Farhat, etal. 1
In the last few decades, people have become more aware about the pollution we are putting into the environment from toxic chemicals to plastics to food waste. However, now living in a digital age, there is one form of waste that is not as prioritized as it should be: electronic waste. Electronic waste, or “e-waste” for short, are electronics that are either broken, out of trend, or are no longer functional. Over the last few years, e-waste has become a massive global problem. According to one source, “People tossed out 44.7 million metric tons of e-waste in 2016, and the figure is expected to reach about 52 million metric tons in 2021” (Kwok 711). This has massive repercussions for the environment as e-waste can take up landfill space and the metals within the electronics can leach toxic chemicals into the ground. The effects of e-waste are one that impacts the whole world, and it impacts nearly every aspect of the ecosystem and society. In an article titled “E-Waste Recycling: Where Does It Go From Here?”, it is explained that disposed electronics contain incredibly “valuable and/or rare materials such as gold, palladium, copper, and plastics”, more than usual mines and enough to “partially fulfill the global demand for metals, especially in regions enduring resource shortages” (Zhang, Kai, et al.). Clearly, it is important to address the economic, social, and environmental areas such technology can benefit.
But what kinds of technology can be used to solve this issue? Some common technologies in use are called pyrometallurgy and hydrometallurgy. “Pyrometallurgy involves heating e-waste to more than 1,000 °C, requiring a lot of energy and releasing toxic gases. Hydrometallurgy, a process that uses chemicals such as acids or cyanide to leach metals, generates toxic effluent” (Kwok 711). Since burning techniques like pyrometallurgy need toxic chemicals and produce pollution, newer sustainable solutions are imperative. To fill this role, scientists have looked to natural solutions, and one of the most promising comes in the form of microbes. A microbe is “a living thing that is too small to be seen with the naked eye. We need to use a microscope to see them” (What are microbes?). There are countless types of microbes which can be divided into five major categories: Bacteria, Archaea, Fungi, Protists, and Viruses
(What are microbes?). This paper will be focused upon two types of bacteria: Brevibacterium and Ensifer.
Currently, the recycling of e-waste using microbial species is a technology that is still under development and improvement. However, there are already some very promising ventures. One such company comes out of Auckland, New Zealand. MINT Innovation, is a company working to recycle old electronics, namely circuit boards, and retrieve the precious metals gold, copper, platinum, cobalt, palladium, and lithium (mint). The process begins when the circuit boards arrive at their center shredded and destroyed. These shredded circuit boards are then pulverized into a sand-like material and then mixed with chemicals inside of a reactor. Then solids and liquids are separated using a filter system. The liquid will contain metals of lower value such as copper and tin which are removed from the solution using electrical currents. The more valuable metals like gold and palladium remain in the sand-like solid. To retrieve these metals, they must go through another chemical bath, and then the microbial process begins. Different species of fungi and bacteria are placed in a vat with the solid materials where they begin to absorb the metal ions and gain weight. This process creates a paste with microbes and metal particles. Finally, the pastes are subjected to high heat. The microbial pieces are burnt away, leaving a metal ash which is then sent to a refinery and turned into metal pieces. This process has great potential for recycling e-waste. However, currently one ton of circuit boards is needed to retrieve 150 grams of gold and is quite costly, meaning there are still improvements to be made until this process can be used on a large scale.
Another means of recycling e-waste using microbes is through a process known as bioleaching. This is a process that has been used by miners in the past to remove metal ore from rock, but is now being studied to tackle the e-waste problem. Researchers have been using a bacteria called C. violaceum to remove gold from electronics. According to the researchers “The microbe produces an enzyme that converts glycine to hydrogen cyanide, and the cyanide ions in liquid solution bind to gold atoms, grabbing them from solid electronic scrap. The bacterium even cleans up after itself: It later converts unused cyanide to a nontoxic chemical called β-cyanoalanine.” (Kwok 712) This makes the process promising for the sustainable recycling of e-waste. However, there is an issue. Currently, C.violaceum cannot efficiently remove gold because it does not produce enough gold. To combat this problem, researchers have used a promoter to modify the DNA of the microbe and as a result saw the amount of gold recovered rise from 11% to 69% (Kwok 712). There is still room to improve this process but it shows that there is potential for microbes to efficiently recycle our e-waste in the near future.
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The experiment for this project involved 5 steps: sample collection, laboratory growth, DNA isolation, DNA sequencing, and genome assembly. First, the bacteria were isolated from pokeweed and acid mine drainage, and then cultured in the lab (BIT295). Next, they were isolated by individual colonies, and the colonies were then cultured individually (BIT295). Following this, DNA from each culture was lysed and the DNA was sequenced using MinION (BIT295). The genomes were then assembled using the CLC Genomics workbench (BIT295).
With the minION resource, we will further analyze components of the MinION sequencer. As we learn more about the specific components of the technology, we can get a deeper understanding of the experimental approach. Its unrestricted read length of sequences as well as its portable and compact design make it an ideal candidate to further investigate (Nanopore). Furthermore, looking into the biotechnology products that QIAGEN produces, we will learn more about the technology behind the sequencing of DNA. QIAGEN’s focus on DNA sequencing is demonstrated with their kits and panels of sequencing (QIAGEN).
For the purposes of this project, we will be focusing upon this genus of bacteria: Brevibacterium. Brevibacterium are “irregular rods arranged singly or in pairs. They often orientate at angles to give a V shape…They are strictly aerobic and the colonies are often pigmented with yellow or purple coloration” (Brevibacterium). Besides these interesting characteristics, Brevibacterium has been found to cause spoilage of dairy products and the decay of other organic matter, but most importantly it has been linked to the removal of heavy metals from soil (Brevibacterium).
After thorough research into the specific metals that Brevibacterium is particularly effective in removing, it was found that it works especially well with lead and cadmium (Halttunen, 2006). It was then found that lead and cadmium are found in high concentrations in rechargeable computer batteries and cathode ray tubes in computer and TV screens, which leads one to believe that Brevibacterium would be especially beneficial and effective with these specific types of electronics (ECHA). The effectiveness of the microbe Brevibacterium on lead and cadmium combined in e-waste would be fairly effective on them together, but more so on the lead. This is based on an analysis of previous studies of interactions between the microbe and two metals as well as the prominence of the metals in specific electronics such as rechargeable batteries and cathode ray tubes (Halttunen, 2006). For our own experiment, we will be seeing the effect of Brevibacterium on lead and cadmium separately, and one together, creating three variables based off the specific e-waste that has been researched containing them.
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Future experiments should be conducted to test the effectiveness of Ensifer at extracting arsenic from drinking water. Our hypothesis is that Ensifer will effectively remove arsenic from water, but we will have to examine the data. In North Carolina, specifically the Piedmont area, arsenic levels are high in drinking water (Hoban). An experiment can be conducted to test the effectiveness of Ensifer. The first step in the experiment is to gather samples from a variety of different wells in North Carolina. The next step is to measure the arsenic levels in the water, this can be done using water testing kits. Next, we will set up our experiment by taking the water and putting it into 5 different incubators, one with water from the wells, 3 with varying concentrations of ensifer and water from the wells, and the last with just water and no arsenic. We will then measure the arsenic concentrations in each beaker and compare our results to the initial concentrations. After completing this experiment, we should be able to see if Ensifer is effective at removing arsenic from water.
Graphical Abstract of the Removal of Ensifer from Water
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- “Batteries for IT Systems: Environmental Issues.” GreenBiz, GreenIT, www.greenbiz.com/sites/default/files/document/CustomO16C45F94108.pdf. BIT295: Biotechnology and Sustainability. (2022). Genomic investigation of microbial species for sustainable electronic waste recycling.
- https://docs.google.com/document/d/1xqKYLeBJnFfC5c0DeZtS8vdNo6Oc7u-NgI4FvG Jkog4/edit#heading=h.uq3zl9n74m8v.
- “Brevibacterium.” ScienceDirect.com | Science, Health and Medical Journals, Full Text Articles and Books, www.sciencedirect.com/topics/agricultural-and-biological-sciences/brevibacterium. ECHA. (n.d.). Know your electronics and their chemicals. European Chemicals Agency. https://chemicalsinourlife.echa.europa.eu/en/web/chemicals-in-our-life/know-your-electr onics
- Halttunen, T., Salminen, S., & Tahvonen, R. (n.d.). Rapid removal of lead and cadmium from water by specific lactic acid bacteria. Int J Food Microbiol, 114(1). https://doi.org/10.1016/j.ijfoodmicro.2006.10.040.
- “How microbes influence mineral growth and dissolution.” ScienceDirect.com | Science, health and medical journals, full text articles and books, www.sciencedirect.com/science/article/pii/S0009254196000356.
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- Hoban, R. (2021, October 19). UNC analysis finds arsenic, metals in North Carolina wells. North Carolina Health News. https://www.northcarolinahealthnews.org/2012/07/13/unc-analysis-finds-arsenic-metals-i n-north-carolina-wells/
- Kwok, Roberta. “How bacteria could help recycle electronic waste.” PNAS, vol. 116, no. 3, 2019, pp. 711-713. INNER WORKINGS, https://www.pnas.org/doi/full/10.1073/pnas.1820329116.
- mint. (2022, February 8). E-Waste Recycling | Mint Innovation. https://www.mint.bio/what-we-do
- Nanopore Technologies. (n.d.). MinION. Nanopore Technologies . https://nanoporetech.com/products/minion.
- QIAGEN. (n.d.). Products – DNA Sequencing . QIAGEN. https://www.qiagen.com/us/product-categories/next-generation-sequencing/dna-sequenci ng/.
- “Substance Information.” ECHA, www.echa.europa.eu/web/guest/substance-information/-/substanceinfo/100.028.320. Wei, Liu, et al. “Nano-hydroxyapatite Alleviates the Detrimental Effects of Heavy Metals on Plant Growth and Soil Microbes in E-waste-contaminated Soil.” RSC Publishing Home – Chemical Science Journals, Books and Databases,
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- “What are microbes?” Learn.Genetics, learn.genetics.utah.edu/content/microbiome/intro. Zhang, Kai, et al.
- “E-waste Recycling: Where Does It Go from Here?” pubs.acs.org/doi/pdf/10.1021/es303166s.