Sustainability

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14 pages, 2416 KiB

Open AccessArticle

Characterization of Cross-Linking in Guar Gum Hydrogels via the Analysis of Thermal Decomposition Behavior and Water Uptake Kinetics

by Yanjiao Lan, Zhoujian Xie, Ting Wang, Jianfang Lu, Pengfei Li and Jianxin Jiang

Sustainability 2023, 15(12), 9778; https://doi.org/10.3390/su15129778 - 19 Jun 2023

Cited by 2 | Viewed by 1448

Abstract

This study aimed to explore a test method for evaluating the effective cross-linking density of hydrogels. A guar gum–epichlorohydrin hydrogel (GEH) was prepared using guar gum (GG) as the raw material and epichlorohydrin (ECH) as the cross-linking agent. The thermal and mechanical properties, [...] Read more.

This study aimed to explore a test method for evaluating the effective cross-linking density of hydrogels. A guar gum–epichlorohydrin hydrogel (GEH) was prepared using guar gum (GG) as the raw material and epichlorohydrin (ECH) as the cross-linking agent. The thermal and mechanical properties, equilibrium swelling rate (ESR), water uptake (WU), and mass cross-linking degree of the hydrogels were assessed. Furthermore, the diffusion behavior of water molecules in the freeze-dried GEH was investigated. The experimental results showed the significance of the initial decomposition temperature (T_i) and final decomposition temperature (T_f) of the freeze-dried GEHs in determining the effective cross-linking density. The water uptake kinetics of the freeze-dried GEH was consistent with the linear fitting of the pseudo-second-order kinetic model and nonlinear fitting of the Fickian diffusion model, suggesting that chemisorption dominated the water absorption process in the GEH. Therefore, the effective cross-linking density of the hydrogels could be determined from the thermodynamic analysis and the diffusive behavior of water molecules in the gels. The thermal stability and water diffusion kinetics of the hydrogels were closely linked to the effective cross-linking density and pendant modification. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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10 pages, 2070 KiB

Open AccessArticle

Morphological Differences between Virgin and Secondary Fibers

by Edyta Małachowska, Marcin Dubowik and Piotr Przybysz

Sustainability 2023, 15(10), 8334; https://doi.org/10.3390/su15108334 - 20 May 2023

Viewed by 1265

Abstract

The properties of the fibers determine the quality of the pulp and, thus, the quality of the paper made from it. Recognition of properties, which fiber and paper pulp should be characterized by, in order to achieve required paper properties, is, therefore, a [...] Read more.

The properties of the fibers determine the quality of the pulp and, thus, the quality of the paper made from it. Recognition of properties, which fiber and paper pulp should be characterized by, in order to achieve required paper properties, is, therefore, a subject of research and interest of many papermaking research experts and scientists. Fibers are subject to deformation and possible weakening under the influence of chemical and mechanical factors, and therefore the quality of the fibers decreases each time they are used in production when it comes to recycled pulps. Then again, the key factor determining the quality of the primary fiber is the degree of pulp delignification. In the article, an attempt was made to define the impact of delignification of virgin pulp on morphological properties of fibers, and compare them with the properties of recycled paper pulp, in order to find correlations. The current economic and raw material situations in the wood market force one to seek new solutions to limit the use of virgin fibers, which is extremely important for the economy of the paper mill, environmental protection and raw material management. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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16 pages, 4086 KiB

Open AccessArticle

Study on the Solubility of Industrial Lignin in Choline Chloride-Based Deep Eutectic Solvents

by Haiyu Chen, Ailin Wang, Cancan Yan, Shiwei Liu, Lu Li, Qiong Wu, Yue Liu, Yuxiang Liu, Genkuo Nie, Shuangxi Nie, Shuangquan Yao and Hailong Yu

Sustainability 2023, 15(9), 7118; https://doi.org/10.3390/su15097118 - 24 Apr 2023

Cited by 7 | Viewed by 1613

Abstract

Deep eutectic solvents (DESs) have emerged as a promising class of solvents for lignin dissolution, which could significantly expand the application potential of lignin. In this study, over forty ChCl-based DESs of three major types were synthesized and subjected to investigate the solubilisation [...] Read more.

Deep eutectic solvents (DESs) have emerged as a promising class of solvents for lignin dissolution, which could significantly expand the application potential of lignin. In this study, over forty ChCl-based DESs of three major types were synthesized and subjected to investigate the solubilisation of two industrial lignins in DES. The results showed that higher HBD content, shorter carbon chain length in the HBD, and fewer functional groups favored lignin solubilization. DESs containing carboxyl groups were found to be more favorable for breaking β-O-4 bonds and solubilizing lignin. Additionally, high temperature and appropriate water content were observed to promote lignin solubilization. The pretreatment of poplar and maize straw with ChC/FA(1:3), ChC/LA(1:3), ChC/Gly(1:3), ChC/EG(1:3), ChC/Urea(1:3), and ChC/TEOA(1:3) showed good solubilization of lignin, with ChCl/FA(1:3) being particularly effective in solubilizing poplar lignin and maize straw lignin, achieving lignin solubilization of 82% and 57%, respectively. Overall, these findings suggest that DESs have great potential as solvents for lignin dissolution. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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12 pages, 2347 KiB

Open AccessArticle

Understanding the Inhibition Mechanism of Lignin Adsorption to Cellulase in Terms of Changes in Composition and Conformation of Free Enzymes

by Can Cui, Cancan Yan, Ailin Wang, Cui Chen, Dan Chen, Shiwei Liu, Lu Li, Qiong Wu, Yue Liu, Yuxiang Liu, Genkuo Nie, Xiaoqing Jiang, Shuangxi Nie, Shuangquan Yao and Hailong Yu

Sustainability 2023, 15(7), 6057; https://doi.org/10.3390/su15076057 - 31 Mar 2023

Cited by 3 | Viewed by 1200

Abstract

The adsorption of lignin to cellulase is the major obstacle in the sugar-platform conversion of lignocellulosic bioresources. In this study, the adsorption behavior of untreated and pretreated lignin samples from corn stover to cellulase was investigated, in particular the effects of lignin adsorption [...] Read more.

The adsorption of lignin to cellulase is the major obstacle in the sugar-platform conversion of lignocellulosic bioresources. In this study, the adsorption behavior of untreated and pretreated lignin samples from corn stover to cellulase was investigated, in particular the effects of lignin adsorption on the composition and spatial conformation of free enzymes were explored. The results showed that pretreatments decreased the hydrophobic groups contents of lignin, i.e., aromatic ring, ether and carbonyl, as well as the content of ionizable group, i.e., carboxyl, which reduced its hydrophobicity and negative charge density, thus weakening the adsorption ability of lignin to cellulase. The lignin samples mainly adsorbed the CBHII component of cellulase to inhibit the synergistic effect of free enzymes. Lignin adsorption altered the spatial position of tryptophan residues in free enzymes, exposing them to the protein surface. In addition, the secondary structure of free enzymes was altered, with a decrease in the alpha-helix content and an increase in the random coil content, thus loosening the spatial conformation of free enzymes. The change degree in the spatial structure of free enzymes correlated with the adsorption capacity of the lignin, i.e., lignin with low adsorption capacity caused the least damage to free enzyme, with NaOH pretreated lignin being the best. It appears that appropriate pretreatment and chemical modification of enzymes to resist lignin adsorption is a promising long-term pathway to overcome the lignin inhibition during sugar-platform conversion of lignocellulosic bioresources. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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15 pages, 4236 KiB

Open AccessArticle

Unraveling the Effect of Kraft and Organosolv Processes on the Physicochemical Properties and Thermal Stability of Cellulose and Its Microcrystals Produced from Eucalyptus Globulus

by Wissam Bessa, Djalal Trache, Ahmed Fouzi Tarchoun, Amir Abdelaziz, Mohd Hazwan Hussin and Nicolas Brosse

Sustainability 2023, 15(4), 3384; https://doi.org/10.3390/su15043384 - 13 Feb 2023

Cited by 5 | Viewed by 1418

Abstract

Eucalyptus Globulus (EG) is a virtually untapped forest source that belongs to the hardwood family. The objective of this research is to understand the effect of two different isolation techniques, i.e., kraft and organosolv procedures, followed by either acidified sodium chlorite or alkaline [...] Read more.

Eucalyptus Globulus (EG) is a virtually untapped forest source that belongs to the hardwood family. The objective of this research is to understand the effect of two different isolation techniques, i.e., kraft and organosolv procedures, followed by either acidified sodium chlorite or alkaline hydrogen peroxide treatment on the properties of cellulose and microcrystalline cellulose (MCC) derived from EG. The MCC samples were successfully prepared from cellulose via acid hydrolysis. A comparative study was carried out on the extracted cellulose fibers and MCC samples through deep characterizations of lignocellulosic content, functional groups, crystallinity, thermal properties, and surface morphology. The detailed analyses exhibited that the prepared MCC samples using various approaches are similar to those of commercial MCC. It is revealed that the organosolv treatment followed by acidic bleaching provides the purest MCC with good thermal features, where the obtained cellulose has a glucose content of more than 97% and a degradation temperature of around 343 °C. The present work provides new insight into the effect of various extraction procedures on EG-MCC; these procedures are expected to be used in different industrial applications such as in biorefinery, dietary food, packaging, films, or reinforcement of polymer matrices. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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13 pages, 1684 KiB

Open AccessArticle

Which Wastepaper Should Not Be Processed?

by Edyta Małachowska, Aneta Lipkiewicz, Marcin Dubowik and Piotr Przybysz

Sustainability 2023, 15(4), 2850; https://doi.org/10.3390/su15042850 - 4 Feb 2023

Cited by 4 | Viewed by 1565

Abstract

In the 21st century, numerous economic and environmental initiatives have significantly increased paper recycling, which continues to expand due to environmental awareness. With increasing recycling rate, low-quality paper fractions may be included in the process, leading to the overproduction of very low-value papers [...] Read more.

In the 21st century, numerous economic and environmental initiatives have significantly increased paper recycling, which continues to expand due to environmental awareness. With increasing recycling rate, low-quality paper fractions may be included in the process, leading to the overproduction of very low-value papers that cannot be reprocessed. Moreover, the production of paper from poor-quality wastepaper can result in the introduction of chemicals from the recycled paper into the recycling loop and unintended spread of chemical substances. Therefore, reliable and conscious selection of recycled pulp is imperative. To this end, the present study verified the properties of recycled pulp critical for the assessment of its papermaking ability for the production of high-quality sanitary paper. Following an examination of samples, it was found that the key parameters that influence the papermaking ability of wastepaper include presence of impurities, content of extractive substances, freeness, and length of fiber. On this basis, types of wastepaper that, at the very beginning, did not portend well for obtaining paper products with high potential for utility were eliminated. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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15 pages, 1982 KiB

Open AccessArticle

New Biotechnological Production of EPA by Pythium irregulare Using Alternative Sustainable Media Obtained from Food Industry By-Products and Waste

by Giovanni Luca Russo, Antonio Luca Langellotti, Beatriz Martín-García, Vito Verardo, Raffaele Romano, Raffaele Sacchi and Paolo Masi

Sustainability 2023, 15(2), 1147; https://doi.org/10.3390/su15021147 - 7 Jan 2023

Cited by 7 | Viewed by 1461

Abstract

Long-chain polyunsaturated fatty acids (LC-PUFAs) have multiple beneficial effects on human health, in particular docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3). A variety of microorganisms has been used for the commercial production of non-animal-source LC-PUFAs. The oomycetes of the [...] Read more.

Long-chain polyunsaturated fatty acids (LC-PUFAs) have multiple beneficial effects on human health, in particular docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3). A variety of microorganisms has been used for the commercial production of non-animal-source LC-PUFAs. The oomycetes of the Pythium family are promising EPA producers, and in this work, the optimization of Pythium irregulare growth using food industry by-products and wastes as cheap sources of nutrients was carried out. Sugar cane molasses (SCM), spent brewery yeast (SBY), cheese whey (CW), and expired orange juice (EFJ) were tested. A combination of SBY as a source of nitrogen and EFJ as a source of organic carbon resulted in the best outcome among the other sustainable media ingredients. The optimization of the new medium was conducted through a response surface methodology using EFJ and SBY as factors. The results show a significant positive impact of these factors on biomass productivity (p < 0.005), with an optimized biomass yield of 14.22 g L⁻¹, a lipid yield of 2.23 g L⁻¹, and an EPA concentration of 155 mg L⁻¹. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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16 pages, 13701 KiB

Open AccessArticle

An Alternative Carbon Source from Cassava Residue Saccharification Liquid for In-Situ Fabrication of Polysaccharide Macromolecule/Bacterial Cellulose Composite Hydrogel: A Comparative Study

by Li Ji, Wenwen Xue, Liwei Zhu and Jianxin Jiang

Sustainability 2022, 14(21), 14277; https://doi.org/10.3390/su142114277 - 1 Nov 2022

Cited by 1 | Viewed by 1160

Abstract

Bacterial cellulose (BC) is a biopolymer with vast application prospects, and its production demands culture media rich in carbon sources. Here, we researched a modified in situ strategy for preparing composite hydrogels comprising BC and sodium alginate (SA) or sodium hyaluronate (SH), termed [...] Read more.

Bacterial cellulose (BC) is a biopolymer with vast application prospects, and its production demands culture media rich in carbon sources. Here, we researched a modified in situ strategy for preparing composite hydrogels comprising BC and sodium alginate (SA) or sodium hyaluronate (SH), termed as SA-BC and SH-BC, respectively. A new carbon source for BC generation was successfully developed from cassava residue saccharification liquid (CSL), in an attempt to better exploit the residue and decrease the costs of BC production. SA or SH was mechanically hydrogen-bonded with BC nanofibers to form porous nanostructures. Compared to the native BC, the mechanical strength of SH-BC with 1% SH was 61% higher and the thermal stability was also improved. A considerable difference in the cumulative drug-release rate of 93% in 66 h revealed that SA-BC with 0.5% SA exhibited a higher pH sensitivity due to its abundant fibrous layers, the -COO^--electrostatic repulsion, and the weakened hydrogen-bonding at pH 7.4. Such in situ-derived composite hydrogels could provide insights for BC functionalization and advance understanding of polysaccharides’ conversion to biomaterials with favorable biocompatibility and sustainability. Full article

(This article belongs to the Special Issue Recent Advances in Sustainable Bio-Based Materials: Preparation, Modification and Utilization)

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