Hydrolysis Of Polyethylene Terephthalate Research Articles

Facile Recycling Strategy of Dyed Polyester Waste by Template-Based Synthesis of UiO-66 for Value-Added Transformation into Self-detoxifying Fabrics.

Polyethylene terephthalate (PET) accounts for a significant portion of textile waste, and recycling strategies for this material have attracted much attention. This study proposes a facile and innovative PET recycling method applicable to environmental remediation that involves the conversion of dyed PET fabric waste into a value-added fabric. Herein, a template-based synthesis approach capable of growing a UiO-66 metal-organic framework (MOF) directly on a dyed PET fabric is reported. The advantage of this process lies in its simplicity, where the partial hydrolysis of PET followed by a zirconium chloride treatment results in the successful growth of UiO-66 on a dyed PET fabric with the concurrent removal of the dye without additional steps. The catalytic performance of the UiO-66-grown fabric was evaluated through the degradation of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant. The fabric produced by the simple metal treatment (Zr@PEThyd) exhibited excellent DMNP degradation performance with t1/2 = 43.3 min and maintained functional stability after a harsh washing procedure, an outcome attributed to the surface-assisted UiO-66 growth that ensured good bonding stability. The developed process is innovative in that it uses dyed PET waste as a template for the direct growth of UiO-66, simplifying the process without compromising the catalytic functionality. This research provides an informative option for a sustainable textile recycling strategy by transforming dyed PET waste into an advanced self-detoxifying material.

Conversion of PET Bottle Waste into a Terephthalic Acid-Based Metal-Organic Framework for Removing Plastic Nanoparticles from Water

Micro- and nanoparticles of plastic waste are considered emerging pollutants with significant environmental and health impacts at high concentrations or prolonged exposure time. Here we report the synthesis and characterization of a known metal-organic framework (MOF) using terephthalic acid (TPA) recovered from the hydrolysis of polyethylene terephthalate (PET) bottle waste. This approach adds value to the existing large amounts of bottle waste in the environment. Fully characterized zinc-TPA MOF (MOF-5) was used for the extraction and removal of engineered polyvinyl chloride (PVC) and polymethylmethacrylate (PMMA) nanoparticles from water with a high efficiency of 97% and 95%, respectively. Kinetic and isotherm models for the adsorption of polymer nanoparticles (PNPs) on the MOF surface were investigated to understand the mechanism. The Qmax for PVC and PMMA NPs were recorded as 56.65 mg/g and 33.32 mg/g, respectively. MOF-5 was characterized before and after adsorption of PNPs on the surface of MOF-5 using a range of techniques. After adsorption, the MOF-5 was successfully regenerated and reused for the adsorption and removal of PNPs, showing consistent results for five adsorption cycles with a removal rate of 83–85%. MOF-5 was characterized before and after adsorption of PNPs on the surface using a range of techniques. The MOF-5 with PNPs on the surface was successfully regenerated and reused for the adsorption and removal of polymer nanoparticles, showing consistent results for five extraction cycles. As a proof of concept, MOF-5 was also used to remove plastic particles from commercially available body scrub gel solutions. Such methods and materials are needed to mitigate the health hazards caused by emerging micro- and nanoplastic pollutants in the environment.

Polyethylene Terephthalate Hydrolases in Human Gut Microbiota and Their Implications for Human Health.

Polyethylene terephthalate (PET), primarily utilized for food and beverage packaging, consistently finds its way into the human gut, thereby exerting adverse effects on human health. PET hydrolases, critical for the degradation of PET, have been predominantly sourced from environmental microbial communities. Given the fact that the human gut harbors a vast and intricate consortium of microorganisms, inquiry into the presence of potential PET hydrolases within the human gut microbiota becomes imperative. In this investigation, we meticulously screened 22,156 homologous sequences that could potentially encode PET hydrolases using the hidden Markov model (HMM) paradigm, drawing from 4984 cultivated genomes of healthy human gut bacteria. Subsequently, we methodically validated the hydrolytic efficacy of five selected candidate PET hydrolases on both PET films and powders composed of micro-plastics (MPs). Notably, our study also unveiled the influence of both diverse PET MP powders and their resultant hydrolysates on the modulation of cytokine expression in macrophages. In summary, our research underscores the ubiquitous prevalence and considerable potential of the human gut microbiota in PET hydrolysis. Furthermore, our study significantly contributes to the holistic evaluation of the potential health hazards posed by PET MPs to human well-being.

Highly Sensitive Acetylcholine Biosensing Via Chemical Amplification of Enzymatic Processes in Single Track-Etched Nanochannels

Neurotransmitters are endogenous chemical messengers that play crucial roles in the transmission, enhancement and conversion of specific signals between neurons and other cells and are considered biomarkers of neurodegenerative diseases.[1] Neurodegenerative diseases cause progressive loss of cognitive and/or motor function and, as life expectancy rises, they imply major challenges for societies with rapidly aging populations.[2] As a result, monitoring neurotransmitters is becoming increasingly relevant in clinical environments. Acetylcholine (Ach) is a neurotransmitter that plays a key role in the communication between neurons in the spinal cord and nerve skeletal junctions in vertebrates. [3] Since an abnormal concentration of Ach has proven to be related to neurodegenerative diseases, novel strategies for highly sensitive and specific Ach (bio)sensing are in great demand.In this work we present the construction of Ach enzymatic biosensors with remarkable sensitivity by acetylcholinesterase immobilization on polyamine-modified single nanochannels via electrostatic self-assembly. [4] To fabricate bullet-shaped single nanochannels in polyethylene terephthalate (PET), 12 µm thick PET foils are irradiated with a single swift heavy ion. The resulting ion track consists of highly localized damaged material along the ion trajectory and is selectively dissolved in a highly basic aqueous solution under asymmetric conditions to obtain a bullet-shaped channel. The controlled PET hydrolysis exposes carboxylic groups at the channel surface (negative charge at pH < 4), which allows the immobilization of further functional groups to design and construct the biosensor.Here, we will discuss in detail the sensor design, the applied functionalization strategy, and the performance of the sensor. In short, changes in the surface charge of the nanochannel lead to measurable changes in the transmembrane current in a steady-state configuration. We will show experimental results that evidence that the designed sensor successfully transduces the presence of acetylcholine into measurable ionic signals with a 16 nM low limit of detection.[1] World Health Organization, Neurological Disorders: Public Health Challenges, World Health Organization Press, Geneva, Switzerland,2007.[2] L. Gan, M. R. Cookson, L. Petrucelli and A. R. La Spada,Nat. Neurosci., 2018, 21, 1300–1309.[3] M. Hasanzadeh, N. Shadjou and M. de la Guardia, TrAC, Trends Anal. Chem., 2017, 86, 107–121.[4] Yamili Toum Terrones, Gregorio Laucirica, Vanina M. Cayón, Gonzalo E. Fenoy, M. Lorena Cortez, María Eugenia Toimil-Molares, Christina Trautmann, Waldemar A. Mamisollé and Omar Azzaroni, Chem. Commun., 2022, 58, 10166

Hydrolysis of polyethylene terephthalate by ZSM-5 combined with supercritical carbon dioxide under neutral environment

Polyethylene terephthalate (PET) is a kind of stable polyester, which is difficult to be degraded in the natural environment, and the waste PET causes severe environmental problems. To achieve efficient and environmentally friendly hydrolysis of PET, we employed ZSM-5 as a catalyst for neutral hydrolysis of PET in the presence of supercritical carbon dioxide (SCCO2). This study demonstrates that the existence of SCCO2 in the system enhances PET hydrolysis efficiency. The swelling effect of SCCO2 on PET can relax the PET segment and promote the mass transfer of water molecules in the PET bulk phase. However, excessive pressure of SCCO2 leads to plasticization of PET which increases the crystallinity of PET and hinders hydrolysis. The activation energy was measured under different pressures, revealing a decrease in activation energy with increasing pressure below 7.5 MPa. When the pressure exceeds 7.5 MPa, the activation energy increases due to plasticization. Through the density functional theory (DFT) analysis combined with the experimental results, it has been confirmed that Brønsted acid on ZSM-5 plays a more important role than Lewis acid in the system.

Enzymatic Degradation of PET plastic

Polyethylene terephthalate (PET) plastic is one of the most commonly used polymers worldwide and found in high rates as environmental waste. Previous studies have shown that the degradation of plastics using commercial grade enzymes is possible and highly effective in lab settings. However, the effectiveness and rates of enzymatic plastic degradation at environmentally relevant conditions is less known. In this study, we set up a series of sacrificial incubation experiments using a commercial enzyme, Humicola insolens cutinase (HiC), to examine the effect of various environmental variables, including temperature, pH, and salinity, on the hydrolytic degradation of PET. This was performed by measuring the mass loss at different time points during degradation, dissolved organic carbon produced in solution by PET hydrolysis, the Fourier transform infrared (FTIR) spectra of the PET surfaces, and scanning electron microscope (SEM) images of the PET surfaces. The results indicate that the degradation rate is 15-times faster at 55 °C than at 40 °C at pH 8 (1.93 mg day-1 versus 0.13 mg day-1), giving an initial estimate for the activation energy of PET hydrolysis of 2.2 kJ mol-1. In the 55 °C experiment which ran for 10 days, there was a noticeable decrease in the plastic strength and deformation of the plastic after 1 week of degradation. In the 40 °C experiment (duration 16 weeks), FTIR spectral changes were observed as early as week 6, with peaks of interest at 2,970 cm-1, 2,350 cm-1, 1,240 cm-1 , and between 1,300-1,000 cm-1. Ongoing experiments with pH and salinity will provide insight into their effects on the PET degradation rate. Altogether, these results will provide a comprehensive framework for predicting PET degradation rates, and by extension, other plastics that are degraded by hydrolysis, at environmentally relevant pH, temperature, and salinity conditions. In addition, these results provide insight into the effect of degradation on the chemical spectra of plastics and microplastics.

Biodegradation of poly(ethylene terephthalate) through PETase surface-display: From function to structure

Polyethylene terephthalate (PET) is one of the most used plastics which has caused some environmental pollution and social problems. Although many newly discovered or modified PET hydrolases have been reported at present, there is still a lack of comparison between their hydrolytic capacities, as well as the need for new biotechnology to apply them for the PET treatment. Here, we systematically studied the surface-display technology for PET hydrolysis using several PET hydrolases. It is found that anchoring protein types had little influence on the surface-display result under T7 promoter, while the PET hydrolase types were more important. By contrast, the newly reported FAST-PETase showed the strongest hydrolysis effect, achieving 71.3% PET hydrolysis in 24 h by pGSA-FAST-PETase. Via model calculation, FAST-PETase indeed exhibited higher temperature tolerance and catalytic capacity. Besides, smaller particle size and lower crystallinity favored the hydrolysis of PET pellets. Through protein structure comparison, we summarized the common characteristics of efficient PET-hydrolyzing enzymes and proposed three main crystal structures of PET enzymes via crystal structural analysis, with ISPETase being the representative and main structure. Surface co-display of FAST-PETase and MHETase can promote the hydrolysis of PET, and the C-terminal of the fusion protein is crucial for PET hydrolysis. The results of our research can be helpful for PET contamination removal as well as other areas involving the application of enzymes. SynopsisThis research can promote the development of better PET hydrolase and its applications in PET pollution treatment via bacteria surface-display.

Development of reusable Ni/γ-Al2O3 catalyst for catalytic hydrolysis of waste PET bottles into terephthalic acid.

In order to efficiently recycle waste polyethylene terephthalate (PET) bottles, this study aimed to enhance the hydrolysis process to convert PET bottle into valuable terephthalic acid (TPA) by developing effective and reusable Ni/γ-Al2O3 catalysts. A series of Ni/γ-Al2O3 catalyst was prepared by the impregnation method with different Ni loadings (5-15 wt%) and was characterized by various techniques including XRD, SEM-EDX, and N2 adsorption-desorption. The prepared catalysts were employed in the catalytic hydrolysis of PET under varied influencing factors, namely reaction temperature (220-280 °C), reaction time (20-60 min), and Ni loading. The response surface methodology (RSM) was used to optimize the operating condition to produce the maximum TPA yield, and the optimal values were determined as follows: reaction temperature = 267.07 °C, reaction time = 48.54 min, and Ni loading = 12.90 wt%, giving the highest TPA yield of 97.06%. The R2, F-value, and P-value of the analysis of variance (ANOVA) were 0.9982, 424.96, and <0.0001, respectively, indicating a good fit of the model. The results from XRD and FTIR measurement of the produced TPA indicated the high purity and comparable chemical structures to the TPA standard. In addition, the 12.9Ni/Al catalyst exhibited high catalytic activity in repeated cycles of hydrolysis process of PET and could be regenerated by calcination to restore its catalytic activity. This finding could be a promising alternative for an effective TPA recovery from waste plastic bottles.

Engineering the catalytic activity of an Antarctic PET-degrading enzyme by loop exchange.

Several hydrolases have been described to degrade polyethylene terephthalate (PET) at moderate temperatures ranging from 25°C to 40°C. These mesophilic PET hydrolases (PETases) are less efficient in degrading this plastic polymer than their thermophilic homologs and have, therefore, been the subject of many protein engineering campaigns. However, enhancing their enzymatic activity through rational design or directed evolution poses a formidable challenge due to the need for exploring a large number of mutations. Additionally, evaluating the improvements in both activity and stability requires screening numerous variants, either individually or using high-throughput screening methods. Here, we utilize instead the design of chimeras as a protein engineering strategy to increase the activity and stability of Mors1, an Antarctic PETase active at 25°C. First, we obtained the crystal structure of Mors1 at 1.6 Å resolution, which we used as a scaffold for structure- and sequence-based chimeric design. Then, we designed a Mors1 chimera via loop exchange of a highly divergent active site loop from the thermophilic leaf-branch compost cutinase (LCC) into the equivalent region in Mors1. After restitution of an active site disulfide bond into this chimera, the enzyme exhibited a shift in optimal temperature for activity to 45°C and an increase in fivefold in PET hydrolysis when compared with wild-type Mors1 at 25°C. Our results serve as a proof of concept of the utility of chimeric design to further improve the activity and stability of PETases active at moderate temperatures.

Catalytic upgrading of PET to acid by engineering bimetallic AuCu/CNT catalyst

AbstractBACKGROUNDRecycling waste polyethylene terephthalate (PET) plastic can prolong its life cycle, reduce the consumption of non‐renewable resources, prevent plastic pollution and also protect the ecological environment. Traditional chemical recycling of waste PET plastic can depolymerize PET into terephthalic acid (TPA) and ethylene glycol (EG).RESULTSA strategy was proposed to directly depolymerize PET into TPA and acid, which shows significantly higher values than conventional EG. This is achieved over a carbon nanotube (CNT)‐supported AuCu catalyst (AuCu/CNT) prepared using an evaporative impregnation method. Comprehensive analyses of the catalyst were conducted using X‐ray diffraction, N2 adsorption/desorption, transmission electron microscopy, X‐ray photoelectron spectroscopy, H2‐temperature=programmed reduction, and so on. It was found that Cu species in the AuCu/CNT catalyst mainly existed in the form of CuO, forming new reaction adsorption sites and providing active AuCu alloy sites, thereby improving the catalytic performance of AuCu/CNT. This results in simultaneously superior acid selectivity and EG conversion over AuCu/CNT compared with Au/CNT and Cu/CNT.CONCLUSIONThis study indicates that the hydrolysis of PET is highly significant in preparing value‐added products. © 2023 Society of Chemical Industry.

The interactions between mixed waste from discarded surgical masks and face shields during the degradation in supercritical water

The widespread use of surgical masks made of polyolefin and face shields made of polyester during pandemics contributes significantly to plastic pollution. An eco-friendly approach to process plastic waste is using supercritical water, but the reaction of mixed polyolefin and polyester in this solvent is not well understood, which hinders practical applications. This study aimed to investigate the reaction of waste surgical masks (SM) and face shields (FS) mixed in supercritical water. Results showed that the optimal treatment conditions were 400 °C and 60 min, achieving a liquid oil yield of 823.03 mg·g−1 with 25 wt% FS. The interaction between polypropylene (PP), polyethylene terephthalate (PET), and iron (Fe) in SM and FS mainly determined the production of liquid oil products such as olefins and benzoic acid. The methyl-branched structure of PP enhanced PET hydrolysis, resulting in higher production of terephthalic acid (TPA). The degradation of PP was facilitated by the acidic environment created by TPA and benzoic acid in the reaction. Moreover, the hydrolysis of PET produced carboxylic acid, which coordinated with Fe3+ to form Fe-H that catalyzed the polymerization of small olefins, contributing to higher selectivity for C9 olefins. Therefore, this study provides valuable insights into the degradation mechanism of mixed PPE waste in supercritical water and guidance for industrial treatment.

Expression, purification and characterization of a novel bis (hydroxyethyl) terephthalate hydrolase from Hydrogenobacter thermophilus

PET (polyethylene terephthalate) is one of the most important petrochemicals that is widely used in mineral water bottles, food and beverage packaging and textile industry. Because of its stability under environmental conditions, the massive amount of PET wastes caused serious environmental pollution. The use of enzymes to depolymerize PET wastes and upcycling is one of the important directions for plastics pollution control, among which the key is the depolymerization efficiency of PET by PET hydrolase. BHET (bis(hydroxyethyl) terephthalate) is the main intermediate of PET hydrolysis, its accumulation can hinder the degradation efficiency of PET hydrolase significantly, and the synergistic use of PET hydrolase and BHET hydrolase can improve the PET hydrolysis efficiency. In this study, a dienolactone hydrolase from Hydrogenobacter thermophilus which can degrade BHET (HtBHETase) was identified. After heterologous expression in Escherichia coli and purification, the enzymatic properties of HtBHETase were studied. HtBHETase shows higher catalytic activity towards esters with short carbon chains such as p-nitrophenol acetate. The optimal pH and temperature of the reaction with BHET were 5.0 and 55 ℃, respectively. HtBHETase exhibited excellent thermostability, and retained over 80% residual activity after treatment at 80 ℃ for 1 hour. These results indicate that HtBHETase has potential in biological PET depolymerization, which may facilitate the enzymatic degradation of PET.

Prediction of terephthalic acid yield in aqueous hydrolysis of polyethylene terephthalate

AbstractAqueous hydrolysis is used to chemically recycle polyethylene terephthalate (PET) due to production of high‐quality terephthalic acid (TPA), the PET monomer. PET hydrolysis depends on various factors including PET size, catalyst concentration, and reaction temperature. So, modeling PET hydrolysis by considering the effective factors can provide useful information for material researchers to specify how to design and run these reactions. It will save time, energy, and materials by optimizing the hydrolysis conditions. Machine learning algorithms enable to design models to predict the output results. For the first time, 381 experimental data were gathered to model aqueous hydrolysis of PET. Effective factors on PET hydrolysis were connected to the TPA yield. The logistic regression was applied to rank the effective factors. Two algorithms were proposed, artificial neural network multi‐layer perceptron (ANN‐MLP) and adaptive network‐based fuzzy inference system (ANFIS). The dataset was divided into training, validating, and testing sets to train, validate, and test the models, respectively. The models predicted TPA yield sufficiently where the ANFIS model outperformed. R‐squared (R2) and Root Mean Square Error (RMSE) loss functions were employed to measure the efficiency of the models and evaluate their performance.

Recent Advancements and Mechanism of Plastics Biodegradation Promoted by Bacteria: A Key for Sustainable Remediation for Plastic Wastes

ABSTRACT: Plastic has become an indispensable part of our lives and cutting down plastic consumption entirely is difficult to achieve. The recalcitrant and non-biodegradable nature of plastic leads to accumulation of tons of plastic in landfills and water bodies which further risks marine life and human life too causing serious health issues. In recent years, several microbial enzymes have been discovered that have the ability to degrade plastic. The present review highlights the recent discovery and properties of the plastic-eating bacteria, Ideonella sakaiensis, that has potential to be used for plastic degradation and recycling. The bacteria possess unique enzymes that allow it to utilise Polyethylene terephthalate (PET) plastic, thereby degrading it to relatively safer monomeric forms that can be further degraded and purified to manufacture recycled plastics. The review focuses on the mechanism of PET hydrolysis, recent advances in the field to escalate enzymatic efficiency and development of new bacterial and enzymatic strains through genetic engineering which can enhance its catalytic competence and make the process time and cost-effective. The plastic metabolising bacteria can thus be a potential and efficient bio-alternative to degrade plastic in a biological and sustainable manner thereby helping scale the otherwise insurmountable plastic pollution crisis.

Conversion of polyethylene terephthalate waste into high-yield porous carbon adsorbent via pyrolysis of dipotassium terephthalate

A method for conversion of polyethylene terephthalate (PET) waste into porous carbon material is proposed. The recycling of PET bottle waste includes the stages of low-temperature hydrolysis of the polymer and subsequent pyrolysis at 800 °C. To provide PET hydrolysis at ∼150 °C and atmospheric pressure, the polymer was pre-dissolved in dimethyl sulfoxide and then an aqueous solution of potassium hydroxide was added. The potassium terephthalate formed as a result of the alkaline hydrolysis of PET allows the carbon-containing precursor to be preserved for further activation to temperatures beyond 600 °C. The proposed method leads to the formation of a porous carbon material, increasing the yield of carbon residue to 25 wt%, which is higher compared to the yield of carbon residue in the direct pyrolysis of PET. The obtained porous carbon is characterized by graphite-like structure and specific surface area of ∼1100 m2 g−1. It has been shown that PET-derived carbon material can be used to remove pollutants from aqueous media. The adsorption properties of the carbon material were demonstrated by adsorption of methylene blue from an aqueous solution. The capacity of the carbon material was found to be 443 mg g−1.

Rapid hydrolysis of PET in high-concentration alcohol aqueous solution by pore formation and spontaneous separation of terephthalate

Recovery of terephthalic acid (TPA) from waste polyethylene terephthalate (PET) should overcome the long-existing issues of low operation efficiency or massive wastewater generation during the hydrolysis and subsequent separation process to balance economics and environmental friendliness. Here, a high-concentration ethanol aqueous solution of 90 vol% is developed to achieve high-efficiency hydrolysis of PET by selectively cleaving C-O bonds and spontaneous separation of terephthalate using KOH as catalyst at 80 °C for 60 min. More than 98 % of TPA is recovered. It was attributed to the accelerated diffusion of the solvent in a reflux state due to the pore formation in PET and improved wettability between the solvent and PET. Notably, the terephthalate precipitated automatically from the reaction system due to low solubility in the solvent and separated by simple filtration, which avoids a large amount of waste water and acid in the following neutralization of terephthalate. The high efficiency of recycled reaction solution remained within several successive runs. The hydrolysis system is also applicable for degradation of other polymers containing ester groups and shows combined advantages of simplicity, high efficiency and eco-friendliness.

Technical, Economic, and Environmental Comparison of Closed-Loop Recycling Technologies for Common Plastics

Over 400 million metric tons of plastic waste are generated globally each year, resulting in pollution and lost resources. Recycling strategies can recapture this wasted material, but there is a lack of quantitative and transparent data on the capabilities and impacts of these processes. Here, we develop a data set of material quality, material retention, circularity, contamination tolerance, minimum selling price, greenhouse gas emissions, energy use, land use, toxicity, waste generation, and water use metrics for closed-loop polymer recycling technologies, including mechanical recycling and solvent-based dissolution of polyethylene, polyethylene terephthalate (PET), and polypropylene, as well as enzymatic hydrolysis, glycolysis, and vapor methanolysis of PET. Mechanical recycling and PET glycolysis display the best economic (9%–73% lower than competing technologies) and environmental (7%–88% lower) performances, while dissolution, enzymatic hydrolysis, and methanolysis provide the best recyclate material qualities (2%–27% higher). We identify electricity, steam, and organic solvents as top process contributors to these metrics and apply sensitivity and multicriteria decision analyses to highlight key future research areas. The estimates derived in this work provide a quantitative baseline for comparing and improving recycling technologies, can help reclaimers identify optimal end-of-life routes for given waste streams, and serve as a framework for assessing future innovations.

Thermophilic bacteria from Peruvian hot springs with high potential application in environmental biotechnology

ABSTRACT Hot springs are extreme environments in which well-adapted microorganisms with biotechnological applications can thrive naturally. These thermal environments across Peruvian territory have, until now, remained poorly investigated. In this study, two hot springs, El Tragadero and Quilcate, located in Cajamarca (Peru) were selected in order to investigate the biotechnological potential of indigenous thermophilic bacteria. Enrichment and isolation processes were carried out using microbial mats, sediments, biofilms, and plastic polymers as samples. Screening for biosurfactants and siderophores production, as well as for polyethylene terephthalate (PET) hydrolysis was done using culture-dependent techniques. After molecular identification, Bacillus was found as the most abundant genus in both hot springs. Bacillus velezensis was found producing biosurfactants under high-level temperature. Anoxybacillus species (A. salavatliensis and A. gonensis) are here reported as siderophore-producing bacteria for the first time. Additionally, Brevibacillus and the less-known bacterium Tistrella mobilis were found demonstrating PET hydrolysis activity. Our study provides the first report of thermophilic bacteria isolated from Peruvian hot springs with biotechnological potential for the bioremediation of oil-, metal- and plastic-polluted environments.

Efficient depolymerization of polyethylene terephthalate (PET) and polyethylene furanoate by engineered PET hydrolase Cut190

The enzymatic recycling of polyethylene terephthalate (PET) can be a promising approach to tackle the problem of plastic waste. The thermostability and activity of PET-hydrolyzing enzymes are still insufficient for practical application. Pretreatment of PET waste is needed for bio-recycling. Here, we analyzed the degradation of PET films, packages, and bottles using the newly engineered cutinase Cut190. Using gel permeation chromatography and high-performance liquid chromatography, the degradation of PET films by the Cut190 variant was shown to proceed via a repeating two-step hydrolysis process; initial endo-type scission of a surface polymer chain, followed by exo-type hydrolysis to produce mono/bis(2-hydroxyethyl) terephthalate and terephthalate from the ends of fragmented polymer molecules. Amorphous PET powders were degraded more than twofold higher than amorphous PET film with the same weight. Moreover, homogenization of post-consumer PET products, such as packages and bottles, increased their degradability, indicating the importance of surface area for the enzymatic hydrolysis of PET. In addition, it was required to maintain an alkaline pH to enable continuous enzymatic hydrolysis, by increasing the buffer concentration (HEPES, pH 9.0) depending on the level of the acidic products formed. The cationic surfactant dodecyltrimethylammonium chloride promoted PET degradation via adsorption on the PET surface and binding to the anionic surface of the Cut190 variant. The Cut190 variant also hydrolyzed polyethylene furanoate. Using the best performing Cut190 variant (L136F/Q138A/S226P/R228S/D250C-E296C/Q123H/N202H/K305del/L306del/N307del) and amorphous PET powders, more than 90 mM degradation products were obtained in 3 days and approximately 80 mM in 1 day.Graphical

Valorization of Polyethylene Terephthalate to Muconic Acid by Engineering Pseudomonas Putida.

Plastic waste is rapidly accumulating in the environment and becoming a huge global challenge. Many studies have highlighted the role of microbial metabolic engineering for the valorization of polyethylene terephthalate (PET) waste. In this study, we proposed a new conceptual scheme for upcycling of PET. We constructed a multifunctional Pseudomonas putida KT2440 to simultaneously secrete PET hydrolase LCC, a leaf-branch compost cutinase, and synthesize muconic acid (MA) using the PET hydrolysate. The final product MA and extracellular LCC can be separated from the supernatant of the culture by ultrafiltration, and the latter was used for the next round of PET hydrolysis. A total of 0.50 g MA was produced from 1 g PET in each cycle of the whole biological processes, reaching 68% of the theoretical conversion. This new conceptual scheme for the valorization of PET waste should have advantages over existing PET upcycling schemes and provides new ideas for the utilization of other macromolecular resources that are difficult to decompose, such as lignin.