The PeelTowel

Summary

2.5 billion people or 35% of the world does not have access to proper hygiene. This leads to the spread of multiple bacterial infections from person to person. In addition, 85,000,000 tons of paper are used every year, adding to US landfills. To solve these problems, we hypothesized that the PeelTowel made up of typically discarded Kiwi, Orange, or Lime peels combined with recycled paper will kill either Escherichia coli or Staphylococcus epidermidis and absorb equal to or more water than the standard paper towel.  Kiwi, orange, and lime peels were chosen for this purpose because they contain antibacterial vitamin C and citric acid as well as water-absorbing cellulose. PeelTowels were produced by creating a paste of crushed fruit peels and paper and then drying thin films of this paste on screens. We tested the PeelTowel at Northwestern Feinberg School of Medicine under the guidance of Dr. Alan Hauser through the drip plating method (Figure 1). The Lime PeelTowel effectively killed 95% of E. coli bacteria and successfully absorbed three times more water than the standard Paper Towel. Additionally, the Orange Towel killed 94% of E. coli bacteria and absorbed around equal to the standard Paper Towel at 10%. In the future, we plan on further testing the PeelTowel against different types of bacteria, optimizing the peel to paper ratio, and improving the PeelTowel’s shelf life. We believe the PeelTowel will foster environmentally-friendly and disease free families and communities in the US and throughout the world.

Question / Proposal

The World Health Organization (WHO) mentions that globally, around 2.5 billion people lack adequate access to hygiene, which comprises  35% of the world’s population. In addition, the WHO estimates that 1.5 million children around the world die from hygiene issues. Also, during our travels to developing nations, we observed that people lacked personal hygiene and could not afford basic hygiene products. Due to this, many diseases are spread from person to person (Figure 2 and 3).

Furthermore, according to the University of Southern Indiana, an average American uses 680 pounds of paper annually, resulting in 2,000,000,000 trees chopped. Additionally, 6.5 million tons of paper towels are used and 15.6 million tons of citrus peel waste are created annually, adding to the growing waste piles and leading to eventual harm to the environment.

Question: Can a paper towel made from typically discarded fruit peels kill more than 75% bacteria and absorb water?

Past research indicates that Vitamin C and Citric Acid are effective in killing bacteria. Additionally, cellulose is a water absorbing compound.  These are present in kiwi, orange, and lime peels. 

We hypothesize that the PeelTowel made up of typically discarded Kiwi, Orange, and Lime peels combined with recycled paper will kill at least 75% of either Escherichia coli or Staphylococcus epidermidis and absorb equal to or more water than the current paper towel.

We believe that the PeelTowel will successfully be able to meet all the criteria stated in the hypothesis. We expect our results to support our hypothesis. 

Research

Vitamin C and Citric Acid

In 1984, H.J.H. Fenton discovered that several metals have special oxygen transfer properties that result in the generation of reactive oxygen species (ROS). This discovery led to the founding of the Fenton Reaction. In the Fenton Reaction, through a two step process, ferrous ions and hydrogen peroxide result in three ROS (a hydroxyl radical, hydroxide ion, and a perhydroxide radical) with the potential to kill bacteria. Vitamin C helps promote the Fenton reaction by recycling ferrous ions (Figure 4). Hence, ROS is continuously generated causing harm to bacteria. According to a study done in 2013 by Nature Communications, ROS produced by the Fenton Reaction did indeed cause the death of one type of gut bacteria, Escherichia coli. Likewise, Mycobacterium tuberculosis is also susceptible to death by vitamin C due to ROS that are produced. This past research confirms that vitamin C has antibacterial properties.

In addition to Vitamin C, citric acid has been seen to be an effective antibacterial. Due to the typical alkaline environment that bacteria usually thrive in, any acidic change in pH causes harm to unadapted bacterial cells. Citric acid, at a pH of 3-4, causes this harmful change to the bacteria’s environment leading to difficulty in bacterial reproduction. For example, in a study done on adapted and unadapted E. coli cells exposed to various acids, no sign of bacterial cell growth was seen when unadapted cells were exposed to citric acid (at pH 4.2). Furthermore, citric acid acts as a great disinfectant and is used in cleaning products

Research demonstrates that Kiwi, Orange, and Limes all contain the highest levels of Vitamin C and citric acid (Figure 5).

Cellulose Properties

Paper and paper towels are made of a material known as cellulose. Cellulose is a complex carbohydrate made of long chains of glucose that serves as an effective water-absorber. Since sugar has the opposite polarity of water, glucose molecules in cellulose are attracted to water. Therefore, when paper towels are placed in water, incoming water molecules attract and attach to the oppositely charged glucose molecules. This is the reason paper towels are very effective in cleaning up spills.

Research shows that kiwi, orange, and lemon peels all contain cellulose (Figure 5).

Existing Solutions

Current solutions to improve personal hygiene include washing hands frequently using antiseptics or using alcohol-based hand rubs. However, for people in rural areas lacking access to hygiene or water, these solutions are unaffordable or inaccessible. Additionally, many of these products contain chemicals and are not environmentally-friendly.

Currently, much of paper and organic wastage is piled up in landfills. While efforts are being made to encourage paper recycling and composting, these processes can be expensive and time-consuming.

Our Solution - PeelTowel

Based on our research, we aimed to create an environmentally-friendly, accessible, and affordable PeelTowel, made from typically discarded fruit peels and recycled paper (binding agent), that effectively kills bacteria and absorbs water. The PeelTowel would solve the issues of inaccessible hygiene and wastage under one solution.  

Method / Testing and Redesign

Location, Experimentation, and Seven Conditions

The PeelTowel was created in a home environment (Figure 5). We performed three experiments: Experiment 1 observed growth of E.coli and Staph. Experiment 2 tested these bacteria against kiwi peels, orange peels, and lime peels, Kiwi PeelTowels, Orange PeelTowels, and Lime PeelTowels, and paper towels (seven conditions). Experiment 3 tested water absorption of these seven conditions.Experiments 1 and 2 were conducted in a sterile environment at Feinberg School of Medicine - Northwestern University, under Dr. Alan R. Hauser, MD, PhD. Experiment 3 was conducted in a clean space at home.

Experiment 1

Estimating the amount of bacteria

  1. Add 1 ml of Luria Broth (LB) into two vials, and using a tungsten rod place bacteria in one vial
  2. Calculate bacterial density using light diffraction machine, OD600 (Figure 7). Continue diluting until a value of 0.0125 is shown (approximately 108 Colony Forming Units (CFU)/ml)
  3. Repeat above steps for both bacteria
  4. These 2 vials of 108 bacteria are known as “Estimated Bacteria”

Dilutions

  1. Perform 10-fold dilutions (100 µl bacteria, 900 µl LB) using microcentrifuge tubes and pipettes (Figure 8, 9). Change pipette tip for each dilution. Dilution process below:
    1. Remove 100 µl from estimated bacteria and add 900 µl of LB (1:10).
    2. Remove 100 µl from the previous vial and add 900 µl of LB (1:102).
    3. Continue dilutions:
      1. Dilution 1.1 (1:103)
      2. Dilution 1.2 (1:104)
      3. Dilution 1.3 (1:105)

Drip Plating

  1. Drip two separate 10 µl drops of Dilution 1.1 on an agar plate (Figure 10). Repeat for other dilutions on the same plate (total of 6 drops)
  2. Hold the plate vertically
  3. Repeat above steps for three trials of both bacteria separately
  4. Incubate plates for 24 hours
  5. Count colonies present 

Experiment 2: 

  1. Grind peels with water. Using a pipette, extract the peel paste and place in new vials. Repeat for all fruit peels.
  2. Add fruit peel paste, paper towel, or PeelTowels
    1. Add 900 µl of LB solution to a vial
    2. To this add 100 µl of the peel paste or 1 cm x 1 cm piece of the PeelTowel or paper towel
    3. Add 10 µl of estimated bacteria solution
  3. Make 3 dilutions for drip plating and count the number of colonies left (Figure 11):
    1. Dilution 2.1 (1:10)
    2. Dilution 2.2 (1:102)
    3. Dilution 2.3 (1:103)
  4. For the one hour and eighteen-hour experiments, let the vials sit for their respective times.
  5. Drip plate Dilution 2.1, 2.2, and 2.3 as explained in Experiment 1
  6. Leave samples in the incubator at 37oC overnight
  7. Count colonies grown (Figure 12, 13) 
  8. Repeat in triplicate for each condition

Experiment 3: Water Absorption Test (Figure 14)

  1. Cut each condition into a 2 cm by 1 cm rectangle piece
  2. Using a syringe, place 3 ml of water inside each of three microcentrifuge tubes
  3. In each tube, place one piece of the condition
  4. Wait ten seconds and remove the condition with forceps.
  5. Using the syringe, draw the remaining water from the test tubes, measure and record the readings 
  6. Repeat above steps for each sample for three trials

 

Results

Data was collected from Experiment 1 and Experiment 2 by counting the number of colonies grown on incubated agar plates. However, before performing analysis on collected results, the bacteria present was quantified. This was done by backtracking the number of dilutions performed and multiplying by the respective power of 10 to reach the same level as the initial bacteria count. This process is shown in the below (Figure 15, Figure 16). 

Statistical Significance

All experiments were performed in triplicate and standard errors were calculated. Two-sample t-tests were performed comparing each condition to the Inoculum for Experiment 2 and comparing each condition to the Paper Towel for Experiment 3. Statistical significance was defined as p less than or equal to 0.05.  

Results

The results from Experiment 1 demonstrated the difference between the estimated bacteria of 108 CFU and the grown bacteria count (Table 1). On average, the E. Coli bacteria count was fairly close to the estimated count of bacteria with only a 23% difference. On the other hand, there was an 81% difference between the grown Staph bacteria and the estimated value (108). Due to the wide difference between the actual and estimated Staph bacteria, Staph data was not analyzed when forming final conclusions.

The results from Experiment 2, 1hr exposure showed that all three PeelTowels grew fewer bacteria compared to the inoculum (Figure 15). On the contrary, the Paper Towel grew 51% more bacteria (Table 3). The Lime Towel performed significantly better than the inoculum killing 91% of bacteria (p = 6.85E-5). Likewise, the Lime Peels killed 100% of the bacteria (p = 0.002). The Kiwi Towel and Orange Towel also killed 81% (p = 0.0001) and 69% respectively (p = 0.002).

The results from Experiment 2, 18hr exposure showed that while Orange Towel and Lime Towel killed bacteria, the Kiwi Towel and Paper Towel grew more bacteria compared to the Inoculum (Figure 16). The Paper Towel grew more than 5 times more bacteria at 286% (Table 4) On the other hand, the Lime Towel and Orange Towel performed significantly better than the inoculum killing 95% (p = 0.0001) and 94% of bacteria (p = 0.0007) respectively. Unfortunately, after 18 hours of exposure to E.coli, the Kiwi Towel, in fact, grew more bacteria likely due to its lacking in citric acid.

The results from Experiment 3, showed that Lime Towel performed better than all other conditions absorbing 0.93mL of water (Table 5). The Lime Towel absorbed significantly more water than the Paper Towel at 31% (p = 0.0006). Additionally, the Orange Towel absorbed 10%, around the same as the Paper Towel at 11% (p = 0.36).

Based on these results, our hypothesis was supported. We were able to create the Lime PeelTowel, made from lime peels and recycled paper, that significantly kills 95% of E.coli, and absorbs three times more than the current paper towel. Additionally, we developed the Orange PeelTowel that kills 94% of E.coli and absorbs almost equal to the standard paper towel.

Conclusion

The results of our experiments supported our hypothesis as at least one PeelTowel killed more than 75% of E.coli and absorbed equal to or more water than the standard Paper Towel. The results demonstrated that 2 of the 3 PeelTowels were both antibacterial and water absorbent. At 1 hr of exposure to E.coli, the Lime Towel and Orange Towel performed significantly better than the Inoculum killing 91% of E.coli (p = 6.05E-5) and 69% (p = 0.002) respectively. At 18 hr of exposure to E.coli, once again both the Lime Towel and Orange Towel performed significantly better than the Inoculum killing 95% (p = 0.0007) and 94% (p = 0.0001) respectively. In contrast, the Kiwi PeelTowel performed well at 1 hr but poorly at 18 hr of exposure to E.coli. This is likely due to the lack of citric acid found in kiwi peels. The ability of E.coli bacteria to survive and multiply over longer times in the presence of kiwi peels suggests that it may not be as effective in facilitating hand hygiene as the other types of PeelTowels.

During our water absorption testing, our results demonstrated that our Lime PeelTowel was the most water absorbent Towel. Our Lime PeelTowel absorbed 31% of water, approximately 3 times more than a paper towel, demonstrating it was significantly more effective than the standard Paper Towel (p = .0006). Furthermore, the Orange PeelTowel had approximately the same absorption capabilities of the Paper Towel (p = 0.36).

Because our PeelTowels were homemade, bacteria or fungi may have been present at the start of each experiment, and these microbes may have been counted as E.coli. We only tested E.coli bacteria, so we are unsure how PeelTowels will perform against other bacteria for hand hygiene, such as Salmonella and Shigella. Finally, we measured the performance of the PeelTowel under laboratory conditions, which may not accurately reflect their antibacterial and absorbance under real-use conditions.

In future studies, several additional aspects of PeelTowels should be examined such as shelf life and the tensile strength of PeelTowels since an organic material is prone to rotting over time. Other fruit peels with high concentrations of Vitamin C, citric acid, or different antibacterial compounds, such as acetic acid, should also be tested. Due to a 2:1 ratio of peels to paper, there will be fewer trees chopped as our PeelTowel, in the future, will use fewer amounts of paper than a typical paper towel. This will reduce waste over long periods of time. Our product is also the perfect solution for the US Army that is posted in places that have scarce water supply and low hygienic conditions.

The mayors of Aurora and Naperville were very encouraging and impressed with the work we had done. Finally, apart from improving our prototypes and creating new ones, we would like to implement our solution in third world countries and make an impact by adopting villages where there is a lack of personal hygiene.

About me

Hi! We are a team of three 10th graders, Milind Sagaram, Prarthana Prashanth, and Srikant Lokesh, from Aurora and Naperville, Illinois. 4 years ago we formed a science team hoping to learn something new! That year, after studying HFCS awareness, we were thrilled to be named the Ecybermission 6th-grade Regional Winner and National Finalists. Over the next 3 years, we created hail resistant shingles, an energy storage mechanism, and an antibacterial paper towel (PeelTowel). These projects have led us to work with experts from Fermilab and Feinberg School of Medicine. Outside of research, we enjoy different musical activities!

We are grateful to have received Ecybermission’s 2nd place in the State, Paradigm Challenge Finalist, and Illinois Tech Innovation Challenge’s 2nd place, for the PeelTowel. Additionally, we have a provisional patent and are working on publishing the study’s results in a journal.

We admire Edward Jenner, inventor of the first vaccine, Steve Jobs, founder of Apple, and Rosalind Franklin for her contributions to the field of genetics, revolutionizing today’s medical and technological fields.

It has been our dream to participate in the Google Science Fair since 6th grade. Winning an award will help us achieve our goals of attending top universities and pursuing STEM jobs. Additionally, it will legitimize our product, will allow us to bring our idea to the mainstream and will enable us to provide more donations of the PeelTowel to Third World Countries. We hope the PeelTowel gains recognition, fostering safe and healthy communities around the world!

 

Health & Safety

Bibliography, references, and acknowledgements

Acknowledgements

While we came up with the idea of the PeelTowel, researched it, and created it on our own, we required the help of experienced individuals when it came to testing the PeelTowel in the lab. We used the guidance of experts to learn bacterial testing procedures, to quantify collected data, and to choose tests for statistical significance. However, Experiment 3, all data tables, figures, statistical significance testing and analysis, and writing of the report was done on our own.

Dr. Julie Gibbs, Ph.D, Prof. of Biology, College of Dupage, Glen Ellyn

Julie Gibbs was our initial mentor. We contacted her through email, in the hope of seeking advice on testing our designs. As we talked to her through a phone conference, she educated us on the current testing process used in microbiology. We received valuable feedback from Dr. Gibbs on methods to improve the PeelTowel and that it must be tested in a sterile environment in order to get accurate results. We improved our design based on Dr. Gibbs advice and contacted various professors including Dr. Alan R. Hauser.

Dr. Alan R. Hauser, MD, Ph.D, Departments of Microbiology/Immunology and Medicine-Infectious Diseases, Northwestern University, Chicago

Alan R. Hauser is a professor at Northwestern’s Feinberg School of Medicine in the Microbiology field. Hoping to experiment in a sterile lab, we decided to search and email professors working at nearby colleges. Dr. Hauser was excited about our project and was quick to offer his help and guidance. He proactively sought approval to lend us his lab for experimentation. He acted as our mentor through assisting us in planning, providing us with materials, and executing our testing. For three days, he guided and trained us in the procedures typically utilized in bacterial testing. By the third day, we were able to independently perform dilutions and execute drip plating with little guidance. While analyzing the data, Dr. Hauser also guided us in quantifying bacteria and choosing statistical tests.

Parents

Our parents were our greatest source of emotional and physical assistance. In fact, they escorted us from our home to the Feinberg lab for 3 consecutive days. They also provided us with the materials, money, and an area to build the PeelTowel and conduct Experiment 3. Finally, they kept us well-fed and energized throughout long project meetings.

Facilities and Equipment Used

Northwestern University’s Feinberg School of Medicine, Hauser Lab

  • OD600 (Light Diffraction Machine)
  • Incubator
  • Sterile LB Agar Plates
  • 10µl, 100µl, 1000µl Pipettes and Pipette Tips
  • Microcentrifuge Tubes (Vials)
  • Vortexer
  • Microcentrifuge and Racks
  • Glass Beads
  • Tungsten Rod
  • Escherichia Coli and Staphylococcus Epidermidis
  • Lab coats and Gloves

Experiment 3 Special Equipment

  • Syringes
  • Microcentrifuge Tubes
  • Forceps

Bibliography/Resources

Journals

Biol Lab Resource Center. (n.d.). Serial Dilutions. Retrieved from

biolabs.tmcc.edu/Micro%20Web/SerialDilutions.pdf

Josef Prousek. (2007). Fenton chemistry in biology and medicine. Pure Application Chemistry,

79(12), 2325–2338. https://doi.org/10.1351/pac200779122325

Ryu, J. H., Deng, Y., & Beuchat, L. R. (1999). Behavior of acid-adapted and unadapted

Escherichia coli O157:H7 when exposed to reduced pH achieved with various organic acids. Journal of Food Protection, 62(5), 451–455.

Ververis, C., Georghiou, K., Danielidis, D., Hatzinikolaou, D. G., Santas, P., Santas, R., & Corleti,

V. (2007). Cellulose, hemicelluloses, lignin and ash content of some organic materials and their suitability for use as paper pulp supplements. Bioresource Technology, 98(2), 296–301. https://doi.org/10.1016/j.biortech.2006.01.007

Vilchèze, C., Hartman, T., Weinrick, B., & Jr, W. R. J. (2013). Mycobacterium tuberculosis is

extraordinarily sensitive to killing by a vitamin C-induced Fenton reaction. Nature Communications, 4, 1881. https://doi.org/10.1038/ncomms2898

Videos

Bio-Rad Laboratories. (n.d.). Serial Dilution and Plate Counts. Retrieved from

https://www.youtube.com/watch?v=pmRUBYlPMBM

David Read. (n.d.). Aseptic techniques in the biology lab. Retrieved from

https://www.youtube.com/watch?v=cuCSELaQ_Go

Microbiologics. (n.d.). How to Perform Serial Dilutions in Microbiology. Retrieved from

https://www.youtube.com/watch?v=Ppe_bgnPFHU

Websites

Aseptic Technique: Uses, Benefits, and Complications. (n.d.-a). Retrieved January 3, 2018, from

https://www.healthline.com/health/aseptic-technique

Autoclave Use. (n.d.-a). Retrieved January 3, 2018, from

https://ehs.princeton.edu/book/export/html/380

Bacterial Growth Curve | MICRB 106. (n.d.-a). Retrieved January 3, 2018, from

https://online.science.psu.edu/micrb106_wd/node/6122

Brown, D. (n.d.). How Do Paper Towels Absorb Water? Retrieved January 4, 2018, from

http://indianapublicmedia.org/amomentofscience/how-do-paper-towels-absorb-water/

Cellulose facts, information, pictures | Encyclopedia.com articles about cellulose. (n.d.-a).

Retrieved January 4, 2018, from http://www.encyclopedia.com/science-and-technology/chemistry/organic-chemistry/cellulose

Citric Acid: Definition, Safety, Cleaning Uses, & More. (n.d.). Retrieved February 8, 2018, from

https://www.thespruce.com/citric-acid-safety-cleaning-uses-1707021

“Clean Hands Protect against Infection.” WHO, World Health Organization,

www.who.int/gpsc/clean_hands_protection/en/.

Does Lemon Juice Kill Germs? | Hunker. (n.d.). Retrieved February 8, 2018, from

https://www.hunker.com/12451993/does-lemon-juice-kill-germs

Davis, C. P. (1996). Normal Flora. In S. Baron (Ed.), Medical Microbiology (4th ed.). Galveston

(TX): University of Texas Medical Branch at Galveston. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK7617/

Fenton’s reaction. (n.d.-a). Retrieved January 4, 2018, from

https://www.lenntech.com/fenton-reaction.htm

Food Composition Databases Show Nutrients List. (n.d.-a). Retrieved January 4, 2018, from

https://ndb.nal.usda.gov/ndb/nutrients/report/nutrientsfrm?max=25&offset=0&totCount=0&nutrient1=401&nutrient2=&nutrient3=&subset=1&fg=9&sort=c&measureby=m

Incubating and viewing plates | Nuffield Foundation. (n.d.-a). Retrieved January 3, 2018, from

http://www.nuffieldfoundation.org/practical-biology/incubating-and-viewing-plates

Khan Academy. (n.d.). Retrieved January 4, 2018, from http://www.khanacademy.org

Kiwi Berries web. (n.d.-a). Retrieved January 4, 2018, from

http://www.kiwiberry.com/nutrition.htm

Kiwi fruit composition. (n.d.). Retrieved February 8, 2018, from

http://www.food-allergens.de/symposium-vol1(1)/data/kiwi/kiwi-composition.htm

Laboratory Centrifuges | Biocompare.com. (n.d.-a). Retrieved January 3, 2018, from

http://www.biocompare.com/Lab-Equipment/Laboratory-Centrifuges/

Lucas, J., October 15, L. S. C. |, & ET, 2015 01:12am. (n.d.). What Are Centrifugal &

Centripetal Forces? Retrieved January 3, 2018, from https://www.livescience.com/52488-centrifugal-centripetal-forces.html

March 16, P., & border-radius: 5px;}, 2011 inShare2 articleContent p search-out { font-size:

14px; width: 380px; color: #282828; line-height: 1 6em; padding: 10px 0; border-bottom: 2px solid #127ec4; border-top: 2px solid #127ec4; } search-out a{font-weight:bold;} FL-screen blue-btn{ float: right; background: #127ec4; text-decoration: none; min-width: 80px; padding: 5px; margin-right: 15px; margin-top:-28px; (n.d.). Microcentrifuges: Careful Choices Make for Easier Experiments. Retrieved January 3, 2018, from http://www.biocompare.com/Editorial-Articles/41804-Microcentrifuges-Careful-Choices-Make-for-Easier-Experiments/

OD600 Spectrophotometer | London Biohackspace. (n.d.). Retrieved January 3, 2018, from

https://biohackspace.org/projects/od600-spectrophotometer/

“Paper Towels – What's the Big Deal Anyway?” Ocean Conservancy, 9 May 2017,

oceanconservancy.org/blog/2012/10/12/paper-towels-whats-the-big-deal-anyway/.

PubMed entry. (n.d.). Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/21413249

Re: How are paper towels made? How do paper towels absorb water? (n.d.-a). Retrieved January

4, 2018, from http://www.madsci.org/posts/archives/1997-12/880215232.Ot.r.html

Resident Flora - Infections. (n.d.). Retrieved January 4, 2018, from

https://www.merckmanuals.com/home/infections/biology-of-infectious-disease/resident-

flora

Resident skin flora. (n.d.). Retrieved January 4, 2018, from

http://www.bode-science-center.com/center/glossary/resident-skin-flora.html

“Sanitation.” World Health Organization, World Health Organization,

www.who.int/mediacentre/factsheets/fs392/en/.

Services, USI Web. “Main Navigation.” University of Southern Indiana,

www.usi.edu/recycle/paper-recycling-facts/.

“Squeezing Oranges to Reduce Waste.” Inside Science, 25 July 2016,

www.insidescience.org/news/squeezing-oranges-reduce-waste.

Staphylococcus Epidermidis Bacteria. (n.d.). Retrieved January 4, 2018, from

http://prod.hopkins-abxguide.org/pathogens/bacteria/aerobic_gram-positive_cocci/staphylococcus_epidermidis.html?contentInstanceId=255870

THE FENTON REACTION: pro-oxydant role of vitamin C. (n.d.-a). Retrieved January 4, 2018,

from http://flipper.diff.org/app/pathways/6861

Vortex-mixers | VWR. (n.d.-a). Retrieved January 3, 2018, from

https://us.vwr.com/store/product/596357/vortex-mixers

What Is E.Coli? (n.d.). Retrieved January 4, 2018, from

https://www.webmd.com/food-recipes/food-poisoning/what-is-e-coli