BACKGROUND: Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable plastic. It was introduced to the plastics market in 1998 and since then has been widely used around the world. The main idea of this research is to perform quantum chemical calculations to study the potential toxicity of PBAT and its degradation products. We analyzed the electron transfer capacity to determine its potential toxicity. We found that biodegradable products formed with benzene rings are as good electron acceptors as PBAT and OOH•. Our results indicate that the biodegradation products are potentially as toxic as PBAT. This might explain why biodegradation products alter the photosynthetic system of plants and inhibit their growth. From this and other previous investigations, we can think that biodegradable plastics could represent a potential environmental risk.
METHODS: All DFT computations were performed using the Gaussian16 at M062x/6-311 + g(2d,p) level of theory without symmetry constraints. Electro-donating (ω-) and electro-accepting (ω +) powers were used as response functions.

Polybutylene adipate terephthalic acid (PBAT) is an emerging biodegradable material in food packaging. However, concerns have been raised regarding the potential hazards it could pose to food safety. In this study, the changes of PBAT films during food contact and the release of small molecules were inestigated by a multiscale approach. On a macro-scale, the surface roughness of the films increased with the reduction in the concentration of food simulants and the increase in contact temperatures, especially after immersion in acidic food environments. On a micro-scale, the crystallinity (Xc) and degradation indexes (DI) of the films increased by 5.7-61.2% and 7.8-48.6%, respectively, which led to a decrease in thermal stability. On a scale approaching the molecular level, 2,4-di-tert-butylphenol (2,4-DTBP) was detected by gas chromatography-mass spectrometry (GC-MS/MS) with the highest migration content, and the release behavior of 2,4-DTBP was further investigated by migration kinetics. In addition, terephthalic acid (TPA), a hydrolysis product of PBAT, was detected in acidic food environments by liquid chromatography-mass spectrometry (LC-MS/MS). The results of this study could provide practical guidance and assistance to promote sustainable development in the field of food packaging.

Poly(ethylene terephthalate) (PET) is a very valuable and beneficial material for industrial purposes, with various different applications. Due to the high annual production volume of over 50 million tons worldwide and the indiscriminate disposal by consumers, the polymers accumulate in the environment, causing negative effects on various ecosystems. Biodegradation via suitable enzymes represents a promising approach to combat the plastic waste issue so validated methods are required to measure the efficiency and efficacy of these enzymes. PETase and MHETase from Ideonella sakaiensis are suitable enzymes needed in combination to completely degrade PET into its environmentally friendly monomers. In this project, we compare and combine a previously described bulk absorbance measurement method with a newly established 1H NMR analysis method of the PET degradation products mono(2-hydroxyethyl) terephthalic acid, bis(2-hydroxyethyl) terephthalic acid and terephthalic acid. Both were optimized regarding different solvents, pH values and drying processes. The accuracy of the measurements can be confirmed with sensitivity limits of 2.5-5 µM for the absorption method and 5-10 µM for the 1H NMR analysis. The combination of the described methods therefore allows a quantitative analysis by using bulk absorption coupled with a qualitative analysis through 1H NMR. The methods established in our work can potentially contribute to the development of suitable recycling strategies of PET using recombinant enzymes.

Terephthalic acid (TPA) is an endocrine disruptor widely used as a plasticizer and as a monomer in the manufacturing of PET bottles. However, because of various harmful effects on humans and the environment, it is now recognized as a priority pollutant whose environmental level needs to be controlled. In the present work, the TPA biodegradation efficacy of the bacterium Rhodococcus erythropolis (MTCC 3951) was studied in mineral salt media with TPA as the sole carbon and energy source. R. erythropolis was observed to degrade 5 mM and 120 mM TPA within 10 h and 84 h of incubation, respectively. The degradation efficiency was further optimized by varying the culture conditions, and the following optimum conditions were obtained: inoculum size- 5% (v/v), temperature- 30 °C, agitation speed- 200 rpm, and pH- 8.0. The bacterium was found to use an ortho-cleavage pathway for TPA degradation determined based on enzymatic and GC-MS studies. Moreover, during the degradation of TPA, the bacterium was observed to produce polyhydroxyalkanoate (PHA)-a biopolymer. Biodegradation of 120 mM TPA resulted in an accumulation of PHA. The PHA granules were visualized using fluorescence and transmission electron microscopy and were later characterized using FTIR spectroscopy. Furthermore, the robustness of the bacterium was demonstrated by its ability to degrade TPA in real industrial wastewater. Overall, R. erythropolis (MTCC 3951) hold the potential for controlling TPA pollution in the environment and vis-à-vis the production of PHA biopolymer.

A new class of lanthanide mixed-carboxylate ligands compounds with formula {[Ln2 (phthgly)4 (bdc)(H2 O)6 ]·(H2 O)4 }∞ , labelled as Ln3+ : Eu (1) and Gd (2) coordination polymers (CP) were synthesized under mild reaction conditions between lanthanide nitrate salts and a solution of N-phthaloylglycine (phthgly) and terephthalic (bdc) ligands. The (1) and (2) coordination polymers were formed by symmetric binuclear units, in which phthgly and bdc carboxylate ligands are coordinated to the lanthanide ions by different coordination modes. Surprisingly, all organic ligands participate in hydrogen bonding interactions, forming an extremally rigid crystalline structure. The red narrow emission bands from the 5 D0 →7 FJ transitions of the Eu3+ ion show a high colour purity. The intramolecular energy transfer process from L→Eu3+ ion has been discussed. The experimental intensity parameters (Ω2,4 ) reflect lower angular distortion and polarizability of the chemical environment around the metal ion compared with other Eu3+ compounds reported in the literature. This novel class of coordination polymer offers a more attractive platform for developing luminescent functional materials for different applications.

BACKGROUND: Plastics are an indispensable part of our daily life. However, mismanagement at their end-of-life results in severe environmental consequences. The microbial conversion of these polymers into new value-added products offers a promising alternative. In this study, we engineered the soil-bacterium Comamonas testosteroni KF-1, a natural degrader of terephthalic acid, for the conversion of the latter to the high-value product 2-pyrone-4,6-dicarboxylic acid.
RESULTS: In order to convert terephthalic acid to 2-pyrone-4,6-dicarboxylic acid, we deleted the native PDC hydrolase and observed only a limited amount of product formation. To test whether this was the result of an inhibition of terephthalic acid uptake by the carbon source for growth (i.e. glycolic acid), the consumption of both carbon sources was monitored in the wild-type strain. Both carbon sources were consumed at the same time, indicating that catabolite repression was not the case. Next, we investigated if the activity of pathway enzymes remained the same in the wild-type and mutant strain. Here again, no statistical differences could be observed. Finally, we hypothesized that the presence of a pmdK variant in the degradation operon could be responsible for the observed phenotype and created a double deletion mutant strain. This newly created strain accumulated PDC to a larger extent and again consumed both carbon sources. The double deletion strain was then used in a bioreactor experiment, leading to the accumulation of 6.5 g/L of product in 24 h with an overall productivity of 0.27 g/L/h.
CONCLUSIONS: This study shows the production of the chemical building block 2-pyrone-4,6-dicarboxylic acid from terephthalic acid through an engineered C. testosteroni KF-1 strain. It was observed that both a deletion of the native PDC hydrolase as well as a pmdK variant is needed to achieve high conversion yields. A product titer of 6.5 g/L in 24 h with an overall productivity of 0.27 g/L/h was achieved.

Poly(ethylene terephthalate) (PET) is one of the world\'s most widely used polyester plastics. Due to its chemical stability, PET is extremely difficult to hydrolyze in a natural environment. Recent discoveries in new polyester hydrolases and breakthroughs in enzyme engineering strategies have inspired enormous research on biorecycling of PET. This study summarizes our research efforts toward large-scale, efficient, and economical biodegradation of post-consumer waste PET, including PET hydrolase selection and optimization, high-yield enzyme production, and high-capacity enzymatic degradation of post-consumer waste PET. First, genes encoding PETase and MHETase from Ideonella sakaiensis and the ICCG variant of leaf-branch compost cutinase (LCCICCG ) were codon-optimized and expressed in Escherichia coli BL21(DE3) for high-yield production. To further lower the enzyme production cost, a pelB leader sequence was fused to LCCICCG so that the enzyme can be secreted into the medium to facilitate recovery. To help bind the enzyme on the hydrophobic surface of PET, a substrate-binding module in a polyhydroxyalkanoate depolymerase from Alcaligenes faecalis (PBM) was fused to the C-terminus of LCCICCG . The resulting four different LCCICCG variants (LCC, PelB-LCC, LCC-PBM, and PelB-LCC-PBM), together with PETase and MHETase, were compared for PET degradation efficiency. A fed-batch fermentation process was developed to produce the target enzymes up to 1.2 g L-1 . Finally, the best enzyme, PelB-LCC, was selected and used for the efficient degradation of 200 g L-1 recycled PET in a well-controlled, stirred-tank reactor. The results will help develop an economical and scalable biorecycling process toward a circular PET economy.

CoNi-LDH (layered CoNi double hydroxides) hollow nanocages with specific morphology are obtained by Ni ion etching of ZIF-67 (Zeolitic imidazolate framework-67). The structure of the layered materials is further modified by molecular intercalation. The original interlayer anions are replaced by the ion exchange effect of terephthalic acid, which helps to increase the interlayer distance of the material. The intercalated cage-like structures not only benefit for the storage of oxygen, and the discharge product reaction, but also have more support between the material layers. The experimental results show that the excessive use of intercalation agent will affect structural stability of the intercalated CoNi-LDH. By adjusting the amount of terephthalic acid, the intercalated CoNi-LDH-2 (with 0.02 mmol terephthalic acid intercalated) is not easy to collapse after 209 cycles and shows the best electrochemical performance in Li-O2 battery.

The multistep synthesis of novel bis-terephthalthioamides based on methyl esters of amino acids (AAs) was proposed using conventional heating and microwave-assisted approaches. In fact, the comparative case study on the thionation of new symmetrical diamides with Lawesson\'s reagent (LR) was performed. The microwave-accelerated small-scale methodology was successfully employed on the whole pathway from substrates (Gly, Ala, Val, Tyr, Ser) to products (symmetrical dithioamides of terephthalic acid), resulting in significantly reduced reaction time, energy requirements, and slightly increased reaction yields when compared to conventional heating. Moreover, the intermolecular similarity of novel terephthalic acid derivatives was estimated in the multidimensional space (mDS) of the structure/property-related in silico descriptors using principal component analysis (PCA) and hierarchical clustering analysis (HCA). The distance-oriented structure/property distribution was also correlated with the experimental lipophilic data.

The degradation process of different types of mulch in agriculture and its effect on soil ecosystem should be considered comprehensively. To this end, the changes in performance, structure, morphology, and composition of PBAT film during the degradation process were examined through a multiscale approach in comparison with several PE films and their effects on the soil physicochemical properties were investigated. At the macroscopic scale, the load and elongation of all films decreased with increasing ages and depths. At the microscopic scale, the stretching vibration peak intensity (SVPI) for PBAT and PE films decreased by 48.8 ∼ 60.2% and 9.3 ∼ 38.6%, respectively. The crystallinity index (CI) increased by 67.3 ∼ 209.6% and 15.6 ∼ 21.8%, respectively. At the molecules scale, terephthalic acid (TPA) was detected in localized soil with PBAT mulch after 180 d. In short, the degradation characteristics of PE films were depended on their thickness and density. The PBAT film exhibited the highest degree of degradation. Simultaneously, the soil physicochemical properties such as soil aggregates, microbial biomass and pH were affected by the changes of film structure and components during the degradation process. This work has practical implications for the sustainable development of agriculture.