inside the cell relieves repression of genes under the control of the NahR/Psal promoter system. This causes a series of enzymes to get expressed and secreted outside the cell, oxidising and cleaving the ring structures of the carcinogenic compounds, making them available for downstream biodegradation. To increase the degradation efficiency our system also produces rhamnolipids.