Today, more than 250,000 tons of plastic waste floats in the waters of the world's oceans. The Pacific Ocean is estimated to be the most polluted body of water in the Northern Hemisphere, while in the Southern Hemisphere the Indian Ocean is dirtier than the Pacific and Atlantic combined. In doing so, the Pacific Ocean is described as the most plastic-polluted ocean on Earth. Plastic pollution travels throughout the world's oceans under the influence of prevailing winds and currents. This has been shown for the northern hemisphere, where long-term, multi-year transport of water and thus waste leads to the accumulation of plastic debris in the center of ocean basins,. Similar patterns have been established for all the oceans in the southern hemisphere. Surprisingly, the total amount of plastic determined for the southern hemisphere oceans is in the same quantitative range as for the northern hemisphere oceans, which is unexpected, given that the northern hemisphere has significantly more sources of plastic than the southern hemisphere. This means that plastics move and redistribute more easily between ocean currents and between hemispheres than previously thought.

However, the ultimate fate of floating microplastics is not on the ocean surface. Observations that there is far less microplastics on the sea surface than would be expected suggest that there are some processes in place to remove plastic waste from the water surface. However, the ultimate fate of floating microplastics is not on the ocean surface. Observations that there is far less microplastics on the sea surface than would be expected suggest that there are some processes in place to remove plastic waste from the water surface. These include ultraviolet degradation, biodegradation, ingestion by organisms, reduction in buoyancy due to fouling by organisms and settling to the bottom, and release to shore.

Plastic waste can be degraded either by physical and chemical (abiotic) processes or by biodegradation (biotic). The degradation of polymeric material by physical forces of a mechanical nature is usually considered to be the first step, which plays a vital role in any degradation process. Environmental degradation of plastics can occur by one or a combination of four basic mechanisms: photodegradation, hydrolysis, thermal oxidative degradation and biodegradation. Under natural conditions (e.g. in the marine environment), degradation of conventional plastics such as HDPE, LDPE and PP starts with photodegradation (mainly by UV-B radiation) and continues with thermal oxidation and, to a lesser extent, degradation by water - hydrolysis.

A new study published by scientists at the Woods Hole Oceanographic Institution shows that polystyrene (PS), one of the world's most common plastics, can take decades or centuries to decompose when exposed to sunlight, not thousands of years as previously thought. Partial decomposition of polystyrene takes only 10-50 years, depending on the type of plastic. And its complete photochemical oxidation is possible in 300-450 years. Sunlight causes not only the physical destruction of plastics, but also their chemical decomposition into dissolved organic carbon and a small amount of carbon dioxide that enters the atmosphere.

Degradation processes lead to the fragmentation of plastics as they break into smaller pieces and to a decrease in the molecular weight of the polymers. These low molecular weight substances can then be metabolized by microbes. In any case, the entire process is usually so slow that it can take more than 50 years for other organisms to completely degrade plastic polymers.

Many complex natural and synthetic compounds are biodegraded by microbial consortia rather than by individual strains, which is probably due to the limited metabolic capabilities of individual organisms. Therefore, it can be assumed that plastic waste, as one of the major environmental problems faced by modern society, may be more efficiently biodegraded by the association of different groups of organisms. Biodegradation of plastics refers mainly to the conversion of polymeric materials into biogas and biomass in the absence of air by anaerobic microorganisms,,, which can effectively use polymers as a source of carbon for their growth. However, the very nature of plastics, as well as their special physical and chemical properties, prevent their biodegradation, making them a weak substrate for growth.

Biodegradation of plastic waste begins with the enzymatic cleavage of the polymer chain into compounds with low molecular weight, such as oligomers, dimers and monomers, which occurs by binding the enzyme to the polymer and catalyzing (accelerating) its hydrolytic cleavage. The process ends with the conversion of these low molecular weight compounds into carbon dioxide and water. Bacteria, fungi and algae are reported to be effective organisms capable of degrading plastic polymers.

Fungi play a key role in the degradation of polymeric materials. The mycelium of a fungus can effectively penetrate its surface deep into its mass to degrade the maximum amount of this substrate. In addition, the fungus mycelium can secrete extracellular enzymes (e.g., depolymerases) and decompose the polymeric substrate into oligomers, dimers, and monomers, that is, fragments with a low molecular weight,. These monomers are then absorbed by the fungi and either assimilated or converted into carbon dioxide and water by their intracellular enzymatic system. From this point of view, white and brown rot fungi are often cited as effective degraders of polymeric plastics.

Similarly, bacterial strains can degrade plastic polymers in contaminated water or soil. A number of studies have reported that biodegradation of plastic by specialized bacteria may be a promising bioremediation strategy for contaminated ecosystems. Bacterial strains such as Pseudomonas spp., Bacillus spp. and Streptomyces spp. show high efficiency in degrading various plastic polymers,. In any case, the rate of degradation of plastics by fungi is higher than that achieved by individual bacterial strains. But on the other hand, some authors report that bacteria are easier to grow and degrade polymeric materials using them than fungi, which require more stable conditions.

Only a few studies to date have reported on the ability of algal species to mitigate plastic waste pollution. This observation concerned the ability of filamentous algae to colonize the surface of plastic waste due to the presence of environmental factors such as sunlight, nutrients and water, which are vital for algae growth,. Several non-hazardous and non-toxic species of algae from Bacillariophyceae, Chlorophyceae and Cyanophyceae were found to be able to grow on polyethylene surfaces and form algal biofilms in various polluted water bodies such as ponds, lakes and wastewater. In this regard, the authors report that the simply isolated and fast-growing Phormidium lucidum and Oscillatoria subbrevis (freshwater non-toxic cyanobacteria) can form colonies on PE surfaces and effectively degrade HDPE without pretreatment.

Moreover, some species of bacteria and fungi, such as Ideonella sakaiensis and Pestalotiopsis microspore, used to produce the PETase enzyme are poorly adapted to the marine environment where most plastic waste accumulates. The diatom alga Phaeodactylum tricornutum has been shown to be successful as a microbial factory for producing the developed PETase, which has activity against PET and co-polymer PETG (polyethylene terephthalate glycol-modified).

And several invertebrates, such as the superworm Zophobas atratus, Indian fly moth Plodia interpunctella, large wax moth Galleria mellonella, larvae of the mealworm Tenebrio molitor, small wax moth Achroia grisella, land snails (Achatina fulica), termites and other invertebrates have confirmed polymer biodegradation. This outstanding activity in the decomposition of plastic polymers is usually attributed to their intestinal microbial symbionts,, since it is with their participation that certain invertebrate species have the ability to feed on wood or other polymeric compounds.

Plastics have found widespread use because of their unique properties and are therefore considered one of the most essential materials in our lives. However, the harmful effects of plastic waste are proportional to their use and accumulation in the environment. Accordingly, the characteristics of plastic materials are a real challenge for microbes to decompose or even colonize on their surface. The involvement of several microorganisms and invertebrates in the biodegradation of plastic has been noted by many researchers, indicating their fundamental role in the biodegradation of the material.

With this in mind, expert scientists emphasize the role and importance of plastic waste pretreatment (physical and/or chemical) as a first and important step, which is often a prerequisite for the microbial degradation of plastic polymers. Microorganisms, algae, plastic-eating insects, and other invertebrate species may play an important role in the biodegradation of plastic in the future. Research suggests the creation of an environmentally friendly, efficient and inexpensive technology for recycling and decomposing plastic waste in order to overcome the accumulation of plastic waste in the environment.

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