Potential Use of Microbial Enzymes for the Conversion of Plastic Waste Into Value-Added Products: A Viable Solution

Muhammad Tamoor; Nadia A Samak; Yunpu Jia; Muhammad Umar Mushtaq; Hassan Sher; Maryam Bibi; Jianmin Xing

doi:10.3389/fmicb.2021.777727

Potential Use of Microbial Enzymes for the Conversion of Plastic Waste Into Value-Added Products: A Viable Solution

Front Microbiol. 2021 Nov 30:12:777727. doi: 10.3389/fmicb.2021.777727. eCollection 2021.

Authors

Muhammad Tamoor^{1

2}, Nadia A Samak^{1

3}, Yunpu Jia^{1

2}, Muhammad Umar Mushtaq^{1

2

4}, Hassan Sher^{1

2}, Maryam Bibi⁴, Jianmin Xing^{1

2

5}

Affiliations

¹ CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
² College of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, China.
³ Biofilm Centre, Aquatic Microbiology Department, Faculty of Chemistry, University Duisburg-Essen, Essen, Germany.
⁴ Department of Chemical Engineering, Wah Engineering College, University of Wah, Wah Cantt, Pakistan.
⁵ Chemistry and Chemical Engineering Guangdong Laboratory, Shantou, China.

Abstract

The widespread use of commercial polymers composed of a mixture of polylactic acid and polyethene terephthalate (PLA-PET) in bottles and other packaging materials has caused a massive environmental crisis. The valorization of these contaminants via cost-effective technologies is urgently needed to achieve a circular economy. The enzymatic hydrolysis of PLA-PET contaminants plays a vital role in environmentally friendly strategies for plastic waste recycling and degradation. In this review, the potential roles of microbial enzymes for solving this critical problem are highlighted. Various enzymes involved in PLA-PET recycling and bioconversion, such as PETase and MHETase produced by Ideonella sakaiensis; esterases produced by Bacillus and Nocardia; lipases produced by Thermomyces lanuginosus, Candida antarctica, Triticum aestivum, and Burkholderia spp.; and leaf-branch compost cutinases are critically discussed. Strategies for the utilization of PLA-PET's carbon content as C1 building blocks were investigated for the production of new plastic monomers and different value-added products, such as cyclic acetals, 1,3-propanediol, and vanillin. The bioconversion of PET-PLA degradation monomers to polyhydroxyalkanoate biopolymers by Pseudomonas and Halomonas strains was addressed in detail. Different solutions to the production of biodegradable plastics from food waste, agricultural residues, and polyhydroxybutyrate (PHB)-accumulating bacteria were discussed. Fuel oil production via PLA-PET thermal pyrolysis and possible hybrid integration techniques for the incorporation of thermostable plastic degradation enzymes for the conversion into fuel oil is explained in detail.

Keywords: PLA-PET waste; bioconversion; circular economy; fuel oil; polyhydroxyalkanoates.

Publication types

Review