Decrease In Molecular Weight Research Articles

Characterization and degradation mechanism of a newly isolated hydrolyzed polyacrylamide-degrading bacterium Alcaligenes faecalis EPDB-5 from the oilfield sludge

Hydrolyzed polyacrylamide (HPAM) is posing serious threats to ecosystems. However, biodegradation is an effective method to remove HPAM owing to its low cost and environmental friendliness. In this study, Alcaligenes faecalis EPDB-5 was isolated as a highly efficient HPAM degrading strain from sludge contaminated with polymerized produced water from Daqing oilfield. Under the optimal conditions, the strain EPDB-5 demonstrated an impressive HPAM degradation rate of 86.05%, the total nitrogen (TN) removal of 71.96% and chemical oxygen demand (COD) removal of 67.98%. Meanwhile, it can maintain a stable degradation rate higher than 75% under different pH and temperature conditions. 27 genes that play a key role in HPAM degradation were annotated by metagenomics sequencing. The key genes were involved in multiple KEGG pathways, including biofilm formation, biosynthesis secondary metabolites, and metabolic pathways. SEM, GPC, and FTIR analyses revealed that the structure of HPAM after biodegradation showed pores, a significant decrease in molecular weight, -NH2 detachment, and carbon chain breakage. Particularly, we propose a possible mechanism of biofilm formation - HPAM degradation - biofilm disappearance and reorganization. Moreover, the degradation rate of strain EPDB-5 on real wastewater containing HPAM was 29.97% in only three days. This work expands our knowledge boundary about the HPAM degradation mechanism at the functional gene level, and supports the potential of strain EPDB-5 as a novel auxiliary microbial resource for the practical application of HPAM.

Enzymatic synthesis of aromatic biobased polymers in green, low-boiling solvents

Given the urge to accelerate the substitution of petrol-derived solvents not only in more traditional fields like pharmaceuticals, personal care, or electronics but also in innovative research processes, this work focuses on the utilisation of four biobased solvents as media for the enzymatic synthesis of aliphatic-aromatic polyesters. As building blocks, the lignin-derived diethyl-2,4-pyridinedicarboxylate was selected as the potentially biobased, aromatic component while more classical diols such as 1,4-butanediol and 1,8-octanediol were used as the aliphatic portion. Results show that among the tested green solvents (cyclohexanone, phenetole, anisole and eucalyptol), the most suitable medium for lipase B from Candida antarctica-catalysed polycondensation reactions was eucalyptol that allowed reach monomer conversions >95 % and number average molecular weights up to 3500 g·mol−1. On the other hand, cyclohexanone led to the lowest monomer conversions (<80 %) and molecular weights (Mn<500 g·mol−1) confirming once again the unsuitability of ketone-containing solvents for enzymatic esterification and transesterification reactions. The lipase could be used up to three times, in eucalyptol as a solvent, without a significant decrease in monomer conversion or molecular weight.

Upcycling of polyethylene waste to biodegradable adhesive and coating via Baeyer-Villiger reaction: A new view on oxidation-fracture mechanism and structure-function relationship

Non-biodegradable polyethylene waste accumulates in large quantities in the environment posing a serious threat to the survival of creatures. Meanwhile, polyethylene suffers from inherent polarity limitations that curtails its application scope. Oxidation is an efficient approach of upcycling waste polyethylene through introduction of hydrophilic functional groups (such as –COOH, –OH), yet often at the expense of their original hydrophobicity. Herein, the hydrophobic ester groups, were introduced via Baeyer-Villiger oxidation to ingeniously balance the contradiction among hydrophobicity, interfacial forces and sustainability of polyethylene oxidation products. A tandem conversion mechanism among the oxidative groups was proposed while the decrease in molecular weight and branching degree was clarified to be a result of β-scissions occurring the branches during the oxidation. Meanwhile, the effect of oxidation degree and molecular weight on interfacial forces was revealed. The excellent hydrophobicity and corrosion resistance of the oxidized polyethylene coating can be attributed to the low content of carboxyl/hydroxyl groups, rich hydrophobic ester groups and the retained long carbon chain structure. Besides, the introduced ester groups and lower molecular weight also provided the oxidation products with potential biodegradability. This work provided a new insight on the Baeyer-Villiger oxidation of polyethylene and the potential for upcycling of polyethylene waste into sustainable materials.

Synthesis and characteristics properties of lignified PVA copolymer with enhanced UV-blocking performance and water solubility

The increasing environmental concerns have heightened the pursuit of sustainable materials, with a particular emphasis on biodegradable polymers. Polyvinyl alcohol (PVA), a recognized biodegradable synthetic polymer, faces challenges such as cost, slow biodegradation, and limited UV resistance. This study explores lignin, an abundant and eco-friendly biopolymer, as a cost-effective additive to enhance PVA properties via the copolymerization technique. The Mannich reaction was utilized to effectively alkylate lignin with allylthiourea, leading to the synthesis of a lignin-based macromonomer (LATU). Subsequently, the LATU macromonomer was copolymerized with vinyl acetate, producing Poly(VAc-Co-LATU) copolymer in a reaction conducted at 70 °C for 6 h. Finally, the copolymers were hydrolyzed (saponification) with potassium hydroxide to obtain Poly(VA-Co-LATU) copolymers. Extensive investigations, including FTIR, XPS, XRD, and 1H NMR, effectively validated the synthesis of the copolymers. The high monomer conversion rate above 89 % emphasizes the effectiveness of the synthesis method. The addition of LATU has a direct impact on the crystalline structure of the copolymer. X-ray diffraction patterns indicate a reduction in crystallinity, which in turn affects the other properties of the synthesized copolymers. Consequently, the lignified copolymer, Poly(VA-co-LATU), exhibited slight decrease in molecular weight (Mw), improved UV-blocking effectiveness, and greater solubility in water as comparison to PVA. This study demonstrates the feasibility of using lignin as a monomer to create novel bio-based polymeric materials that exhibit the necessary properties for certain applications.

Acid resistance of different polysaccharide hydrocolloids: pH effects

The acid resistance of polysaccharide hydrocolloids is very important for its application in food industry. In this study, the acid resistance of tamarind seed polysaccharide (TSP), xanthan gum (XG), and locust bean gum (LBG) at different pH was investigated. Results showed that the shear viscosity of TSP and LBG was significantly decreased at pH 1. Structural analyses showed that molecular degradation on the side chain of TSP and LBG occurred at pH 1, whereas the composition of the monosaccharides of XG showed no significant difference. Molecular degradation led to a decrease in the molecular weight of TSP and LBG with the gradual decrease of pH, accompanied by a shift in solution conformation, i.e., from semi-flexible chain to rigid rod for TSP and LBG, whereas XG did not undergo significant structural changes with the gradual decrease of pH. In addition, the SEM results showed that with the gradual decrease of molecular weight, the structures of TSP and LBG were gradually broken and showed fragmentation, while XG only showed slight cracks. These results show that the structure of the polysaccharides changes with the gradual decrease of pH, resulting in a change in the solution conformation and a decrease in viscosity. This study provides a new theoretical basis for the application of these polysaccharide hydrocolloids in food processing.

A multi-analytical approach to evaluate the removal efficiency of polystyrene nanoparticles in water treatment processes

The removal of nanoplastics (NP) from water using various treatment processes has gained significant attention recently. This study comprehensively characterizes the degradation of polystyrene nanoparticles (concentration: 200 ppm, diameter: 140 nm) through UVC irradiation. For the first time, we compared four analytical methods to monitor removal efficiency: Py-GCMS, UV–Visible spectroscopy, TOC, and Turbidity. Additionally, DLS, TEM, and SEC were used to understand changes in particle size, morphology, and molecular weight. Results showed that Py-GCMS overestimated the removal rate by a factor of 2 compared to Turbidity and UV–Visible measurements, which were in agreement. Furthermore, after 200 h of irradiation, the styrene signal disappears from the pyrogram, although the mineralization rate reaches only 50%, as determined by total organic carbon (TOC) analysis. The particle size decreased slowly, reaching 100 nm after 150 h, while a significant decrease in molecular weight indicated high chain-scission. These findings emphasize the importance of a multi-analytical approach to accurately assess NP removal efficiency and understand degradation mechanisms.

Lysine 473 Regulates the Progression of SLC7A11, the Cystine/Glutamate Exchanger, through the Secretory Pathway.

System xc-, the cystine/glutamate exchanger, is a membrane transporter that plays a critical role in the antioxidant response of cells. Recent work has shown that System xc- localizes to the plasma membrane during oxidative stress, allowing for increased activity to support the production of glutathione. In this study, we used site-directed mutagenesis to examine the role of C-terminal lysine residues (K422, K472, and K473) of xCT (SLC7A11) in regulating System xc-. We observed that K473R exhibits loss of transporter activity and membrane localization and is 7.5 kD lower in molecular weight, suggesting that K473 regulates System xc- trafficking and is modified under basal conditions. After ruling out ubiquitination and neddylation, we demonstrated that unlike WT xCT, K473R lacks N- and O-glycosylation and is sequestered in the endoplasmic reticulum. Next, we demonstrated that K473Q, a constitutively acetylated lysine mimic, also exhibits loss of transporter activity, decreased membrane expression, and a 4 kD decrease in molecular weight; however, it is N- and O-glycosylated and localized to the endoplasmic reticulum and Golgi. These results suggest that acetylation and deacetylation of K473 in the endoplasmic reticulum and Golgi, respectively, serve to regulate the progression of the transporter through the biosynthetic pathway.

The role of duel hydrolysis of soybean on functional properties and protein digestibility: a sustainable approach.

Protein hydrolysates derived from food sources contains enormous number of peptides which are composed of amino acid possessess various bioactive properties. However, the use of protein hydrolysates as a nutraceutical is hindered due to their unpleasant flavour. The study aims to enhance the biological activity and palatability of protein hydrolysates. In the present study, soybean protein hydrolysate (SPH) was prepared using alcalase for 4 h (control). Modification of hydrolysis (MPH) was carried out by reiterating the hydrolysis of the supernatant obtained after 2 h of hydrolysis using an enzyme to 50% of alcalase during each successive hydrolysis. Samples were characterised by their physio-chemical and functional properties. Furthermore, the effect of modification on the protein digestibility and bitterness intensity using e-tongue was studied. The suppressive effect on retrogradation of corn starch was analysed using texture profile analysis. The results demonstrated increased protein content by 1.6 and 1.9% in MPH compared to SPH and UNH, respectively. MPH showed 1.5- and 1.6-fold higher DH% than SPH before and after gastrointestinal digestion (p < 0.05). A decrease in molecular weight was found in the order of UNH > SPH > MPH. Nevertheless, MPH displayed significantly higher functional properties (p ≤ 0.05). The hardness of retrograded corn starch was significantly reduced in the MPH (1.21N) than SPH (1.55 N) and UNH (1.81N) compared to control (1.71N) during 7-day storage at 4°C (p ≤ 0.05). E-tongue analysis of MPH showed a 4-fold reduction in bitterness than SPH. Modification of hydrolysis of soybean has demonstrated its significance in improved DH% functional properties and palatability. In addition, improved protein digestibility with promising benefits in deferral action on retrogradation of starch over the traditional process of hydrolysis was observed. The outcome of this study contributes to the potential utilisation of MPH as an ingredient in the formulation of nutraceutical products.

Structure-property correlations study in biochar-enhanced polyamide composites for sustainable materials development

This study explores the synthesis and characterization of polyamide/biochar composites via in situ polymerization of 12-aminolauric acid with varying biochar concentrations. The motivation behind this research is to enhance the properties of polyamide 12 (PA12) by integrating biochar, a sustainable material derived from biomass, to improve both performance and environmental impact. A detailed structure-property correlation analysis was conducted to assess the effects of biochar on PA12's morphology, mechanical behavior, crystallinity, thermal stability, viscoelastic performance, and environmental sustainability. Key findings include successful PA12 synthesis, confirmed by FTIR and 1H NMR spectroscopy. Increased biochar content led to a decrease in molecular weight and an increase in crystallinity from 27 % to 38 %, suggesting enhanced nucleation effects. SEM analysis showed excellent dispersion and compatibility of biochar within the PA12 matrix, leading to significant improvements in tensile strength (from 38 ± 1 MPa to 54 ± 2 MPa) and modulus (from 745 ± 30 MPa to 2055 ± 65 MPa). Rheological tests demonstrated shear-thinning behavior, facilitating effective extrusion-based 3D printing of a complex object with 50 wt% biochar. A life cycle assessment revealed substantial environmental benefits, including a net reduction of 1.83 kg·CO₂ equiv.·kg⁻1 due to the use of biochar derived from wood pyrolysis. These findings highlight the potential of PA12/biochar composites as environmentally sustainable structural materials, combining enhanced functional properties with significant ecological advantages.

Accelerated hydrolytic degradation of poly(l-lactide) by blending with poly(ether-block-amide)

A continuing challenge in the most common biodegradable polyester of poly(l-lactide) (PLLA) is to improve the degradation rate in the environment, though it has been widely used in packaging and medical applications. In this study, PLLA/poly(ether-block-amide) (PEBA) blends are prepared by melt blending to investigate the effect of PEBA component on the phase morphology, thermal behavior, mechanical properties, and hydrolytic degradation of the blends. The incorporation of PEBA component is beneficial to the improved toughness and increased water absorption of the blends, and accelerated hydrolytic degradation of PLLA. The blend exhibits the optimal mechanical and hydrolytic degradation properties when the blend mass ratio of PLLA/PEBA is 80/20. The toughness of the blend is increased by 390 % compared to that of pure PLLA. After being hydrolyzed at 58 °C for 240 h, the water absorption, the mass loss and the decrease of molecular weight of the blend is increased by 138 %, 160 % and 40 %, respectively, indicating faster hydrolytic degradation rate of the blend than that of pure PLLA. Furthermore, the accelerated hydrolytic degradation mechanism of PLLA in the blend is revealed. The amorphous region of PLLA is hydrolyzed initially at the phase interface of the blend, and subsequently the crystalline structure of PLLA is degraded. The hydrolysis process causes a change in the relative content of crystalline regions in the system, resulting in an increase in crystallinity of PLLA first and then decrease. These findings provide a new strategy for the design of novel degradable PLLA materials for practical applications.

Evolution of multi-scale structure and microbiota metabolism of lentil resistant starch during the dynamic fermentation in vitro

This study investigated the structural changes of resistant starch (RS) derived from autoclaved lentil starch (ALRS) and untreated lentil starch (ULRS) during in vitro colonic fermentation, as well as their regulatory effects on the composition of the intestinal microbiota. Following in vitro fermentation, both RS samples exhibited a progressive decrease in molecular weight and a gradual increase in double helix/order. Bifidobacterium was more abundant in ULRS during the initial period of fermentation, while ALRS showed higher abundance in the later stage. ALRS demonstrated greater production of short-chain fatty acids (SCFAs) compared to ULRS, likely attributed to its higher structural order and faster fermentation pattern. The distinct surface morphologies of ULRS and ALRS played a crucial role in determining the accessibility of RS substrates for microbial fermentation. These different structural patterns also influenced the shifts in microbial composition in fecal cultures, leading to variations in SCFAs production through anaerobic fermentation.

Electrooxidation of Poly(methyl-methacrylate) and Poly(ethylene glycol): Hydrogen Production from Plastic Wastes Electrolysis

Introduction. Green H2 production by water electrolysis at low temperature has some bottlenecks mostly dealing with the anodic reaction, the oxygen evolution reaction (OER), given its thermodynamic and kinetic limitations [1]. One strategy to reduce the energy requirements for this H2 production route is the replacement of the conventional OER (with a thermodynamic potential of 1.23 V vs. Reversible Hydrogen Electrode (RHE)) by a less-energy intensive reaction like the electrooxidation of organic molecules (in some cases presenting a thermodynamic potential as low as c.a. 0 V vs RHE). This approach also addresses the possibility of converting organic wastes into value-added chemicals avoiding the CO2 emissions derived from conventional treatments (e.g., incineration) [2, 3]. Our research group is focused on the electrochemical valorization of several organic wastes like polyethylene glycol (PEG) or poly(methyl-methacrylate) (PMMA). Both are commonly found in urban and industrial water effluents and concern has been raised about the true fate of these polymers in the environment. Herein, the possibility of generating H2 and value-added organic molecules from these plastic wastes has been explored. Experimental. A binary solvent strategy was followed to dissolve the PMMA polymer, by using 1 M H2SO4 in 80% v/v 2-propanol/water electrolyte. Then the electrooxidation of PMMA was studied in a 2-electrode batch cell at 70ºC with different PMMA concentrations (0.1-2 wt.%). On the other hand, the electrooxidation of ethylene glycol (EG) and PEG with various molecular weights (from 200 to 4000 g mol-1), which are soluble in water, was carried out in aqueous solutions (PEG concentrations from 1 to 20 g/L) between 30 and 80 °C by using a Polymer Electrolyte Membrane (PEM) reactor. Pt/C electrodes were used in all cases. A commercial Pt cathode was employed and the anode material was prepared by the spray-deposition of a Pt(20 wt.%)/C catalyst powder onto a carbon paper gas-diffusion layer. The liquid products at the anodic compartment were analysed by size-exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy while the production of hydrogen in the cathodic compartment was online monitored with a mass spectroscopy. Results and discussion. In the case of PMMA electrooxidation, despite the dissolution challenge, polymer macromolecules showed to partially block the accessibility of the Pt active sites on the electrode and strongly degraded its electrochemical performance [4]. In the case of PEG, it was much more easily electrooxidised, at low cell voltages, from around 0.4 V at 80°C (Figure 1a), near to values recorded with EG, suggesting a first step linked with the electrooxidation of the terminal groups of the macromolecules chain. Current densities larger than 100 mA.cm-2 at 0.8 V and 80°C were achieved for low molecular mass molecules (200 and 400 g/mol). A decrease of the PEG molecular weight in the anodic solution was demonstrated by SEC, confirming that the electro-oxidation process likely follows two main mechanisms, involving the consumption of terminal –OH or intermediate -C-O-C- bonds cleavage (Figure 1b), depending on the polymer molecular weight. This study demonstrates the proof-of-concept of the low-temperature electro-oxidation of polymers containing C-O bonds in their main chain. Conclusions. With a further macroporous electrode enegineering and catalyst development, the electrolysis of plastic wastes stands as a promising technology not only for the production of hydrogen from macromolecules by electrochemical means, but also as a potential pathway to depolymarize plastic wastes, thus increasing their degradability. References. [1]. Y. Cheng, S.P. Jiang, Advances in electrocatalysts for oxygen evolution reaction of water electrolysis-from metal oxides to carbon nanotubes, Prog. Nat. Sci.: Mater. 25 (2015) 545-553.[2]. M. Simões, S. Baranton, C. Coutanceau, Electrochemical valorisation of glycerol, ChemSusChem. 5 (2012) 2106–2124[3]. Y.X. Chen, A. Lavacchi, H.A. Miller, M. Bevilacqua, J. Filippi, M. Innocenti, et al. Nanotechnology makes biomass electrolysis more energy efficient than water electrolysis. Nat. Commun. 5 (2014) 1-6.[4]. N. Grimaldos-Osorio, F. Sordello, M. Passananti, J. González-Cobos, A. Bonhommé, P. Vernoux, A. Caravaca. From plastic-waste to H2: A first approach to the electrochemical reforming of dissolved Poly(methyl methacrylate) particles. Int. J. Hydrogen Energy. 48 (2023) 11899-11913. Acknowledgments The authors gratefully acknowledge the French institution “Ecole Urbaine de Lyon” (EUL - Institut de Convergences) for funding a PhD grant of Dr. N. Grimaldos-Osorio. Figure 1

Solvent-based synthesis, structural elucidation and thermal characterisation of free radical grafted PHBV

This study investigates the solvent-based free-radical graft copolymerization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with C11 (undecenoic acid, UDA), C12 (dodecene, DD), and C18 (octadecene, OD) alkene substrates using dicumyl peroxide as an initiator. Comprehensive Nuclear Magnetic Resonance (NMR) spectroscopy was employed to confirm and quantify grafting, which was achieved at up to 5.8 mol% of monomer units. Thermal analysis revealed a significant reduction in melting temperature for all modified PHBVs, ranging from 10-20°C decrease in comparison to virgin PHBV. A decrease in crystallisation temperature and a reduction in glass transition temperature was measured for the UDA and DD grafted PHBV. Additionally, molecular weight analysis showed a marked decrease in weight average molecular weight (M¯w) and number average molecular weight (M¯n) for PHBV grafted with UDA, which was attributed to the presence of carboxylic acid functionality, which accelerates chain scission. The molecular weight profiles of the dodecene and octadecene grafted PHBV were only marginally reduced (32% and 18% reductions in M¯w, respectively), which is a much less severe reduction than has been previously observed for similar chemistries. Overall, this work demonstrates that solvent-based free-radical graft copolymerization can reduce the melting temperature and disrupt the crystallinity of PHBV, hence improving its processability and progressing the field of PHA modification and application.

Measuring Erosion of Biodegradable Polymers in Brimonidine Drug Delivery Implants by Quantitative Proton NMR Spectroscopy (q-HNMR)

Erosion of biodegradable polymeric excipients, such as polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA), is generally characterized by microbalance for the remaining mass of PLA and/or PLGA and Gel Permeation Chromatography (GPC) for molecular weight (MW) decrease. For polymer erosion studies of intravitreal sustained release brimonidine implants, however, both microbalance and GPC present several challenges. Mass loss measurement by microbalance does not have specificity for excipient polymers and drug substances. Accuracy of the remaining mass by weighing could also be low due to sample mass loss through retrieval-drying steps, especially at later drug release (DR) time points. When measuring the decrease of polymer MW by GPC, trace amounts of polymeric degradants (oligomers and/or monomers) trapped inside the implants during DR tests may not be measurable due to sensitivity limitations of the GPC detector and column MW range. Previous efforts to measure remained PLGA weight of dexamethasone micro-implants using qNMR with external calibration have been performed, however, these measurements do not account for chemical structure changes (i.e. LA to GA ratio changes from time zero) of PLGA implants during drug release tests. Here, a qNMR method with an internal standard was developed to monitor the following changes in micro-implants during drug release tests: 1. The remaining overall PLA/PLGA mass. 2. The remaining lactic acid (LA), glycolic acid (GA) unit and PLGA's lauryl ester end group percentages. 3. The trace content of PLA/PLGA oligomers as degradants retained in the implants. Unlike microbalance analysis, qNMR has both specificity for drug substance, excipient polymer, and accuracy due to minimal implant loss during sample preparation. Compared to the overall PLA/PLGA remaining mass generally monitored in erosion studies, the percentage of remaining LA, GA, and the ester end group provide more information about the microstructure change (such as hydrophobicity) of PLA/PLGA. Additionally, the qNMR method can complement GPC methods by measuring the change of remaining PLA and PLGA oligomer concentrations in brimonidine implants, with tenfold less sample and no MW cutoff. The qNMR method can be used as a sensitive tool for both polymer excipient characterization and kinetics studies of brimonidine implant erosion.

Quantification of PLA degradation in the melt phase using a parallel plate rheometer

Bioplastics like poly(lactic acid) or PLA have received significant attention over the last years, triggered by global environmental and climate concerns linked to the use of petroleum-based plastics. However, the ester bonds in PLA that are responsible for its biodegradable character are also vulnerable linkages during polymer processing. Melt processing of polymers typically involves high temperatures and shear loading. Hence, understanding degradation of PLA in the melt phase is crucial to minimize the molecular weight decrease, since it is directly linked to deterioration of mechanical, thermal and rheological properties. In this study, we performed a 24 full factorial design to investigate melt-phase degradation using a parallel plate rheometer. We investigated the effect of four parameters on the molecular weight: moisture content in the PLA, processing temperature, residence time, and shear stress. In addition, we explored whether the percentage of d-isomer significantly influences the degradation, through selecting three PLA-grades with different optical purity. The results showed that moisture content is the dominant factor in the molecular weight decrease, followed by a significant effect of processing temperature. Notably, the significant interaction between moisture content and processing temperature highlights the importance of studying interaction effects, an aspect often overlooked in current literature. Moreover, only the effect of moisture content is influenced by the percentage of d-isomer, whereas the numerical values of other significant effects are similar across the three PLA-grades. The small, yet significant effect of residence time, along with the unexpected insignificant effect of shear stress, may be explained by the use of small amplitude oscillatory deformations in a parallel plate rheometer as testing method in this study. In conclusion, the findings of this study offer polymer processors and researchers valuable insights, which can help with the selection and prediction of processing conditions that minimize degradation, ultimately saving time and raw materials during production.

Effects of cold plasma pretreatment before different drying process on the structural and functional properties of starch in Chinese yam

This article compared the effects of hot air drying (HAD), infrared drying (IRD), and cold plasma (CP) as a pretreatment on the structure, quality, and digestive characteristics of starch extracted from yam. As the most commonly used drying method, HAD was used as a control. SEM and CLSM images showed that all treatments preserve the integrity of the yam starch. CP caused some cracks and breaks in the starch granules. IRD did not destroy the crystal structure of starch molecules, but made the spiral structure tighter and increased short-range orderliness. However, CP led to the depolymerization and dispersion of starch molecular chains, resulting in a decrease in average molecular weight and relative crystallinity. These molecular conformation changes caused by different processes led to differences in solubility, swelling power, pasting parameters, digestion characteristics, and functional characteristics. This study provided an important basis for the reasonable drying preparation and utilization of yam starch.

Effects of Molecular Weight on the Marine Biodegradability of Poly(l-lactic acid).

Poly(l-lactic acid) (PLA) is a biodegradable bioplastic with limited marine degradation. This study examines the impact of molecular weight on PLA's marine biodegradability. We synthesized PLA with terminal hydroxyl groups (PLA-OH) with degrees of polymerization (DP) between 14 and 642 and conducted biochemical oxygen demand (BOD) tests. Samples with a DP of 422 or 642 did not degrade, like commercial PLA. However, PLA-OH with a DP below 314 showed biodegradability, with DP 14 exhibiting a higher degradability than cellulose. Size exclusion chromatography (SEC) confirmed a decrease in molecular weight for samples with DPs below 314, indicating extracellular microbial activity. These findings suggest that PLA-OH with a DP under 314 can be degraded in marine conditions, unlike high-molecular-weight PLA. If the DP of high-molecular-weight PLA can be reduced to 314 by some specific method, then it is expected that PLA can be used to create marine biodegradable materials.

Highly adhesive and impact‐strengthening supramolecular polyurethane derived from facile incorporation of UPy motifs toward energy dissipation binding applications

AbstractThe implementation of hot melt adhesives reaching structural adhesion with both impact resistance and detachability is of prospective industry value but still remains challenging. In this work, 2‐amino‐4‐hydroxy‐6‐methylpyrimidine serving as both chain extender and end‐capping reagent due to its isomerism, was developed to construct a supramolecular polyurethane‐derived hot melt structural adhesive. The as‐synthesized PUM elastomers occurs obvious decrease of molecular weight at 80°C compared to room temperature, revealing the existence of self‐complementary 2‐ureido‐4[1H]‐pyrimidinone (UPy) motifs at chain ends. This unique structure allows to chemically incorporate abundant hierarchical and quadruple hydrogen bonding moieties, which results in remarkable enhancement of shear strength, ranging from 6.4 to 16.6 MPa. More importantly, it also exhibits unique impact‐strengthening and reproducible adhering ability. The Hopkinson‐press‐bar and cyclic tensile tests manifest that quadruple hydrogen bonds play a pivotal role in buffering external forces and increasing energy dissipation when exposed to high velocity impacts. The true stress and strain synchronously increase as the strain rate augments while the shear strength can even roar up to ~18 MPa at high tensile speed. With regard to mild synthetic conditions, atomic economic use of reactants, it is promising that this material has industrial potential to be utilized in applications referred to energy‐absorption and reproducible structural adhesion.

Biodegradation Mechanism of Polystyrene by Mealworms (Tenebrio molitor) and Nutrients Influencing Their Growth

A degradation mechanism of polystyrene (PS) in mealworms reared on expanded PS (EPS) was investigated by its decrease in molecular weight and change in chemical structure. A 33% decrease in molecular weight was observed for the digested PS in the frass after 1 week of feeding to mealworms. The FT-IR and py-GC/MS spectra of the digested PS showed radical oxidative reactions taking place in the mealworm body. The presence of hydroperoxide, alcohol and phenol groups was confirmed, and dimer fragments of styrene with quinone and phenol groups were obtained. The decrease in molecular weight and the alternation of benzene rings indicated that autoxidation and quinonization via phenolic intermediates occurred simultaneously in the mealworm body. The survival rate of mealworms reared on EPS was higher than that of starved worms, indicating that EPS was a nutrient source. However, no weight gain was observed in mealworms fed EPS alone. Comparison with the mixed diets with bran or urethane foams (PU) indicated that protein, phosphorus and magnesium components absent from EPS were required for mealworm growth.

Glycerol-driven adaptive evolution for the production of low-molecular-weight Welan gum: Characterization and activity evaluation

Through adaptive laboratory evolution (ALE) of Sphingomonas sp. ATCC 31555, fermentation for production of low-molecular-weight welan gum (LMW-WG) was performed using glycerol as sole carbon source. During ALE, GPC-MALS analysis revealed a gradual decrease in WG molecular weight with the increase of adaptation cycles, accompanied by changes in solution conformation. LMW-WG was purified and structurally analyzed using GPC-MALS, monosaccharide composition analysis, infrared spectroscopy, NMR analysis, atomic force microscopy, and scanning electron microscopy. Subsequently, LMW-WG obtains hydration, transparency, antioxidant activity, and rheological properties. Finally, an in vitro simulation colon reactor was used to evaluate potential prebiotic properties of LMW-WG as dietary fiber. Compared with WG produced using sucrose as substrate, LMW-WG exhibited a fourfold reduction in molecular weight while maintaining moderate viscosity. Structurally, L-Rha nearly completely replaced L-Man. Furthermore, LMW-WG demonstrated excellent hydration, antioxidant activity, and high transparency. It also exhibited resistance to saliva and gastrointestinal digestion, showcasing a favorable colonization effect on Bifidobacterium, making it a promising symbiotic agent.