Promising results and new challenges

The results of laboratory tests on the degradation of pollutants such as aromatic hydrocarbons showed immediately promising results. They then rose to new challenges concerning applications in real environmental conditions. In the laboratory, “we chose phenol and biphenyl-type pollutant molecules in order to be able to efficiently and rapidly determine the results of biodegradation over the course of time.” These pollutants are placed in an aerated aqueous phase ( oxygen in the ambient air is necessary for the growth of microorganisms, a little like fish in an aquarium) and is then put in contact with individual microorganisms or a mixture of microorganisms and nanoparticles encapsulated into  silica. “We observed the degradation over time and followed parameters such as temperature and pH, to achieve an extra 70% level of degradation of pollutants in 18 days when the nanoparticles accompany the microorganisms. In real environmental conditions, other parameters need to be taken into consideration. We noticed that when working in real conditions, the speed of degradation is much slower: the presence of inhibitors strongly influences the process of degradation and “uncoupling” the hydrocarbonated pollution from the soil matrix in order to make it accessible as a nutritive element for the microorganisms represents a sizeable challenge which we are actively working on to find original solutions”. The presence of compounds such as nitrates and chlorides that are sometimes present in polluted underground water can also affect the degradation reaction which can require a pre-treatment before beginning the degradation proper, so to speak. On the other hand, the results obtained were surprising for other families of pollutants but confidentiality is the order of the day.

In terms of prospects, the project, after four years of activity will certainly open the door to in-depth fundamental research on the exact impact of the exact interaction between microorganisms and nanoparticles of which very little is still known. Indeed, the nanoparticles in this case are encapsulated in a porous silica powder which means that they cannot enter into direct contact with the microorganism. One theory that has been offered is that the microorganism can secrete an enzyme which can interact with the nanoparticles to catalyze the speed of degradation of the aromatic compounds. The mechanisms involved in this need to be precisely understood. For the moment, the encounter between microorganisms and nanoparticles remains “an extraordinary aspect of the NANOMICRO project, which is both captivating and innovative at the same time”.