Functional expression of polyethylene terephthalate-degrading enzyme (PETase) in green microalgae

Abstract

Background For decades, plastic has been a valuable global product due to its convenience and low price. For example, polyethylene terephthalate (PET) was one of the most popular materials for disposable bottles due to its beneficial properties, namely impact resistance, high clarity, and light weight. Increasing demand of plastic resulted in indiscriminate disposal by consumers, causing severe accumulation of plastic wastes. Because of this, scientists have made great efforts to find a way to biologically treat plastic wastes. As a result, a novel plastic degradation enzyme, PETase, which can hydrolyze PET, was discovered in Ideonella sakaiensis 201-F6 in 2016. Results A green algae, Chlamydomonas reinhardtii, which produces PETase, was developed for this study. Two representative strains (C. reinhardtii CC-124 and CC-503) were examined, and we found that CC-124 could express PETase well. To verify the catalytic activity of PETase produced by C. reinhardtii, cell lysate of the transformant and PET samples were co-incubated at 30 °C for up to 4 weeks. After incubation, terephthalic acid (TPA), i.e. the fully-degraded form of PET, was detected by high performance liquid chromatography analysis. Additionally, morphological changes, such as holes and dents on the surface of PET film, were observed using scanning electron microscopy. Conclusions A PET hydrolyzing enzyme, PETase, was successfully expressed in C. reinhardtii, and its catalytic activity was demonstrated. To the best of our knowledge, this is the first case of PETase expression in green algae.

A Critical Review on the Impacts of Nanoplastics and Microplastics on Aquatic and Terrestrial Photosynthetic Organisms

“…On the other hand, some author used genetically modified microalgae to produce PETase. For instance, a lysate of modified C. reinhardtii incubating at 30°C for 4 weeks led to the apparition of dents and holes on a PET film and the detection of terephtalic acid (TPA) which is the fully degraded form of PET 86 . The same was also achieved by using Phaeodactylum tricornutum (diatoms) cells in growing medium under more environmentally relevant conditions 87 .…”

Perspectives on the Role of Enzymatic Biocatalysis for the Degradation of Plastic PET

“…Inspired by the advantages of using microalgae for expression and production of plastic degrading enzymes, Moog et al [ 87 ] employed P. tricornutum for Is PETase production and Kim et al [ 88 ] used C. reinhardtii microalgae. In both studies, Is PETase activity with morphological changes on PET substrate and production of PET degradation metabolites such as TPA was observed.…”

“…In both studies, Is PETase activity with morphological changes on PET substrate and production of PET degradation metabolites such as TPA was observed. These studies suggest that using microalgae for Is PETase expression and introduction in the environment is an attractive and promising strategy, especially given the natural characteristics of microalgae—their abundance and low maintenance growth in natural aqueous systems with no endotoxin production [ 88 ].…”

Development of a Biocontained Toluene-Degrading Bacterium for Environmental Protection

“…Advances in synthetic biology have prompted the use of genetically engineered microorganisms (GEMs) as versatile agents for biomedical, industrial, and environmental applications ( 1 – 3 ). Regarding environmental applications, GEMs can be used for sensing and eliminating environmental pollutants, such as organic xenobiotics, robust polymers, and toxic metals ( 4 – 6 ). However, the risks of GEM release into the environment have been debated because the spread and proliferation of GEMs may adversely affect the ecosystem.…”