AuthorBY- Jyotsna R Pollution of natural resources has become a common problem wherein the fact that it was restricted only to land and air has now extended to the marine ecosystem as well. The increased use of the water resource to satisfy human needs has led to the introduction of several undesirable materials into the marine ecosystem especially the plastics and more dangerously the microplastics. Impact of microplastics on the environment Microplastics have high durability and hence can persist in the environment for several hundred years. The first organisms that get affected are the aquatic flora and fauna. But they become more dangerous when they reach the higher orders of the food chain. The accumulation of microplastics with sizes less than 10 μm can penetrate the body organs and can affect the physical functions or interfere with lipid metabolism in the human body. Due to the increased microplastic pollution, especially in the oceans, there is an increased need for its degradation biologically which does not have any negative impact on the environment. There are several bio-degradation strategies for microplastics, which include: In-vivo degradation It involves the degradation of plastics within the organisms. The lesser waxworm called Achroia grisella shows enhanced degradation on high-density polyethylene (HDPE). These insects degraded the HDPE which got converted to hydroxy that was released through their excreta. The intestinal microorganisms Enterobacteriaceae, Triponomeaceae, and Enterococcus helped in degrading the plastic. Thus reducing the concentration of HDPE in the water body while themselves showing proper growth and lifecycle. Microbiological degradation The degradation of plastics (polymer chains) in the microbial body is called microbiological degradation. The microbes were found to be more efficient at hyperthermophilic composting conditions where the temperature range was around 70 o C in 56 days. The microbes converted the insoluble microplastics to water-soluble degradation products like Butylated Hydroxytoluene (C15H24O), 2-Isopropyl-5-methyl-1-heptanol (C11H26O), 1,3-Propanediol, ethyl tetradecyl ether (C19H40O2), etc. The microbes Bacillus, Thermus, and Geobacillus are found to be of high concentration in these conditions. Enzymatic degradation
Enzymes are called biological catalysts which are highly specific and are greatly influenced by environmental conditions like pH, temperature, etc. as adverse values of these conditions will harm the enzymes and lead to their degradation. Currently, the use of enzymes in microplastic degradation is still at the research level wherein the enzyme LCC cutinase(leaf branch composed cutinase) is being worked upon for the degradation of polyethylene glycol terephthalate (PET). The ester group was cut off by the LCC enzyme and converted to terephthalic acid and ethylene glycol. But the enzyme conversion rate was much slower when compared to the rate of PET generated. Furthur working is being done to improve the thermostability of the enzyme to use it at highly elevated temperatures. Outlook for other novel strategies for microplastic degradation Apart from the above biological methods, it is necessary to realize the kind of damage that is being caused to the environment due to hazardous chemicals used in plastic production so optimization of the choice of monomers used should be of prime concern. The classification and segregation of plastics before their disposal and following the three R’s are essential steps to reduce microplastic entry into water bodies. Although there is work being carried out for microplastic degradation our prime aim should be to reduce the number of plastics that we use so that the new methods developed can help reduce the microplastic pollution at a faster rate.
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