Search

Biodegradation, particularly via enzymatic degradation, has emerged as an efficient and eco-friendly solution for Poly (ethylene terephthalate) (PET) pollution. The production of PET hydrolases plays a role in the large-scale enzymatic degradation. However, an effective variant, 4Mz, derived from Thermobifida fusca cutinase (Tfu_0883), was previously associated with a significant reduction in yield when compared to the wild-type enzyme. In this study, a novel cell membrane protection strategy was developed to enhance the yield of 4Mz. This approach increased the yield of 4Mz by 18.2-fold from shaken flasks to 3-L bioreactors, reaching a yield of 3.1 g·L -1 , the highest yield of a PET hydrolase described thus far. In addition, the raw culture broth from 4Mz was applied directly for the enzymatic degradation of PET bottles, achieving a 91.2 % degradation rate. These advancements render the large-scale enzymatic degradation of PET more feasible, thus contributing to the more sustainable management of plastic waste., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Poly(ethylene terephthalate) (PET) is a widely used plastic, but its improper disposal has caused serious environmental pollution. The development of bioconversion for PET waste into high-value chemicals has gained significant attention as an innovative solution. In this study, a novel guided screening strategy involving mixed-bacteria fermentation and partitioned purification (MBF) was proposed to first successful isolate Rhodococcus jostii LETBE 8896, a strain capable of naturally producing 4 μg/L of lycopene from PET hydrolysate. Transcriptomic analysis identified the methylerythritol 4-phosphate (MEP) pathway as key to lycopene biosynthesis, with IspG identified as a critical regulatory enzyme. R. jostii with ispG overexpression enhanced lycopene production, with 819 μg/L in the simulated PET hydrolysate and 650 μg/L in the PET hydrolysate. Additionally, the use of butylated hydroxytoluene (BHT) as an antioxidant significantly improved lycopene production at 1 L scale level, achieving a maximum yield of 1865 μg/L with a molar conversion rate of 50.36 % from the PET hydrolysate, the highest reported for PET hydrolysate to date. These findings highlight the dual potential of R. jostii as a chassis strain for high-value chemical production and as a sustainable solution for PET upcycling. This study provides a novel approach to plastic waste management, contributing to the circular economy and global sustainability goals., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Polyethylene terephthalate (PET) waste presents a significant environmental challenge due to its durability and resistance to degradation. Innovative approaches for upcycling PET waste into high-value chemicals can mitigate these issues while contributing to a circular economy. In this study, we developed a multi-enzyme cascade system in E. coli to convert PET-derived monomer terephthalic acid (TPA) into vanillin (VAN). The metabolic engineering approach was then employed to increase VAN production, including 1) inhibition of VAN degradation by knocking out endogenous aldehyde reductases and alcohol dehydrogenases and 2) enhancement of TPA uptake by modifying membrane proteins to increase cell permeability. The engineered E. coli demonstrated a VAN production of 658.55 mg/L from 1992 mg/L of TPA with a molar conversion rate of 71.1 %, representing the highest production of VAN using TPA as the substrate. Additionally, the engineered E. coli effectively converted post-consumer PET waste into VAN under mild conditions, with the highest production of 259.2 mg/L in 20× diluted PET hydrolysates, highlighting its potential for application in PET waste upcycling. This approach not only provides an environmentally friendly alternative to traditional chemical synthesis but also offers substantial economic benefits by transforming low-value waste into high-value chemicals., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Polyethylene terephthalate (PET) microplastics pose significant environmental and human health risks due to their resistance to degradation and accumulation in ecosystems. In this study, we engineered Stenotrophomonas pavanii JWG-G1, a robust biofilm-forming bacterium, to overexpress the PET hydrolase (DuraPETase) for PET microplastics degradation at ambient temperature. Nine endogenous PET hydrolases were identified through genome sequencing of S. pavanii, and were successfully expressed in Escherichia coli BL21(DE3). Among them, hydrolase Est_B achieved 100% degradation of bis(2-hydroxyethyl) terephthalate (BHET) at an initial concentration of 0.23 mg/mL at 30 °C within 4 h, identifying it as a novel BHETase. However, the PET degradation performance of all endogenous PET hydrolases was inferior to that of DuraPETase. The engineered strain overexpressing DuraPETase demonstrated a significant enhancement in PET degradation, achieving a 38.04 μM total product release of high-crystallinity PET microplastics after 30 days at 30 °C. The degradation extent was greater than that of low biofilm-forming engineered strains, attributing to the aggregation of DuraPETase on the PET surface in the presence of biofilm. Additionally, this engineered strain also maintained PET degradation activity across various water environments and demonstrated effectiveness in degrading other polyester plastics. This is the first report demonstrating that an engineered strain of Stenotrophomonas species is capable of simultaneously secreting exogenous hydrolase and degrading polyester microplastics, representing a novel approach in the development of engineered bacteria with potential applications in bioreactor systems and environmental remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Polyethylene terephthalate (PET) is one of the most widely used plastics, but its fragmentation into microplastics poses significant environmental challenges. The recycling of PET microplastics is hindered by their low solubility and widespread dispersion in the environment, making microbial in-situ degradation a promising solution. However, existing PET-degrading strains exhibited the limited effectiveness, primarily due to the diffusion of secreted hydrolases away from the PET surface. In this study, Stenotrophomonas pavanii JWG-G1 was engineered to achieve the targeted aggregation of PET hydrolase PETase on the cell surface by fusing it with an endogenous anchor protein. This approach aims to maximise the local concentration of PETase around PET, thereby increasing the overall rate of PET degradation. The PETase surface-aggregated system, S. pavanii/PaL-PETase, demonstrated the highest degradation efficiency, achieving 63.3 % degradation of low-crystallinity PET (lcPET) and 27.3 % degradation of high-crystallinity PET bottles (hcPET) at 30 °C. This represents the highest degradation rate reported for a displayed whole-cell system at ambient temperature. Furthermore, this system exhibited broad-spectrum degradation activity against various polyesters. These findings suggest that this system offers a promising, eco-friendly solution to PET and other polyester pollution, with potential implications for environmental bioremediation strategies., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The rising accumulation of poly(ethylene terephthalate) (PET) waste presents an urgent ecological challenge, necessitating an efficient and economical treatment technology. Here, we developed chemical-biological module clusters that perform chemical pretreatment, enzymatic degradation, and microbial assimilation for the large-scale treatment of PET waste. This module cluster included (i) a chemical pretreatment that involves incorporating polycaprolactone (PCL) at a weight ratio of 2% (PET:PCL = 98:2) into PET via mechanical blending, which effectively reduces the crystallinity and enhances degradation; (ii) enzymatic degradation using Thermobifida fusca cutinase variant (4Mz), that achieves complete degradation of pretreated PET at 300 g/L PET, with an enzymatic loading of 1 mg protein per gram of PET; and (iii) microbial assimilation, where Rhodococcus jostii RHA1 metabolizes the degradation products, assimilating each monomer at a rate above 90%. A comparative life cycle assessment demonstrated that the carbon emissions from our module clusters (0.25 kg CO 2 -eq/kg PET) are lower than those from other established approaches. This study pioneers a closed-loop system that seamlessly incorporates pretreatment, degradation, and assimilation processes, thus mitigating the environmental impacts of PET waste and propelling the development of a circular PET economy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Enzymatic degradation has been proposed as a suitable solution for addressing PET pollution, but approximately 10 % of PET is left as nonbiodegradable. Microbes can completely degrade PET at the gram level per year. Based on the complementary benefits of microbes and enzymes, a microbe-enzyme system was created to completely degrade PET. Here, a thermophilic microbe-enzyme (TME) system composed of Bacillus thermoamylovorans JQ3 and leaf-branch compost cutinase variant (ICCG) was used to demonstrate the synergistic degradation of PET, enabling 100 % degradation of PET waste at a high PET loading level (360 g/L). Six endogenous PET hydrolases of strain JQ3 were discovered by employing an ester bond hydrolysis function-first genome mining (EGM) strategy and first successfully expressed in E. coli. These hydrolases could release TPA as the final product from PET and preferentially degraded BHET instead of MHET. Of these, carboxylesterase 39_5 and ICCG could degrade PET in a synergistic manner to generate 50 μM of TPA, which was greater than the sum of the individual treatments. Finally, the degradation pathway of the TME system was speculated to include biofilm formation, PET degradation and utilization. The successful implementation of this study rendered a scale-up degradation feasible of PET at a lower cost., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Polyethylene terephthalate (PET) is a general plastic that produces a significant amount of waste due to its non-biodagradable properties. We obtained four bacteria (Stenotrophomonas pavanii JWG-G1, Comamonas thiooxydans CG-1, Comamonas koreensis CG-2 and Fulvimonas soli GM-1) that utilize PET as a sole carbon source through a novel stepwise screening and verification strategy. PET films pretreated with S. pavanii JWG-G1 exhibited weight loss of 91.4% following subsequent degradation by Thermobifida fusca cutinase (TfC). S. pavanii JWG-G1 was able to colonize the PET surface and maintain high cell viability (over 50%) in biofilm, accelerating PET degradation. Compared with PET films with no pretreatment, pretreatment with S. pavanii JWG-G1 caused the PET surface to be significantly rougher with greater hydrophilicity (contact angle of 86.3 ± 2° vs. 96.6 ± 2°), providing better opportunities for TfC to contact and act on PET. Our study indicates that S. pavanii JWG-G1 could be used as a novel pretreatment for efficiently accelerating PET biodegradation by TfC., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Poly(ethylene terephthalate) (PET) is a major source of plastic pollution. Biodegradation technologies are of paramount interest in reducing or recycling PET waste. In particular, a synergistic microbe-enzyme treatment may prove to be a promising approach. In this study, a synergistic system composed of Microbacterium oleivorans JWG-G2 and Thermobifida fusca cutinase (referred to as TfC) was employed to degrade bis(hydroxyethyl) terephthalate (BHET) oligomers and a high crystalline PET film. A novel degradation product that was obtained by M. oleivorans JWG-G2 treatment alone was identified as ethylene glycol terephthalate (EGT). With the addition of TfC as a second biocatalyst, the highest synergy degrees for BHET oligomers and PET film degradation were 2.79 and 2.26, respectively. The largest amounts of terephthalic acid (TPA) and mono(2-hydroxyethyl) terephthalate (MHET) (47 nM and 330 nM, respectively) were detected after combined treatment of PET film with M. oleivorans JWG-G2 at 5 × 10 3 μL/cm 2 and TfC at 120 μg/cm 2 , and the degree of PET film surface destruction was more significant than those produced by each treatment alone. The presence of extracellular PET hydrolases in M. oleivorans JWG-G2, including three carboxylesterases, an esterase and a lipase, was predicted by whole genome sequencing analysis, and a predicted PET degradation pathway was proposed for the synergistic microbe-enzyme treatment. The results indicated that synergistic microbe-enzyme treatment may serve as a potentially promising tool for the future development of effective PET degradation. KEY POINTS: • An ecofriendly synergistic microbe-enzyme PET degradation system operating at room temperature was first introduced for degrading PET. • A novel product (EGT) was first identified during PET degradation. • Potential PET hydrolases in M. oleivorans JWG-G2 were predicted by whole genome sequencing analysis.