Abstract
Polyethylene terephthalate (PET) is a mass-produced petroleum-based non-biodegradable plastic that contributes to the global plastic pollution. Recently, biocatalytic degradation has emerged as a viable recycling approach for PET waste, especially with thermophilic polyester hydrolases such as a cutinase (LCC) isolated from a leaf-branch compost metagenome and its variants. To improve the enzymatic PET hydrolysis performance, we fused a chitin-binding domain (ChBD) from Chitinolyticbacter meiyuanensis SYBC-H1 to the C-terminus of the previously reported LCCICCG variant, demonstrating higher adsorption to PET substrates and, as a result, improved degradation performance by up to 19.6% compared to with its precursor enzyme without the binding module. For compare hydrolysis with different binding module, the catalytic activity of LCCICCG-ChBD, LCCICCG-CBM, LCCICCG-PBM and LCCICCG-HFB4 were further investigated with PET substrates of various crystallinity and it showed measurable activity on high crystalline PET with 40% crystallinity. These results indicated that fusing a polymer-binding module to LCCICCG is a promising method stimulating the enzymatic hydrolysis of PET.
Highlights
Plastics are being used in an increasing number of applications in our society
The gene encoding LCCICCG cutinase, carbohydrate binding modules (CBM), polyhydroxyalkanoate binding modules (PBM) and HFB4 were synthesized based on previous studies (Ribitsch et al, 2013; Ribitsch et al, 2015; Tournier et al, 2020) and that for chitin-binding domain (ChBD) was derived from the genome of Chitinolyticbacter meiyuanensis SYBCH1 (Zhang et al, 2018)
An engineered cutinase (LCCICCG) (Tournier et al, 2020) previously published for Polyethylene terephthalate (PET) hydrolysis was fused with a C-terminal chitinbinding module from chitinase CmChi1 from Chitinolyticbacter meiyuanensis SYBCH1 (LCCICCG-ChBD)
Summary
Plastics are being used in an increasing number of applications in our society. Improperly disposed waste plastics have resulted in environmental pollution, which has garnered increasing attention in recent decades. Global plastics production has reached nearly 368 million tons in 2019 (PlasticsEurope, 2020). 70% of plastic waste is landfilled or discarded carelessly, 11% is incinerated, and only 19% is recycled (Kaza et al, 2018). PET has been widely used in the production of beverage bottles and synthetic fibers because of its excellent mechanical and thermal properties (Wei and Zimmermann, 2017; Kawai et al, 2019; Chen et al, 2020). Chemical and mechanical recycling of PET involve harsh chemicals and energy-intensive physicochemical treatments (Ragaert et al, 2017). Enzymatic hydrolysis under mild reaction conditions has recently been recognized as an eco-friendly
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