Biocorrosion of Synthetic Plastics: Degradation Mechanisms and Methods of Protection
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Biocorrosion of Synthetic Plastics: Degradation Mechanisms and Methods of Protection V. K. Plakunova, A. V. Gannesena, S. V. Mart’yanova, and M. V. Zhurinaa, * a
Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071 Russia *e-mail: [email protected] Received June 17, 2020; revised June 22, 2020; accepted July 29, 2020
Abstract—The mechanisms of microbial action on synthetic plastics are analyzed, with the focus on the most widespread polymers produced on an industrial scale. The effect of microbial enzymes on plastic biodegradation and the role of multispecies biofilms in biocorrosion are considered. The main approaches for protection of synthetic plastics from microbially caused damage are discussed. Keywords: synthetic plastics, biocorrosion, microbial enzymes, multispecies biofilms, plastic protection from biological damage 10.1134/S0026261720060144
INTRODUCTION The constantly increasing industrial production of synthetic polymer materials (plastics) leads to largescale environmental pollution with their waste, which threatens to become catastrophic. The goal of this review is to present up-to-date information from recent research concerning the problems related to biocorrosion of synthetic plastics. The ubiquitous use of plastics in technical and household applications makes it hardly possible to implement a universal system of plastic waste collection and recycling. As a result, there arise two seemingly different but in fact closely related problems: first, prolonging the operational life of plastic technical items by preventing their corrosion, including microbial biocorrosion, and second, accelerating the biodegradation of plastic waste accumulating after these items come out of use. The first problem can be solved by introducing stabilizing and biocide additives into the polymer, while the second one requires additives that facilitate degradation of plastics exposed to physicochemical environmental factors and make them accessible to microbial consumers. Although the principal focus of our review will be on the first problem (which will be mainly considered on examples of widely employed plastics), we also feel it necessary to discuss briefly the methods of increasing accessibility of synthetic plastics for microbial degradation. Production of so-called bioplastics based on biological polymers (e.g., starch, cellulose, chitin,
alginate, polyhydroxyalkanoates) or monomers (e.g., lactic acid as a source of polylactide) is a separate large issue of critical importance, which, however, lies beyond the scope of this work; it has been comprehensively discussed in recent reviews (Roohi et al., 2017; Iram et al., 2019) and in a monograph by Ciardelli et al. (2019). Degradability and bioavailability of plastics can be improved using two principal approaches. The first one does not directly involve microorganisms but relies on physicochemical procedures, e.g., exposure to elevated temperatures or UV radiation, as well as incorporation of additives t
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