Tunable structure and linear viscoelastic properties of poly(glycerol adipate urethane)-based elastomeric composites for tissue regeneration

Elastomeric biocomposites based on poly(glycerol adipate urethane) and hydroxyapatite were fabricated for tissue regeneration. The poly(glycerol adipate urethane) (PGAU) elastomeric composite matrices were obtained by chemical crosslinking of the poly(glycerol adipate) prepolymer (pPGA) with diisocyanate derivative of L-lysine. Two series of composites varying in the amount of L-lysine diisocyanate ethyl ester (LDI) used as a crosslinking agent were manufactured. As a ceramic filler both unmodified and L-lysine surface-modified hydroxyapatite (HAP) particles were used. The novelty of our research consists in the manufactured elastomeric materials and characterization of their linear viscoelastic (LVE) properties. The LVE properties of the composites were investigated by means of dynamic thermomechanical analysis. Frequency sweep and amplitude sweep measurements were performed in shear mode. The influence of the crosslinking agent (LDI) amount, HAP content and surface modification of HAP on the LVE properties of the composites was determined based on the analysis of the master curves of storage (G') and loss (G″) moduli and of tanδ of the composites. Depending on the amount of LDI, HAP and surface modification, the materials differ in the values of rubber elasticity plateau modulus (G0) and G' and G″ determined at selected shear frequencies and at the glassy state. G0 ranges from 278 kPa to 3.98 MPa, G' in the glassy state is within the range of 219 MPa-459 MPa. The G0 values of the PGAU-based composites are within the stiffness range of soft tissue. In view of the choice of HAP as the ceramic component and the G0 values, elastomeric composites have the potential to be used as filling materials in small bone defects (due to their mechanical similarity to osteoid) as well as materials for cartilage tissue regeneration.

Metagenomic investigations into the microbial consortia, degradation pathways, and enzyme systems involved in the biodegradation of plastics in a tropical lentic pond sediment

The exploitation of exciting features of plastics for diverse applications has resulted in significant plastic waste generation, which negatively impacts environmental compartments, metabolic processes, and the well-being of aquatic ecosystems biota. A shotgun metagenomic approach was deployed to investigate the microbial consortia, degradation pathways, and enzyme systems involved in the degradation of plastics in a tropical lentic pond sediment (APS). Functional annotation of the APS proteome (ORFs) using the PlasticDB database revealed annotation of 1015 proteins of enzymes such as depolymerase, esterase, lipase, hydrolase, nitrobenzylesterase, chitinase, carboxylesterase, polyesterase, oxidoreductase, polyamidase, PETase, MHETase, laccase, alkane monooxygenase, among others involved in the depolymerization of the plastic polymers. It also revealed that polyethylene glycol (PEG), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polyethylene terephthalate (PET), and nylon have the highest number of annotated enzymes. Further annotation using the KEGG GhostKOALA revealed that except for terephthalate, all the other degradation products of the plastic polymers depolymerization such as glyoxylate, adipate, succinate, 1,4-butanediol, ethylene glycol, lactate, and acetaldehyde were further metabolized to intermediates of the tricarboxylic acid cycle. Taxonomic characterization of the annotated proteins using the AAI Profiler and BLASTP revealed that Pseudomonadota members dominate most plastic types, followed by Actinomycetota and Acidobacteriota. The study reveals novel plastic degraders from diverse phyla hitherto not reported to be involved in plastic degradation. This suggests that plastic pollution in aquatic environments is prevalent with well-adapted degrading communities and could be the silver lining in mitigating the impacts of plastic pollution in aquatic environments.

Possible hazards from biodegradation of soil plastic mulch: Increases in microplastics and CO2 emissions

Biodegradable mulches are widely recognized as ecologically friendly substances. However, their degradation percentage upon entering soils may vary based on mulch type and soil microbial activities, raising concerns about potential increases in microplastics (MPs). The effects of using different types of mulch on soil carbon pools and its potential to accelerate their depletion have not yet well understood. Therefore, we conducted an 18-month experiment to investigate mulch biodegradation and its effects on CO2 emissions. The experiment included burying soil with biodegradable mulch made of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT), and control treatments with traditional mulch (PE) and no mulch (CK). The results indicated that PE did not degrade, and the degradation percentage of PLA and PBAT were 46.2% and 88.1%, and the MPs produced by the degradation were 6.7 × 104 and 37.2 × 104 items/m2, respectively. Biodegradable mulch, particularly PLA, can enhance soil microbial diversity and foster more intricate bacterial communities compared to PE. The CO2 emissions were 0.58, 0.74, 0.99, and 0.86 g C/kg in CK, PE, PLA, , PBAT, respectively. A positive correlation was observed between microbial abundance and diversity with CO2 emissions, while a negative correlation was observed with soil total organic carbon. Biodegradable mulch enhanced the transformation of soil organic C into CO2 by stimulating microbial activity.

Fractionated lignin as a green compatibilizer to improve the compatibility of poly (butylene adipate-co-terephthalate) /polylactic acid composites

Blending poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA) is a cost-effective strategy to obtain biodegradable plastic with complementary properties. However, the incompatibility between PBAT and PLA is a great challenge for fabricating high-performance composite films. Herein, the ethyl acetate fractionated lignin with the small glass transition temperature and low molecular weight was achieved and incorporated into the PBAT/PLA composite as a compatibilizer. The fractionated lignin can be uniformly dispersed within the PBAT/PLA matrix through a melt blending process and interact with the molecular chain of PBAT and PLA as a bonding bridge, which enhances the intermolecular interactions and reduces the interfacial tension of PBAT/PLA. By adding fractionated lignin, the tensile strength of the PBAT/PLA composite increased by 35.4 % and the yield strength increased by 37.7 %. Owing to lignin, the composite films possessed the ultraviolet shielding function and exhibited better water vapor barrier properties (1.73 ± 0.08 × 10-13 g·cm/cm2·s·Pa). This work conclusively demonstrated that fractionated lignin can be used as a green compatibilizer and a low-cost functional filler for PBAT/PLA materials, and provides guidance for the application of lignin in biodegradable plastics.

Highly impact toughened and excellent flame-retardant polylactide/poly(butylene adipate-co-terephthalate) blend foams with phosphorus-containing and food waste-derived flame retardants

Green polymeric foams are an important research topic for sustainable development. In this study, a natural multifunctional flame-retardant additive based on food waste was developed and evaluated for its ability to replace the commercial additives tricresyl phosphate (TCP) and trioctyl phosphate (TOP) in a polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) foam. A series of blend foams with additives were prepared by melt extrusion. According to the results, the blend foam with 20 phr of TCP showed the best combination of impact toughness and flame retardancy. TCP, however, poses health and environmental risks. Therefore, natural flame retardants (NFRs) were used to partially replace the commercial flame retardant (CFR). A combination of TCP and soybean residue (SB) produced an impact toughened and flame-retardant blend foam. When compared to the neat PLA/PBAT foam, the impact toughness of the best sample was increased by about 256 %. The optimal foam showed excellent flame resistance with a V-0 UL-94 rating and a high LOI value (31.8 %). SB has the potential to partially replace TCP as flame retardant and could be used in a broad range of PLA/PBAT foam applications.

Glycerol- and diglycerol-based polyesters: Evaluation of backbone alterations upon nano-formulation performance

Despite the success of polyethylene glycol-based (PEGylated) polyesters in the drug delivery and biomedical fields, concerns have arisen regarding PEG's immunogenicity and limited biodegradability. In addition, inherent limitations, including limited chemical handles as well as highly hydrophobic nature, can restrict their effectiveness in physiological conditions of the polyester counterpart. To address these matters, an increasing amount of research has been focused towards identifying alternatives to PEG. One promising strategy involves the use of bio-derived polyols, such as glycerol. In particular, glycerol is a hydrophilic, non-toxic, untapped waste resource and as other polyols, can be incorporated into polyesters via enzymatic catalysis routes. In the present study, a systematic screening is conducted focusing on the incorporation of 1,6-hexanediol (Hex) (hydrophobic diol) into both poly(glycerol adipate) (PGA) and poly(diglycerol adipate) (PDGA) at different (di)glycerol:hex ratios (30:70; 50:50 and 70:30 mol/mol) and its effect on purification upon NPs formation. By varying the amphiphilicity of the backbone, we demonstrated that minor adjustments influence the NPs formation, NPs stability, drug encapsulation, and degradation of these polymers, despite the high chemical similarity. Moreover, the best performing materials have shown good biocompatibility in both in vitro and in vivo (whole organism) tests. As preliminary result, the sample containing diglycerol and Hex in a 70:30 ratio, named as PDGA-Hex 30%, has shown to be the most promising candidate in this small library analysed. It demonstrated comparable stability to the glycerol-based samples in various media but exhibited superior encapsulation efficiency of a model hydrophobic dye. This in-depth investigation provides new insights into the design and modification of biodegradable (di)glycerol-based polyesters, potentially paving the way for more effective and sustainable PEG-free drug delivery nano-systems in the pharmaceutical and biomedical fields.

Fungal biodegradation of poly(butylene adipate-co-terephthalate)-polylactic acid-thermoplastic starch based commercial bio-plastic film at ambient conditions

Microbial biodegradation of commercially available poly(butylene adipate-co-terephthalate)-polylactic acid-thermoplastic starch based bio-plastic has been pursued at high temperatures exceeding 55 °C. Herein, we first reported three newly isolated fungal strains from farmland soil samples of Republic of Korea namely, Pyrenochaetopsis sp. strain K2, Staphylotrichum sp. S2-1, and Humicola sp. strain S2-3 were capable of degrading a commercial bio-plastic film with degradation rates of 9.5, 8.6, and 12.2%, respectively after 3 months incubation at ambient conditions. Scanning electron microscopy (SEM) analyses showed that bio-plastic film was extensively fragmented with severe cracking on the surface structure after incubation with isolated fungal strains. X-ray diffraction (XRD) analysis also revealed that high crystallinity of the commercial bio-plastic film was significantly decreased after degradation by fungal strains. Liquid chromatography-mass spectrometry (LC-MS) analyses of the fungal culture supernatants containing the bio-plastic film showed the peaks for adipic acid, terephthalic acid (TPA), and terephthalate-butylene (TB) as major metabolites, suggesting cleavage of ester bonds and accumulation of TPA. Furthermore, a consortium of fungal strain K2 with TPA degrading bacterium Pigmentiphaga sp. strain P3-2 isolated from the same sampling site exhibited faster degradation rate of the bio-plastic film within 1 month of incubation with achieving complete biodegradation of accumulated TPA. We assume that the extracellular lipase activity presented in the fungal cultures could hydrolyze the ester bonds of PBAT component of bio-plastic film. Taken together, the fungal and bacterial consortium investigated herein could be beneficial for efficient biodegradation of the commercial bio-plastic film at ambient conditions.

Effect of migration on the functionality of zinc oxide nanoparticle in polybutylene adipate terephthalate/thermoplastic starch films: A food simulant study

Active packaging relies on controlled release of antimicrobials for food protection; however, uncontrolled migration due to environmental factors poses safety and functionality challenges. This study investigated the stability of zinc oxide nanoparticle (ZnONP) in poly(butylene-adipate-co-terephthalate)/thermoplastic starch (PBAT/TPS) biopolymer film for active food packaging applications. While incorporating ZnONP significantly enhanced the properties and active functionalities (UV-light blocking, antimicrobial activity) of PBAT/TPS film, food simulants posed significant stability challenges. Notably, exposure to 3 % acetic acid (acidic food simulant) triggered complete detachment and dissolution of ZnONPs from the film surface, leading to pore formation and subsequent internal ZnO dissolution. This resulted in dramatic alterations to the bionanocomposite films, including increased opacity, water vapor permeability, and decreased thermal stability, mechanical properties, and active functionalities. In contrast, 10 % ethanol (aqueous food simulant) had minimal impact, suggesting higher ZnO stability in neutral environments. Importantly, ZnO migration analysis revealed thresholds for safe application: 1 % ZnONP for acidic food contact and up to 5 % for aqueous foodstuffs. These findings highlight the critical role of environmental factors in ZnONP stability and emphasize the need for strategic optimization of ZnO content for achieving both functionality and safety in active biopolymer packaging.

Pseudomonas-associated bacteria play a key role in obtaining nutrition from bamboo for the giant panda (Ailuropoda melanoleuca)

Gut microbiota plays a vital role in obtaining nutrition from bamboo for giant pandas. However, low cellulase activity has been observed in the panda's gut. Besides, no specific pathway has been implicated in lignin digestion by gut microbiota of pandas. Therefore, the mechanism by which they obtain nutrients is still controversial. It is necessary to elucidate the precise pathways employed by gut microbiota of pandas to degrade lignin. Here, the metabolic pathways for lignin degradation in pandas were explored by comparing 209 metagenomic sequencing data from wild species with different feeding habits. Lignin degradation central pathways, including beta-ketoadipate and homogentisate pathway, were enriched in the gut of wild bamboo-eating pandas. The gut microbiome of wild bamboo-eating specialists was enriched with genes from pathways implicated in degrading ferulate and p-coumarate into acetyl-CoA and succinyl-CoA, which can potentially provide the raw materials for metabolism in pandas. Specifically, Pseudomonas, as the most dominant gut bacteria genus, was found to be the main bacteria to provide genes involved in lignin or lignin derivative degradation. Herein, three Pseudomonas-associated strains isolated from the feces of wild pandas showed the laccase, lignin peroxidase, and manganese peroxidase activity and extracellular lignin degradation ability in vitro. A potential mechanism for pandas to obtain nutrition from bamboo was proposed based on the results. This study provides novel insights into the adaptive evolution of pandas from the perspective of lignin metabolism.

IMPORTANCE

Although giant pandas only feed on bamboo, the mechanism of lignin digestion in pandas is unclear. Here, the metabolic pathways for lignin degradation in wild pandas were explored by comparing gut metagenomic from species with different feeding habits. Results showed that lignin degradation central pathways, including beta-ketoadipate and homogentisate pathway, were enriched in the gut of wild bamboo-eating pandas. Genes from pathways involved in degrading ferulate and p-coumarate via beta-ketoadipate pathway were also enriched in bamboo-eating pandas. The final products of the above process, such as acetyl-CoA, can potentially provide the raw materials for metabolism in pandas. Specifically, Pseudomonas, as the most dominant gut bacteria genus, mainly provides genes involved in lignin degradation. Herein, Pseudomonas-associated strains isolated from the feces of pandas could degrade extracellular lignin. These findings suggest that gut microbiome of pandas is crucial in obtaining nutrition from lignin via Pseudomonas, as the main lignin-degrading bacteria.

Evaluation of the sorption/desorption processes of pesticides in biodegradable mulch films used in agriculture

Microplastics from mulch films can be a source of chemical contamination to agricultural soils. In this context, biodegradable films have been widely positioned as a greener choice. However, their sorption/desorption capabilities, in contrast to the conventional plastic types remain understudied. It is for this reason that objective evaluation of their interactions with residual agricultural contaminants becomes important. Our findings reveal that polyethylene (PE) mulch films retained lower amounts of pesticide residues and demonstrated a higher desorption/release [median desorption = 71.86 μg/L or about 50%], while polybutylene adipate terephthalate (PBAT) mulch films retained higher amounts of pesticide residues onto their surface and demonstrated a much lower desorption [median desorption = 24.27 μg/L or about 17%] after a spraying event. A higher ambient temperature had no significant effect on final desorption amounts in both PE [median = 65.27 μg/L at 20 °C and 74.23 μg/L at 40 °C] and PBAT [median = 24.26 μg/L at 20 °C and 24.78 μg/L at 40 °C] mulch films. However, it did favour a faster desorption pace in PE films. Desorption in PBAT and PE plastic types was correlated with the log Kow value [Spearman's correlation: 0.857 and 0.837 respectively, p < 0.05]. However, only a moderate correlation with pKa was observed in PBAT [Spearman's correlation: 0.478, p < 0.05], while none for PE plastic type. Sorption of pesticides onto biodegradable PBAT microplastics were best explained by Elovich [R2: 0.937-0.959] and pseudo-second order kinetics [R2: 0.942-0.987], suggesting the presence of chemisorption. Furthermore, Weber Morris plots suggested the presence of a multi-step process and Boyd plots indicated that film diffusion or chemical bond formation was the rate-limiting step governing this phenomenon.

A reactive compatibilization with the compound containing four epoxy groups for polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch ternary bio-composites

How to effectively improve the poor interfacial adhesion between polylactic acid/poly(butylene adipate-co-terephthalate) (PLA/PBAT) matrix and thermoplastic starch (TPS) is still a challenge. Therefore, this work aims to introduce a convenient method to enhance the performance of PLA/PBAT/TPS blend by melt reactive extrusion. Here, using 4,4'-methylene-bis(N,N-diglycidyl-aniline) (MBDG) containing four epoxy groups as a reactive compatibilizer, and respectively using 1-methylimidazole (MI) or triethylenediamine (TD) as a catalyzer, serial PLA/PBAT/TPS ternary bio-composites are successfully prepared via melt reactive extrusion. The results showed that, under the catalysis of organic base, especially MI, the epoxy groups of MBDG can effectively react with hydroxyl and carboxyl groups of PLA/PBAT and hydroxyl groups in TPS to form chain-expanded and cross-linked structures. The tensile strength of the composites is increased by 20.0 % from 21.1 MPa, and the elongation at break is increased by 182.4 % from 17.6 % owing to the chain extension and the forming of cross-linked structures. The molecular weight, thermal stability, crystallinity, and surface hydrophobicity of the materials are gradually improved with the increase of MBDG content. The melt fluidity of the composites is also improved due to the enhancement of compatibility. The obtained PLA/PBAT/TPS materials have the potential to be green plastic products with good properties.

Biodegradable reactive compatibilizers for efficient in-situ compatibilization of poly (lactic acid)/poly (butylene adipate-terephthalate) blends

The wide application of fully biodegradable polylactic acid/polybutylene terephthalate (PLA/PBAT) blends in environmentally friendly packaging were limited because of poor compatibility. Normal compatibilizers suffer from poor thermal stability and non-biodegradability. In this work, epoxy copolymer (MDOG) with different molecular structures were made of 2-methylene-1, 3-dioxoheptane, and glycidyl methacrylate as raw materials by free radical copolymerization. MDOG copolymers have good biodegradability and a high thermal decomposition temperature of 361 °C. The chemical reaction of the epoxy groups in MDOG with PLA and PBAT during the melting reaction improved the interfacial bonding by decreasing the particle size of PBAT. Compared to the PLA/PBAT blends, the tensile strength and fracture toughness of PLA/PBAT/MDOG blends were enhanced to 34.6 MPa and 115.8 MJ/m3, which are 25 % and 81 % higher, respectively. As a result, this work offers new methods for developing thermally stable and biodegradable compatibilizers, which will hopefully promote the development of packaging industry.

Exploring the potential of lignin nanoparticles in enhancing the mechanical, thermal, and bioactive properties of poly (butylene adipate-co-terephthalate)

The preparation and characterization of lignin nanoparticles (LNPs) were described. LNPs were produced via the precipitation technique. Nanocomposites of LNPs with poly (butylene adipate-co-terephthalate) (PBAT) were prepared by melt mixing with various concentrations up to 6 wt% of LNPs. The assessment of the effects of LNP addition on the mechanical, thermal, morphological, cytotoxicity, antioxidant, antibacterial, and antiviral properties of nanocomposites was carefully performed. The addition of LNPs to PBAT enhances the thermal stability of the nanocomposites. The antioxidant effect of LNPs on PBAT increased with increasing filler content. LNPs showed higher efficiency as antioxidant agents than lignin particles (LP). The tensile modulus increased by 20 % for the nanocomposites with 6 % LNPs in comparison with neat PBAT. The crystallization peak temperature of PBAT was 80 °C, which increased to 104.6 °C with the addition of 6 wt% of LNPs, suggesting their strong nucleation activity. Antibacterial tests demonstrated the bacteriostatic activities of LNP, LP, and nanocomposites. Both LP and LNP showed considerable antiviral activity against herpes simplex virus type 1 and human coronavirus 229e. The antiviral activity of LNP was concentration-dependent. The findings suggest that LNP is a promising bio-additive for PBAT and can enhance its properties for various applications, including food packaging.

Stable nanoscale sea-island structure of biobased polyamide 56/poly (butylene adipate-co-terephthalate) blends compatibilized by interfacial hyperbranched structure: Toward biobased polymer blends with ultrahigh toughness

Developing biobased materials is a considerably effective approach to save fossil resources and reduce emissions. Biobased polyamide 56 (PA56) is an excellent engineering material, but it has low toughness. Herein, to enhance the toughness of PA56, an ultra-tough biodegradable material, i.e., poly (butylene adipate-co-terephthalate) (PBAT) was introduced into PA56. Moreover, a self-synthesized epoxy-terminated hyperbranched polyester (EHBP) was used to improve the compatibility of the blended materials. The results of differential scanning calorimetry and Fourier-transform infrared spectroscopy indicated that the epoxide group of EHBP could react with PA56 and PBAT to form a block-like polymer structure and limit the crystallization behavior of the blends. The scanning electron microscopy results show that the addition of EHBP considerably reduced the dispersed-phase size in the blends, forming a nanoscale island structure. Moreover, the hydrogen bonds formed between EHBP and PA56/PBAT enhanced the intermolecular interaction between the two materials. Thus, PA56 blends with ultrahigh toughness were successfully prepared. The prepared PA56/PBAT/EHBP blend exhibited a notch impact strength of 20.71 kJ/m2 and a breaking elongation of 38.3 %, which represent increases of 427.3 % and 252.8 %, respectively, compared with those of pure PA56. Thus, the proposed method is suitable for toughening PA56 and broadening its applications.

New attempts on acidic anaerobic digestion of poly (butylene adipate-co-terephthalate) wastewater in upflow anaerobic sludge blanket reactor

Poly (butylene adipate-co-terephthalate) (PBAT) wastewater is a highly concentrated, acidic, and toxic wastewater generated from biodegradable plastics production. Large amounts of alkali would be consumed when treating PBAT wastewater by anaerobic digestion due to the low pH value. This study employed acidic anaerobic digestion to treat PBAT wastewater and compared to neutral anaerobic digestion. The results indicated that the COD removal rates in the acidic upflow anaerobic sludge blanket (UASB) reactor were 65.5% and 59.9%, respectively at influent pH 6.0 and 5.0 with the COD concentration of around 11,000 mg L-1, and the methane conversion efficiency were 172.5 and 183.8 mLCH4/gCODr (gCODr: COD removed amount), respectively. Correspondingly, the average COD removal and methane conversion efficiency in the neutral UASB reactor were 63.2% and 188.0 mLCH4/gCODr, respectively. The treatment efficiency of acidic and neutral UASB reactors for PBAT wastewater was similar. The hydrogenotrophic methanogenic activity was further enhanced in the acidic UASB reactor compared to the neutral one. The increase of alkalinity in the acidic UASB reactor (2.4 mmol L-1) was higher than the neutral (2.0 mmol L-1). A higher level of syntrophic acetate oxidation bacteria and hydrogenotrophic methanogen was enriched in the acidic UASB reactor, ensuring efficient treatment and saving costs.

POSS(epoxy)8 reinforced poly (butylene adipate-co-terephthalate)/lignin biodegradable films: Fabrication, enhanced mechanical properties and UV aging resistance

To reduce the white pollution, the eco-friendly biodegradable poly (butylene adipate-co-terephthalate) (PBAT)-based films had attracted increasing interests worldwide. However, the high-cost of the PBAT had limited the large-scale development and application. In this work, 10 wt% low-cost lignin was introduced into the PBAT to prepare composite films by melt blending and blow molding, and the POSS(epoxy)8 was selected as the compatibilizer to improve the compatibility of PBAT and lignin. The maximum tensile strength and the nominal strain at break subsequently increased by 48.2 % and 21.4 % respectively, while the water vapor permeability enhanced by 9.9 %. Furthermore, the UV aging resistance of PBAT/lignin films were significantly improved, with only 1 wt% POSS(epoxy)8 content. This work provides an efficient strategy to foster the end-user confidence in the low-cost and eco-friendly biodegradable polymer materials with efficient performance.

Engineering of Yarrowia lipolytica as a platform strain for producing adipic acid from renewable resource

There is an increasing demand for bio-based dicarboxylic acids (DCA) as an eco-friendly alternatives to chemically synthesized DCA. Adipic acid, which is not naturally produced by microorganisms, is an essential DCA with significant industrial importance. This study aimed to develop a platform strain using Yarrowia lipolytica for efficient bioconversion of renewable resources into adipic acid. To prevent the complete oxidation of adipic acid, peroxisomal β-oxidation was engineered by selectively disrupting acyl-CoA oxidases. Furthermore, ω-oxidation activity was improved via introducing an additional copy of cytochrome P450 monooxygenase (ALK5) and reductase (CPR1) with fatty alcohol oxidase (FAO1). The production phase used SP92D medium in a two-stage bioconversion process, during which the engineered strain exhibited the highest production level, achieving a remarkable 9.7-fold increase compared to that of the parental strain. To our knowledge, this is the first report demonstrating that engineered Y. lipolytica can produce adipic acid from fatty acid methyl esters.

Poly(glycidyl methacrylate) modified cellulose nanocrystals and their PBAT-based nanocomposites

Melt processing of cellulose nanocrystals (CNCs) reinforced nanocomposites is still a serious challenge due to the hydrophilic nature of CNCs and their severe agglomeration tendency within the polymer melt. In this study, chemical modification of CNC through grafting poly(glycidyl methacrylate) (PGMA) with various degrees was implemented. Wettability of the modified CNCs (mCNCs) were controlled and their structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), optical microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The nanocomposites of polybutylene adipate terephthalate (PBAT) with 3 wt% CNC and mCNC were prepared using an internal melt mixer. To differentiate the effects of CNC and PGMA molecules on the final properties of nanocomposites, PBAT/PGMA compounds were separately prepared. To confirm the chain characterization and molecular weight of the synthesized PGMAs, 1H NMR and gel permeation chromatography (GPC) analysis were conducted. Melt rheological analysis, dynamic mechanical analysis (DMA), DSC, and atomic force microscopy (AFM) were used to monitor the mCNC dispersion quality and the effect of PGMA modification in PBAT compounds. The results revealed that grafting CNC with longer PGMA considerably improved the CNCs' dispersion quality within PBAT. Such dispersion enhancement of long-chain mCNCs and interfacial interaction of PGMA and PBAT resulted in a noticeable increase in storage modulus and complex viscosity of the final nanocomposites.

Biobased Biodegradable Copolyesters from 2,5-Thiophenedicarboxylic Acid: Effect of Aliphatic Diols on Barrier Properties and Degradation

The demand for sustainable development has led to increasing attention in biobased polyesters due to their adjustable thermal and mechanical properties and biodegradability. In this study, we used a novel bioderived aromatic diacid, 2,5-thiophenedicarboxylic acid (TDCA) to synthesize a list of novel aromatic-aliphatic poly(alkylene adipate-co-thiophenedicarboxylate) (PAATh) copolyesters through a facile melt polycondensation method. PAAThs are random copolyesters with weight-average molecular weights of 58400 to 84200 g·mol-1 and intrinsic viscosities of 0.80 to 1.27 dL·g-1. All PAAThs exhibit sufficiently high thermal stability as well as the highest tensile strength of 6.2 MPa and the best gas barrier performances against CO2 and O2, 4.3- and 3.3-fold better than those of poly(butylene adipate-co-terephthalate) (PBAT). The biodegradability of PAAThs was fully evaluated through a degradation experiment and various experimental parameters, including residue weights, surface morphology, and molecular compositions. The state-of-the-art molecular dynamics (MD) simulations were applied to elucidate the different enzymatic degradation behaviors of PAAThs due to the effect of diols with different chain structures. The sterically hindered carbonyl carbon of the PHATh-enzyme complex was more susceptible to nucleophilic attack and exhibited a higher tendency to enter a prereaction state. This study has introduced a group of novel biobased copolyesters with their structure-property relationships investigated thoroughly, and the effect of diol components on the enzymatic degradation was revealed by computational analysis. These findings may lay the foundation for the development of promising substitutes for commercial biodegradable polyesters and shed light on their complicated degradation mechanisms.

Phthalates, adipates, BPA, and pesticides in school meals

BACKGROUND

Exposure to phthalates, adipates, bisphenol-A (BPA), and pesticides may have important health consequences for children, but little is known regarding their presence in school meals, a major food source for children. The aims of this study were to determine the presence of phthalates, adipates, BPA, and pesticides in school meals.

METHODS

Using a cross-sectional design, n = 50 school meal components were collected from four school districts in New England (n = 8 elementary/K-8 schools) differing preparation methods (on-site scratch cooking and pre-packaged heat and serve meals with plastic films) between 2019 and 2021. Meal components were tested for the presence of phthalates, adipates, BPA, and pesticides by an independent laboratory.

RESULTS

One adipate, DEHA, was detected in 42% of samples (range 0.08 mg/kg - 50.39 mg/kg). Among the prepackaged foods, DEHA was detected in 86% of samples, which also contained the highest average concentrations among all the samples tested. The phthalate Diisononyl phthalate (DINP) was detected in only one sample, and BPA was not detected in any of the samples tested. Pesticides were detected in 64% of produce and 27% of entrées, but most had levels that were lower than the average levels detected by the USDA's Pesticide Data Program and only one sample had levels that exceeded those detected by the USDA (Cyfluthrin levels in one sample of apples were 0.038 mg/kg compared with an USDA average range of 0.004-0.032 mg/kg).

CONCLUSIONS

Overall pesticides and phthalate levels in school meals are low and BPA was not detected. However, this study suggests that manufacturers may be changing to less studied plasticizers such as DEHA. More studies should examine the impact of DEHA on human health, particularly among children. As schools transition back from the COVID-19 pandemic, foods packaged in plastic should be minimized where possible. Overall, school meals remain one of the healthiest options for children and policies that support on site cooking can further strengthen the quality of school meals.

Poly(butylene adipate-co-terephthalate) biodegradation by Purpureocillium lilacinum strain BA1S

Poly(butylene adipate-co-terephthalate) (PBAT), a promising biodegradable aliphatic-aromatic copolyester material, can be applied as an alternative material to reduce the adverse effects of conventional plastics. However, the degradation of PBAT plastics in soil is time-consuming, and effective PBAT-degrading microorganisms have rarely been reported. In this study, the biodegradation properties of PBAT by an elite fungal strain and related mechanisms were elucidated. Four PBAT-degrading fungal strains were isolated from farmland soils, and Purpureocillium lilacinum strain BA1S showed a prominent degradation rate. It decomposed approximately 15 wt.% of the PBAT films 30 days after inoculation. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Liquid chromatography mass spectrometry (LC‒MS) were conducted to analyze the physicochemical properties and composition of the byproducts after biodegradation. In the presence of PBAT, the lipolytic enzyme activities of BA1S were remarkably induced, and its cutinase gene was also significantly upregulated. Of note, the utilization of PBAT in BA1S cells was closely correlated with intracellular cytochrome P450 (CYP) monooxygenase. Furthermore, CreA-mediated carbon catabolite repression was confirmed to be involved in regulating PBAT-degrading hydrolases and affected the degradation efficiency. This study provides new insight into the degradation of PBAT by elite fungal strains and increases knowledge on the mechanism, which can be applied to control the biodegradability of PBAT films in the future. KEY POINTS: • Purpureocillium lilacinum strain BA1S was isolated from farmland soils and degraded PBAT plastic films at a prominent rate. • The lipolytic enzyme activities of strain BA1S were induced during coculture with PBAT, and the cutinase gene was significantly upregulated during PBAT degradation. • CreA-mediated carbon catabolite repression of BA1S plays an essential role in regulating the expression of PBAT-degrading hydrolases.

Advantages of treating sponge-gourd waste by mechanical refining on the properties of fiber-based poly(butylene adipate-co-terephthalate)/polylactide biocomposites

This study compares the morphology, thermal, and dynamic-mechanical properties of composites based on polybutylene adipate terephthalate/polylactide biocomposites with sponge gourd waste treated code as R, and non-treated sponge gourd, coded as NR, by mechanical disc refining after milled process. Extrusion followed by compression molding was used to produce biocomposites with fiber contents of 0, 2.5, 5, 10, and 15% wt/wt for R and NR sponge gourd fibers. Scanning electron microscopy analysis reveals that NR has the morphology of a rigid tubular shape, whereas R is a thinner, twisted, and fibrillated fiber. Regardless of the type of sponge gourd fiber used, the thermal stability of the composite decreases as the sponge gourd content increases. At 25°C, the biocomposite with 10%wt/wt R fiber has the highest storage modulus value. The comparison of Tangent  peak values reveals that the presence of sponge gourd fibers reduces the energy dissipation of the biocomposites. The analysis of the loss modulus at 25°C reveals that R fiber contributes more to the reduction of energy dissipation of the biocomposites than NR. Furthermore, the Cole-Cole plot shows that R and NR fibers are dispersed and do not significantly change the homogeneity of the biopolymer systems.

Functional analysis of the protocatechuate branch of the β-ketoadipate pathway in Aspergillus niger

Bacteria and fungi catabolize plant-derived aromatic compounds by funneling into one of seven dihydroxylated aromatic intermediates, which then undergo ring fission and conversion to TCA cycle intermediates. Two of these intermediates, protocatechuic acid and catechol, converge on β-ketoadipate which is further cleaved to succinyl-CoA and acetyl-CoA. These β-ketoadipate pathways have been well characterized in bacteria. The corresponding knowledge of these pathways in fungi is incomplete. Characterization of these pathways in fungi would expand our knowledge and improve the valorization of lignin-derived compounds. Here, we used homology to characterize bacterial or fungal genes to predict the genes involved in the β-ketoadipate pathway for protocatechuate utilization in the filamentous fungus Aspergillus niger. We further used the following approaches to refine the assignment of the pathway genes: whole transcriptome sequencing to reveal genes upregulated in the presence of protocatechuic acid; deletion of candidate genes to observe their ability to grow on protocatechuic acid; determination by mass spectrometry of metabolites accumulated by deletion mutants; and enzyme assays of the recombinant proteins encoded by candidate genes. Based on the aggregate experimental evidence, we assigned the genes for the five pathway enzymes as follows: NRRL3_01405 (prcA) encodes protocatechuate 3,4-dioxygenase; NRRL3_02586 (cmcA) encodes 3-carboxy-cis,cis-muconate cyclase; NRRL3_01409 (chdA) encodes 3-carboxymuconolactone hydrolase/decarboxylase; NRRL3_01886 (kstA) encodes β-ketoadipate:succinyl-CoA transferase; and NRRL3_01526 (kctA) encodes β-ketoadipyl-CoA thiolase. Strain carrying ΔNRRL3_00837 could not grow on protocatechuic acid, suggesting that it is essential for protocatechuate catabolism. Its function is unknown as recombinant NRRL3_00837 did not affect the in vitro conversion of protocatechuic acid to β-ketoadipate.

Molecular insights into effects of PBAT microplastics on latosol microbial diversity and DOM chemodiversity

The impact of biodegradable microplastics on the microbial community and dissolved organic matter (DOM) in latosol has not been well reported. In this study, an incubation experiment at 25 ºC for 120 days using latosol amended with low (5%) and high (10%) concentrations of polybutylene adipate terephthalate (PBAT) microplastics was carried out to explore the impacts of PBAT microplastics on soil microbial communities and DOM chemodiversity, and the intrinsic interactions between their shifts. The main bacterial and fungal phyla in soil, namely Chloroflexi, Actinobacteria, Chytridiomycota, and Rozellomycota showed a nonlinear relationship with PBAT concentration and played a pivotal role in shaping DOM chemodiversity. A higher decreased levels of lignin-like compounds and increased levels of protein-like and condensed aromatic compounds in the 5% treatment were observed than that in the 10% treatment. Furthermore, a higher increase relative abundance of CHO compounds in the 5% treatment than in the 10% treatment was ascribed to its higher oxidation degree. Co-occurrence network analysis suggested that bacteria formed more complex relationships with DOM molecules than fungi did, indicating their critical roles in DOM transformation. Our study has important implications for understanding the potential influence of biodegradable microplastics on carbon biogeochemical roles in soil.

Study on the biodegradation of polybutylene adipate-co-terephthalate/starch film containing deep eutectic solvent

Poly (butylene adipate-co-terephthalate) (PBAT) has attracted much attention as a biodegradable polymer, but its biodegradation speed is slow. Starch was blended with PBAT to develop daily packing film with high biodegradation speed, and deep eutectic solvent (DES) composed of choline chloride (CHCl)/glycerol (Gly) (molar ratio of 1:2) was used as a novel plasticizer. The hydrophilic starch is in favor of the breeding of microorganisms, at the same time DES can provide energy for the breeding. The degradation was traced in a simulated composting test using kitchen waste. After the PBAT/starch-DES film was buried in a mixture of food residue for 90 D, the relative weight molecular weight (M_w) of the PBAT decreased by about 50%. Furthermore, with the help of DES, the compatibility between PBAT and starch was improved, the PBAT/starch-DES film became more transparent than the PBAT and PBAT/starch film, and its tensile strength reached 7.9 MPa with an elongation at break of 335.6%. This work provided a simple and efficient solution to obtain rapidly degradable films.

Biodegradable Nanofibrillated Cellulose/Poly-(butylene adipate-co-terephthalate) Composite Film with Enhanced Barrier Properties for Food Packaging

Biodegradable composites consisting of Poly-(butylene adipate-co-terephthalate) (PBAT), thermoplastic starch, hydrophobically modified nanofibrillated cellulose (HMNC), and green surfactant (sucrose fatty acid ester) were prepared via the melt-mixing and film-blowing process (PBAT-HMNC). The composites were characterized using the Fourier transform infrared spectroscope (FT-IR), scanning electron microscope (SEM), and thermogravimetric analyzer (TGA). The mechanical and barrier properties were systematically studied. The results indicated that PBAT-HMNC composites exhibited excellent mechanical and barrier properties. The tensile strength reached the maximum value (over 13 MPa) when the HMNC content was 0.6% and the thermal decomposition temperature decreased by 1 to 2 °C. The lowest values of the water vapor transmission rate (WVTR) and the oxygen transmission rate (OTR) were obtained from the composite with 0.6 wt% HMNC, prepared via the film-bowing process with the values of 389 g/(m2·day) and 782 cc/(m2·day), which decreased by 51.3% and 42.1%, respectively. The Agaricus mushrooms still had a commodity value after 11 days of preservation using the film with 0.6 wt% HMNC. PBAT-HMNC composites have been proven to be promising nanocomposite materials for packaging.

Adsorption and desorption mechanisms of oxytetracycline on poly(butylene adipate-co-terephthalate) microplastics after degradation: The effects of biofilms, Cu(II), water pH, and dissolved organic matter

As the application of biodegradable polymers has grown, so has the interest in exploring the environmental behaviors of biodegradable microplastics (MPs). In this study, we investigated the interaction of oxytetracycline (OTC) with poly(butylene adipate-co-terephthalate) (PBAT) MPs after biodegradation, and explored the effect of the coexisting Cu(II) on OTC adsorption and desorption processes. The maximum adsorption amounts of virgin PBAT, biofilm PBAT, and degraded PBAT reached 692.05 μg·g^-1, 1396.21 μg·g^-1, and 1869.93 μg·g^-1, respectively, and the presence of Cu(II) increased the OTC adsorption capacities by 431.16 %, 165.99 %, and 132.94 %, respectively. The enhanced adsorption capacities were attributed to the formation of PBAT-Cu-OTC complexes. The remarkable desorption hysteresis of OTC was observed on the degraded PBAT but not on the biofilm PBAT when Cu(II) was present, due to the complexation between Cu(II) and biofilms. The effect of Cu(II) varied depending on the MP physiochemical properties (e.g., surface areas, zeta potentials, and functional groups) and the environmental factors (e.g., the solution pH and coexisting dissolved organic matter). Fourier transform infrared spectroscopy (FTIR) coupled with X-ray photoelectron spectroscopy (XPS) identified the Cu(II) bridging effect, and various interaction forces between PBAT and OTC, including hydrogen-bonding, π-π, cation-π, and electrostatic interactions.

DEHA-Net: A Dual-Encoder-Based Hard Attention Network with an Adaptive ROI Mechanism for Lung Nodule Segmentation

Measuring pulmonary nodules accurately can help the early diagnosis of lung cancer, which can increase the survival rate among patients. Numerous techniques for lung nodule segmentation have been developed; however, most of them either rely on the 3D volumetric region of interest (VOI) input by radiologists or use the 2D fixed region of interest (ROI) for all the slices of computed tomography (CT) scan. These methods only consider the presence of nodules within the given VOI, which limits the networks' ability to detect nodules outside the VOI and can also encompass unnecessary structures in the VOI, leading to potentially inaccurate segmentation. In this work, we propose a novel approach for 3D lung nodule segmentation that utilizes the 2D region of interest (ROI) inputted from a radiologist or computer-aided detection (CADe) system. Concretely, we developed a two-stage lung nodule segmentation technique. Firstly, we designed a dual-encoder-based hard attention network (DEHA-Net) in which the full axial slice of thoracic computed tomography (CT) scan, along with an ROI mask, were considered as input to segment the lung nodule in the given slice. The output of DEHA-Net, the segmentation mask of the lung nodule, was inputted to the adaptive region of interest (A-ROI) algorithm to automatically generate the ROI masks for the surrounding slices, which eliminated the need for any further inputs from radiologists. After extracting the segmentation along the axial axis, at the second stage, we further investigated the lung nodule along sagittal and coronal views by employing DEHA-Net. All the estimated masks were inputted into the consensus module to obtain the final volumetric segmentation of the nodule. The proposed scheme was rigorously evaluated on the lung image database consortium and image database resource initiative (LIDC/IDRI) dataset, and an extensive analysis of the results was performed. The quantitative analysis showed that the proposed method not only improved the existing state-of-the-art methods in terms of dice score but also showed significant robustness against different types, shapes, and dimensions of the lung nodules. The proposed framework achieved the average dice score, sensitivity, and positive predictive value of 87.91%, 90.84%, and 89.56%, respectively.

Aging of poly (lactic acid)/poly (butylene adipate-co-terephthalate) blends under different conditions: Environmental concerns on biodegradable plastic

Biodegradable plastics (BPs) have been used to replace conventional plastics owing to their environmental harmless and ease of degradation. However, the aging processes of BPs in different environments remain unclear. In this study, we used poly (lactic acid)/poly (butylene adipate-co-terephthalate) (PLA/PBAT) films as model BPs and investigated the 30-d aging behavior of PLA/PBAT films under four conditions (i.e., air without ultraviolet (UV) irradiation, water without UV irradiation, air with UV irradiation, and water with UV irradiation). Our results showed that the aging of PLA/PBAT films was insignificant in all groups except the water with UV irradiation group. In the physical characterization, the PLA/PBAT films exhibited layered structures in water with UV irradiation condition, and the submicron- and nano-sized particles adhered to the bigger-sized fragments. In the chemical characterization, the carbonyl index (CI) of PLA/PBAT films in water with UV irradiation condition decreased from 3.84 to 1.36, and the oxygen-to-carbon (O/C) ratio reached a maximum of 1.78 at 20 d and declined to 0.49 at 30 d, indicating that the oxygen-containing functional groups underwent bond breaking and showed a rapid aging process. This is mainly attributed to the combined effect of hydrolysis and photolysis increases the contact area of PLA/PBAT films and accelerates the aging process. Furthermore, based on two-dimensional correlation spectroscopy (2D-COS) analysis, we suggest that free radicals generated in water with UV irradiation conditions also accelerate the aging process of PLA/PBAT films. This study explored the aging processes of PLA/PBAT films under different conditions, which could aid in clarifying the environmental behavior and provide further information to assess the potential risks of BPs.

Effects of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) biodegradable microplastics on the abundance and diversity of denitrifying and anammox bacteria in freshwater sediment

Microplastics (MPs) have been widely distributed on Earth and have drawn global concern for freshwater and marine ecosystems. Biodegradable plastics have risen in popularity to replace nonbiodegradable plastics all over the world. The effects of biodegradable plastics on denitrifying and anammox bacteria in freshwater sediment remain largely unknown. In this study, water column reactors containing polylactic acid (PLA) or polybutylene adipate-co-terephthalate (PBAT) MPs in sediment were established to simulate lake ecosystems and analyze the effects of biodegradable MPs on sedimentary nitrogen transformation microorganisms. The total organic carbon (TOC) concentrations in the PLA and PBAT groups were slightly higher than those in the control group, which might be related to the slow degradation of these two plastics. Denitrifying and anammox bacterial diversities decreased after adding MPs to sediments for 30 days, and the dominant OTUs of these two bacteria were differentiated from the control. The abundance levels of nirS denitrifying and anammox bacteria on the PLA MP surface were significantly higher than those in the other groups (P < 0.05), but they were lower in the PBAT groups than in the other groups. As an excellent electron donor for the denitrification process, lactic acid release from PLA degradation resulted in the enrichment of denitrifying and anammox bacteria on the MP surfaces. However, PBAT led to various responses of bacteria in an anaerobic environment. In addition, the redundancy analysis results indicated that total phosphorus, TOC and nitrate were strongly negatively correlated with the abundance levels of denitrifying and anammox bacteria. Our findings provided insight into the effects of MPs, especially the biodegradable ones, on sedimentary nitrogen-transformation bacteria.

Polyglycerol Adipate-Grafted Polycaprolactone Nanoparticles as Carriers for the Antimicrobial Compound Usnic Acid

Nanoparticle (NP) drug delivery systems are known to potentially enhance the efficacy of therapeutic agents. As for antimicrobial drugs, therapeutic solutions against drug-resistant microbes are urgently needed due to the worldwide antimicrobial resistance issue. Usnic acid is a widely investigated antimicrobial agent suffering from poor water solubility. In this study, polymer nanoparticles based on polyglycerol adipate (PGA) grafted with polycaprolactone (PCL) were developed as carriers for usnic acid. We demonstrated the potential of the developed systems in ensuring prolonged bactericidal activity against a model bacterial species, Staphylococcus epidermidis. The macromolecular architecture changes produced by PCL grafted from PGA significantly influenced the drug release profile and mechanism. Specifically, by varying the length of PCL arms linked to the PGA backbone, it was possible to tune the drug release from a burst anomalous drug release (high PCL chain length) to a slow diffusion-controlled release (low PCL chain length). The developed nanosystems showed a prolonged antimicrobial activity (up to at least 7 days) which could be used in preventing/treating infections occurring at different body sites, including medical device-related infection and mucosal/skin surface, where Gram-positive bacteria are commonly involved.

Degradation of polylactic acid/polybutylene adipate films in different ratios and the response of bacterial community in soil environments

Biodegradable plastic mulch film (BDM) is an environmentally friendly alternative to conventional polyethylene mulch, and has been growingly used in agriculture. However, practical degradation performance of BDM, especially the widely used type of blended polylactic acid (PLA)/polybutylene adipate (PBAT) in different ratios, and microbial alteration in soil environments, remain largely unrevealed. In this study, four types of BDM blended with 40-80% PLA and 20-60% PBAT were comparatively investigated through microcosm soil incubation experiments for 105 days, and combined with conditions of different soil moisture or pH. Microbiome within film-surrounding soil were assayed using 16 S rRNA high-throughput sequencing. Results showed a trend of increasing degradation efficiency with the increase of PLA proportion, and 70% PLA and 30% PBAT group presented the highest weight loss rate, i.e., 60.16 ± 5.86%. In addition, degradation and aging of PLA/PBAT varied among different soil moisture and pH values. A moderate moisture, i.e., 60% and a neutral pH7.0 caused significantly high degradation efficiency compared to other moisture or pH conditions. Moreover, bacterial abundance and community structure in the surrounding soil were related to soil moisture and pH. PLA/PBAT incubation treatment induced a remarkable increase in abundance of degradation-related species Pseudomonas and Sphingomonas. Bacterial richness and diversity in soil correspondingly respond to ratio-different PLA/PBAT's degradation under moisture/pH-different conditions through a redundancy analysis. Altogether, these findings indicate that practical degradation of PLA/PBAT film is closely related to soil environments and bacterial community. It is significant for the application of biodegradable plastics in agriculture on the perspective of soil sustainability.

Thyroid hormone disruption by bis-(2-ethylhexyl) phthalate (DEHP) and bis-(2-ethylhexyl) adipate (DEHA) in Japanese medaka Oryzias latipes

Pollution of water bodies with plasticizers is a serious environmental problem worldwide. In this study, we investigated the effects of plasticizers bis-(2-ethylhexyl) phthalate (DEHP) and bis-(2-ethylhexyl) adipate (DEHA) in Japanese medaka (Oryzias latipes). DEHP significantly increased the expression of all the genes tested: thyroid stimulating hormone beta subunit (tshβ-like), tshβ, deiodinase 1 (dio1), deiodinase 2 (dio2), and thyroid hormone receptor alpha (trα) and beta (trβ). However, DEHA only significantly increased tshβ at 7.4 µg/L but significantly decreased dio2 expression at 25.8, 111.1, and 412.6 4 µg/L, while other genes were not significantly affected. Both chemicals reduced eye size and total body length, but did not affect embryo development, hatching time and rate, and swimming performance. DEHA alone affected swim bladder inflation and not DEHP. This is the first report that not only DEHP but also DEHA disrupt thyroid hormone activity in fish. DEHP contamination (13.2 μg/L) was detected in tap water from Kobe, Japan; thus, tap water itself may disrupt thyroid hormone activity in Japanese medaka. Importantly, the effective concentration of DEHP for thyroid hormone-related gene expression and growth was close to or lower than DEHP concentrations reported in surface water elsewhere, indicating that DEHP contamination is a serious aquatic pollution.

Novel silver-modified carboxymethyl chitosan antibacterial membranes using environment-friendly polymers

The rapid reproduction of foodborne bacteria in food packaging threatens the health of consumers, the massive use and waste of packaging also causes serious environmental pollution. In this study, novel biodegradable antibacterial membranes based on silver-modified carboxymethyl chitosan (Ag-CMCS) were prepared. Polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) were used as the base membrane materials. Characterization of the prepared membranes was performed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), water contact angle, and so on. Especially, the silver on the surface of Ag-CMCS was proved to be metallic silver. For the first cycle of zone of inhibition test, the diameter of inhibition zone could reach up to 17 mm while the mass of silver released was negligible. The prepared antibacterial membranes could kill almost 100% of bacteria under certain conditions and inhibition zone still existed after more than 7 cycles of tests, indicating the prepared antibacterial membranes were effective. This study could provide new ideas for preparing efficient and environment-friendly antibacterial food packaging membranes.

Biowastes for biodegradable bioplastics production and end-of-life scenarios in circular bioeconomy and biorefinery concept

Due to global urbanization, industrialization, and economic development, biowastes generation represents negative consequences on the environment and human health. The use of generated biowastes as a feedstock for biodegradable bioplastic production has opened a new avenue for environmental sustainability from the circular (bio)economy standpoint. Biodegradable bioplastic production can contribute to the sustainability pillars (environmental, economic, and social). Furthermore, bioenergy, biomass, and biopolymers production after recycling of biodegradable bioplastic can help to maintain the energy-environment balance. Several types of biodegradable bioplastic, such as starch-based, polyhydroxyalkanoates, polylactic acid, and polybutylene adipate terephthalate, can achieve this aim. In this review, an overview of the main biowastes valorization routes and the main biodegradable bioplastic types of production, application, and biodegradability are discussed to achieve the transition to the circular economy. Additionally, end-of-life scenarios (up-cycle and down-cycle) are reviewed to attain the maximum environmental, social, and economic benefit from biodegradable bioplastic products under biorefinery concept.

Biodegradation of polybutylene adipate-co-terephthalate by Priestia megaterium, Pseudomonas mendocina, and Pseudomonas pseudoalcaligenes following incubation in the soil

Soil that contained polybutylene adipate-co-terephthalate (PBAT) was incubated with Priestia megaterium, Pseudomonas mendocina, and Pseudomonas pseudoalcaligenes to improve the biodegradative process of this polymer. The mixture of Pr. megaterium and Ps. mendocina was highly effective at biodegrading the PBAT, and after eight weeks of soil incubation, approximately 84% of the PBAT film weight was lost. Mixtures of the other two species also positively affected the synergistic degradation of PBAT film in the soil, but the mixture of three species had a negative effect. The residual PBAT film microstructure clearly demonstrated the degradation of PBAT, and the degree of degradation was related to the different species. Cleavage of the PBAT film ester bond after soil microbial action affected its properties. The incubation of PBAT in soil that contained these species affected soil dehydrogenase and soil lipase in particular. The secretion of lipase by these species could play an important role in the degradation of PBAT in the soil.

Chemical Composition, Antifungal and Anti-Biofilm Activities of Volatile Fractions of Convolvulus althaeoides L. Roots from Tunisia

The antifungal drugs currently available and mostly used for the treatment of candidiasis exhibit the phenomena of toxicity and increasing resistance. In this context, plant materials might represent promising sources of antifungal agents. The aim of this study is to evaluate for the first time the chemical content of the volatile fractions (VFs) along with the antifungal and anti-biofilm of Convolvulus althaeoides L. roots. The chemical composition was determined by gas chromatography coupled to a flame ionization detector and mass spectrometry. In total, 73 and 86 chemical compounds were detected in the n-hexane (VF1) and chloroform (VF2) fractions, respectively. Analysis revealed the presence of four main compounds: n-hexadecenoic acid (29.77%), 4-vinyl guaiacol (12.2%), bis(2-ethylhexyl)-adipate (9.69%) and eicosane (3.98%) in the VF extracted by hexane (VF1). n-hexadecenoic acid (34.04%), benzyl alcohol (7.86%) and linoleic acid (7.30%) were the main compounds found in the VF extracted with chloroform (VF2). The antifungal minimum inhibitory concentrations (MICs) of the obtained fractions against Candida albicans, Candida glabrata and Candida tropicalis were determined by the micro-dilution technique and values against Candida spp. ranged from 0.87 to 3.5 mg/mL. The biofilm inhibitory concentrations (IBF) and sustained inhibition (BSI) assays on C. albicans, C. glabrata and C. tropicalis were also investigated. The VFs inhibited biofilm formation up to 0.87 mg/mL for C. albicans, up to 1.75 mg/mL against C. glabrata and up to 0.87 mg/mL against C. tropicalis. The obtained results highlighted the synergistic mechanism of the detected molecules in the prevention of candidosic biofilm formation.

Poly(cannabinoid)s: Hemp-Derived Biocompatible Thermoplastic Polyesters with Inherent Antioxidant Properties

The legalization of hemp cultivation in the United States has caused the price of hemp-derived cannabinoids to decrease 10-fold within 2 years. Cannabidiol (CBD), one of many naturally occurring diols found in hemp, can be purified in high yield for low cost, making it an interesting candidate for polymer feedstock. In this study, two polyesters were synthesized from the condensation of either CBD or cannabigerol (CBG) with adipoyl chloride. Poly(CBD-Adipate) was cast into free-standing films and subjected to thermal, mechanical, and biological characterization. Poly(CBD-Adipate) films exhibited a lack of cytotoxicity toward adipose-derived stem cells while displaying an inherent antioxidant activity compared to poly(lactide) films. Additionally, this material was found to be semi-crystalline and able to be melt-processed into a plastic hemp leaf using a silicone baking mold.

Poly(Butylene Adipate/Terephthalate-Co-Glycolate) Copolyester Synthesis Based on Methyl Glycolate with Improved Barrier Properties: From Synthesis to Structure-Property

The main problem of manufacturing with traditional biodegradable plastics is that it is more expensive than manufacturing with polymers derived from petroleum, and the application scope is currently limited due to poor comprehensive performance. In this study, a novel biodegradable poly(butylene adipic acid/terephthalate-co-glycolic acid) (PBATGA) copolyester with 25–60% glycolic acid units was successfully synthesized by esterification and polycondensation using cheap coal chemical byproduct methyl glycolate instead of expensive glycolic acid. The structure of the copolyester was characterized by ATR-FTIR, 1H NMR, DSC, and XRD; and its barrier property, water contact angle, heat resistance, and mechanical properties were tested. According to the experiment result, the PBATGA copolyesters showed improved oxygen (O2) and water vapor barrier character, and better hydrophilicity when compared with PBAT. The crystallization peaks of PBATGAs were elevated from 64 °C to 77 °C when the content of the GA unit was 25 mol %, meanwhile, the elongation at the break of PBATGA25 was more than 1300%. These results indicate that PBATGA copolyesters have good potentiality in high O2 and water vapor barrier and degradable packaging material.

A proteomics-MM/PBSA dual approach for the analysis of SARS-CoV-2 main protease substrate peptide specificity

The main protease M^pro of SARS-CoV-2 is a well-studied major drug target. Additionally, it has been linked to this virus' pathogenicity, possibly through off-target effects. It is also an interesting diagnostic target. To obtain more data on possible substrates as well as to assess the enzyme's primary specificity a two-step approach was introduced. First, Terminal Amine Isobaric Labeling of Substrates (TAILS) was employed to identify novel M^pro cleavage sites in a mouse lung proteome library. In a second step, using a structural homology model, the MM/PBSA variant MM/GBSA (Molecular Mechanics Poisson-Boltzmann/Generalized Born Surface Area) free binding energy calculations were carried out to determine relevant interacting amino acids. As a result, 58 unique cleavage sites were detected, including six that displayed glutamine at the P1 position. Furthermore, modeling results indicated that M^pro has a far higher potential promiscuity towards substrates than expected. The combination of proteomics and MM/PBSA modeling analysis can thus be useful for elucidating the specificity of M^pro, and thus open novel perspectives for the development of future peptidomimetic drugs against COVID-19, as well as diagnostic tools.

Synthesis, Physical Properties, and In Vitro-Simulated Gastrointestinal Digestion of Hydrophilic β-Sitosterol Sugar Esters

Hydrophilic β-sitosterol sugar esters were synthesized by a two-step biocatalytic approach using β-sitosterol vinyl adipate as an intermediate. The maximum conversion (above 90%) of β-sitosterol vinyl adipate was achieved using the saccharides glucose, sucrose, and raffinose. The chemical structure of the synthesized esters was confirmed by various techniques. The investigation of physical properties revealed that β-sitosterol sugar esters had enhanced water solubility (3.0-8.0 mM at 35 °C), reduced crystallinity, and high wettability. Their lyotropic liquid crystal properties were observed by polarized light microscopy. Furthermore, β-sitosterol sugar esters could be hydrolyzed into β-sitosterol adipate under simulated intestinal conditions at a low rate (2.83-18.14%). Most β-sitosterol sugar esters probably entered into intestinal bile salt micelles with ester bonds intact and showed up to 10-fold higher in vitro bioaccessibility than free β-sitosterol in non-fat systems. The excellent physical and functional characteristics of β-sitosterol sugar esters suggested their great potential application in the food industry.

A New Family of Renewable Thermosets: Kraft Lignin Poly-adipates

Thermosetting polymeric materials have advantageous properties and are therefore used in numerous applications. In this study, it was hypothesized and ultimately shown that thermosets could be derived from comparably sustainable sub-components. A two-step procedure to produce a thermoset comprising of Kraft lignin (KL) and the cross-linker adipic acid (AdA) was developed. The cross-linking was activated by means of an acetylating agent comprising isopropenyl acetate (IPA) to form a cross-linking mixture (CLM). The cross-linking was confirmed by FTIR and solid-state NMR spectroscopy, and the esterification reactions were further studied using model compounds. When the KL lignin was mixed with the CLM, partial esterification occurred to yield a homogeneous viscous liquid that could easily be poured into a mold, as the first step in the procedure. Without any additions, the mold was heated and the material transformed into a thermoset by reaction of the two carboxylic acid-derivatives of AdA and KL in the second step.

Efficient Production of Adipic Acid by a Two-Step Catalytic Reaction of Biomass-Derived 2,5-Furandicarboxylic Acid

Efficient catalytic ring-opening coupled with hydrogenation is a promising but challenging reaction for producing adipic acid (AA) from 2,5-furan dicarboxylic acid (FDCA). In this study, AA synthesis is carried out in two steps from FDCA via tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) over a recyclable Ru/Al₂ O₃ and an ionic liquid, [MIM(CH₂ )₄ SO₃ H]I (MIM=methylimidazolium) to deliver 99 % overall yield of AA. Ru/Al₂ O₃ is found to be an efficient catalyst for hydrogenation and hydrogenolysis of FDCA to deliver THFDCA and 2-hydroxyadipic acid (HAA), respectively, where ruthenium is more economically viable than well-known palladium or rhodium hydrogenation catalysts. H₂ chemisorption shows that the alumina phase strongly affects the interaction between Ru nanoparticles (NPs) and supports, resulting in materials with high dispersion and small size of Ru NPs, which in turn are responsible for the high conversion of FDCA. An ionic liquid system, [MIM(CH₂ )₄ SO₃ H]I is applied to the hydrogenolysis of THFDCA for AA production. The [MIM(CH₂ )₄ SO₃ H]I exhibits superior activity, enables simple product isolation with high purity, and reduces the severe corrosion problems caused by the conventional hydroiodic acid catalytic system.

Delivery of acetogenin-enriched Annona muricata Linn leaf extract by folic acid-conjugated and triphenylphosphonium-conjugated poly(glycerol adipate) nanoparticles to enhance toxicity against ovarian cancer cells

The study demonstrated the fabrication of new poly(glycerol adipate) (PGA) nanoparticles decorated with folic acid (FOL-PGA) and triphenylphosphonium (TPP-PGA) and the potential on the delivery of acetogenin-enriched Annona muricata Linn leaf extract to ovarian cancer cells. FOL-PGA and TPP-PGA were successfully synthesized and used to fabricate FOL-decorated nanoparticles (FOL-NPs) and FOL-/TPP- decorated nanoparticles (FOL/TPP-NPs) by blending two polymers at a mass ratio of 1:1. All nanoparticles had small size of around 100 nm, narrow size distribution and high negative surface charge about -30 mV. The stable FOL/TPP-NPs showed highest drug loading of 14.9 ± 1.9% at 1:5 ratio of extract to polymer and reached to 35.8 ± 2.1% at higher ratio. Both nanoparticles released the extract in a biphasic sustained release manner over 5 days. The toxicity of the extract to SKOV3 cells was potentiated by FOL-NPs and FOL/TPP-NPs by 2.0 - 2.6 fold through induction of cell apoptosis. FOL/TPP-NPs showed lower IC₅₀ and higher cellular uptake as compared to FOL-NPs. FOL-NPs exhibited folate receptor-mediated endocytosis. FOL/TPP-NPs provided more advantages than FOL-NPs in terms of stability in physiological fluid, uptake efficiency and targeting ability to mitochondria and showed a promising potential PGA platform for targeted delivery of herbal cytotoxic extracts.

Mechanochemical Synthesis of Polymorphic Urea ⋅ Adipic Acid Cocrystal as a Sustained-Release Nitrogen Source

A 2 : 1 urea ⋅ adipic acid cocrystal was obtained in two polymorphic forms (Form I reported earlier, and Form II synthesized in this study) using mechanochemistry as well as solution crystallization. Lower solubility and leaching study showed the newly synthesized urea ⋅ adipic acid 2 : 1 cocrystal to be an efficient sustained-release nitrogen fertilizer compared to commercially available urea.

Sustainable Routes for the Synthesis of Renewable Adipic Acid from Biomass Derivatives

Adipic acid (AA) is a key industrial dicarboxylic acid intermediate used in nylon manufacturing. Unfortunately, the traditional process technology is accompanied by serious environmental pollution. Given the growing demand for adipic acid and the desire to reduce its negative impact on the environment, considerable efforts have been devoted to developing more green and friendly routes. This Review is focused on the latest advances in the sustainable preparation of AA from biomass-based platform molecules, including 5-hydroxymethylfufural, glucose, γ-valerolactone, and phenolic compounds, through biocatalysis, chemocatalysis, and the combination of both. Additionally, the development of state-of-the-art catalysts for different catalytic systems systematically is discussed and summarized, as well as their reaction mechanisms. Finally, the prospects for all preparation routes are critically evaluated and key technical challenges in the development of green and sustainable processes for the manufacture of AA are highlighted. It is hoped that the green adipic acid synthesis pathways presented can provide insights and guidance for further research into other industrial processes for the production of nylon precursors in the future.

A new method for detecting micro-fragments of biodegradable mulch films containing poly(butylene adipate-co-terephthalate) (PBAT) in soil

Biodegradable mulch (BDM) is a potentially sustainable alternative to polyethylene plastic mulch film for intensive crop production. Certified BDMs must demonstrate >90% biodegradation in compost and agricultural soil, but the environmental fate of BDM micro-fragments is usually not measured. While using fatty acid methyl ester (FAME) analysis to study changes in soil microbial communities under different BDMs and management conditions, two peaks were detected by gas chromatography that were derived from a BDM containing poly(butylene adipate-co-terephthalate) (PBAT). The largest peak was identified as 1,4-benzenedicarboxylic acid, dimethyl ester, or dimethyl terephthalate (DMT). The smaller peak was hexanedioic acid dimethyl ester or dimethyl adipate. From this observation we hypothesized that the FAME method could be used to detect and quantify micro-fragments (<5 mm in length) of PBAT-containing BDM in soil. To test this, fragments of two commercially available BDMs were added to soil and extracted for FAME analyses. Linear relationships were observed between DMT and mulch mass added to soil for both BDMs when the initial mass of fragments was <3.5 mg (r²   > .99). Based on our findings, the FAME method could be redeployed to study the environmental fate and possible accumulation of BDM micro-fragments in soil over time.

Lignin valorization through efficient microbial production of β-ketoadipate from industrial black liquor

Vanillin and vanillate are the major lignin-derived aromatic compounds produced through the alkaline oxidation of softwood lignin. Because the production of higher-value added chemicals from these compounds is essential for lignin valorization, the microbial production of β-ketoadipate, a promising raw material for the synthesis of novel nylons, from lignin was considered. Pseudomonas putida KT2440 was engineered to convert vanillin and vanillate to β-ketoadipate. By examining the culture conditions with an initial culture volume of 1 L, the engineered strain completely converted 25 g of vanillin and 25 g of vanillate and produced approximately 23 g of β-ketoadipate from each of them with a yield of 93% or higher. Furthermore, this strain showed the ability to efficiently produce β-ketoadipate from softwood lignin extracts in black liquor, a byproduct of pulp production. These results suggest that the production of β-ketoadipate from industrial black liquor is highly feasible for substantial lignin valorization.

Passive Air Sampling of PCDD/Fs, PCBs, PAEs, DEHA, and PAHs from Informal Electronic Waste Recycling and Allied Sectors in Indian Megacities

Xenobiotic chemical emissions from the informal electronic waste recycling (EW) sector are emerging problem for developing countries, with scale and impacts that are yet to be evaluated. We report an intensive polyurethane foam disk passive air sampling study in four megacities in India to investigate atmospheric organic pollutants along five transects viz., EW, information technology (IT), industrial, residential, and dumpsites. Intraurban emission sources were estimated and attributed by trajectory modeling and positive matrix factorization (PMF). ∑₁₇PCDD/Fs, ∑₂₅PCBs, ∑₇plasticizers, and ∑₁₅PAHs concentrations ranged from 3.1 to 26 pg/m³ (14 ± 7; Avg ± SD), 0.5-52 ng/m³ (9 ± 12); 7.5-520 ng/m³, (63 ± 107) and 6-33 ng/m³ (17 ± 6), respectively. EW contributed 45% of total PCB concentrations in this study and was evidenced as a major factor by PMF. The dominance of dioxin-like PCBs (dl-PCBs), particularly PCB-126, reflects combustion as the possible primary emission source. PCDD/Fs, PCBs and plasticizers were consistently highest at EW transect, while PAHs were maximum in industrial transect followed by EW. Concentrations of marker plasticizers (DnBP and DEHP) released during EW activities were significantly higher (p < 0.05) in Bangalore than in other cities. Toxic equivalents (TEQs) due to dl-PCBs was maximum in the EW transect and PCB-126 was the major contributor. For both youth and adult, the highest estimated inhalation risks for dl-PCBs and plasticizers were seen at the EW transect in Bangalore, followed by Chennai and New Delhi.

Degradation of poly(butylene adipate-co-terephthalate) by Stenotrophomonas sp. YCJ1 isolated from farmland soil

In recent years, poly (butylene adipate-co-terephthalate) (PBAT) has been widely used. However, PBAT-degrading bacteria have rarely been reported. PBAT-degrading bacteria were isolated from farmland soil and identified. The effects of growth factors on the degradation of PBAT and the lipase activity of PBAT-degrading bacteria were assessed. The degradation mechanism was analyzed using scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, X-ray diffraction, and liquid chromatography-mass spectrometry. The results showed that Stenotrophomonas sp. YCJ1 had a significant degrading effect on PBAT. Under certain conditions, the strain could secrete 10.53 U/mL of lipase activity and degrade 10.14 wt.% of PBAT films. The strain secreted lipase to catalyze the degradation of the ester bonds in PBAT, resulting in the production of degradation products such as terephthalic acid, 1,4-butanediol, and adipic acid. Furthermore, the degradation products could participate in the metabolism of YCJ1 as carbon sources to facilitate complete degradation of PBAT, indicating that the strain has potential value for the bioremediation of PBAT in the environment.