Degradation of plastics and plastic-degrading bacteria in cold marine habitats

Applied Microbiology and Biotechnology (2018) 102:7669–7678 https://doi.org/10.1007/s00253-018-9195-y MINI-REVIEW Degradation of plastics and plastic-degrading bacteria in cold marine habitats Aneta K. Urbanek 1 & Waldemar Rymowicz 1 & Aleksandra M. Mirończuk 1 Received: 28 February 2018 / Revised: 18 June 2018 / Accepted: 26 June 2018 / Published online: 11 July 2018 # The Author(s) 2018 Abstract Synthetic plastics present in everyday materials constitute the main anthropogenic debris entering the Earth’s oceans. The oceans provide important and valuable resources such as food, energy, and water. They are also the main way of international trade and the main stabilizer of the climate. Hence, changes in the marine ecosystem caused by anthropogenic influences such as plastic pollution can have a dramatic impact on a global scale. Although the problem of plastics still remains unsolved, different ways are being considered to reduce their impact on the environment. One of them is to use microorganisms capable of degradation of plastic. A particularly interesting area is the application of microorganisms isolated from cold regions in view of their unique characteristics. Nevertheless, the interactions between plastic and microorganisms are still poorly known. Here, we present a review of current knowledge on plastic degradation and plastic-microorganism interactions in cold marine habitats. Moreover, we highlight the advantages of microorganisms isolated from this environment for eliminating plastic waste from ecosystems. Keywords Plastic wastes . Biofilm . Microorganisms . Cold marine environment . Biodegradation Introduction Synthetic plastic production is one of the fastest growing fields of global industry. Despite the fact that plastics have been used in daily life for 100 years, the beginning of largescale production dates back to 1950 (Geyer et al. 2017). The numerous properties that make plastics superior to other materials in many applications have led to a 20-fold increase in the scale of plastic production over the five decades since 1964 (Ellen MacArthur Foundation 2016), exceeding 300 million tons per year (PlasticsEurope 2015) and reaching 335 million tons in 2015 (PlasticsEurope 2017). Furthermore, it is foreseen that production of plastics will double over the next 20 years and almost quadruple by 2050 (Ellen MacArthur Foundation 2016). About 80% of the total global plastic usage constitutes petrochemical plastic, such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) * Aleksandra M. Mirończuk 1 Department of Biotechnology and Food Microbiology, Wroclaw University of Environmental and Life Sciences, Chełmońskiego 37, 51-630 Wrocław, Poland (Fig. 1). Although plastic materials constitute an integral part of the global economy, the issues associated with their extensive application cannot be ignored. Accumulation of plastic litter occurs in the marine environment mostly, where it is hard to find any area that is unaffected by human influence (Halpern et al. 2008). Worldwide accumulation of plastic on the surface of the open ocean is frequently found in the convergence zones of each of the five subtropical gyres (Cózar et al. 2014). However, plastic debris has been found in high concentrations (hundreds of thousands of pieces per square kilometer) of the Greenland and Barents seas (Cózar et al. 2017). Also, in the Antarctic marine system (Southern Ocean), plastic debris has been found on the surface and in deep-sea sediments. In these regions, mainly microplastics (< 5 mm) and mesoplastics (< 5 cm) have been found (Waller et al. 2017). It was estimated that every year, 10 to 20 million tons of plastics leak into the oceans (UNEP 2014). Since 2015, approximately 6300 million tons of plastic waste have been generated (Geyer et al. 2017), of which a significant percentage has found its way to the environment as a result of uncontrolled dumping of wastes. The main limitation of conventional petroleum-based plastics is the fact that they fragmented under abiotic factors (UV radiation, temperature, physical stress) in a long time, and they cannot be completely decomposed and assimilated by microorganisms (biotic 7670 Fig. 1 Structures of the common plastics Appl Microbiol Biotechnol (2018) 102:7669–7678 Appl Microbiol Biotechnol (2018) 102:7669–7678 factors) in a biodegradation process. Crucial characteristics responsible for plastics’ resistance to biodegradation include a long-chain polymer structure, a high molecular weight (MW), lack of a favorable functional group, hydrophobicity, and crystallinity (Wilkes and Aristilde 2017). A high MW is a crucial obstacle, because large compounds cannot be transported across the cellular membrane of microorganisms. Thus, long-chain polymers have to be first depolymerized to smaller monomers before they can cross the cell membrane (Shah et al., 2008). Next, monomers can pass through the cell membrane, followed by assimilation by intracellular metabolism (Kolvenbach et al. 2014). Due to the fact that most petrochemical plastics are not biodegradable, new biodegradable plastics (BPs) have been developed and some of them have already been introduced to the market. Nowadays, there are many products available (bottles, packages) that are made from biodegradable plastics such as poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBS), or poly(butylene succinate-co-butylene adipate) (PBSA) (Fig. 1). Biodegradable plastics, which may be classified as being either bio-based or petrochemical-based (Song et al. 2009), can be degraded in an eco-friendly way by microorganisms, resulting in the fragmentation of material via microbial enzymatic activities and bond cleavage (Pathak and Navneet 2017). Plastic wastes might be dangerous for the natural environment due to accumulation in the rivers and oceans, where the formation of plastic islands (e.g., the Great Pacific Garbage Patch) is confirmed (Eriksen et al. 2014, Lebreton et al., 2018). Moreover, as the result of abiotic degradation of conventional plastic caused by UV radiation, oxygen, temperature, and physical stress (Geweret et al. 2015), slowly degrading large plastic items generate microplastic particles which can spread over long distances by wind-driven ocean surface layer circulation (Thevenon et al. 2014). Thus, places located far away from pollution sources are affected by plastic wastes. There is also a concern that plastic is a source of toxic chemicals such as polychlorinated biphenyls or phthalates and bisphenol A (Bryant et al. 2016). These contaminations have also a significant influence on marine fauna due to entanglement, suffocation, and disruption of digestion in birds, fish, mammals, and turtles (Derraik 2002). According to research of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, 1506 species are affected by the litter (...truncated)