Microbial Polyethylene Terephthalate Hydrolases: Current and Future Perspectives

Abstract

Plastic has rapidly transformed our world, with many aspects of human life now relying on a variety of plastic materials. Biological plastic degradation, which employs microorganisms and their degradative enzymes, has emerged as one way to address the unforeseen consequences of the waste streams that have resulted from mass plastic production. The focus of this review is microbial hydrolase enzymes which have been found to act on polyethylene terephthalate (PET) plastic. The best characterized examples are discussed together with the use of genomic and protein engineering technologies to obtain PET hydrolase enzymes for different applications. In addition, the obstacles which are currently limiting the development of efficient PET bioprocessing are presented. By continuing to study the possible mechanisms and the structural elements of key enzymes involved in microbial PET hydrolysis, and by assessing the ability of PET hydrolase enzymes to work under practical conditions, this research will help inform large-scale waste management operations. Finally, the contribution of microbial PET hydrolases in creating a potential circular PET economy will be explored. This review combines the current knowledge on enzymatic PET processing with proposed strategies for optimization and use, to help clarify the next steps in addressing pollution by PET and other plastics.

Structural basis of terephthalate recognition by solute binding protein TphC

“…The presence of 2,5-pyridinedicarboxylate (2) and 2,6-naphthalenedicarboxylate (22) have less pronounced, but still signi cant, stabilising interactions with TphC, displaying ΔT m s of 1.4 ± 1.1°C and 1.4 ± 0.7°C, respectively. The other para-substituted dicarboxylate analogues (3,(5)(6)(8)(9)(10)(11) regioisomers (12)(13), hetero-aromatics (14)(15)(16)(17)(18)(19), bicyclic aromatics (20,23), the mono-carboxylate and carboxylate isosteres , unsaturated phenylpropanoates (45)(46)(47)(48)(49)(50), phenols (51)(52), aromatic esters (53)(54)(55)(56) and aliphatic dicarboxylates (57-61) had either negligible effect on ΔT m s or their interactions with TphC were found to be slightly destabilising under the assay conditions. This indicates that for optimal interaction a six-membered para-substituted aromatic dicarboxylate is required, that limited additional substitution with hydroxyl groups around the ring and minor heteroaromatic modi cations are tolerated, and that extended aromatic systems are partially tolerated.…”

“…Therefore, there is great interest in nding better strategies for PET bioconversion and recycling through engineering robust enzymes and microbial strains for its degradation, uptake and assimilation. Terephthalic acid (TPA) and ethylene glycol (EG), which together form a polymer chain, are the basic building blocks of PET and can be released by enzymatic hydrolysis via the action of different types of bacterial and fungal origin hydrolases, such as esterases, lipases, cutinases and carboxylesterases [17][18][19][20][21][22][23][24] . A bacterial strain, Ideonella sakaiensis was discovered that secreted two enzymes PETase, and MHETase which enable the microbe to grow on PET as a sole carbon source 25 .…”

<em> </em>Current Research on Microbe-Plastic Interactions in the Marine Environment

“…(i) use multi-OMIC and interdisciplinary approaches to understand the role of the plastisphere in plastic biodegradation as well as in determining the mechanisms and pathways used for biodegradation 19,151,157,161,164,170,172,175,178,180,181,183,184,188,189,191,194,196,[198][199][200][204][205][206][207] ;…”

Engineering Microbes to Bio-Upcycle Polyethylene Terephthalate

“…The discovery of the bacterium Ideonella sakaiensis harboring hydrolyzing enzymes PETase and MHETase has revolutionized the field. These enzymes can completely degrade the synthetic polymer PET to its monomers TPA and EG at ambient temperature (Yoshida et al, 2016;Carr et al, 2020). Employing biological catalysis for commercial PET depolymerization is challenging due to the limited accessibility of polymer's high crystalline ester linkages.…”