They use bacteria to extract gold and silver from electronic waste

They use bacteria to extract gold and silver from electronic waste

The bacteria genetically modified by the young engineers have an additional capacity: they also consume cyanide, so that the process of releasing metals does not generate toxic waste for the environment.
This research, which corresponds to the field of Bioprocesses and Synthetic Biology, presents an alternative for the management of technological waste that generates fewer pollutants than the normal leachate processes used for metal recovery and was selected as the best student research of the year 2016 , from ITESM and therefore received the Rómulo Garza Award for Research and Development 2016.

The metal extraction project had the participation of 14 students from Biotechnology Engineering, Industrial Physics and Computation. In October 2016, this same project was selected as the winner of the gold medal in the iGem international biotechnology competition, held in Boston, United States.

Trash or Resource

The bacterium that the Tec de Monterrey engineering students worked with is called Chromobacterium violaceum and there was already a history of its ability to generate substances that intervene in the separation of metals.
According to Alejandra Vela Elizondo, project coordinator and a ninth-semester biotechnology engineering student, the bacterium produces cyanide by itself.

“Cyanide forms complex ions with silver and gold, which are dissolved in the middle. Then they are transferred to an electrochemical cell and, by means of enzymes, the metals alone are precipitated and separated ”, explained the young student.

The first achievement of the Tec de Monterrey team was to have cyanide produced by the bacteria to achieve the dissolution of gold and silver present, for example, in the part called "motherboard" of computers. However, this first step posed a second challenge: How to handle cyanide, which is a highly polluting substance?

To solve the problem, the students turned to genetic engineering. "We made a genetic modification to the bacteria so that it was not affected by the cyanide in the environment, and we also managed to process it and turn it into its own food," explained Alejandra Vela, 22 years old.

The research also worked with Acidithiobacillus ferrooxidans, another bacterium that also gave excellent results in the separation of metals such as copper, nickel and zinc, which can be reused in the manufacture of new computers.

This metal separation process is in the prototype phase and it will be sought to integrate it into a production line of a company, for which intellectual property protection and patenting procedures are carried out.
In an interview with Tec Review magazine, after the team's triumph in Boston, the coordinator, Alejandra Vela, explained that this type of project allows her vision of science to be crystallized as an activity that generates useful knowledge for any other discipline that seeks to improve quality. life of the human being.

“For example, if I did not study medicine, it was because I believe that with biotechnology engineering I can help many more people. A doctor needs medicines, vaccines, to know how a bacterium works ... and all that science that the doctor uses is produced by a biotechnologist ”, indicated Vela Elizondo.

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Video: Getting started in gold recovery from electronic waste - part 3 (May 2021).