Biodegradation of polyethylene terephthalate: a review / 生物工程学报

Plastics are widely used in human daily life, which bring great convenience. Nevertheless, the disposal of a large amount of plastic wastes also brings great pressure to the environment. Polyethylene terephthalate (PET) is a polymer thermoplastic material produced from petroleum. It has become one of the most commonly used plastics in the world due to its durability, high transparency, light weight and other characteristics. PET can exist in nature for a long time due to its complex structure and the difficulty in degradation, which causes serious pollution to the global ecological environment, and threatens human health. The degradation of PET wastes has since become one of the global challenges. Compared with physical and chemical methods, biodegradation is the greenest way for treating PET wastes. This review summarizes the recent advances on PET biodegradation including microbial and enzymatic degradation of PET, biodegradation pathway, biodegradation mechanisms, and molecular modification of PET-degrading enzymes. In addition, the prospect for achieveing efficient degradation of PET, searching and improving microorganisms or enzymes that can degrade PET of high crystallinity are presented, with the aimto facilitate the development, application and molecular modification of PET biodegradation microorganisms or enzymes.

Detection methods for polyethylene terephthalate degrading enzymes: a review / 生物工程学报

Polyethylene terephthalate (PET) is one of the most widely used synthetic polyester. It poses serious threat to terrestrial, aquatic ecosystems and human health since it is difficult to be broken down and deposited in the environment. The biodegradation based on enzymatic catalysis offers a sustainable method for recycling PET. A number of PET hydrolases have been discovered in the last 20 years, and protein engineering has increased their degradation capabilities. However, no PET hydrolases that are practical for widespread industrial use have been identified. Screening of PET hydrolase using conventional detection techniques is laborious and inefficient process. Effective detection techniques are required to promote the commercialization of PET hydrolases. Using efficient detection techniques to screen potent industrial enzymes is essential for supporting the widespread industrial implementation of PET hydrolases. To define PET hydrolase, scientists have created a number of analytical techniques recently. The detection techniques that can be used to screen PET hydrolase, including high performance liquid chromatography, ultraviolet absorption spectrometric, and fluorescence activated droplet sorting method, are summarized in this study along with their potential applications.

Engineering the plastic degradation enzyme Ple629 from marine consortium to improve its thermal stability / 生物工程学报

Petrochemical-derived polyester plastics such as polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) have been widely used. However, the difficulty to be degraded in nature (PET) or the long biodegradation cycle (PBAT) resulted in serious environmental pollution. In this connection, treating these plastic wastes properly becomes one of the challenges of environment protection. From the perspective of circular economy, biologically depolymerizing the waste of polyester plastics and reusing the depolymerized products is one of the most promising directions. Recent years have seen many reports on polyester plastics degrading organisms and enzymes. Highly efficient degrading enzymes, especially those with better thermal stability, will be conducive to their application. The mesophilic plastic-degrading enzyme Ple629 from the marine microbial metagenome is capable of degrading PET and PBAT at room temperature, but it cannot tolerate high temperature, which hampers its potential application. On the basis of the three-dimensional structure of Ple629 obtained from our previous study, we identified some sites which might be important for its thermal stability by structural comparison and mutation energy analysis. We carried out transformation design, and performed expression, purification and thermal stability determination of the mutants. The melting temperature (Tm) values of mutants V80C and D226C/S281C were increased by 5.2 ℃ and 6.9 ℃, respectively, and the activity of mutant D226C/S281C was also increased by 1.5 times compared with that of the wild-type enzyme. These results provide useful information for future engineering and application of Ple629 in polyester plastic degradation.

Migração de partícula alergênica através de embalagem pet / Migration of allergen particles through pet

Para garantia da segurança dos consumidores muitas decisões na indústria alimentícia são tomadas com "margem de segurança", uma delas é a dispersão de partículas alergênicas em contaminações cruzadas. Em estoques de bebidas embaladas, diversas unidades que não possuem ingredientes alergênicos ou traços são descartadas quando um produto alergênico entra em contato, mesmo que pela parte externa. O presente estudo teve como objetivo avaliar se a partícula alergênica externa migra pela embalagem de PET e contamina a bebida não alergênico. Para isso, um produto em embalagem PET sem ingredientes ou partículas alergênicas (água) teve sua parte externa exposta a um ingrediente alergênico (soja) em meio aquoso e oleoso por 1, 24, 48 e 72 horas, demonstrando que não há migração para a parte interna.

To ensure the safety of consumers, many decisions in the food industry are made with "margin of safety", one is the dispersion of allergenic particles in cross-contamination. In stocks of packaged beverages, several units that do not contain allergenic ingredients or traces are discarded when an allergenic product comes into contact, even out of pack. The objective of this study is to evaluate whether the external allergenic particle migrates through the PET packaging and contaminates the non-allergenic food. A product in PET packaging without allergenic ingredients or particles (water) has your external part exposed to an allergenic ingredient (soy) in an aqueous and oily medium for 1, 24, 48 and 72 hours, and tested if are migration.

The application of carbohydrate binding module-Thermobifida fusca cutinase fusion protein in polyethylene terephthalate degradation / 生物工程学报

With the development of global economy, the dramatically increased production of polyethylene terephthalate (PET) plastics has led to a remarkably increased amount of plastic waste. PET waste can be treated by landfill, incineration, or biodegradation. While landfilling and incineration may cause secondary pollution, biodegradation has since received increased attentions due to its environmental friendliness. Recent studies have indicated that the carbohydrate binding module (CBM) can effectively enhance the binding of PET degrading enzymes to PET, and consequently increasing PET degradation rate. Here we constructed a fusion protein BaCBM2-Tfuc containing the BaCBM2 from Bacillus anthraci and the cutinase Tfuc from Thermobifida fusca, by megaprimer PCR of whole plasmids (MEGAWHOP). Notabaly, the PET film degradation efficiency (at 60 ℃) of BaCBM2-Tfuc was 2.8 times that of Tfuc. This study may provide technical support for constructing fusion proteins capable of efficiently degrading PET.

Efecto de la temperatura y concentración de microplásticos en la tasa de filtración del mejillón Semimytilus algosus (Mytiloida: Mytilidae) / Effect of temperature and microplastic concentration on the filtration rate of the mussel Semimytilus algosus (Myiloida: Mytilidae)

Resumen Introducción: La presencia de microplásticos (MPs, partículas menores a 5 mm) y el incremento de la temperatura en los océanos, vienen generando perturbaciones en la vida marina, que se pueden relacionar con alteraciones en el metabolismo de organismos filtradores, como los mitílidos. Objetivo: Se evalúa el efecto de diferentes temperaturas y concentraciones de MPs sobre la tasa de filtración (TF) de Semimytilus algosus. Métodos: Una muestra de organismos (N = 72) fue expuesta a cuatro temperaturas (17, 20, 23 y 26 °C), y un testigo sin microplásticos (MPs0) y dos concentraciones de MPs (< 125 µm) de 0.125 mg/l (MPs1) y 0.250 mg/l (MPs2), todos en combinación con la microalga Isochrysis galbana (1x106 cel/ml/día) por 21 días. Resultados: A medida que aumentó la concentración de MPs, se redujo la TF de S. algosus. Respecto a la temperatura, durante el día 7 se observó una mayor TF a 23 °C en todos los tratamientos, y para los días 14 y 21 se obtuvieron los menores valores de TF a 23 y 26 °C. La acción conjunta del incremento de temperatura y MPs, afectó negativamente la TF de S. algosus, donde ambos factores ocasionaron el descenso de la TF para todos los tiempos de evaluación. No se registró mortalidad a 17 °C para ningún tratamiento, y en el caso de mitílidos expuestos a MPs1 y temperaturas de 20 y 26 °C se presentó la mayor mortalidad (67 %). Conclusiones: El estudio demuestra el efecto adverso del incremento de temperatura y MPs sobre la TF de S. algosus.

Abstract Introduction: The presence of microplastics (MPs, particles smaller than 5 mm) and the increase in temperature in the oceans, have been generating disturbances in marine life, which can be related to alterations in the metabolism of filter-feeders, such as Mythilids. Objective: The effect of different temperatures and concentrations of MPs on the filtration rate (TF) of Semimytilus algosus is evaluated. Methods: A sample of organisms (N = 72) was exposed to four temperatures (17, 20, 23 and 26 °C), and a control without microplastics (MPs0) and two concentrations of MPs (< 125 µm) of 0.125 mg/l (MPs1) and 0.250 mg/l (MPs2), all in combination with Isochrysis galbana microalgae (1x106 cells/ml/day) for 21 days. Results: As the concentration of MPs increased, the TF of S. algosus decreased. Regarding temperature, during day 7 a higher TF was observed at 23 °C in all treatments, and during days 14 and 21 the lowest TF values were obtained at 23 and 26 °C. The joint action of the increase in temperature and MPs, negatively affected the TF of S. algosus, where both factors caused the decrease in TF for all evaluation times. No mortality was recorded at 17 °C for any treatment, and in the case of mytylids exposed to MPs1 at 20 °C and 26 °C, the highest mortality (67 %) occurred. Conclusions: The study demonstrates the adverse effect of the increase in temperature and MPs on the TF of S. algosus.

Advances in microbial degradation of plastics / 生物工程学报

Plastics are widely used in daily life. Due to poor management and disposal, about 80% of plastic wastes were buried in landfills and eventually became land and ocean waste, causing serious environmental pollution. Recycling plastics is a desirable approach, but not applicable for most of the plastic waste. Microbial degradation offers an environmentally friendly way to degrade the plastic wastes, and this review summarizes the potential microbes, enzymes, and the underpinning mechanisms for degrading six most commonly used plastics including polyethylene terephthalate, polyethylene, polyvinyl chloride, polypropylene, polystyrene and polyurethane. The challenges and future perspectives on microbial degradation of plastics were proposed.

Avaliação da energia incorporada e da emissão de CO2 em recipientes para refrigerantes: PET versus vidro / Evaluation of energy and CO 2 emissions in soft drink containers: PET versus Glass

RESUMO Este artigo busca avaliar e comparar qual material (PET ou vidro) proporciona um ciclo de vida mais sustentável para os recipientes utilizados no envase de refrigerantes. Foram comparados quatro recipientes de vidro - três retornáveis e um descartável - com cinco recipientes em polietileno tereftalato (PET) - três descartáveis produzidos com material virgem, um descartável produzido com 20% de material reciclado e um retornável (RefPET). Utilizou-se como ferramenta o programa CES-Selector/EcoAudit, o qual considera cinco etapas principais do ciclo de vida do produto - material (obtenção de matéria-prima), produção, transporte, uso e descarte. Os indicadores resultantes foram a energia incorporada e a quantidade de CO2 emitida. Os resultados, para cada 1.000 L de refrigerante envasado, comprovam que a reutilização do recipiente é a escolha ambientalmente mais correta e mostram que, nas garrafas de PET, quanto maior a capacidade do recipiente, menor a quantidade de material de PET utilizado, menor a energia incorporada e menor a emissão de CO2. Por outro lado, para as garrafas de vidro, o resultado é oposto, ou seja, quanto maior a capacidade do recipiente, maior a quantidade de material utilizado, maior a energia incorporada e maior será a quantidade de CO2 emitida. Considerando a energia incorporada e o CO2 gerado, o resultado final mostra que, para envasar pequenos volumes (vidro de 290 mL e PET de 250 mL), os recipientes de vidro apresentam resultados melhores, enquanto, para envasar volumes maiores (acima de 600 mL), os recipientes de PET são os mais indicados.

ABSTRACT The present paper aims to assess and compare which material (PET or glass) provides a more sustainable life cycle for soft drink containers. Four glass containers, three returnable ones and one disposable were compared to five PET containers (polyethylene terephthalate), three disposable ones made from virgin material, one disposable made from 20% of recycled material and one returnable (RefPet). The CES-Selector/EcoAudit program, which considers five main stages of the product life cycle - material (obtaining raw material), production, transportation, use and disposal - , was used. The resulting indicators were the energy and the amount of CO2 emission. The results, for every 1,000 liters of soft drink bottled, prove that the reuse of containers is the most environmentally correct choice and show that in PET bottles the larger the container capacity the smaller the amount of PET material used, lower the energy and the lower the CO2 emission. On the other hand, for glass bottles, the result is opposite, that is, the larger the container capacity, the greater the amount of material used, the greater the embodied energy and the greater the CO2 emission. Considering the incorporated energy and the CO2 generated, the final result shows that glass containers present better results when filling small-volume packages (290 ml glass and 250 ml PET), while PET containers are the most suitable ones for larger volumes (above 600 ml).

Recycled plastics: An alternative material for prosthetic check socket fabrication / The Health Sciences Journal

INTRODUCTION@#Polyethylene terephthalate glycol (PETG), the material used to fabricate prosthetic check sockets is expensive and not locally available. This study aimed to develop an alternative material for fabricating prosthetic check sockets. Specifically, it aimed to determine the material properties of the alternative and to compare it against the standard check socket, PETG.@*METHODS@#Alternative materials were made from recycled plastic bottles (PETR), sando bags (PER) and a plasticizer. A two-roll mill and a compression molder were used to fabricate the alternative materials. All samples were prepared and tested according to the American Society for Testing and Materials for each property test. Kruskal-Wallis test with post-hoc analysis of Mann-Whitney-U test was used for impact resistance test results while descriptive analysis was used for Vicat softening point and tensile strength test results.@*RESULTS@#PER performed well against PETR in all tests and exhibited acceptable Vicat softening point (126 vs 75ºC) and impact resistance (235 vs 71 J/m) compared to the standard PETG. On the other hand, PETR performed poorly in all three tests: tensile strength (0 vs 56 MPa), Vicat softening point (0 vs 75ºC) and impact resistance (20.3 vs 71 J/m).@*CONCLUSION@#PER was shown to have acceptable properties as an alternative to the standard material. However, further testing must be implemented to improve its tensile strength.

The Osteogenesis of Hydroxyapatite and Gelatin Coating on the Polyethylene Terephthalate Artificial Ligament Graft / 中国运动医学杂志

Ojective To explore the effect of the hydroxyapatite(HAp)and gelatin(Gel)coating on the healing of the polyethylene terephthalate(PET)artificial ligament.Methods The artificial ligaments were divided into a PET group with a pure PET surface and a PET/HAp/Gel group coated with HAp and Gel.Both coatings were observed using the scanning electron microscope(SEM).Forty-eight male New Zealand rabbits were randomly divided into two groups and underwent anterior cruciate ligament reconstruction,before two kinds of artificial ligaments were implanted respectively.Four weeks and 8 weeks after the operation,the rabbits were sacrificed,and histological hematoxylin and eosin (HE)staining as well as the biomechanical examination were performed.Results HAp/Gel coating was found depositing on the surface of PET artificial ligaments.Histological HE staining showed a thick fibrous connective tissue forming at the graft-host bone interface 4 weeks postoperatively,and the interface width of both groups were narrowed,with significantly more shrinking in the PET/HAp/Gel coating group.And new bone tissues were found in the interface of PET/HAp/Gel group 8 weeks after the operation.The biomechanical examination found significant differences in the failure load between the PET(46.16 ± 2.88 N) and PET/HAp/Gel group(71.32 ± 3.92 N)8 weeks after the surgery(P=0.0021).And 4 weeks and 8 weeks after the surgery,significant differences were found in the stiffness between the PET group and the PET/HAp/Gel group(11.06 ± 1.14 N/mm vs 16.20 ± 1.17 N/mm,P=0.0199;14.37 ± 0.88 N/mm vs 24.35 ± 1.35 N/mm,P=0.0008).Conclusion HAp/Gel coating can enhance the osteogenesis of PET artificial ligaments,promoting the new bone formation at the graft-host bone interface and herein strengthening the graft-host bone healing.

A Comparative Evaluation of Absorbable and Nonabsorbable Sutures for Open Repair of Achilles Tendon Rupture: A Pilot Study / 체질인류학회지

This pilot study was performed to compare the functional and clinical results including complications after surgery in the open repair of Achilles tendon rupture with regard to the type of suture material. A consecutive series of twenty patients with acute Achilles tendon rupture who underwent open repair were enrolled in this pilot study. The patients were divided equally into 2 groups according to suture type. In the nonabsorbable suture group, No. 2 braided nonabsorbable polyethylene terephthalate sutures were used, and in the absorbable suture group, braided absorbable polyglactin sutures were used. The Korean version of the Foot and Ankle Outcome Score (FAOS) and complications were assessed to evaluate functional and clinical result. Mean total Foot and Ankle Outcome Score (FAOS) was 89.8 (range, 71.1~100) in the nonabsorbable suture group and 82.7 (range, 61.9~92.5) in the absorbable suture group (p=0.22). All patients returned to their previous life activity. The absorbable suture group had fewer postoperative complications (10%) than the nonabsorbable suture group (20%), but there was no significant difference between two groups (p=0.45). This pilot study showed that use of an absorbable suture for Achilles tendon repair had functional and clinical results comparable to those of the nonabsorbable suture. However, a use of an absorbable suture was associated with a lower incidence of complications than the use of nonabsorbable suture. Therefore, these results have to be confirmed in a randomized controlled cohort trial with larger population.

Foreign Body Reaction after Implantation of a Device for Intervertebral Assisted Motion

The device for intervertebral assisted motion (DIAM) is a dynamic implant that consists of a silicone bumper enveloped by a polyethylene terephthalate (PET) fiber sack. Silicone and PET were used because of their biological inertness, but repetitive motion of the spine can cause wear on the implant nonetheless. The purpose of this study is to report a case of foreign body reaction (FBR) against a DIAM. A 72-year-old female patient presented with lower back pain and both legs radiating pain. She had undergone DIAM implantation at L4–5 for spinal stenosis 5 years previously. The intervertebral disc space of L4–5, where the DIAM was inserted, had collapsed and degenerative scoliosis had developed due to left-side collapse. MRI showed L3–4 thecal sac compression and left L4–5 foraminal stenosis. The patient underwent removal of the DIAM and instrumented fusion from L3 to L5. During surgery, fluid and granulation tissue were evident around the DIAM. Histopathology showed scattered wear debris from the DIAM causing chronic inflammation due to the resulting FBR. A FBR due to wear debris of a DIAM can induce a hypersensitivity reaction and bone resorption around the implant, causing it to loosen.

Recent curative effect of polyethylene terephthalate artificial ligament reconstruction for the treatment of distal tibiofibular syndesmosis injury / 局解手术学杂志

Objective To explore the effect of polyethylene terephthalate artificial ligament revascularization on the treatment of distal tibiofibular syndesmosis injury .Methods The data of 18 patients with distal tibiofibular syndesmosis injury in our hospital from March 2013 to March 2014 were retrospectively analyzed .Fourteen patients received the bilateral suspension fixed technology ,and 4 cases were fixed with unilateral suspension fixation by extrusion screw which could be absorbed .The ankle joint mobility was measured during the follow-up,which were evaluated by American orthopedic foot and ankle society ( AOFAS) .Results Eighteen patients with distal tibiofibular syndesmosis in-jury were followed up for 12~17 months,with an average of 13.5 months.Imagings showed that the tibiofibular space was normal on postop-erative X-ray films,and there was no lost in 1 year.The PET of artificial ligaments were taken out ,and the artificial ligament and bone tissue were combined with a good ligament toughness .The pathological examination revealed the fibrous tissue grew in the artificial ligaments .Ac-cording to AOFAS ankle function grading evaluation of curative effect ,11 cases were excellent ,6 cases were good ,and 1 case was not obvious . Conclusion PET artificial ligament revascularization can recover the hinge functions of tibiofibular syndesmosis for patients with early recov -ery of ankle plantar flexion range in a short time .Different ways of fixed ligament had no obvious effect on functional recovery ,however,the extrusion screw technology can shorten the time of surgery .

Adsorption studies on plastic packaging materials of Shuangbai Film Spraying Agent / 中草药

Objective: To investigate the components adsorbability of Shuangbai Film Spraying Agent (SFSA) packaged by three types of plastic medicinal materials, and to optimize the packaging material for SFSA. Methods: SFSA was dispensed in polyethylene terephthalate (PET), polypropylene (PP), and high density polyethylene (HDPE) plastic spraying bottles and the factors influencing test and conventional sample test were carried out. The characteristics of sample solution and spraying bottles and the internal color of spraying bottles were inspected, the optimal packaging material was screened for compatibility long-term test, the wall color changes of spraying bottles were observed, and the contents of drug concentration and the bottle wall adsorption were determined by HPLC. Results: The degree of change in color after six months of the three types of drug packaging material was HDPE > PP > PET; The hardness and impact strength of PP bottle decreased. PET bottles only adsorbed small quantities of aloe-emodin, rhein, emodin, chrysophanol, emodin, and none of the other ingredients. The chrysophanol and emodin were unstable in the aqueous solution, and the contents of other indicator components of SFSA in the PET bottle were stable. Conclusion: PET is suitable to be the packaging materials of SFSA.