Reduction In Molar Mass Research Articles

Effect of ethylene oxide and gamma sterilization on surface texture of films and electrospun poly(ε-caprolactone-co-p-dioxanone) (PCLDX) scaffolds

In the field of tissue engineering, synthetic and degradable polyesters like poly(ε-caprolactone) (PCL) and poly(ε-caprolactone-co-p-dioxanone) (PCLDX) are widely used as scaffolds. Our previous research revealed that thermal storage conditions could alter the surface texture of PCL and PCLDX scaffolds, which might influence cell-scaffold interactions in tissue engineering applications. These findings highlighted the importance of multi-scale characterization techniques to identify the scales most sensitive to external changes and the need for personalized surface texture analysis. Sterilization techniques, such as ethylene oxide and gamma radiation, are essential for ensuring the sterility of polymeric medical devices. However, these processes can significantly impact the bulk polymer properties and/or surface texture of the scaffolds, potentially affecting their biocompatibility, safety, and overall performance. Therefore, the influence of sterilization processes on the surface texture of PCLDX films and electrospun nanofibers and to correlate these findings with the thermal and physical properties of the polymer are essential and have been assessed. Our results demonstrated that ethylene oxide maintained the structural integrity and surface texture of PCLDX scaffolds, while gamma irradiation caused a significant reduction in molar mass and increased the number of hills (Shn) and dales (Sdn) on PCLDX samples. Despite these changes, both sterilization methods showed minimal effects on the thermal properties, such as melting temperature and degree of crystallinity, and surface wettability of the scaffolds. This comprehensive surface texture analysis highlights the importance of evaluating feature parameters such as Shn and Sdn for optimizing the performance and biocompatibility of polymeric scaffolds in tissue engineering.

Tailoring the mechanical and rheological properties of poly(lactic acid) by sterilizing UV-C irradiation

In this study, we irradiated amorphous (A) and semi-crystalline (SC) poly(lactic acid) (PLA) with different UV-C doses up to 2214 kJ/m2. We achieved an average crystallinity of 43 % by heat treatment, which was unaffected by UV-C irradiation. Modulated differential scanning calorimetry showed that crystal polymorphs and the ratio of rigid amorphous and mobile amorphous phases were also unaffected. Using gel permeation chromatography analysis, we showed that the degradation mechanism was noncatalytic random scission, and the initial molar mass was reduced by >90 % at a dose of 2214 kJ/m2 for both A- and SC-PLA samples. Our Raman spectroscopy results indicated that the probability of the formation of oxygen-containing groups increases with increasing UV-C doses. Since we found that the mechanical properties of PLA films can be tailored with UV-C light, we proposed a method to predict the overall tensile curve as a function of the UV-C dose. We also proposed a modified Cross-WLF model to describe the effect of UV-C irradiation on viscosity up to 55 % molar mass reduction. The models allow us to estimate the limits of recyclability and reusability of sterilised PLA products.

Colloidal and thermal properties of poly(hydroxyethyl caprolactone acrylate‐co‐methyl methacrylate)‐g‐pullulan latex obtained by seeded semi‐batch emulsion polymerization

AbstractIn this study, the influence that the monomer composition of hydroxyethyl caprolactone acrylate/methyl methacrylate (HECLA/MMA) has on the properties of the latex films, including contact angle, thermogravimetric analysis, and mechanical properties was evaluated. The polymerization process to obtain small particle sizes, good colloidal stability, and polymer films was optimized through the use of pullulan (Pull) and different ratios of HECLA and MMA. The results revealed a substantial impact of the monomer composition and polymerization processes on the particle size and latex film properties. The use of seed latex obtained in situ reduces particle size and particle size distribution. Additionally, it was observed that the contact angle of the polymer films increased as the concentration of HECLA increased. Furthermore, the water absorption of the polymer films exhibited a decreasing trend after reaching an 80/20 monomer composition of HECLA/MMA. An increase in HECLA contents in the recipe showed a reduction in tensile strength, elastic modulus, hardness, and elongation at break. Conversely, higher HECLA contents contributed to improving the thermal properties of the polymer films. Finally, the optimal ratio of HECLA/MMA to improve the thermal degradation and tensile mechanical properties of the polymer film was 50/50 wt%. The results found in this work allow additional data for producing poly(HECLA‐co‐MMA)‐g‐Pull latexes by manipulating the ratios of HECLA and MMA, which can create new potential applications in various industrial settings for a wide range of polysaccharides.Highlights Poly(HECLA‐co‐MMA)‐g‐Pull with different ratios of HECLA/MMA were successfully obtained. The use of Pull after molar mass reduction had a significant effect on colloidal stability. A reduction in tensile strength and elongation at break was obtained by increasing the amount of HECLA. Thermal stability of the latex films showed a direct relationship with the content of HECLA. Poly(HECLA‐co‐MMA)‐g‐Pull latexes can be used in agricultural applications.

Evaluation of the polycaprolactone hydrolytic degradation in acid solvent and its influence on the electrospinning process

AbstractPolycaprolactone (PCL) is a pivotal biopolymer in biomedicine, especially in tissue engineering for scaffolds and biomaterials. Recognized for its effectiveness as a drug carrier with superior controlled release properties, PCL is commonly processed via electrospinning, typically employing chlorinated or fluorinated solvents known for cellular toxicity. As an environmentally conscious alternative, this study explores glacial acetic acid (AA) as a solvent for electrospinning solutions. Investigating PCL's molecular degradation through acid hydrolysis in acidic solvents (AA/formic acid) (FA), the study assesses the impact of storage time on resulting structures. Solutions containing 30% PCL in AA/FA (9:1) were stored at 35°C for up to 14 days, revealing a 50% molar mass reduction during solubilization through gel permeation chromatography, x‐ray diffraction, and Fourier‐transform infrared analyses. This reduction influenced chain packing, raising crystallinity indices from approximately 37% to 49% with prolonged storage. The reduced molar mass resulted in unstable Taylor cones, generating diverse mat morphologies. Intriguingly, this degradation enhanced water adsorption capacity, indicating exposed hydrogen bonds from acid hydrolysis as an advantageous trait for regenerative medicine. This underscores the hydrolyzed materials' potential for cell anchoring in tissue engineering.

Investigation on the Durability of a Polypropylene Geotextile under Artificial Aging Scenarios

Geosynthetics are widely used in various civil engineering applications, such as geotextiles in coastal protection, and display a sustainable alternative to natural mineral materials. However, the full benefits of using geosynthetics can only be gained with a long service lifetime of the products. With the use of added stabilizers to the polymers, service lifetimes can be achieved in the range of 100 years. Therefore, accelerated aging methods are needed for the assessment of the long-term performance of geotextiles. In the present study, the behavior of geosynthetic materials made of polypropylene was investigated under artificial aging conditions involving elevated temperatures ranging from 30 to 80 °C, increased oxygen pressures ranging from 10 to 50 bar in water-filled autoclaves, and UV irradiation under atmospheric conditions. ATR-IR spectroscopy was employed to detect the increase in the carbonyl index over various aging durations, indicating the oxidative degradation of the geotextile. The most pronounced increase was observed in the case of aging through UV irradiation, followed by thermal aging. Elevated pressure, on the other hand, had a lower impact on oxidation. High-temperature size exclusion chromatography was utilized to follow the reduction in molar mass under different degradation conditions, and the results were consistent with those obtained from ATR-IR spectroscopy. In polyolefins such as polypropylene, Hindered Amine Stabilizers (HAS) are used to suppress oxidation caused by UV radiation. The quantitative analysis of HAS was carried out using a UV/Vis method and HPLC. The degradation of UV stabilizers during the aging of geotextiles is responsible for the oxidation and the reduction in the molar mass of polypropylene. From the results, it can be concluded that applications of PP geotextile without soil or sand cover might cause the risk of the formation of microplastic particles. Material selection, design, and maintenance of the construction must follow best practices, including the system’s removal or replacement at end-of-life. Otherwise, a sustainable use of geotextiles in civil engineering is not possible.

Multiple mechanical recycling of a post-industrial flexible polypropylene and its nanocomposite with clay: Impact on properties for food packaging applications

The development of polymer nanocomposites for food packaging has been increasing, but there is a lack of studies on their recyclability. The modification of the physical-mechanical properties and overall migration of post-industrial flexible recycled polypropylene (PIPP) and PIPP/compatibilizer/NI.44P clay nanocomposite with the simulated repetitive mechanical recycling were comparatively studied. The structure, thermal properties, crystallinity, and water vapor permeability of the nanocomposite were not significantly affected by multiple recycling (three re-extrsuion cyles). Among the mean findings, the melt flow rate of the polymer was the parameter more affected by the reprocessing, especially in the nanocomposite. PIPP and PIPP nanocomposite tended to molar mass reduction by repetitive reprocessing. However, a narrower molar mass distribution was obtained according to the rheological analysis. Clay addition significantly reduced the ductility of the films in the first reprocessing cycle but interestingly, the tensile properties for PIPP and nanocomposite were similar in the fourth cycle. Prominently, overall migration of the nanocomposite to olive oil diminished by reprocessing cycles, while the opposite was found for the PIPP without clay. Nonetheless, in all cases, the overall migration values to ethanol 10% and olive oil were below the maximum limit permitted for food packaging.

Characterization of the abiotic degradation of oxo-biodegradable polypropylene obtained from transition metal-free pro-oxidant

The pro-oxidant additives used in the production of oxo-biodegradable polymers are generally organic salts of transition metals added during the processing of polyolefins. Transition metals accelerate the photooxidation and thermal oxidation of macromolecules, producing oxygenated fragments which are then used as nutrients by microorganisms in the biodegradation process. However, the use of these additives can lead to contamination of the environment by metals, which come free from the reactions. The aim of this study was to obtain an oxo-biodegradable polypropylene by processing flat films with distinct levels of benzoin, an organic substance free of transition metals, which is biodegradable. After extrusion (t = 0 h), samples were submitted to OIT analysis, which showed that benzoin favors the thermal oxidation process. Subsequently, the samples were subjected to accelerated ageing in a UV chamber and were characterized by dilute solution viscometry (DSV), FTIR, TGA, DSC and SEM. Results of the DSV analysis revealed a significant reduction in the viscosimetric average molar mass of the samples containing the additive, which was accompanied by a considerable increase in carbonyl groups, according to the carbonyl indexes calculated from the FTIR spectra. Thermogravimetric analysis of the aged samples containing benzoin indicated a greater loss of thermal stability and the DSC thermograms revealed a considerable reduction in the melting temperature of the oxo-biodegradable PP. The SEM images of the aged samples indicated that the presence of the additive favored the appearance of regions containing flaking and erosion. In general, the results clearly indicated that benzoin accelerated the photooxidation process during ageing by UV irradiation. Unlike organic salts of transition metals, benzoin seems to act in the initiation step of photo- and thermal oxidation, as demonstrated at the end of this study.

Understanding synchronous regulating effects of starch-protein interactions on starch digestion and retrogradation under thermal shear processing

Although starch-protein interactions have been widely used to regulate starch digestibility and retrogradation during food processings, their synchronous regulating effects on both properties still remain largely unexplored. The effects of interactions with pea protein (PP) under thermal shear processing on the digestion and retrogradation properties of modified chestnut starch were investigated. Results show that thermal shear processing broke starch multi-scale structure, leading to the reduction in molar mass, short-range ordered structure, crystallinity, and starch compactness, in turn increasing starch digestibility and accelerating starch retrogradation. However, PP molecules would interact with chestnut starch through hydrogen bonding to form the starch-protein complexes during thermal shear processing, which caused an increased resistant starch. These starch-protein interactions also inhibited the formation of short-range, long-range ordered structure, aggregate structure during storage, causing a reduced degree of retrogradation. The results provided new insights into the synchronously regulating effects of starch-protein interactions under thermal shear processing on starch digestion and retrogradation, which would facilitate the development of starch-based foods with high nutrition and quality.

Molecular and thermo-mechanical assessment of long-chain branched polypropylene: Effect of irradiation dose, multifunctional monomer content and molecular weight

The influence of irradiation dose, trimetylolpropane trimethacrylate (TMPTMA) amount, as a three-functional monomer, and polypropylene (PP) molecular weight on the performance of irradiation technique to create long chain branched PP (LCB-PP) was investigated through molecular, rheological and thermo-mechanical characterizations. With increasing doses or amount of TMPTMA, a reduction in molar mass and an increment in long chain branches (LCBs) number as well as a change in the topology of LCBs from star to tree-like were found. PP grade with low molar mass had more branching ability and its LCBs topology was different. Irradiation declined the glass transition and melting temperature of PP, while it did not affect its crystallization temperature and its degree. Two opposing effects of molar mass reduction and LCBs formation controlled the tensile strength and toughness of irradiated PP samples.

Degradation of PET – Quantitative estimation of changes in molar mass using mechanical and thermal characterization methods

Polyethylene terephthalate (PET) films are used when mechanical strength, thermal and chemical stability, and barrier properties to atmospheric gases are required in combination with good processability. Hydrolysis leading to embrittlement of the material is a major concern as PET is used in a variety of applications with expected lifetimes of up to decades (e.g., for use in buildings, textiles, or photovoltaic backsheets). Therefore, a comprehensive understanding of the degradation processes and the effects on the molecular mass distribution is of great importance.Usually, the direct determination of molar mass and molar mass distribution involves high effort and sophisticated equipment. Therefore, the main objective of this work is to quantify molar mass changes due to accelerated aging using thermal and mechanical methods. Two stabilized PET films were subjected to seven different accelerated aging conditions (heat; combined heat-humidity). The samples were then characterized by size exclusion chromatography (SEC), tensile tests and differential scanning calorimetry (DSC).A linear correlation was found between crystallization temperature and average molar mass. The values of fracture stress from tensile tests indicate a ductile-brittle transition at a molar mass of 15 000 g mol−1. The study concludes that the crystallization temperature obtained from DSC measurements can be used to estimate changes in the average molar mass of PET after hydrolysis. Crystallization temperatures between 208 °C and 211 °C correspond to a critical reduction in molar mass and severe embrittlement.

Polyethylene-Like Blends Amenable to Abiotic Hydrolytic Degradation.

Long-chain aliphatic polyester-18,18 (PE-18,18) exhibits high density polyethylene-like material properties and, as opposed to high density polyethylene (HDPE), can be recycled in a closed loop via depolymerization to monomers under mild conditions. Despite the in-chain ester groups, its high crystallinity and hydrophobicity render PE-18,18 stable toward hydrolysis even under acidic conditions for one year. Hydrolytic degradability, however, can be a desirable material property as it can serve as a universal backstop to plastic accumulation in the environment. We present an approach to render PE-18,18 hydrolytically degradable by melt blending with long-chain aliphatic poly(H-phosphonate)s (PP). The blends can be processed via common injection molding and 3D printing and exhibit HDPE-like tensile properties, namely, high stiffness (E = 750-940 MPa) and ductility (εtb = 330-460%) over a wide range of blend ratios (0.5-20 wt % PP content). Likewise, the orthorhombic solid-state structure and crystallinity (χ ≈ 70%) of the blends are similar to HDPE. Under aqueous conditions in phosphate-buffered media at 25 °C, the blends' PP component is hydrolyzed completely to the underlying long-chain diol and phosphorous acid within four months, as evidenced by NMR analyses. Concomitant, the PE-18,18 major blend component is partially hydrolyzed, while neat PE-18,18 is inert under identical conditions. The hydrolysis of the blend components proceeded throughout the bulk of the specimens as confirmed by gel permeation chromatography (GPC) measurements. The significant molar mass reduction upon extended immersion in water (M n(virgin blends) ≈ 50-70 kg mol-1; M n(hydrolyzed blends) ≈ 7-11 kg mol-1) resulted in embrittlement and fragmentation of the injection molded specimens. This increases the surface area and is anticipated to promote eventual mineralization by abiotic and biotic pathways of these HDPE-like polyesters in the environment.

Relevance of β-Glucan Molecular Properties on Its Suitability as Health Promoting Bread Ingredient.

The fate of β-glucan (BG) health promoting properties during food production is crucial, but not predictable yet. Therefore, high molar mass BG (hBG) and control BG (cBG) were extracted from two barley varieties, characterized and added to wheat breads at levels of 3% and 6%. Bread quality criteria, carbohydrate contents and BG content and structural properties were determined. Additionally, breads were subjected to an in vitro digestion. The BG content in the chyme, molar mass, molar ratio, viscosity and bile acid retention were determined. The hBG and the cBG decreased loaf volume and increased crumb hardness with increasing BG content. The reduction in BG content during bread making was similar for hBG and cBG, but the molar mass of cBG decreased to a greater extent. As a result, only 10% of cBG entering in vitro digestion were found in the chyme afterwards, while 40% of the ingested hBG were detected. Molar mass reduction was much more severe for cBG compared to hBG. The use of hBG showed higher viscosity and better bile acid retention, indicating cholesterol lowering properties, compared to similar or higher amounts of cBG. These results provide valuable knowledge on the criteria to select BG-rich raw materials for ideal health promoting properties.

Hierarchical structural transformation of corn starch in NaOH solution at room temperature

Starch gelatinization at room temperature is an important concern for industrial communities. Alkali solution can be used for starch gelatinization at room temperature. However, starch multi-scale structural transformation in alkali solution as a function of concentration and its application in starch gelatinization at room temperature were not revealed yet. This study investigated the changes of starch multi-scale structures as a function NaOH concentration (0.10–0.30 M) and presented the underlying mechanism of starch gelatinization. The NaOH solution resulted in degradation of α-1,4 and α-1,6 linkage, and in turn, contributed to a reduction of starch molar mass as a function of NaOH concentration. At low concentration (0.10 M), α-1,6 linkages degraded and ordered structures (e.g., short-range ordered structure, helical structure, crystalline structure, and lamellar structure) slightly disassociated. In the solution with an intermediate NaOH concentration (0.10–0.20 M), both α-1,4 and α-1,6 linkages breakdown and the content of ordered structures significantly decreased along with swelling of semi-crystalline structures. As the NaOH concentration was higher than 0.20 M, both α-1,4 and α-1,6 linkages degraded and the ordered structures seriously disrupted along with compete disappear of helical structure, crystalline structure, and lamellar structure. Comparing with the gelatinization behaviors in ionic liquids with heating, starch did not show a more serious degradation in the NaOH solution. Accordingly, the NaOH solution with a concentration higher than 0.20 M can be used for starch gelatinization at room temperature.

PA6/PA66/talc composite: Effect of reprocessing on the structure and properties

AbstractIn this study the effect of repeated injection molding cycles on the structure and properties of polyamide 6/polyamide 66/talc (PA6/PA66/talc ‐ 35/35/30) composite was investigated for samples subjected to one, four, and seven processing cycles. Their morphology (scanning electron microscopy), structure (Fourier transform infrared spectroscopy), melt viscosity (melt flow index [MFI]), mechanical (tensile, flexural, impact, and fatigue tests), and thermal properties (differential scanning calorimetry and thermogravimetric analysis tests) were analyzed. The increase in MFI value and the decrease in the maximum decomposition temperature of PA6, observed by TG analysis, for samples subjected to seven processing cycles, indicated a possible reduction in molar mass of the PA6/PA66 matrix. These samples presented a decrease in degree of crystallinity of PA6 and PA66, which was more pronounced for PA6. The reprocessing of the composite did not present changes in the mechanical properties up to the fourth processing cycle, except for fatigue life which presented a 59% reduction. Samples subjected to seven processing cycles presented a decrease in tensile and flexural strength as well as in tensile and flexural modulus. Charpy impact strength of the samples did not significantly change upon reprocessing. The micrographs of the fatigue fractured surfaces indicated that the weak talc‐matrix interaction and talc‐matrix debonding became more evident with increasing processing cycles.

Polymer selection for Eustachian tube stent application based on mechanical, thermal and degradation behavior

Abstract The novel concept of stenting the Eustachian tube was established to provide an effective and safe therapy of Eustachian tube dysfunction. Biodegradable polymer stents are being developed to restore impaired tube function. As the supporting effect may be required for different time periods, PLA-co-PEG copolymers, PLLGA, PDLLA and PDS, having shorter degradation times compared to PLLA, were evaluated as potential stent materials. Since tensile tests and thermal analyses of solvent cast films from PLA-co-PEG copolymers showed comparable properties to PLLA, stent samples were manufactured from these materials. Mechanical stent testing revealed an increase of elastic recoil and slight decrease of collapse pressure compared to PLLA. In a short term accelerated degradation study a considerable percentage molar mass reduction and an increasing degree of crystallinity depending on PEG content was found. Based on the results obtained, the tested polymers offer a promising, faster degradable alternative to the established stent material PLLA.

Free radical mechanism for reactive processing of polymers in the presence of organoclay/peroxide nanoreactors: Grafting maleic anhydride onto polypropylene

PP-graft-MA is a common PP compatibilizer, produced via reactive extrusion using peroxides as initiator, which causes severe molar mass reduction. To control PP degradation and increase maleic anhydride grafting, Shi and coworkers (2006), proposed the use of nanoreactors. In this paper we propose a complete new reactive mechanism involving nanoreactors during PP-graft-MA reactive processing. The samples were prepared via melt mixing using nanoreactors with different organoclay: peroxide ratios (oMMT:DCP). Organic MMT showed to absorb not more than 16 wt% of DCP, i.e., diffusional controlled release of alkoxy radical will not be observed at o-MMT:DCP ratios < 5:1. The presence of o-MMT tend to increase MA homopolymerization, which consumes the initiator, interfering with the grafting of succinic groups onto the PP backbone, due to increased hindrance of oligo (MA) formed, thereby reducing degradation of the PP chain. Thus, the use of nanoreactors promotes MA homopolymerization rather than grafting as previously proposed in the literature.

Enzymatic Modification of Granular Potato Starch Using Isoamylase—Investigation of Morphological, Physicochemical, Molecular, and Techno‐Functional Properties

AbstractGranular potato starch is modified using the debranching enzyme isoamylase. The modification is performed in aqueous suspension (40% w/w) at 35 °C by grading the volume (100, 250, and 400 µL/50 g of starch, 200 U · mL−1) of enzyme solution added. The starch products obtained are comprehensively investigated in terms of morphological (scanning electron microscopy), structural (X‐ray diffraction), thermal (differential scanning calorimetry), techno‐functional (solubility, hot paste viscosity, gel strength), and molecular properties (size exclusion chromatography‐multi angle laser light scattering‐differential refractive index detection). The granular integrity is basically preserved after modification and a molecular degradation predominantly of the amylopectin by debranching is proved. However, a slight reduction of the weight average molar mass of the amylose fraction is found too. In addition, the intended partial molecular degradation of the starch polysaccharides, the effect of the preparation procedure including washing with ethanol and grinding impacts several starch characteristics conspicuously.

Promising alternative gum: Extraction, characterization, and oxidation of the galactomannan of Cassia fistula

Galactomannan extracted from Cassia fistula seed endosperm present little data related to the its structural characterization. This study reports the chemical characterization of the galactomannan from Cassia fistula (CF) and their oxidized derivatives. The extracted CF presented a yield of 26.5% (w/w) and the intrinsic viscosity [η] was 9.73 dL/g. 1D and 2D nuclear magnetic resonance spectroscopy (NMR) confirmed that the polysaccharide has a backbone of 4-linked β-D-mannose units, and contains galactose units as pending groups. These galactose units are linked to the central core through a (1→6) linkage and the galactomannan presented Man/Gal ratio of 3.1/1. The galactomannan from Cassia fistula presents low cytotoxicity in Vero cells with a CC50 > 1000 μg/ml. The properties of CF resemble other commercially important galactomannans such as Locust bean gum. Three oxidized derivatives of CF were produced by periodate oxidation, which were carefully characterized by different structural techniques. It was observed that as the degree of oxidation increased, there was an increase in the Man/Gal ratio and a reduction in molar mass and viscosity. The polialdehyde produced may be explored as a versality material to react with amine group of the protein and amined polysaccharide to produce biomaterials.

Influence of substrate and temperature on the biodegradation of polyester-based materials: Polylactide and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) as model cases

The extended use of polymers from renewable resources such as aliphatic polyesters or polyhydroxyalkanoates boosted the necessity to understand their behaviour in an end-of-life scenario. Although they can be degraded in reasonable shorter times than traditional polymers, understanding the degradation mechanisms under dissimilar conditions will contribute to further developments in this field. This work aimed to study the effect of temperature and substrate in the degradation of polylactide (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) in a simulated laboratory scale to ascertain their contribution, separately or in combination. For this purpose, nine parallel degradation assays were performed by means of the combination of mesophilic (25 °C), thermophilic (58 °C) and hyperthermophilic (80 °C) temperatures with enriched synthetic medium, compost and standardised soil substrates. Although the analysis of the surface morphology, the thermal properties and the thermo-oxidative stability revealed changes as a function of time, the evaluation of the molar mass allowed for a more precise determination of the degradation. In general, chain scission was perceived in all cases as a function of time. The effect of temperature was critical, significantly more important than the effect of the substrate, which showed a less significant contribution, especially in terms of molar mass reduction. While for the PLA, biodegradation at 58 °C and thermal degradation at 80 °C resulted in similar consequences, for the PHBH the hyperthermophilic temperature of 80 °C was the most severe condition, regardless of the substrate. From a technological perspective, it may be highlighted that biodegradation at 58 °C may be the most cost-effective condition due to the lower energy supply required and the valuable contribution of the microorganisms.

Cascade extraction of proteins and feruloylated arabinoxylans from wheat bran

A cascade process for the sequential recovery of proteins and feruloylated arabinoxylan from wheat bran is proposed, involving a protein isolation step, enzymatic destarching and subcritical water extraction. The protein isolation step combining lactic acid fermentation and cold alkaline extraction reduced the recalcitrance of wheat bran, thus improving the total yields of the subsequent subcritical water extraction. The time evolution of subcritical water extraction of feruloylated arabinoxylan was compared at two temperatures (160 °C and 180 °C). Longer residence times enhanced the purity of target feruloylated arabinoxylans, whereas higher temperatures resulted in faster extraction at the expense of significant molar mass reduction. The radical scavenging activity of the extracted feruloylated arabinoxylans was preserved after the initial protein isolation step. This study opens new possibilities for the cascade valorization of wheat bran into enriched protein and non-starch polysaccharide fractions, which show potential to be used as functional food ingredients.