HUMANS TRULY ARE an innovative species. The use and control of fire; the simple yet sophisticated wheel; cars, ocean liners, aircrafts, spaceships; and the Internet; these all testify to how creative we can be – and to our ability to communicating as well.
Canadian artist Benjamin Von Wong showcased his construction of a huge sculpture made solely of plastic drinking straws, aptly and ironically named the “Strawpocalypse” in 2019 to draw attention and awareness of yet another one of our joint, though inadvertent creations, The Great Pacific Garbage Patch (Figure 1)1.
Located roughly from 135°W to 155°W and 35°N to 42°N, the Pacific Garbage Patch and its brother, the Atlantic Garbage Patch, are home to a plethora of trash and chemical sludge. Naturally, this has led to the destruction of many coral growths, endemic fish and a host of other organisms.
The high concentration of microscopic plastic particles in these Patches has made their clean-up an extremely difficult task, which can likely lead to biomagnification, i.e. the increasing concentration of a toxic chemical in the tissues of organisms at successively higher levels in a food chain.
In 2008 BBC News reported that approximately one-third of albatross chicks at Midway Atoll die due to being fed plastics by their parents who mistook them for food2.
Decreasing the use of plastics may help combat its ubiquitous pollution, but a better alternative would be to have them replaced with natural, biodegradable materials instead. This sounds simple enough, but recent studies have confirmed suspicions that most of the “biodegradable” or “oxo-biodegradable” alternatives sold at supermarkets are merely a play on words based on loopholes that have gone unnoticed by the public.
An item is considered biodegradable if it can be degraded into non-toxic by-products by the soil microbiota within six months or less3. To be sure, bags marketed as biodegradable often contain more additives to promote degradation compared to conventional plastics. But their degradation often requires temperatures greater than 50°C; this is unattainable when these items are discarded in oceans or buried in soil4.
In fact, these “biodegradable” bags cannot be composted and will end up in landfills, just like conventional plastic bags. In fact, oxo-biodegradable material will not degrade into simpler compounds but instead, fragment into smaller pieces over time, bringing more harm to the environment.
... perhaps in the coming years, we will not have to be as much the ultimate cause of turtles or dolphins choking on ocean plastics as we are now.
Hence, a much better option to adopt are the easily compostable bioplastics derived from natural materials such as plant biomass or bacterial cells. Natural microorganisms help to degrade these into harmless by-products. Single-use plastics currently contribute approximately 32% of plastics found in the ocean, and having a good replacement like compostable bioplastics is necessary for stemming the problem5.
One promising biopolymer is the polyhydroxyalkanoate (PHA) discovered in 1926 by the French scientist Lemoigne. Produced by microorganisms or transgenic plants6 cultivated under specific conditions, PHA possesses properties relatively similar to that of polypropylene (PP) and low-density polyethylene (LDPE). This led to a boom in research and commercialisation efforts of the PHA from the 1960s onwards. Commercial processes for PHA production were initially developed by W.R. Grace and Company in 1959, but for a compound discovered almost a century ago, its popularity is still rather slow to catch on.
Garbage bags “neatly” strewn along the roadside. Spot the used PP surgical mask.
The main bottlenecks hampering its launch into the market are: i) the high cost of production owing to low synthesis efficiency, and ii) issues with purification of the polymer from bacterial cells. As of 2017, polyhydroxybutyrate (PHB; the most common type of PHA) costs approximately USD5.5/kg, whereas conventional plastics such as PP and polyurethane range in price from USD1.3 to USD 1.7/kg7.
Nevertheless, these setbacks have not deterred research into the area. Over the last decade, engineered bacterial strains with improved biosynthesis efficiency and the ability to produce PHA with diverse properties have been developed8. Food crops are also no longer used to generate the carbon substrate required for PHA production. Companies in Brazil have attempted to use waste products from sugar and coffee industries, such as the residual biomass, coffee grinds and wastewater effluents, as carbon sources for sustainable PHA production.
Countries involved in oil production like Malaysia can also produce this polymer using oil waste from the industry9.
There is however some debate surrounding the net ecological effects of PHA. One, in particular, pertains to the use of toxic chemicals in some of its downstream purification processes. But new solutions to these problems are already under way, including extracellular production of the polymer, and the use of a scalable non-toxic process to purify PHA 10, 11. Such advancements have allowed companies such as TianAn Biologic Materials, Danimer Scientific and BioMatera Inc. to embrace PHA for food packaging, cosmetics, inks, etc. Many more companies are expected to join the global bioplastics market soon12.
The Covid-19 pandemic is worrisome, and has caused many governments to repeal the ban on single-use plastics since most personalised protective equipment fall into this category. For safety reasons, they are not reused. Some states in the US have also banned reusable items like mugs and cloth bags to limit the spread of the virus. Many coffee chains have been forced to revert to the use of disposable cups and straws as well.
Environmental activists like Judith Enck believes that there is no strong link between Covid-19 and reusable items, and claims that plastic companies may be using scare tactics to profit from the health crisis13. The fact remains though that this “use and throw” mentality will only lead to an exponential rise in the global accumulation of plastic waste. Unless proper disposal and collection mechanisms are put in place, a domino effect stemming from a series of unfortunate events is quite possible.
The Possibilities of PHA
Now is the perfect time to turn to bioplastics; in fact, bioplastics may help alleviate the environmental load of the global pandemic. In Spain filaments of a biodegradable polymer are being used to print 3D medical masks (currently made of PP) in massive quantities, and to fabricate frames for protective face shields14. PHAs may also be used to replace plastic straws and cutleries at cafes and restaurants since the bioplastic can be discarded together with rotted food wastes and reduce the need to have additional disposal mechanisms.
PHAntastic™ straws. Prototypes of 100% biodegradable straws made in the laboratory using PHA synthesised from plant-based renewable resources.
But of all the biopolymers present, why PHA? As of 2019, various biopolymers have been produced and are even in the market already, including seaweed, cellulose and chitin polymers. But these other polymers have their limitations, e.g. sticky textures, thermal barriers and even immunity reactions if used as implants.
Biosynthesised and biodegradable, PHA boasts many properties that in terms of melting point and flexibility, for example, are similar to that of conventional plastics such as PP and polyethylene (PE)15. The biodegradable nature of this polymer can reduce landfills16. The demand for this polymer may increase ten-fold by the end of 202017, and if PHA production can be performed in tandem with other processes such as wastewater treatment or degradation of conventional plastics, current drawbacks can be negated.
In many supermarkets in the UK at present, plastic packaging of produce has been halted and bioplastics are being put to use. If this trend can be emulated worldwide, perhaps in the coming years, we will not have to be as much the ultimate cause of turtles or dolphins choking on ocean plastics as we are now.
Ardra Nandakumar is a student from the Indian Institute of Science Education and Research Mohali, India, who is currently in the penultimate year of an Integrated BS-MS Programme. At present, she is working as an intern in the lab of Prof Dr. K Sudesh Kumar, a renowned scientist in the field of polyhydroxyalkanoates, at Universiti Sains Malaysia, Penang.
Jo-Ann Chuah was born and raised in Penang, Malaysia. She is currently pursuing a career in the life sciences and is passionate about science communication.
1Benjamin Von Wong - Viral Epic Photographer, Visual Engineer and Storyteller. Retrieved June 3, 2020, from https://www.vonwong.com/
2BBC NEWS | Have Your Say | Q&A: Your Midway questions answered. http://news.bbc.co.uk/2/hi/talking_point/7318837.stm.
2Biodegradability | Knowledge for policy. https://ec.europa.eu/knowledge4policy/glossary/biodegradability_en.
2Biodegradable plastic ‘false solution’ for ocean waste problem | Environment | The Guardian.
5The New Plastics Economy. http://www3.weforum.org/docs/WEF_The_New_Plastics_Economy.pdf (2016).
6Valentin, H. E. et al. PHA production, from bacteria to plants. Int. J. Biol. Macromol.25, 303–306 (1999).
7Prices Bottom Out for Polyolefins; PET, PS, PVC Move Up : Plastics Technology. https://www.ptonline.com/articles/prices-bottom-out-for-polyolefins-pet-ps-pvc-move-up.
8Chen, G.-Q. & Jiang, X.-R. Engineering bacteria for enhanced polyhydroxyalkanoates (PHA) biosynthesis. Synth. Syst. Biotechnol.2, 192–197 (2017).
9Sudesh, K. et al. Synthesis of polyhydroxyalkanoate from palm oil and some new applications. Appl. Microbiol. Biotechnol.89, 1373–1386 (2011).
10Leong, Y. K., Show, P. L., Lan, J. C.-W., Loh, H.-S., Yap, Y. J., & Ling, T. C. (2017). Extraction and purification of Polyhydroxyalkanoates (PHAs): application of Thermoseparating aqueous two-phase extraction. Journal of Polymer Research, 24(10), 158. https://doi.org/10.1007/s10965-017-1307-3
11Rahman, A., Linton, E., Hatch, A. D., Sims, R. C., & Miller, C. D. (2013). Secretion of polyhydroxybutyrate in Escherichia coli using a synthetic biological engineering approach. Journal of Biological Engineering, 7(1), 24. https://doi.org/10.1186/1754-1611-7-24
12Top 6 Vendors in the Polyhydroxyalkanoate Market from 2017 to 2021: Technavio | Business Wire. https://www.businesswire.com/news/home/20170824005079/en/Top-6-Vendors-Polyhydroxyalkanoate-Market-2017-2021.
13Plastic bag bans rolled back for COVID-19. https://cen.acs.org/environment/sustainability/Plastic-bag-bans-rolled-back/98/web/2020/04.
14Bioplastic industry joins fight against Covid-19 – European Bioplastics e.V. https://www.europeanbioplastics.org/bioplastic-industry-joins-fight-againstcovid-19/.
15Al-Kaddo, K. B. et al. Production of P(3HB-co-4HB) copolymer with high 4HB molar fraction by Burkholderia contaminans Kad1 PHA synthase. Biochem. Eng. J.153, 107394 (2020).
16Ivanov, V., Stabnikov, V., Ahmed, Z., Dobrenko, S. & Saliuk, A. Production and applications of crude polyhydroxyalkanoate-containing bioplastic from the organic fraction of municipal solid waste. Int. J. Environ. Sci. Technol.12, 725–738 (2015).
17Are booming bioplastics here to stay? - CNN.com. http://edition.cnn.com/2009/TECH/science/12/15/eco.bioplastics/index.html.