Wastewater treatment plants are successful in removing most contaminants from wastewater and provide the possibility to manage water resources. In recent years, the awareness for water pollution by pharmaceuticals has increased. Chemical compounds like diclofenac or azithromycin accumulate in global food chains as the treated water reenters the environment, endangering animals and humans alike^[3]. For instance, reports show that several species are brought to near-extinction, most likely due to effects of diclofenac accumulation^[4]. Consequently, diclofenac was added to the European Union’s watchlist of priority substances in 2015 due to its rising concentration in European wastewater^[5]. We acknowledge this new threat to the health of our ecosystems and ourselves, and designed wastewater-treating Bacillus subtilis biofilms. These biofilms are capable of enzymatically rendering pharmaceuticals like diclofenac and azithromycin less toxic. The used enzymes, laccases (e.g. CotA or CueO) or esterases (e.g. EreB), are therefore fused to the major biofilm matrix component TasA of B. subtilis biofilms.

Consequently, the biofilm-forming bacterium displays the enzyme in its biofilm matrix, which also allows better contact of the enzyme with its pharmaceutical substrates than in the cytoplasm. The display in a biofilm also eliminates the need for additional enzyme purification and immobilization in the area of application, which saves time and resources. Our system is easy to use, as B. subtilis forms the biofilm and produces the enzymes without any additional efforts by humans. The system’s simplicity and the built-in kill switch ensure biocontainment, while further methods like the decontamination with e.g. ultraviolet light are also applicable. But how do you actually apply our biofilm?

Our engineered biofilm is implemented in wastewater treatment plants by growing B. subtilis biofilms on reuseable biofilm carriers which are floating on the wastewater. The carriers are ping pong ball-sized, porous spheres designed to maximize the surface area between biofilm and wastewater. Here, our pharmaceutical-degrading TasA fusion proteins come into contact with the respective pharmaceutical compounds to render them less toxic. The protein fused to TasA is exchangeable and our engineered biofim can thus target different compounds of various chemical structures. With these simple adaptations, we envision our biofilm to be used in a variety of ways and to be adapted to the respective local needs.

With our project “B-TOX”, we want to contribute to a responsible and sustainable use of water and thereby target two of the 17 substainable development goals of the United Nations:

6. Ensure access to water and sanitation for all^[6].

6.3 “By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.”

14. Conserve and sustainably use the oceans, seas and marine resources^[7].

14.1 “By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution.”

Our project identifies most with target 6.3, since it is our intention to improve water quality by reducing pollution and thereby to enable safe global wastewater reuse. We believe our project can improve water management and quality all around the globe by decreasing the level of micropollutants in treated wastewater. We specifically intended our system’s use to be easy and cost-effective to allow its application in regions with low budgets. The plug-and-play fashion of our degrading biofilm allows future users to adjust the displayed degradation enzyme for their needs by exchanging the enzyme domain fused to the biofilm component TasA.

It is of great importance for us that marine pollution is reduced to a minimum to ensure stable ecosystems for animals and mankind. Consequently, goal 14.1 is also covered with our project. The reduction of marine pollution ensures the reduction of health-risks triggered by the accumulation of pharmaceuticals in the food chain. With the world population increasing, the consumption of pharmaceuticals will also continue to increase, and it thus becomes more important to prevent the pollution of our aquatic ecosystems and food sources.

With our project, we address the sustainable development goals 6 and 14, expressed by the UN, as we want to contribute to better water quality for mankind and the environment. Our system is able to increase the efficiency of wastewater treatment and to decrease environmental pollution by pharmaceutical compounds. We want to stress that our biofilm system is easy to use, affordable for a broad use worldwide and adjustable for further applications. We believe that our project has the potential to be awarded for the best impact on sustainable development.