Terephthalic Acid Concentration Research Articles

Discovery and characterization of two novel polyethylene terephthalate hydrolases: One from a bacterium identified in human feces and one from the Streptomyces genus

Polyethylene terephthalate (PET) is widely used for various industrial applications. However, owing to its extremely slow breakdown rate, PET accumulates as plastic trash, which negatively affects the environment and human health. Here, we report two novel PET hydrolases: PpPETase from Pseudomonas paralcaligenes MRCP1333, identified in human feces, and ScPETase from Streptomyces calvus DSM 41452. These two enzymes can decompose various PET materials, including semicrystalline PET powders (Cry-PET) and low-crystallinity PET films (gf-PET). By structure-guided engineering, two variants, PpPETaseY239R/F244G/Y250G and ScPETaseA212C/T249C/N195H/N243K were obtained that decompose Cry-PET 3.1- and 1.9-fold faster than their wild-type enzymes, respectively. The co-expression of ScPETase and mono-(2-hydroxyethyl) terephthalate hydrolase from Ideonella sakaiensis (IsMHETase) resulted in 1.4-fold more degradation than the single enzyme system. This engineered strain degraded Cry-PET and gf-PET by more than 40% and 6%, respectively, after 30 d. The concentrations of terephthalic acid (TPA) in the Cry-PET and gf-PET degradation products were 37.7% and 25.6%, respectively. The discovery of these two novel PET hydrolases provides opportunities to create more powerful biocatalysts for PET biodegradation.

Experimental Study on Ultrasonic Cavitation Intensity Based on Fluorescence Analysis

The Ultrasonic cavitation effect has been widely used in mechanical engineering, chemical engineering, biomedicine, and many other fields. The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty. Based on this, a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper. In the experiment of fluorescence intensity measurement, terephthalic acid (TA) was used as the fluorescent probe, ultrasonic power, ultrasonic frequency, and irradiation time were independent variables, and fluorescence intensity and fluorescence peak area were used as experimental results. The collapse of cavitation bubble will cause molecular bond breakage and release ·OH, and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with ·OH. The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer. The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment, and then increased slowly with the increase of ultrasonic power, which gradually increased with the increase of irradiation time. They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz. The irradiation time was the most influential factor, and the cavitation intensity of low frequency was higher overall. The fluorescence intensity and fluorescence peak area of the samples increased by 2–20 times after ultrasonic treatment, which could increase from 69 and 5238 to 1387 and 95451, respectively. After the irradiation time exceeded 25 min, the growth rate of fluorescence intensity slowed down, which was caused by the decrease of gas content and TA concentration in the solution. The study quantitatively characterized the cavitation intensity, reflecting the advantages of fluorescence analysis, and provided a basis for the further study of ultrasonic cavitation.

Marine sponges as bioindicators of pollution by synthetic microfibers in Antarctica

Different marine sponge species from Tethys Bay, Antarctica, were analyzed for contamination by polyester and polyamide microplastics (MPs). The PISA (Polymer Identification and Specific Analysis) procedure was adopted as it provides, through depolymerization and HPLC analysis, highly sensitive mass-based quantitative data. The study focused on three analytes resulting from the hydrolytic depolymerization of polyesters and polyamides: terephthalic acid (TPA), 6-aminohexanoic acid (AHA), and 1–6-hexanediamine (HMDA). TPA is a comonomer found in the polyesters poly(ethylene terephthalate) (PET) and poly(butylene adipate co terephthalate) (PBAT), and in polyamides such as poly(1,4-p-phenylene terephthalamide) (Kevlar™ and Twaron™ fibers) and poly(hexamethylene terephthalamide) (nylon 6 T). AHA is the monomer of nylon 6. HMDA is a comonomer of the aliphatic nylon 6,6 (HMDA-co-adipic acid) and of semi-aromatic polyamides such as, again, nylon 6 T (HMDA-co-TPA). Except for the biodegradable PBAT, these polymers exhibit high to extreme mechanical, thermal and chemical resistance. Indeed, they are used as technofibers in protective clothing able to withstand extreme conditions as those typical of Antarctica. Of the two amine monomers, only HMDA was found above the limit of quantification, and only in specimens of Haliclona (Rhizoniera) scotti, at a concentration equivalent to 27 μg/kg of nylon 6,6 in the fresh sponge. Comparatively higher concentrations, corresponding to 2.5–4.1 mg/kg of either PBAT or PPTA, were calculated from the concentration of TPA detected in all sponge species. Unexpectedly, TPA did not originate from PET (the most common textile fiber) as it was detected in the acid hydrolysate, whereas the PISA procedure results in effective PET depolymerization only under alkaline conditions. The obtained results showed that sponges, by capturing and concentrating MPs from large volumes of filtered marine waters, may be considered as effective indicators of the level and type of pollution by MPs and provide early warnings of increasing levels of pollution even in remote areas.

Enzymatic post-consumer poly(ethylene terephthalate) (PET) depolymerization using commercial enzymes.

Poly(ethylene terephthalate) (PET) is a synthetic polymer widely used globally. The high PET resistance to biotic degradation and its improper destination result in the accumulation of this plastic in the environment, largely affecting terrestrial and aquatic animals. This work investigated post-consumer PET (PC-PET) degradation using five commercial hydrolase enzymes (Novozym 51032, CalB, Palatase, Eversa, Lipozyme TL). Humicola insolens cutinase (HiC, Novozym 51032) was the most active among the enzymes studied. Several important reaction parameters (enzyme type, dual enzyme system, enzyme concentration, temperature, ultrasound treatment) were evaluated in PC-PET hydrolysis using HiC. The concentration and the proportion (molar ratio) of hydrolysis products, terephthalic acid (TPA), mono(2-hydroxyethyl) terephthalate (MHET), and bis(2-hydroxyethyl) terephthalate (BHET), were significantly changed depending on the reaction temperature. The TPA released at 70°C was 3.65-fold higher than at 50°C. At higher temperatures, the conversion of MHET into TPA was favored. The enzymatic PET hydrolysis by HiC was very sensitive to the enzyme concentration, indicating that it strongly adsorbs on the polymer surface. The concentration of TPA, MHET, and BHET increased as the enzyme concentration increased, and a maximum was achieved using 40-50 vol % of HiC. The presented results add relevant data to optimizing enzyme-based PET recycling technologies.

Testicular toxicity in mice exposed to terephthalic acid in utero and during lactation.

Terephthalic acid (TPA) is a worldwide aromatic compound widely used to manufacture resins and the raw material for the polymerization reaction with ethylene glycol to produce polyethylene terephthalate, known as PET. The use of TPA extends to the synthesis of phthalates, plasticizers used in various industrialized products such as toys and cosmetics. The present study aimed to evaluate the testicular toxicity of terephthalic acid on male mice exposed in utero and during lactation to TPA in different developmental windows. The animals were treated intragastric with TPA at stock dispersal dosages corresponding to 0.0014g/ml and 0.56g/ml of TPA in 0.5% v/v carboxymethylcellulose as well as the control dose, composed solely of dispersion of carboxymethylcellulose (0.5% v/v). Four experimental windows were established: group I-treatment in utero, in the fetal period (gestational day-GD 10.5-18.5), with euthanasia at GD 18.5; group II-treatment in utero, in the fetal period (GD 10.5-18.5) and the lactational period (postnatal day (PND-15)), with euthanasia at 15days; group III-treatment in utero in the fetal period (DG 10.5-18.5) with euthanasia at 70days (age of sexual maturity, PND 70); group IV-treatment in utero, in the fetal period (GD 10.5-18.5) and the lactational period (PND-15), with euthanasia at 70days (PND70). The results indicate that TPA changes the reproductive parameters (testicular weight, GI, penis size, and anogenital index) only at the dose of 0.56g/ml in the fetal period. Data on the volumetric ratio of the testis elements show that the dispersion with the highest concentration of TPA significantly altered the blood vessel/capillary, lymphatic vessel, and connective tissue percentages. Only at the dose of 0.56g/ml TPA was it effective in decreasing the Leydig and Sertoli cell numbers of the euthanized animals at GD 18.5. In group II, TPA increased the diameter and lumen of seminiferous tubules, which indicates that TPA accelerated the maturation process of Sertoli cells without changing the number and the nuclear volume of these cells. The Sertoli and Leydig cell numbers of the 70-day animals exposed to TPA in the gestational and lactational period were similar to the control. Therefore, the present study is the first in the literature to show that TPA presents a testicular toxicity during fetal (DG18.5) and postnatal life (PND15), without repercussion in adulthood (70days).

Post-Consumer Poly(ethylene terephthalate) (PET) Depolymerization by Yarrowia lipolytica: A Comparison between Hydrolysis Using Cell-Free Enzymatic Extracts and Microbial Submerged Cultivation

Several microorganisms have been reported as capable of acting on poly(ethylene terephthalate) (PET) to some extent, such as Yarrowia lipolytica, which is a yeast known to produce various hydrolases of industrial interest. The present work aims to evaluate PET depolymerization by Y. lipolytica using two different strategies. In the first one, biocatalysts were produced during solid-state fermentation (SSF-YL), extracted and subsequently used for the hydrolysis of PET and bis(2-hydroxyethyl terephthalate) (BHET), a key intermediate in PET hydrolysis. Biocatalysts were able to act on BHET, yielding terephthalic acid (TPA) (131.31 µmol L-1), and on PET, leading to a TPA concentration of 42.80 µmol L-1 after 168 h. In the second strategy, PET depolymerization was evaluated during submerged cultivations of Y. lipolytica using four different culture media, and the use of YT medium ((w/v) yeast extract 1%, tryptone 2%) yielded the highest TPA concentration after 96 h (65.40 µmol L-1). A final TPA concentration of 94.3 µmol L-1 was obtained on a scale-up in benchtop bioreactors using YT medium. The conversion obtained in bioreactors was 121% higher than in systems with SSF-YL. The results of the present work suggest a relevant role of Y. lipolytica cells in the depolymerization process.

Halotolerant Terephthalic Acid-Degrading Bacteria of the Genus Glutamicibacter

Terephthalic acid (TPA) is an isomer of ortho-phthalic acid, which is widely used in the chemical industry to produce artificial fibers and plastics, including polyethylene terephthalate; it is a widespread environmental pollutant. The ability of two strains of Glutamicibacter spp. PB8-1 (=ВКМ Ac-2934D) and BO25 (=ВКМ Ac2935D) isolated from the salt mining area (Perm krai, Russia) to grow using terephthalic acid as the only source of carbon and energy was studied. The strains PB8-1 and BO25 could utilize high concentrations of TPA (30 g/L), which was shown for TPA-degrading bacteria for the first time. Strains PB8-1 and BO25 were halotolerant bacteria: they grew in the NaCl-free medium or at NaCl concentrations of up to 90 g/L in a rich medium and up to 60 g/L in a mineral medium supplemented with TPA. No bacteria capable of degrading TPA under saline conditions were previously described. The growth of the strain BO25 using TPA was accompanied by the accumulation and subsequent degradation of protocatechuic acid (PCA), suggesting that the TPA metabolism occurred through PCA, which was previously described for bacteria of different taxa, including actinobacteria. Thus, TPA-degrading strains Glutamicibacter spp. PB8-1 and BO25 are promising for the development of bioremediation methods for saline soils and wastewater contaminated with TPA.

Polyamine-based thin-film composite nanofiltration membrane embedded with catalytic chemical additive for enhanced separation performance and acid stability

Nanofiltration (NF) membranes with excellent acid stability and enhanced separation performance are of great benefit in treating acid wastewater and meeting freshwater demand. In this study, terephthalic acid (TPA) molecules with unique catalytic reactivity were directly incorporated as a chemical additive into the membrane selective layer via interfacial polymerization reaction to form a novel polyamine-based nanofiltration membrane. The resultant membrane morphology, chemical and functional composition, hydrophilicity, surface charge, separation performance, thermal stability and acid resistance were all investigated. The results showed improved hydrophilicity, electronegativity and cross-linking degree of the membranes. Compared with the bare membrane, the TPA incorporated membrane performance was best at 0.15% TPA concentration with improved water permeability of 14.1 LMH.bar −1 which was 1.6 times the control with an excellent salt rejection of 96.7% for MgCl 2 . Furthermore, after exposure to 5% (w/w) HCl and 20% (w/w) H 2 SO 4 acid solutions at 25 °C for 60-days, the membranes displayed excellent acid stability with appreciable increase and a corresponding decrease in water fluxes and salt rejections. No obvious change was observed in the membrane surface as revealed by the SEM, FTIR and XPS analysis after exposure period expiration. In addition, the membrane showed excellent pressure resistance and long-term stability after acid exposure for 30 days. Overall, incorporating TPA into the membrane provides a scalable system with great potential in water desalination and acid wastewater treatment. • Terephthalic acid (TPA) molecule act as additive/co-monomer for novel TFC membrane. • Incorporation of TPA enhances hydrophilicity, surface charge and thermal stability. • Optimal membrane has 14.1 LMHbar −1 water flux and 96.7% of MgCl 2 rejection. • Optimal membrane shows excellent acid stability after 60 days exposure period. • Membrane shows good prospect in water desalination and acid wastewater treatment.

Fungal and enzymatic bio-depolymerization of waste post-consumer poly(ethylene terephthalate) (PET) bottles using Penicillium species.

Poly(ethylene terephthalate) (PET) is a petroleum-based plastic that is massively produced and used worldwide. A promising PET recycling process to circumvent petroleum feedstock consumption and help to reduce environmental pollution is microbial or enzymatic biodegradation of post-consumer (PC) PET packages to its monomers-terephthalic acid (TPA) and ethylene glycol (EG)-or to key intermediates in PET synthesis-such as mono- and bis-(2-hydroxyethyl) terephthalate (MHET and BHET). Two species of filamentous fungi previously characterized as lipase producers (Penicillium restrictum and P. simplicissimum) were evaluated in submerged fermentation for induction of lipase production by two inducers (BHET and amorphous PET), and for biodegradation of two substrates (BHET and PC-PET). BHET induced lipase production in P. simplicissimum, achieving a peak of 606.4U/L at 49h (12.38U/L.h), representing an almost twofold increase in comparison to the highest peak in the control (without inducers). Microbial biodegradation by P. simplicissimum after 28days led to a 3.09% mass loss on PC-PET fragments. In contrast, enzymatic PC-PET depolymerization by cell-free filtrates from a P. simplicissimum culture resulted in low concentrations of BHET, MHET and TPA (up to 9.51µmol/L), suggesting that there are mechanisms at the organism level that enhance biodegradation. Enzymatic BHET hydrolysis revealed that P. simplicissimum extracellular enzymes catalyze the release of MHET as the predominant product. Our results show that P. simplicissimum is a promising biodegrader of PC-PET that can be further explored for monomer recovery in the context of feedstock recycling processes.

Improved production of biocatalysts by Yarrowia lipolytica using natural sources of the biopolyesters cutin and suberin, and their application in hydrolysis of poly (ethylene terephthalate) (PET).

Since plastic pollution emerged as an urgent environmental problem, different biocatalysts have been tested for poly(ethylene terephthalate) (PET) hydrolysis. This work evaluated three different possible inducers for lipases and/or esterases, two natural sources of biopolymers (apple peels and commercial cork) and PET, as supplements in the solid-state fermentation of soybean bran by Yarrowia lipolytica. The obtained enzymatic extracts displaying different levels of lipase and esterase activities were then tested for PET depolymerization. Supplementation with 5 or 20 wt% of commercial cork led to an increase of 16% in lipase activity and to an increase of 131% in esterase activity, respectively. PET supplementation also led to an increase in the esterase activity of the enzymatic extracts (up to 69%). Enzymes produced in the screening step were able to act as biocatalysts in PET hydrolysis. Enzymatic extracts obtained in fermentation samples supplemented with 20 wt% PET and 20 wt% apple peels led to the highest terephthalic acid concentration (21.2µmol L-1) in 7days, whereas enzymes produced in commercial cork media were more efficient for bis(2-hydroxyethyl) terephthalate (BHET) hydrolysis, one of the key-PET hydrolysis intermediates. Results suggest a good potential of the biocatalysts produced by Y. lipolytica IMUFRJ 50,682 in a low-cost media for subsequent utilization in PET depolymerization reactions. This is one of the few reports on the use of a yeast for this application.

Process strategies to improve biocatalytic depolymerization of post-consumer PET packages in bioreactors, and investigation on consumables cost reduction.

Massive plastics production has raised concerns about low recycling rates and disposal of these materials in nature, causing environmental and economic impacts. Poly(ethylene terephthalate) (PET) is one of main polymers used for manufacture of plastic packaging (e.g. bottles, trays). Enzymatic recycling of PET has been a route of increasing study aiming at to recover its monomers (terephthalic acid and ethylene glycol), resulting in a circular production chain. In this study, investigation of pH control and fractionation of enzyme feeding were explored in post-consumed PET (PC-PET) hydrolysis reactions catalyzed by Humicola insolens cutinase (HiC) in stirred reactors. It was found that the unbuffered reaction provided of pH control by 0.5M NaOH addition showed 2.39-fold improvement in the released monomers (to a total of 26.3mM), comparatively to the Tris-HCl-buffered reaction. In addition, it was observed a possibility of reducing the enzyme loading used in the process by half, leading to an increase of 2.41-fold in the specific terephthalic acid concentration released per protein amount, whilst maintaining a high products concentration (97mM). A simplified cost analysis of reaction consumables was performed, and the data reported here demonstrates that these alternative process strategies contribute to costs reduction on the enzymatic depolymerization reactions of PET.

Supplementation of watermelon peels as an enhancer of lipase and esterase production by Yarrowia lipolytica in solid-state fermentation and their potential use as biocatalysts in poly(ethylene terephthalate) (PET) depolymerization reactions

Yarrowia lipolytica is a yeast that presents high biotechnological potential due to its ability to produce many metabolites, among them lipases and esterases, which are important industrial biocatalysts. Since Brazil is an agroindustrial country, it generates an enormous diversity of residues or byproducts that can be used as a platform for biomolecules production. This work aims to evaluate lipase and esterase production by Y. lipolytica via solid-state fermentation using soybean bran and soybean bran supplemented with watermelon peels in different contents, and subsequent use of the enzyme extracts for poly(ethylene terephthalate) (PET) hydrolysis. Supplementation of watermelon peels in the lowest content led to an improvement of lipase activity in almost 31%, reaching 75.22 U g−1. Esterase productivity was 1.5-fold higher when 20 wt% of watermelon peels were added to the media culture. Timecourse evaluation of enzymes production showed a maximum lipase activity in 14 h and similar esterase activity in 14 and 20 h of fermentation. Proteases production were also intensified in supplemented samples. Enzymes produced with 5 wt% watermelon peels supplementation led to higher terephthalic acid concentration (up to 42.02 µmol L−1) during PET depolymerization. Results suggest a great potential of enzyme production in low cost fermentative media to act as biocatalysts in PET hydrolysis reactions.

Acclimatization of a newly isolated bacteria in monomer tere-phthalic acid (TPA) may enable it to attack the polymer poly-ethylene tere-phthalate(PET)

Environmental persistence of polyethylene terephthalate(PET) has become a vexing problem. PET is a very popular polymer for many desirable properties, especially as a food grade polymer. It is being produced in large quantities and the entire production is not recycled. A large quantity of PET is finding its way to the Municipal Solid Waste (MSW) dumps and even to rivers as microplastics. There are various methods for PET degradation, among which bio-degradation is most environmentally friendly and technologically suitable. Some metagenomic studies have been conducted for isolation of PET degrading bacteria/enzymes. However, all previous studies deal with bacteria directly isolated from contaminated sites. We have isolated one such bacteria Rhococcus sp. SSM1 from a PET rich MSW dump of New Delhi. However, we did not use the bacteria directly for PET degradation. We forced the bacteria to grow on the monomer terephpthalic acid(TPA),the monomer, as the only carbon source for generations. Surprisingly, the Rhococcus sp. SSM1 acclimatized to grow on TPA, was able to attack PET flims, the polymer, resulting in some degradation of the material. This was evidenced by presence of more TPA concentration than supplied at certain time of fermentation and many heavy molecules (heavier than TPA) in the fermentation media which can only come only by degradation of PET. This is a new paradigm in biodegradation research, where acclimatization in the monomer enables a bacteria to attack the polymer. However, we are not claiming that the bacteria can biodegrade bulk PET. It is perhaps surviving on TPA and attacking the surface of the polymer, which is microscopically rough. Bacteria may be recognizing some protruding fingers di, tri or n-mers of TPA from polymer surface and attacking them.

Determination of Hydroxyl Radical Production from Sulfide Oxidation Relevant to Sulfidic Porewaters

Hydroxyl radical (·OH) production from the reaction between aqueous total sulfide ([H2S]T = [H2S] + [HS–] + [S2–]) and dissolved oxygen is potentially an environmentally important reaction when anoxic, sulfidic water is exposed to oxygen. Using hydroxyterephthalate (hTPA) formation from the reaction of terephthalic acid (TPA) with ·OH as a probe for ·OH production, hydrogen peroxide was verified as an essential intermediate, and the production of free ·OH, versus lower energy hydroxylating agents, was established. The optimal conditions for the quantification of ·OH production kinetics and yield were determined by varying TPA and total sulfide concentrations. An initial total sulfide concentration of 10 μM and TPA concentration of 2 mM was used to find a yield of 15 mmol of ·OH per mole [H2S]T. Additionally, a pseudo-first-order model elucidated a maximum rate of production of 1.04 (±0.05) × 10–4 moles of ·OH per hour per mole of [H2S]T. Experiments with sulfidic wetland porewaters containing up to 294 mg/L of dissolved organic carbon (DOC) revealed that [H2S]T, and not reduced DOC, was the dominant source of ·OH. A simple model considering a water containing [H2S]T, DOC, and methane exposed to a constant concentration of oxygen (∼50 μM) gave steady state values of [·OH] ranging from 5.7 × 10–19 to 3.2 × 10–18 M. The results indicate that [H2S]T should be considered a source of dark formation of ·OH in addition to ferrous iron and reduced DOC.

Biodegradation of purified terephthalic acid manufacturing effluent from a petrochemical industry

Purified terephthalic acid (PTA) is the raw material for polyester fibres, plastics, coating and adhesives. Its manufacture generates large volumes of effluent with high concentration of terephthalic acid (500-600 ppm), a critical pollutant. In this study a mixed culture made up of five types of bacteria, derived from the effluent treatment plant (ETP) sludge was used to aerobically treat the PTA effluent, removing all the benzoates [4-carboxybenzyl alcohol, isophthalic acid, terephthalic acid, 4-carboxy benzaldehyde (4-CBA), benzoic acid, p-toluic acid and trimellitic acid] which contribute to its chemical oxygen demand (COD). The study included optimisation of pH (6-9), pH neutralisers and biomass concentration (≥2,000 ppm Mixed liquor suspended solids) for achieving 94–95% COD removal in 72–96 h, the results being supported by HPLC analysis. Metals (Co, Mn and Mg) reduced significantly (88%, ~100% and 83%, respectively), being utilised for growth or getting sequestered in the biomass. Characterisation of the five pure cultures was carried out.

Microplastics in house dust from 12 countries and associated human exposure

Global marine pollution by microplastics (MPs) has received considerable attention in recent years. Nevertheless, little is known about the occurrence of MPs in indoor environments. A novel analytical method was used to quantitatively determine polyethylene terephthalate (PET)- and polycarbonate (PC)- based MPs in 286 indoor dust samples collected from 12 countries. PET-based MPs were detected in all dust samples at concentrations of 38–120,000 µg/g (median: 5900 µg/g), whereas PC-based MPs were measured at <0.11–1700 µg/g (median: 8.8 µg/g). Significant positive correlations were found between the concentrations of terephthalic acid (a PET monomer) and PET as well as between bisphenol A (a PC monomer) and PC. Based on the concentrations of MPs measured in indoor dust, the median daily intake of PET-based MPs calculated for infants was in the range of 4000–150,000 ng/kg-bw/day.

Hygienic and clinical functional aspects of health status in phthalate production

Introduction. Polyesters of terephthalic acids are major products of organic synthesis, widely used in various industries: for packing materials production, including those for foods and medicaments. Polyesters of terephthalic acids are stable chemicals and highly toxic with cumulative eff ects. Phthalates production requires further studies. Objective. To determine hygienic and clinical functional aspects of workers’ health formation in phthalates production. Materials and methods. Special clinical functional study covered workers who first started work activity in production of terephthalic acids, purified terephthalic acid and polyethylene terephthalate over 5 years of JSC “POLYEF” exploitation. Hematologic, cytochemical, biochemical and immunologic studies covered workers with primary 5-year service in the production. Hygienic evaluation covered work conditions of workers engaged into production of terephthalic acid polyesters. Results. Th e work conditions are characterized by increased level of terephthalic acids from 1.5 to 2.8 MACs. By 5 years of service, most the workers demonstrate anemia, reticulocytosis, thrombocytopenia, eosinophilia, lymphocytosis, lower enzymatic activity. Investigations also covered the most marked and early changes in cardiovascular, nervous systems, ENT organs, locomotory system and connective tissue. Major factors infl uencing the stated disorders are acting concentrations of terephthalic acid, exceeding MAC 1.5–2.8 times; character of infl uence caused by complex of chemicals with acute and unidirectional action; occupational noise exceeding MAL of 5–21 dBA. Conclusions. General principles of occupational factors action: anemic syndrome; polymorphic regulatory disorders of metabolism; sensitization, allergization; formation of secondary immune defi ciency of cytopenia type; vegetative vascular disorders — the most fr equent and early syndrome of clinical and structural health disorders; locomotory disorders caused probably by phthalates toxicity; upper respiratory tract disorders (summarized eff ects of chemical irritants); specifi c changes associated with increased noise parameters (vegetative disorders, hypertension, neurosensory deafness, etc.).

High-fold improvement of assorted post-consumer poly(ethylene terephthalate) (PET) packages hydrolysis using Humicola insolens cutinase as a single biocatalyst

Abstract The dissemination of technologies for poly(ethylene terephthalate) (PET) recycling is of paramount importance in the context of the plastics circular economy. One of the most promising alternatives is to use enzymes as catalysts for PET depolymerization to its monomers, but this route still needs improvement, especially regarding titer and productivity. In the present work, a sequential approach comprised of fractional factorial and central composite rotatable designs, the path of steepest ascent and one-way evaluation of variable effect, was performed to address these limitations, during assorted post-consumer PET (PC-PET) hydrolysis catalyzed by Humicola insolens cutinase. The highest terephthalic acid concentration and productivity during PC-PET hydrolysis were 100.9 mM (16.8 g/L) and 14.4 mM/day, corresponding to overall improvements of 10-fold and 20-fold, respectively. These data are among the best results described so far for enzyme-catalyzed hydrolysis of used PET packages. Also, the use of a single enzyme system, instead of multiple biocatalysts to achieve final conversion of PET to its monomers, lowers the process complexity and costs.

Determining the migration of nadic acid, terephthalic acid, isophthalic acid and two oligomers from polyester food cans into food in the U.S. market

Concentrations of three monomers used in the manufacture of polyester resins for food cans, isophthalic acid (IPA), terephthalic acid (TA) and nadic acid (NA), and two oligomers were determined in canned food samples. All canned foods were purchased in local supermarkets in the United States. Concentrations of IPA and TA were determined to be from below the limit of detection in tomato sauce to 69 μg/kg in coconut milk, while the highest concentration of NA was found in pumpkin at 21 μg/kg. Estimated concentrations of oligomers in the food samples ranged from non-detect to 595 μg/kg. The influence of the storage time, lot type, and retail outlet on the migration concentrations was also investigated.

Enhanced efficiency and stability of carbon based perovskite solar cells using terephthalic acid additive

We report an effective method to modulate the perovskite crystallization by incorporating terephthalic acid (TPA) additive into the perovskite precursor solutions. The addition of TPA additive simultaneously facilitate nucleation and modulate the kinetics of crystal growth from solutions, enabling preparation of smooth and compact perovskite morphology with improved crystallization, grain uniformity, loading of perovskite into the TiO2 mesopores and coverage area. Before deposition of perovskite films, an ultrathin wide bandgap dielectric MgO nanolayer is incorporated onto porous TiO2 to retard the carrier recombination at the interface in the devices. The mechanism of the interaction between TPA and Pb2+ on the film-forming process of perovskite crystal was also analyzed. Consequently, by optimizing the TPA concentration, we obtained highly efficient and stable low-temperature processed electron transport material (HTM)-free carbon based perovskite solar cells (PSCs). The performance of the PSCs is significantly improved with the mean efficiency increasing from 11.5% ± 0.67% for the control structure to 14.29% ± 0.37% for the TPA modified structure. Furthermore, the TPA modified perovskite films and devices present much better thermal, UV and ambient air stability than the pristine perovskite films and devices, and the corresponding PSCs with TPA modification show excellent stability with efficiency approaching 94% after being exposed to ambient air for 21 days without encapsulation.