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13 pages, 2842 KiB

Open AccessArticle

Simultaneous Optimization of Deacetylation Degree and Molar Mass of Chitosan from Shrimp Waste

by Daniel Dumitru Dinculescu, Manuela Rossemary Apetroaei, Cristiana Luminița Gîjiu, Mirela Anton, Laura Enache, Verginica Schröder, Raluca Isopescu and Ileana Rău

Polymers 2024, 16(2), 170; https://doi.org/10.3390/polym16020170 - 06 Jan 2024

Cited by 1 | Viewed by 863

Abstract

Shrimp waste is a valuable source for chitin extraction and consequently for chitosan preparation. In the process of obtaining chitosan, a determining step is the chitin deacetylation. The main characteristic of chitosan is the degree of deacetylation, which must be as high as [...] Read more.

Shrimp waste is a valuable source for chitin extraction and consequently for chitosan preparation. In the process of obtaining chitosan, a determining step is the chitin deacetylation. The main characteristic of chitosan is the degree of deacetylation, which must be as high as possible. The molar mass is another important parameter that defines its utilizations, and according to these, high or low molar masses are required. The present study is an attempt to optimize the deacetylation step to obtain chitosan with a high degree of deacetylation and high or low molar mass. The study was carried out based on experimental data obtained in the frame of a central composite design where three working parameters were considered: NaOH concentration, liquid:solid ratio, and process duration. The regression models defined for the degree of deacetylation (DD) and for the mean molar mass (MM) of chitosan powders were used in the formulation of optimization problems. The objectives considered were simultaneous maximum DD and maximum/minimum MM for the final chitosan samples. For these purposes, multiobjective optimization problems were formulated and solved using genetic algorithms implemented in Matlab^®. The multiple optimal solutions represented by trade-offs between the two objectives are presented for each case. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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16 pages, 3647 KiB

Open AccessArticle

Depolymerization of Pine Wood Organosolv Lignin in Ethanol Medium over NiCu/SiO₂ and NiCuMo/SiO₂ Catalysts: Impact of Temperature and Catalyst Composition

by Angelina V. Miroshnikova, Sergey V. Baryshnikov, Yuriy N. Malyar, Xiaomin Li, Maria V. Alekseeva, Boris N. Kuznetsov and Oxana P. Taran

Polymers 2023, 15(24), 4722; https://doi.org/10.3390/polym15244722 - 15 Dec 2023

Cited by 1 | Viewed by 867

Abstract

The process of thermocatalytic conversion of pine ethanol lignin in supercritical ethanol was studied over NiCu/SiO₂ and NiCuMo/SiO₂ catalysts bearing 8.8 and 11.7 wt.% of Mo. The structure and composition of ethanol lignin and the products of its thermocatalytic conversion were [...] Read more.

The process of thermocatalytic conversion of pine ethanol lignin in supercritical ethanol was studied over NiCu/SiO₂ and NiCuMo/SiO₂ catalysts bearing 8.8 and 11.7 wt.% of Mo. The structure and composition of ethanol lignin and the products of its thermocatalytic conversion were characterized via 2D-HSQC NMR spectroscopy, GC-MC. The main aromatic monomers among the liquid products of ethanol lignin conversion were alkyl derivatives of guaiacol (propyl guaiacol, ethyl guaiacol and methyl guaiacol). The total of the monomers yield in this case was 12.1 wt.%. The temperature elevation up to 350 °C led to a slight decrease in the yield (to 11.8 wt.%) and a change in the composition of monomeric compounds. Alkyl derivatives of pyrocatechol, phenol and benzene were observed to form due to deoxygenation processes. The ratio of the yields of these compounds depended on the catalyst, namely, on the content of Mo in the catalyst composition. Thus, the distribution of monomeric compounds used in various industries can be controlled by varying the catalyst composition and the process conditions. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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20 pages, 4042 KiB

Open AccessArticle

Boric Acid as A Low-Temperature Graphitization Aid and Its Impact on Structure and Properties of Cellulose-Based Carbon Fibers

by Tobias Hückstaedt, Jens Erdmann, André Lehmann, Robert Protz and Johannes Ganster

Polymers 2023, 15(21), 4310; https://doi.org/10.3390/polym15214310 - 02 Nov 2023

Viewed by 1091

Abstract

In the present paper, a scalable, economically feasible, and continuous process for making cellulose-based carbon fibers (CFs) is described encompassing precursor spinning, precursor additivation, thermal stabilization, and carbonization. By the use of boric acid (BA) as an additive, the main drawback of cellulose-based [...] Read more.

In the present paper, a scalable, economically feasible, and continuous process for making cellulose-based carbon fibers (CFs) is described encompassing precursor spinning, precursor additivation, thermal stabilization, and carbonization. By the use of boric acid (BA) as an additive, the main drawback of cellulose-based CFs, i.e., the low carbon yield, is overcome while maintaining a high level of mechanical properties. This is demonstrated by a systematic comparison between CFs obtained from a BA-doped and an un-doped cellulose precursor within a temperature range for carbonization between 1000 and 2000 °C. The changes in chemical composition (via elemental analysis) and physical structure (via X-ray scattering) as well as the mechanical and electrical properties of the resulting CFs were investigated. It turned out that, in contrast to current opinion, the catalytic effect of boron in the formation of graphite-like structures sets in already at 1000 °C. It becomes more and more effective with increasing temperature. The catalytic effect of boron significantly affects crystallite sizes (L_a, L_c), lattice plane spacings (d₀₀₂), and orientation of the crystallites. Using BA, the carbon yield increased by 71%, Young’s modulus by 27%, and conductivity by 168%, reaching 135,000 S/m. At the same time, a moderate decrease in tensile strength by 25% and an increase in density of 14% are observed. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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20 pages, 3725 KiB

Open AccessArticle

Switchable Deep Eutectic Solvents for Lignin Dissolution and Regeneration

by Debao Li, Letian Qi, Mengru Yang, Yujie Gu, Yu Xue, Jiachuan Chen, Ming He and Guihua Yang

Polymers 2023, 15(21), 4233; https://doi.org/10.3390/polym15214233 - 26 Oct 2023

Cited by 1 | Viewed by 1228

Abstract

Deep eutectic solvents (DESs) are promising for lignin dissolution and extraction. However, they usually possess high polarity and are difficult to recycle. To overcome this drawback, a variety of switchable ionic liquids (SILs) composed of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and alcohols was synthesized and screened. [...] Read more.

Deep eutectic solvents (DESs) are promising for lignin dissolution and extraction. However, they usually possess high polarity and are difficult to recycle. To overcome this drawback, a variety of switchable ionic liquids (SILs) composed of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and alcohols was synthesized and screened. According to the thermodynamic modeling suggestions, the selected DBU–HexOH SIL was coupled with hydrogen-bond donors to form switchable-DES (SDES) systems with moderated viscosity, conductivity, and pH while maintaining switchability. The SDESs produced a well-improved lignin and lignin model compound solubility compared with those of SILs; charging CO₂ into SDES (SDES_CO2) caused a further increase in solubility. The solubility (25 °C) of syringic acid, ferulic acid, and milled wood lignin in SDES_CO2 reached 230.57, 452.17, and 279.12 mg/g, respectively. Such SDES-dissolved lignin can be regenerated using acetone as an anti-solvent. The SDES-regenerated lignin exhibited a well-preserved structure with no noticeable chemical modifications. Furthermore, the SDES_CO2 lignin possessed a higher molecular weight (Mw = 10,340 g/mol; Mn = 7672 g/mol), improved uniformity (polydispersity index = 1.35), and a higher guaiacyl lignin unit content compared with the original milled wood lignin. The SDES system proposed in the present work could benefit the fractionation of lignin compounds and facilitate downstream industrial processes. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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24 pages, 9951 KiB

Open AccessArticle

Chitosan/Alginate Polymeric Nanoparticle-Loaded α-Mangostin: Characterization, Cytotoxicity, and In Vivo Evaluation against Breast Cancer Cells

by Muchtaridi Muchtaridi, Ade Irma Suryani, Nasrul Wathoni, Yedi Herdiana, Ahmed Fouad Abdelwahab Mohammed, Amirah Mohd Gazzali, Ronny Lesmana and I. Made Joni

Polymers 2023, 15(18), 3658; https://doi.org/10.3390/polym15183658 - 05 Sep 2023

Viewed by 2378

Abstract

α-mangostin (Amg), a compound isolated from the mangosteen rind (Garcinia mangostana, L.), has demonstrated promising anticancer activity. However, its low solubility and selectivity against cancer cells limit its efficacy. To address this issue, researchers have developed chitosan/alginate polymeric nanoparticles (NANO-AMCAL) [...] Read more.

α-mangostin (Amg), a compound isolated from the mangosteen rind (Garcinia mangostana, L.), has demonstrated promising anticancer activity. However, its low solubility and selectivity against cancer cells limit its efficacy. To address this issue, researchers have developed chitosan/alginate polymeric nanoparticles (NANO-AMCAL) to enhance the effectiveness of Amg. In vitro studies have demonstrated that NANO-AMCAL is highly active against breast cancer cells. Therefore, an in vivo study was conducted to evaluate the efficacy of NANO-AMCAL in treating breast cancer in Wistar rats (Rattus norvegicus) and determine the effective dose. The rats were divided into seven treatment groups, including positive control, negative control, pure Amg, and NANO-AMCAL 5 mg, 10 mg, and 20 mg. The rats were injected subcutaneously with a carcinogenic agent, 7,12-dimethylbenz(a)anthracene (DMBA) and were evaluated for weight and tumor volume every three days during treatment. Surgery was performed on day 14, and histopathological studies were carried out on breast and lung cancer tissues. The results showed that NANO-AMCAL significantly enhanced the anticancer activity of Amg in treating breast cancer in Wistar rats. NANO-AMCAL containing 0.33 mg of Amg had a healing effect three times better than 20 mg pure Amg and was comparable to tamoxifen. The effective dose of NANO-AMCAL for anti-breast cancer treatment in Wistar rats was found to be 20 mg, which exhibited a good healing response, and the tumor volume continued to decrease up to 17.43% on the 14th day. Furthermore, histopathological tests showed tissue repair and no metastases. These findings suggest that NANO-AMCAL may be a promising therapeutic option for breast cancer treatment. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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13 pages, 1905 KiB

Open AccessArticle

Macromolecular Hydrodynamics and Fractal Structures of the Lignins of Fir Wood and Oat Husks

by Anatoly Karmanov, Lyudmila Kocheva, Mikhail Borisenkov and Vladimir Belyi

Polymers 2023, 15(17), 3624; https://doi.org/10.3390/polym15173624 - 01 Sep 2023

Cited by 1 | Viewed by 778

Abstract

The topological structure of the macromolecules of lignins isolated from oat husk and fir wood was studied by means of macromolecular hydrodynamic methods. The macromolecular properties were analyzed by evaluating the intrinsic viscosity and coefficients of the translational diffusion and the sedimentation velocity [...] Read more.

The topological structure of the macromolecules of lignins isolated from oat husk and fir wood was studied by means of macromolecular hydrodynamic methods. The macromolecular properties were analyzed by evaluating the intrinsic viscosity and coefficients of the translational diffusion and the sedimentation velocity of the lignins in dilute dimethylformamide solutions. The average molecular weights (M_Dη) and polydispersity parameters were calculated based on the results of the fractionation, as follows: M_w = 14.6 × 10³, M_n = 9.0, and M_w/M_n = 1.62 for lignins from fir wood and M_w = 14.9 M_n = 13.5 and M_w/M_n = 1.1 for lignins from oat husks. The fractal analysis of the lignin macromolecules allowed us to identify the distinctive characteristics of the fractal and topological structures of these lignins. The measurements indicated that the fractal dimension (d_f) values of the guaiacyl-syringyl lignins from oat husks were between 1.71 and 1.85, while the d_f of a typical guaiacyl lignin from fir wood was ~2.3. Thus, we determined that the lignin macromolecules of oat husks belong to the diffusion-limited aggregation-type cluster–cluster class of fractals of the Meakin–Kolb type, with a predominance of characteristics common to a linear configuration. The lignins of softwood fir trees exhibited a branched topological structure, and they belong to the diffusion-limited aggregation-type particle–cluster class of fractals of the Witten–Sander type. Lignins from oat husks have the linear topology of macromolecules while the macromolecules of the lignins from fir wood can be characterized as highly branched polymers. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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10 pages, 3349 KiB

Open AccessArticle

Potential of Nanocellulose as a Dietary Fiber Isolated from Brewer’s Spent Grain

by Abraham Azael Morales-Juárez, Luis Daniel Terrazas Armendáriz, Juan Manuel Alcocer-González and Leonardo Chávez-Guerrero

Polymers 2023, 15(17), 3613; https://doi.org/10.3390/polym15173613 - 31 Aug 2023

Cited by 1 | Viewed by 1084

Abstract

Steady growth in beer production is increasing the number of by-products named brewers’ spent grain. Such by-products are a source of several components, where cellulose is usually present in high amounts. The aim of this study was to develop a protocol to obtain [...] Read more.

Steady growth in beer production is increasing the number of by-products named brewers’ spent grain. Such by-products are a source of several components, where cellulose is usually present in high amounts. The aim of this study was to develop a protocol to obtain a mix of cellulose microfibers with an average diameter of 8–12 µm and cellulose nanoplatelets with an average thickness of 100 nm, which has several applications in the food industry. The process comprised one alkaline treatment followed by acid hydrolysis, giving a new mix of micro and nanocellulose. This mix was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and laser scanning microscopy corroborating the presence and measurements of the cellulose nanostructure, showing an aspect ratio of up to 500. Finally, we demonstrated that the administration of this new type of nanocellulose allowed us to control the weight of mice (feed intake), showing a significant percentage of weight reduction (4.96%) after 15 days compared with their initial weight, indicating the possibility of using this material as a dietary fiber. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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15 pages, 7856 KiB

Open AccessArticle

Physicochemical Characterization and Antimicrobial Analysis of Vegetal Chitosan Extracted from Distinct Forest Fungi Species

by Iversen Luk Jun Lam, Mariah Aqilah Mohd Affandy, Nasir Md Nur ‘Aqilah, Joseph Merillyn Vonnie, Wen Xia Ling Felicia and Kobun Rovina

Polymers 2023, 15(10), 2328; https://doi.org/10.3390/polym15102328 - 16 May 2023

Viewed by 1481

Abstract

The main goal of this investigation is to conduct a thorough analysis of the physical, chemical, and morphological characteristics of chitosan derived from various forest fungi. Additionally, the study aims to determine the effectiveness of this vegetal chitosan as an antimicrobial agent. In [...] Read more.

The main goal of this investigation is to conduct a thorough analysis of the physical, chemical, and morphological characteristics of chitosan derived from various forest fungi. Additionally, the study aims to determine the effectiveness of this vegetal chitosan as an antimicrobial agent. In this study, Auricularia auricula-judae, Hericium erinaceus, Pleurotus ostreatus, Tremella fuciformis, and Lentinula edodes were examined. The fungi samples were subjected to a series of rigorous chemical extraction procedures, including demineralization, deproteinization, discoloration, and deacetylation. Subsequently, the chitosan samples were subjected to a comprehensive physicochemical characterization analysis, encompassing Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), degree of deacetylation determination, ash content determination, moisture content determination, and solubility determination. To evaluate the antimicrobial efficacy of the vegetal chitosan samples, two different sampling parameters were employed, namely human hand and banana, to assess their effectiveness in inhibiting microbial growth. Notably, the percentage of chitin and chitosan varied significantly among the distinct fungal species examined. Moreover, EDX spectroscopy confirmed the extraction of chitosan from H. erinaceus, L. edodes, P. ostreatus, and T. fuciformis. The FTIR spectra of all samples revealed a similar absorbance pattern, albeit with varying peak intensities. Furthermore, the XRD patterns for each sample were nearly identical, with the exception of the A. auricula-judae sample, which exhibited sharp peaks at ~37° and ~51°, while the crystallinity index of this same sample was approximately 17% lower than the others. The moisture content results indicated that the L. edodes sample was the least stable, while the P. ostreatus sample was the most stable, in terms of degradation rate. Similarly, the solubility of the samples showed substantial variation among each species, with the H. erinaceus sample displaying the highest solubility among the rest. Lastly, the antimicrobial activity of the chitosan solutions exhibited different efficacies in inhibiting microbial growth of skin microflora and microbes found on the peel of Musa acuminata × balbisiana. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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Review

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16 pages, 2218 KiB

Open AccessReview

Recent Progress in Cellulose Hydrophobization by Gaseous Plasma Treatments

by Gregor Primc, Alenka Vesel, Rok Zaplotnik, Marija Gorjanc, Peter Gselman, Marián Lehocký and Miran Mozetič

Polymers 2024, 16(6), 789; https://doi.org/10.3390/polym16060789 - 12 Mar 2024

Viewed by 643

Abstract

Cellulose is an abundant natural polymer and is thus promising for enforcing biobased plastics. A broader application of cellulose fibers as a filler in polymer composites is limited because of their hydrophilicity and hygroscopicity. The recent scientific literature on plasma methods for the [...] Read more.

Cellulose is an abundant natural polymer and is thus promising for enforcing biobased plastics. A broader application of cellulose fibers as a filler in polymer composites is limited because of their hydrophilicity and hygroscopicity. The recent scientific literature on plasma methods for the hydrophobization of cellulose materials is reviewed and critically evaluated. All authors focused on the application of plasmas sustained in fluorine or silicon-containing gases, particularly tetrafluoromethane, and hexamethyldisiloxane. The cellulose materials should be pre-treated with another plasma (typically oxygen) for better adhesion of the silicon-containing hydrophobic coating. In contrast, deposition of fluorine-containing coatings does not require pre-treatment, which is explained by mild etching of the cellulose upon treatment with F atoms and ions. The discrepancy between the results reported by different authors is explained by details in the gas phase and surface kinetics, including the heating of samples due to exothermic surface reactions, desorption of water vapor, competition between etching and deposition, the influence of plasma radiation, and formation of dusty plasma. Scientific and technological challenges are highlighted, and the directions for further research are provided. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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28 pages, 1435 KiB

Open AccessReview

Chitosan-Based Nano Systems for Natural Antioxidants in Breast Cancer Therapy

by Yedi Herdiana, Patihul Husni, Siti Nurhasanah, Shaharum Shamsuddin and Nasrul Wathoni

Polymers 2023, 15(13), 2953; https://doi.org/10.3390/polym15132953 - 05 Jul 2023

Cited by 9 | Viewed by 1982

Abstract

Breast cancer is a major cause of death globally, accounting for around 13% of all deaths. Chemotherapy, the common treatment for cancer, can have side effects that lead to the production of reactive oxygen species (ROS) and an increase in oxidative stress in [...] Read more.

Breast cancer is a major cause of death globally, accounting for around 13% of all deaths. Chemotherapy, the common treatment for cancer, can have side effects that lead to the production of reactive oxygen species (ROS) and an increase in oxidative stress in the body. Antioxidants are important for maintaining the health of cells and helping the immune system function properly. They play a crucial role in balancing the body’s internal environment. Using natural antioxidants is an alternative to mitigate the harmful effects of oxidative stress. However, around 80% of natural antioxidants have limited effectiveness when taken orally because they do not dissolve well in water or other solvents. This poor solubility affects their ability to be absorbed by the body and limits their bioavailability. One strategy that has been considered is to increase their water solubility to increase their oral bioavailability. Chitosan-based nanoparticle (CSNP) systems have been extensively explored due to their reliability and simpler synthesis routes. This review focuses on the various methods of chitosan-based nanoformulation for developing effective oral dosage forms for natural antioxidants based on the pharmacokinetics and pharmacodynamics properties. Chitosan (CS) could be a model, because of its wide use in polymeric NPs research, thus providing a better understanding of the role of vehicles that carry natural antioxidants in maintaining the stability and enhancing the performance of cancer drugs. Full article

(This article belongs to the Special Issue Natural Polymer Materials: Cellulose, Lignin and Chitosan)

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