Electronic components such as printed circuit boards (PCB) and radio frequency identification (RFID) tags are ubiquitous in our daily-lives, with smartness being embedded in a multitude of products. In an era of technological innovation, they usually have a short life-cycle and eventually end up as e-waste. Metals are central to the functioning of these items. However, this usually comes with an ecological footprint since metals are non-renewable resources and more than 80% of end-of-life electronic products are not recycled. Paper electronics represent a sustainable alternative to standard FR4 PCBs since paper can be recycled, albeit the end-of-life treatment of the established silver or copper printed metallizations remain a major issue. Here, we propose their biorecycling, where paper would be used as a carbon source for microbial growth while the metallic traces could be recovered through microbe-metal interactions, including solubilization and biomineralization. For this, we investigated a selection of fungal and bacterial strains for their ability to thrive on technical paper for electronics. Further, by using mock printed circuits, we assessed whether Cu and/or Ag could be solubilized from printed tracks and transported to a remote area through fungal and/bacterial activities. Finally, we also tested whether alternative carbon sources from organic waste, spent coffee grounds and digested sewage sludge may help trigger microbial growth and activity in order to optimize the process. Our results show that microbial activity can effectively lead to metal mobilization and then immobilization by the formation of both extra- and intracellular (as Me-NPs) precipitates. The presence of bacteria associated to fungi altered the architecture of the mycelial network, eventually modulating the amount of metal transformed. While the biodegradation process is still slow to be considered on a commercial scale for metal biorecovery, we believe that our results give a clear signal to the biotechnology communities that valorizing organic and electronic waste together is a potential and sustainable solution to follow.

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Bio

Saskia Bindscheder is currently a researcher and lecturer in geomicrobiology at the University of Neuchâtel. She graduated with a MSc in Biogeosciences from the University of Neuchâtel and obtained her PhD in Environmental Sciences from the University of Lausanne in the field of microbial biomineralization. She then continued with a SNSF Postdoc Mobility fellowship at the Helmholtz center for Environmental Research in Leipzig to investigate the role of bacterial-fungal interactions in biogeochemical processes. She then joined the group of Prof. Pilar Junier at the laboratory of microbiology where she focuses on fungal interactions with both living and mineral components of ecosystem with a focus on biotechnological applications, either in the field of plant protection but also for metal recovery from waste materials.