Engineering environmental bacteria for whole-cell PET hydrolysis and assimilation.

Enzymatic degradation of plastic and optimization of microbial system for the production of its degrading enzymes

This study outlines existing metabolic engineering techniques for bio-upcycling PET into high-value compounds, as well as a number of engineering approaches intended to improve the performance of PET-degrading enzymes. One of the most popular aromatic polyesters in the world, polyethylene terephthalate (PET) has an annual demand of over 29 million metric tons in 2022 and is expected to rise by 40% by 2030. Due to the growing amount of PET waste and the existing insufficiency of recycling techniques, it has accumulated in terrestrial ecosystems, posing serious hazards to world health. These technologies seek to convert recovered PET into more valuable items in order to address energy issues as well as environmental sustainability. One potentially biosustainable technique for handling and recycling plastics is enzyme-mediated biocatalytic depolymerization. Protein engineering developments have been applied to modify and improve the many plastic-degrading enzymes that have been discovered from microbial sources. Additionally, microbial metabolic engineering makes it possible to create customized microbial chassis that can break down PET substrates and transform the resulting monomers into compounds that are useful for industry.

Isolation of Marine-Derived Microorganisms for PET Biodegradation

This study isolated 305 marine-derived microorganisms with potential PET-degrading capability from samples collected from mangrove areas of Zhanjiang and the intertidal zones of Daya Bay, Shenzhen, China, using PET powder as a major carbon source and reveals the genetic basis underlying PET degradation and associated metabolic pathways in strain SCSIO 85700.

A theoretical systems-biology framework for the degradation of mixed plastics and conversion into fertilizer-grade compounds via engineered microbial consortia

Plastic pollution is a global environmental challenge of increasing severity. Global plastic production reached approximately 413.8 million metric tonnes in 2023, yet global assessments, including those by Geyer et al., suggest that fewer than 10% of post-consumer plastics are effectively recycled. Here we present a theoretical Plastic-to-Fertilizer (P2F) framework that proposes an engineered four-member microbial consortium capable of partially depolymerizing mixed plastic waste, including polyethylene terephthalate (PET), high-density polyethylene (HDPE), polystyrene (PS), and polypropylene (PP), and channeling selected plastic-derived carbon intermediates toward biosynthesis of agronomically beneficial compounds, including organic acids, amino acids, and humic-like macromolecules (HLMs). The proposed consortium comprises an engineered Pseudomonas putida KT2440 chassis expressing heterologous PETase and MHETase [mono(2-hydroxyethyl) terephthalate hydrolase] for PET depolymerization and harboring a native styrene catabolic pathway for PS intermediates; Bacillus subtilis 168 providing CotA laccase-mediated polyolefin surface oxidation; Aspergillus niger serving as a biofilm scaffold and oxidative enzyme source; and a biocontained Azotobacter vinelandii strain with a conditionally active, speculative nitrogen-fixation module. A theoretical mathematical framework encompassing Langmuir-adsorption-based surface degradation kinetics, substrate-specific Haldane-Andrews growth models, and enzyme synergy quantification is presented alongside a corrected stoichiometric mass balance for the P2F metabolic funnel. Techno-economic projections are presented as illustrative scenarios only, given the current technology readiness level (TRL 1–2). Key biological constraints are explicitly acknowledged throughout: HDPE and PP are highly crystalline polymers requiring mandatory abiotic pre-treatment before enzymatic action is feasible; PS depolymerization to metabolisable intermediates requires abiotic pre-treatment as no biological route has been demonstrated for bulk PS; heterologous nitrogen fixation is technically challenging and is framed as a speculative high-risk long-term aspiration rather than a functional module; and all stoichiometric yields are theoretical upper bounds. This paper provides a conceptual foundation, a corrected mathematical framework, and a five-phase experimental roadmap intended to guide empirical validation.

Ester bond pre-activation for high-efficiency biodegradation: A self-reinforcing degradation strategy for PET via an evolved bacterium.

Polyethylene terephthalate (PET) is a hazardous environmental contaminant that contributes to both plastic and microplastic pollution, with its biodegradation severely limited by the kinetic stability of ester bonds-particularly in alkaline industrial wastewater (pH 9-11) where most known biocatalysts are inactive. To overcome this, evolutionary engineering was employed to construct a whole-cell biocatalyst for alkaline environments. Through UV-LiCl mutagenesis and adaptive laboratory evolution, an alkaline-adapted Comamonas testosteroni strain F6 was developed, thriving at pH 10 with PET as sole carbon source. Strain F6 increased weight loss from 2.4% to 6.1% in 3 days and accelerated terephthalic acid release versus the wild-type under neutral conditions. This improvement arises from a synergistic mechanism: alkaline conditions chemically pre-activate ester bonds, and the released monomers fuel microbial growth and enzyme secretion, establishing a self-reinforcing degradation cycle. This feedback-driven process caused severe surface erosion, reducing fiber diameter from 20.2 to 18.1 μm. The system operates at mild pH 10 and 37 °C with a self-moderating effect that partially neutralizes alkalinity, contrasting with harsh chemical hydrolysis (pH >13, high temperature). This work provides a theoretical basis for using substrate pre-activation and evolved biocatalysis to treat PET-contaminated alkaline industrial effluents.

Screening for potent Polyethylene terephthalate (PET) degrading fungi: optimization of lipase production media and assessment of PET fabric waste degradation

Programmable biodegradation: Lipase-driven microplastic degradation via AI and omics.