Once the platinum is leached, we need to recover it. If leaching (by biological or chemical methods) is clearly recommended to improves solubilization of metals, it does not improves the concentrations. As we worked with synthetic biology, we decided to use what it is commonly employed by cells to catch metals, i.e. siderophore. Siderophores are well known to catch iron most of all but some of them have an affinity with others metals as platinum. So in our process, we planned to work with such a siderophore, called Desferrioxamine B. This one is already employed to recover platinum in mines, and have shown high capacity to recover platinum from ores <ref>Bau and al., 2015 http://dx.doi.org.gate1.inist.fr/10.1016/j.hydromet.2015.01.002</ref>.  

Recovery  yields with Desferrioxamine B can reach 75% of the total platinum if both of these conditions are fully respected: a lowering pH level leaching step should be performed, as well as a alcanization of medium (until a pH range between 8 and 9) before addition of siderophore. The last step devoted to rise up the pH level will be realized using a standard buffer, e.g. a Tris buffer.   

So where is the innovation in this step? Firstly, in our case, Desferrioxamine B won't be applied on the same materials where is commonly used, in our cases not ores but a leachate of ashes. Basically the main difference will be the metal concentration.

Secondly, desferrioxamine B is usually synthesized chemically, we'll rather produce it in high amounts with bacteria. Indeed, [[Team:Aix-Marseille/Description#Overview|operon]] of the Desferrioxamine B biosynthesis will be cloned into a E. coli bacteria strains in order to produce it, hence lowering the costs of required basic matter as production by bacteria needs especially an appropriate medium and good growth conditions.

If we follow the conditions of uses of Desferrioxamine B,