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Swimming with wool

degradation of wool fibre in the marine environment

The degradation of wool swimsuits is unavoidable in the natural marine environment. The alkaline condition in seawater and the presence of microbes that secrete proteases are the major factors in its degradation. Nonetheless, one of the features of natural fibre is its high degradability. According to some swimsuit brands, a synthetic swimsuit should last between three months to a year, depending on the wearing condition. A swimsuit's lifespan is so short compared with other apparel, and it is not a bad idea to decompose naturally in the marine environment through microbes and seawater and back to the natural food web.

*If you see ⁍ , hovering over for more information

Wool swimsuit

Back in the 18th century, swimwear was made from natural fibres such as wool before nylon and polyester replaced them.

History of swimsuit materials in Olympics

At the early stagings of the Games: one-piece swimsuits made of wool

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Sources: https://www.swimming.org/sport/history-of-competitive-swimwear/

And Now...

The industry brings back the wool swimwear

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Maker unknown (American). Bathing suit, 1890-95. Wool, cotton.

New York: The Metropolitan Museum of Art, 1975.227.6. Gift of Theodore Fischer Ells, 1975. Source: The Met

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Woollen bathing costume, 1945

Source: Victoria and Albert Museum, London

Compared with synthetic fibres like nylon and polyester, wool is less durable and has high water absorption.

 

The durability of wool is a significant concern as wool can be damaged by the natural environment more quickly than artificial materials.

Let’s find out how wool works in the ocean and what happens with your wool swimwear if you swim it in the sea!

1932⁍

Australian swimmer wore a silk swimsuit

1950⁍

Swimwear with the use of nylon

2000⁍

Swimsuits made of nylon or a blend of nylon/polyester and lycra 

2009⁍

Pure polyurethane swimsuits

Before the next section, you can...

Learn more about wool from Woolmark

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Or you can take a look at

my summary of wool 

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Characteristics of seawater

Alkaline seawater & Marine microbe

pH level

  • Carbon dioxide (CO2) is dissolved in water (H2O), forms carbonic acid (H2CO3), and breaks down into bicarbonate ions (HCO3-) and hydrogen ions (H+) 1 

Natural carbonate ocean buffer system helps maintain the sea surface's pH level

  • The released bicarbonates (HCO3-) are converted to carbonates (CO3(2-)) by marine living for shell forming 2

  • These carbonate ions (CO3(2-)) can also be hydrolysed to form hydroxide (OH-) and bicarbonate ions (HCO3-) 3

Marine microbe

Microbes comprise nearly 98 per cent of the global marine biomass  4

  • Absorb the waste or dead bodies of other living and cycle the resources and energy from the waste into the food web 5

  • Different species of marine microbes, including bacteria and fungi 

Marine bacteria and fungi are the two major aquatic microflora  6

  • Proportion of lipolytic and proteolytic bacteria: closely high (43-100%)  7

Microbes’ ability to create proteolytic enzymes to break the protein fibre and cleave it into peptides 11​

Keratinase

  • Hydrolytic protease catalysing keratin degradation 12

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  • ​ Main contributors of alkalinity in the marine ecosystem:

      ‣ The water-dissolved basic minerals

      ‣The carbonate and bicarbonate ions in the water

Seawater is alkaline. The average pH at the sea surface is around 8.1 1⁍ 

The higher concentration of H+, the more acidic the solution

Therefore, even though water reacts with carbon hydroxide and forms free hydrogen ions, the pH level would be basic due to the higher concentration of bicarbonate ions from carbonic acid and the carbonate buffer system 1

‣  The ability of marine fungi to secrete proteases to break down proteins has been researched in different studies, showing that 13 out of 14 species of marine fungi had the proteolytic enzyme 10

  • These enzymes, including amylases, proteases, and cellulases, can also be produced by marine fungi 8 9 ⁍

‣  Bacteria, such as Bacillus licheniformis, B. subtilis and Stenotrophomonas maltophilia  12

‣  Fungi, such as Trichophyton rubrum and Microsporum canis 12

  • The microbes that secrete keratinases are present in the marine ecosystem 13 14 15

  • The proteolytic enzyme is known as keratinase if the target protein is keratin.

Degradation of wool in the ocean

Alkaline hydrolysis & enzymatical degradation

Alkaline hydrolysis

The bicarbonate ions (HCO3-) are one of the main contributors to the basic pH of seawater 1

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Bicarbonate ions (HCO3-) undergo hydrolysis with the water (H2O) in the marine environment to generate hydroxide ions (OH-)

HCO3- + H2O -> H2CO3 (aq)+ OH- (aq)

Carbonic acid (H2CO3):  weak acid

  • Most of them are stable together and would not liberate hydrogen ions (H+) 3

  • Hence, the increased concentration of hydroxide ions (OH-) makes the seawater alkaline. This includes the hydroxide (OH-) that is released from the hydrolysed carbonate ions (CO2−3) 3

Disulphide bonds: link cystine amino acids together and create a network of polypeptide chains of Keratin fibre  16

  • These disulphide cross-links are broken down into the thiol side group and sulfenic acid side group once they are ruptured by alkaline (OH-)

Alkaline hydrolysis of wool fibre 17

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The speed of alkaline hydrolysis is also affected by the solution temperature

  • The higher the temperature, the more weight loss of the wool 18

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Weight loss of wool in NaOH solution at different temperatures 18

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Enzymatical degradation

  • The sea surface temperature is variable

  • Average temperature range is 20 °C to 30 °C 19

‣   However, in their research (2015) they use sodium hydroxide (NaOH) solution for wool basic hydrolysis tests, which has higher alkalinity (~pH 10) than seawater (~pH 8.1) and creates a chain reaction on the rupture of disulphide linkages, causing greater damage than seawater

‣   Sodium hydroxide: synthetically manufactured substance

‣   Wool degraded by alkaline hydrolysis in the seawater would be much slower and mild than in the laboratory test with sodium hydroxide.

  • In the research by Zhao et al. (2015) 18, the percentage of wool weight loss at 20 °C to 30 °C is around 2% in alkaline solution. ⁍

Keratinase:

  • Work at neutral or alkaline pH, from 6 to 9 20

  • pH 8.1 in seawater is an optimum condition for these enzymes’ work.

Degradation of Lipid F-layer:

The cuticle layer:

  • Mostly constructed by keratin

  • The high amount of disulphide bonds in keratin makes enzymatical degradation difficult 22

  • Once the disulphide linkages have been ruptured:
    Enzymes can catalyse keratin degradation by breaking peptide bonds      23

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Lipid F-layer of cuticle cell

‣  Lipases hydrolyse the lipid into fatty acid and glycerol molecules 21

‣   ​Lipolytic bacteria take up the resulting components for nutrition

  • Lies on the outer shell of the cuticle, which repeals liquid 

  • Lipolytic bacteria secrete lipases and degrade this lipid membrane. ⁍

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‣  Break the disulphide bonds and make proteins accessible to the enzymes 25

  • Additional enzymes or chemicals, e.g. disulphide reductase from coral are required 20 24

Sulphitolysis (S—S bond breakage) and proteolysis are involved in the keratinolytic process 26 27

Process of keratin degradation by the keratineases, 
This schematic was reorganised from Nnolim et al. (2020) 11 and Li (2021) 29 articles

  • Sulphitolysis denatures the protein by breaking the disulphide bonds 

  • Proteolysis from proteases and keratinases break peptides into amino acids 25

  • A biofilm is formed upon the wool fibres by the microbes in the ocean

  • The keratin in the cuticle is degraded first and exposes the cortical cells to further degradation 6 28

  • Water would quickly be absorbed into the fibre after the enzymes remove the proteolipid F-layer and the highly cross-linked exocuticle layer

  • The fibre will eventually degrade into amino acids and be absorbed by the micro-organisms

  • The hydrophilic cortex layer absorbs water and speeds up proteolysis

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The end-of-life stage of wool swimsuit

  • Wool fibre:

  • Store moisture by swelling the cortex layer 

  • Keeping the surface dry by the water vapour adsorption and desorption in the wool fibres 30

  • Therefore, a swimsuit made of wool can remove seawater from the fabric surface and transfer moisture from the wearer's skin simultaneously

  • Prolonged exposure to the marine environment will destroy the fibre, which cannot be avoided 

  • Marine microbes secrete proteases to degrade the keratin in wool fibre

  • The high pH level of seawater also breaks the disulphide cross-links. 

  • The revealed cortex:

  • Absorb the water directly and lose the water-repellent function of the wool swimsuit. 

  • Seawater absorption speeds up the degradation, causing strength loss and damage like holes and tears

Microfibre issue

  • The fabric strength is lost

  • Wool fibres are easier to loosen and split away from the swimsuit fabric. 

  • Although wool fibre can be naturally degraded into amino acids

  • The dyestuff, trims, and other possible additional chemicals might not decompose 

  • Polluted the marine ecosystem

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Conclusion

  • The degradation of wool swimsuits is unavoidable in the natural marine environment

  • The alkaline condition in seawater 

  • The presence of microbes which secrete keratinases 

  • Nonetheless, one of the features of natural fibre is its high degradability.

  • A synthetic swimsuit should last between three months to a year 31
    Short lifespan: Durability could be less concerning

  • But no worry if you are having you wool swimsuit as a normal use - especially if it was rinsed or washed between uses!

What are your thoughts?

References

1 NOAA. (2020). Ocean acidification. National Oceanic and Atmospheric Administration. https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean- acidification#:~:text=The%20ocean’s%20average%20pH%20is,the%20ocean%20becomes%20more%20acidic

2 Savitri. (2021, December 30). Ph of seawater - acidic or alkaline? Techiescientist. Retrieved November 14, 2022, from https://techiescientist.com/ph-of-seawater/

3 Goyal, V. (2022). Is h2co3 an acid or base or both? strong or weak - carbonic acid. Topblogtenz. https://topblogtenz.com/is-h2co3-an-acid-or-base-strong-or-weak-carbonic-acid

4 NOAA. (2013). Marine Microbes: Did You Know? What are marine microbes?

5 Hall, D. (2021). Marine microbes. . Smithsonian Ocean. . https://ocean.si.edu/ocean-life/microbes/marine-microbes

6 Brown, R. M. (1994). THE MICROBIAL DEGRADATION OF WOOL IN THE MARINE ENVIRONMENT.

7 Kjelleberg and Hakansson, 1977, as cited in 6

8 Genitsaris, S. (2020). Biodiversity of marine microbes. In Diversity (Vol. 12, Issue 6). MDPI AG. https://doi.org/10.3390/D12060247

9 Vashist, P., Kanchana, R., Devasia, V. L. A., Shirodkar, P. v., & Muraleedharan, U. D. (2019). Biotechnological implications of hydrolytic enzymes from marine microbes. In Advances in Biological Science Research: A Practical Approach (pp. 103–118). Elsevier. https://doi.org/10.1016/B978-0-12-817497-5.00007-0

10  Pisano et al., 1964, as cited in 6

11 Nnolim, N. E., Udenigwe, C. C., Okoh, A. I., & Nwodo, U. U. (2020). Microbial Keratinase: Next Generation Green Catalyst and Prospective Applications. In Frontiers in Microbiology (Vol. 11). Frontiers Media S.A. https://doi.org/10.3389/fmicb.2020.580164

12 Qiu, J., Wilkens, C., Barrett, K., & Meyer, A. S. (2020). Microbial enzymes catalyzing keratin degradation: Classification, structure, function. In Biotechnology Advances (Vol. 44). Elsevier Inc. https://doi.org/10.1016/j.biotechadv.2020.107607

13 Amoli, R. I., Nowroozi, J., Sabokbar, A., Fattahi, S., & Amirbozorgi, G. (2017). Isolation of Stenotrophomonas maltophilia from water and water tap. www.biomedres.info

14 Gu, H. J., Sun, Q. L., Luo, J. C., Zhang, J., & Sun, L. (2019). A first study of the virulence potential of a bacillus subtilis isolate from deep-sea hydrothermal vent. Frontiers in Cellular and Infection Microbiology, 9(MAY). https://doi.org/10.3389/fcimb.2019.00183

15 Prieto, M. L., O’Sullivan, L., Tan, S. P., McLoughlin, P., Hughes, H., O’Connor, P. M., Cotter, P. D., Lawlor, P. G., & Gardiner, G. E. (2012). Assessment of the bacteriocinogenic potential of marine bacteria reveals lichenicidin production by seaweed-derived Bacillus spp. Marine Drugs, 10(10), 2280–2299. https://doi.org/10.3390/md10102280

16 Matthews, 1967, as cited in 6

17 Tímar-Balázsy, Á and Eastop, D. (1998). Chemical principles of textile conservation (pp.25-55). Oxford: Butterworth-Heinemann.

18 Zhao, Q., Zhao, X., Cui, Z., & Chen, W. (2015). The dissolution of wool in alkali solution and the changes of fiber structure and performance. Key Engineering Materials, 671, 95–100. https://doi.org/10.4028/www.scientific.net/KEM.671.95

19 Roemmich, D. (2014). Voyager: How long until ocean temperature goes up a few more degrees? Scripps Institution of Oceanography. https://scripps.ucsd.edu/news/voyager-how-long-until-ocean-temperature-goes-few-more-degrees

20 Korniłłowicz-Kowalska, T., & Bohacz, J. (2011). Biodegradation of keratin waste: Theory and practical aspects. In Waste Management (Vol. 31, Issue 8, pp. 1689–1701). https://doi.org/10.1016/j.wasman.2011.03.024

21 Britannica, T. (n.d.). Lipase. Encyclopedia Britannica. Retrieved November 13, 2022, from https://www.britannica.com/science/lipase

22Eslahi, N., Dadashian, F., & Nejad, N. H. (2013). An investigation on keratin extraction from wool and feather waste by enzymatic hydrolysis. Preparative Biochemistry and Biotechnology, 43(7), 624–648. https://doi.org/10.1080/10826068.2013.763826

23 Gupta, R., & Ramnani, P. (2006). Microbial keratinases and their prospective applications: An overview. In Applied Microbiology and Biotechnology (Vol. 70, Issue 1, pp. 21–33). https://doi.org/10.1007/s00253-005-0239-8

24 Dunlap, W. C., Starcevic, A., Baranasic, D., Diminic, J., Zucko, J., Gacesa, R., van Oppen, M. J. H., Hranueli, D., Cullum, J., & Long, P. F. (2013). KEGG orthology-based annotation of the predicted proteome of Acropora digitifera: ZoophyteBase - an open access and searchable database of a coral genome. BMC Genomics, 14(1). https://doi.org/10.1186/1471-2164-14-509

25 Kasperova, A., Kunert, J., & Raska, M. (2013). The possible role of dermatophyte cysteine dioxygenase in keratin degradation. In Medical Mycology (Vol. 51, Issue 5, pp. 449–454). Oxford University Press. https://doi.org/10.3109/13693786.2013.794310

26 Lange, L., Huang, Y., & Busk, P. K. (2016). Microbial decomposition of keratin in nature—a new hypothesis of industrial relevance. In Applied Microbiology and Biotechnology (Vol. 100, Issue 5, pp. 2083–2096). Springer Verlag. https://doi.org/10.1007/s00253-015-7262-1

27 Peng, Z., Mao, X., Zhang, J., Du, G., & Chen, J. (2019). Effective biodegradation of chicken feather waste by co-cultivation of keratinase producing strains. Microbial Cell Factories, 18(1). https://doi.org/10.1186/s12934-019-1134-9

28 Barzkar, N. (2020). Marine microbial alkaline protease: recent developments in biofilm n ideal choice for industrial application. In International Journal of Biological Macromolecules (Vol. 161, pp. 1216–1229). Elsevier B.V. https://doi.org/10.1016/j.ijbiomac.2020.06.072

29 Li, Q. (2021). Structure, Application, and Biochemistry of Microbial Keratinases. In Frontiers in Microbiology (Vol. 12). Frontiers Media S.A. https://doi.org/10.3389/fmicb.2021.674345

30  Naylor, G. (2017). The wool fibre and its applications.

31 Land’s End. (n.d.). How Long Should My Swimsuit Last? Land’s End. Retrieved November 12, 2022, from https://www.landsend.com/article/how-long-should-my-swimsuit-last/#:~:text=A%20general%20rule%20of%20thumb,long%20a%20swimsuit%20should%20last

Modified in 10th March 2024

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