Exploring Microbes as a Solution to E-waste

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In the world today, e-waste, a subset of used electronics with inherent value in its materials that’s reaching the end of its life cycle, is a rising issue (US EPA 2018). Each year 50 million tonnes of e-waste is produced and this is projected to grow to 120 million tonnes by 2050 (UN report… 2019). Of this waste, only around 20% is recycled, and the other 80% ends up in landfills or is informally recycled usually in unsafe conditions that expose workers from developing countries to hazardous carcinogens including lead and cadmium (UN report… 2019). The chemicals that are released from e-waste when left in landfills, like fire retardants and heavy metals, can leach into the soil and groundwater. When these come into contact with humans they can cause brain, heart, liver, kidney, and skeletal system damage (E-Waste & its … 2019). With growing e-waste levels in European countries alone increasing to 12.3 million tons by 2020 European countries will contribute to a greater intoxication level in and around Africa where in Nigeria alone there are 100,000 informal e-waste recyclers (UN report… 2019) (Emerging Environmental and Public Health Problem of Electronic Waste in India). With the problem of e-waste growing at such an alarming rate globally, a push for clean and nontoxic ways of disposing of e-waste has become evermore important in creating a sustainable and safe future.

Microbial solutions  

Microbes have the potential to be the clean and nontoxic solution to e-waste. Scientists have discovered that certain microbes such as Sulfobacillus thermosulfidooxidans and Pseudomonas balearica ingest and sequester metals when placed in solutions containing e-waste, making the separation process of precious metals from e-waste easier (Kumer et al. 2017; Ilyas et al. 2021). Bioleaching, one of the main methods used, uses very little energy, leaves a small carbon footprint, and uses no toxic chemicals in most cases (These Microbes Are… 2020). Microorganisms used to bioleach can be genetically modified to improve their efficiency, additionally, the environment in which they sequester metals can be modified to help improve sequestration rates (These Microbes Are… 2020). Microbes like Sulfobacillus thermosulfidooxidans when under intense aeration liberate 92% of copper, 89% of nickel, and 93% of zinc (Ilyas et al. 2021). Pseudomonas balearica can be used in two-step bioleaching to dissolute gold and silver from e-waste and it can also have improved efficiency if placed under favorable conditions (Kumer et al. 2017). With high sequestration rates of the valuable metals left in e-waste and little to no toxic or harmful chemicals or waste being used or produced in the process, microbial sequestration has high potential as a form of formal e-waste recycling.

Experimental approach 

To explore the possibilities of microbial e-waste recycling a found microbe was sequenced. Our microbial samples were collected from a rare-earth metal rich environment with low soil ph, pokeweed, and an acid mine drainage site. These isolates were stored as glycerol stocks at -80°C. Specific bacteria were taken from a larger sample that was collected at the site and streaked onto agar plates to isolate a colony. They were then placed in an incubator which provides a warm and moist environment where they grow and produce individual colonies at 28℃. To lyse open the bacteria a sterile cotton swab was used to obtain individual bacterial colonies, and the colonies were exposed to the enzyme lysozyme. Monarch High Molecular Weight DNA Extraction Kit was then used to isolate our genomic DNA for sequencing. The isolated DNA yield was quantified and assessed for its integrity using a Nanodrop spectrophotometer and Qubit. Agilent TapeStation electrophoresis was used to assess the size of our DNA. Once assessed and quantified we used our gDNA to amplify the 16s gene through a Polymerase Chain Reaction for sanger sequencing, providing us information to identify bacterial species or related species. Finally, our DNA is barcoded using the Oxford Nanopore Technologies Rapid Barcoding Kit and sequenced using the MinION sequencer from Oxford Nanopore Technologies, where the DNA will pass through flowcells where changes in current will be interpreted as bases and different groups of DNA are differentiated by the added barcoded adapter sequences on ends of the genomic DNA.

Kbase Static narrative

KBase Narrative


Microbe species 

After isolation of our DNA and Blast of our 16s gene it was determined that our team’s bacteria was (pseudo) Arthrobacter. Pseudarthrobacter oxydans will ideally be able to aid in the recycling of electronic waste. Our microbe will be strong enough to sustain harsh conditions and break down rare earth metals such as copper and gold (Status of Electronic Waste Recycling Techniques: A Review) found in most printed circuit boards. Based on the difficult environments that our microbes were found in like acid mine drainage and pokeweed, it is reasonable to expect that they will be able to be a new avenue in microbial and biotechnology research to recycle e-waste. Perhaps through processes such as selective biosorption, our microbes will remove rare earth metals to facilitate a healthier, cleaner, safer recycling of e-waste. Furthermore, Arthrobactor is already commonly used in the agricultural industry for bioremediation and can utilize xenobiotics and sequester heavy metals (Roy and Kumar 2020). Species of Arthrobacter known as Arthrobacter citreus can be used for polyamide waste (Baxi 2019). Polyamide is used in fishing nets and industrial applications and the waste generated by this impacts ocean environments and ecosystems (Rietzler et all… 2021). Based on the resilience of Arthrobacter as a genus and its ability to be used for bioremediation through the sequestration of heavy metals and the degradation of polyamide waste, it seems promising that our microbe Pseudarthrobacter oxydans will have applications in e-waste recycling.

Future Directions

Coming away from this research and determining our mystery microbe as (pseudo) Arthrobacter, our group would like to further examine new species of microbes. After finding out how valuable our microbes could be to the fight against e-waste, we would like to test if other locations house microbes that can break down rare earth metals. Some of the strongest microbes can be found in boiling hydrothermal vents in the ocean (Marine Microbes). Our group would like to access microbes harvested from these underwater vents and take on an experiment very similar to the one we have just completed. We would like to know, can underwater microbes housed in boiling hydrothermal vents aid in the fight against e-waste and break down rare earth metals? We can find this out by streaking and growing the microbes on agar plates, isolating and lysing the DNA, finding the highest concentration of bacteria to read, reading and barcoding said bacteria and then sequencing the DNA. We can compare our hydrothermal vent microbes’ genomic sequencing to that of our (pseudo) Arthrobacter and look for similarities. If similarities can be found, we can conclude that this underwater microbe could possibly help break down rare earth metals in a similar fashion to Arthrobacter and of course, help combat e-waste and promote sustainability.

Graphical Abstract Summarizing Research Using Miro

This is our group’s summary of research in graphical form using the platform Miro. Going from left to right, it details the process throughout the entire semester to identify, quantify, and sequence our microorganisms. In the first black box, it discusses where and who our microbes came from. They are from acid mine drainage and pokeweed sites sourced by Dr. Amy Grunden and Jason Whitham of NC State University. Moving along, the next yellow box explains that the bacteria were collected, separated, and grown in soy broth to reproduce. The next yellow box explains that the bacteria were grown on agar plates to be then lysed and isolated using glass beads and inoculation fluids. The red parallelogram says that our DNA samples were tested using a Qubit and a Nanodrop machine. The next yellow box says that the highest concentration of bacteria in a sample was selected to be sequenced. The following pink box says that the sample was prepared for analysis (which was done using library prep). The following black box says that the DNA was fragmented, barcoded, and ran through the Oxford Nanopore Sequencer. The next red parallelogram says that our mystery microbe was Pseudo Arthrobacter! The second to last box says that samples were tested for quantity using Qubit and Tapestation. The last stop sign states that our data was taken to KBase to complete a narrative, further explore our genome, and make a genome announcement. 



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