It is now well known that plastic pollution has become a global scourge. However, the real concern is that of micro and nano-plastic pollution that can cause substantial health ailments. According to National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency (ECA), fragments of plastic of 5 mm in size or less are considered ‘Micro-plastics’. They are plastic debris of extremely small size, which is a real headache for environmental scientists as it has now entered our food chain.
Experimental studies conducted with micro-plastic have shown that it causes extensive cell damage, allergic reaction and cell death. Constant human exposure to microplastic can result in DNA damage, and inflammation, and can cause serious health problems. A recent study revealed that microplastic was detected in 80% of 22 anonymous human blood samples tested.
As microplastic is hard to gather and remove from the environment that resulted in a very slow clearance speed as compared to the speed at which it enters nature. It is still unclear how plastics break down and fragment in the environment. However, our general understanding is that they take a long time to decay. This is partially due to a lack of extensive research and techniques for estimating weathering time.
To counter plastic pollution, various strategies like burning, dumping and reusing are carried out. Each of these techniques has its own advantages and disadvantages. Synthetic plastics mostly derived from petrochemicals are polymers which are very difficult to degrade naturally. Plastic pollution is traditionally thought to be an irreversible threat. As it can take hundreds or thousands of years for plastic to decompose. Recently, microbiologists have found a way to use microbes to trap microplastics, removing them from the environment and making them easier to recycle.
There are mainly 4 mechanisms by which plastic can be degraded i.e., photodegradation, hydrolytic degradation, thermo-oxidative degradation and biodegradation. Biodegradation is a natural phenomenon in which the breakdown of organic matter is done by microorganisms, such as bacteria and fungi. In 2016, Japanese scientists isolated the bacteria Ideonella sakaiensis which can eat plastic from outside of an Osaka bottle factory. The bacterium Rhodococcus ruber was found to actually digest plastic.
From that, many other bacterial species have now been identified that can degrade plastic. Serratia marcescens, Phormidium lucidum, Oscillatoria subbrevis, Enterobacter asburiae YT1 and Bacillus sp. YP1. Several bacterial species were found to assist in the process of biodegradation of plastic including Bacillus subtilis, Bacillus flexus, Pseudomonas stutzeri, Phanerocharte chrysosproium, and Engyodontium album.
Aspergillus tubingensis, a soil fungus, has been identified that produces enzymes which can quickly degrade plastic materials. The fungus capable of degrading polyurethane (PU) plastics has been identified by Chinese researchers. Another rare fungus Pestalotiopsis microspore found in the Amazon rainforest was also shown to have the potential for plastic degradation.The accumulation of plastic particles in our environment is one of the main causes of pollution globally.
Plastic pollution leads to severe impacts on various ecosystems and more importantly, it can adversely affect our health. Hence, neutralizing this pollution through biological means can be considered one of the important discoveries of the modern era. Though the bioremediation of plastic with microbes is still in its infancy; however, future research could definitely strengthen this area and could become an effective answer for plastic pollution.
References:
Bacteria really eat plastic. Science Daily, January 2023.
Cuffari, B. (2022). The Use of microbes in plastic biodegradation. Medical Life Sciences.
Mellor, B. (2022). Tiny particles of plastic have been detected in human blood for the very first time. They can’t be filtered out. Fortune Magazine.
Plastic eating fungus. Synergia Foundation. April 4, 2017.
Tareen, A. Saeed, S. Iqbal, A. Batool, R., Jamil, N. (2022). Biodeterioration of microplastics: a promising step towards plastics waste management. 14, 2275.
Yoshida, S., Hiraga, K., Takehana, T. A (2016) Bacterium that degrades and assimilates poly (ethylene terephthalate). Science; 351 (6278): 1196-1199.