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Lignocellulosic Biomass

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Macromolecular Chemistry".

Deadline for manuscript submissions: closed (31 July 2020) | Viewed by 72883

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Alejandro Rodríguez Pascual

E-Mail Website
Guest Editor
Chemical Engineering Department, Faculty of Science, Universidad de Córdoba, Building Marie-Curie, Campus of Rabanales, 14014 Córdoba, Spain
Interests: biorefinery; cellulose; lignin; lignocellulosic residues; nanocellulose; biobased; biomaterials; paper; papermaking; packaging; biocomposites; environmental remediation
Special Issues, Collections and Topics in MDPI journals
Dr. Eduardo Espinosa Víctor

E-Mail Website
Co-Guest Editor
Chemical Engineering Department, Faculty of Science, Universidad de Córdoba, Building Marie-Curie, Campus of Rabanales, 14014 Córdoba, Spain
Interests: biorefinery; lignocellulosic materials; biomass; cellulose; hemicellulose; lignin; hydrogels; batteries; applications; valorize; residue; agri-food industry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Sustainable development, circular economy, reuse, recycle, valorize, produce rationally, etc., are all concepts that must be part of our daily lives. Their continuing development in most sectors of society can ensure an improved quality of life, both now and for future generations.

In maintaining this process, the scientific community plays a very important role in generating the basic knowledge that gives rise to technology and allows developments in the laboratory to be transferred to society. The integral valorization of lignocellulosic biomass is a fundamental pillar of sustainable development. Given the origin of this biomass, as well as its composition, lignocellulosic biomass is a vast resource. In fact, cellulose, hemicellulose, and lignin, and the extracts they contain, can be applied in multiple sectors: paper, textiles, pharmaceuticals, food, and energy, to name but a few.

In creating this Special Issue, focused on the valorization of lignocellulosic biomass, we aim to establish an invaluable source of information that will serve as a reference for other researchers.

Prof. Dr. Alejandro Rodríguez
Dr. Eduardo Espinosa
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biomass
  • biorefinery
  • pretreatment
  • cellulose
  • hemicellulose
  • lignin
  • nanocellulose
  • biopolymers
  • natural compounds
  • chemicals
  • paper industry
  • energy
  • biobased materials
  • biocomposites
  • drug delivery
  • food industry
  • lignocellulose
  • 3D packaging

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Published Papers (32 papers)

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Editorial

Jump to: Research, Review

4 pages, 218 KiB  
Editorial
Special Issue “Lignocellulosic Biomass II”
by Alejandro Rodríguez, Eduardo Espinosa and Carlos Martín
Molecules 2023, 28(17), 6230; https://doi.org/10.3390/molecules28176230 - 24 Aug 2023
Viewed by 753
Abstract
As a result of human population growth, the availability of residual lignocellulosic materials from agriculture, forestry, food- and wood-processing industries, and other waste streams is continuously increasing [...] Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
3 pages, 207 KiB  
Editorial
Special Issue “Lignocellulosic Biomass”
by Alejandro Rodríguez and Eduardo Espinosa
Molecules 2021, 26(5), 1483; https://doi.org/10.3390/molecules26051483 - 09 Mar 2021
Cited by 4 | Viewed by 1797
Abstract
The use of lignocellulosic biomass as potential raw material for fractionation and transformation into high value-added products or energy is gathering the attention of scientists worldwide in seeking to achieve a green transition in our production systems [...] Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)

Research

Jump to: Editorial, Review

22 pages, 2592 KiB  
Article
Evaluation of the Extraction of Bioactive Compounds and the Saccharification of Cellulose as a Route for the Valorization of Spent Mushroom Substrate
by Sarah J. Klausen, Anne Bergljot Falck-Ytter, Knut Olav Strætkvern and Carlos Martin
Molecules 2023, 28(13), 5140; https://doi.org/10.3390/molecules28135140 - 30 Jun 2023
Cited by 3 | Viewed by 3257
Abstract
The extraction of bioactive compounds and cellulose saccharification are potential directions for the valorization of spent mushroom substrate (SMS). Therefore, investigating the suitability of different extraction methods for recovering bioactive compounds from SMS and how the extraction affects the enzymatic saccharification is of [...] Read more.
The extraction of bioactive compounds and cellulose saccharification are potential directions for the valorization of spent mushroom substrate (SMS). Therefore, investigating the suitability of different extraction methods for recovering bioactive compounds from SMS and how the extraction affects the enzymatic saccharification is of uppermost relevance. In this work, bioactive compounds were extracted from Pleurotus spp. SMS using four extraction methods. For Soxhlet extraction (SoE), a 40:60 ethanol/water mixture gave the highest extraction efficiency (EE) (69.9–71.1%) among the seven solvent systems assayed. Reflux extraction with 40:60 ethanol/water increased the extraction yield and EE compared to SoE. A shorter reflux time yielded a higher extraction of carbohydrates than SoE, while a longer time was more effective for extracting phenolics. The extracts from 240 min of reflux had comparable antioxidant activity (0.3–0.5 mM GAE) with that achieved for SoE. Ultrasound-assisted extraction (UAE) at 65 °C for 60 min allowed an EE (~82%) higher than that achieved by either reflux for up to 150 min or SoE. Subcritical water extraction (SWE) at 150 °C resulted in the best extraction parameters among all the tested methods. Vanillic acid and chlorogenic acid were the primary phenolic acids identified in the extracts. A good correlation between the concentration of caffeic acid and the antioxidant activity of the extracts was found. Saccharification tests revealed an enhancement of the enzymatic digestibility of SMS cellulose after the extraction of bioactive compounds. The findings of this initial study provide indications on new research directions for maximizing the recovery of bioactive compounds and fermentable sugars from SMS. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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13 pages, 1411 KiB  
Article
Utilization Perspectives of Lignin Biochar from Industrial Biomass Residue
by Iliyana Naydenova, Temenuzhka Radoykova, Tsvetelina Petrova, Ognyan Sandov and Ivo Valchev
Molecules 2023, 28(12), 4842; https://doi.org/10.3390/molecules28124842 - 18 Jun 2023
Cited by 2 | Viewed by 1418
Abstract
The present study aimed at utilizing technically hydrolyzed lignin (THL), industrial biomass residue, derived in high-temperature diluted sulfuric acid hydrolysis of softwood and hardwood chips to sugars. The THL was carbonized in a horizontal tube furnace at atmospheric pressure, in inert atmosphere and [...] Read more.
The present study aimed at utilizing technically hydrolyzed lignin (THL), industrial biomass residue, derived in high-temperature diluted sulfuric acid hydrolysis of softwood and hardwood chips to sugars. The THL was carbonized in a horizontal tube furnace at atmospheric pressure, in inert atmosphere and at three different temperatures (500, 600, and 700 °C). Biochar chemical composition was investigated along with its HHV, thermal stability (thermogravimetric analysis), and textural properties. Surface area and pore volume were measured with nitrogen physisorption analysis often named upon Brunauer–Emmett–Teller (BET). Increasing the carbonization temperature reduced volatile organic compounds (40 ÷ 96 wt. %), increased fixed carbon (2.11 to 3.68 times the wt. % of fixed carbon in THL), ash, and C-content. Moreover, H and O were reduced, while N- and S-content were below the detection limit. This suggested biochar application as solid biofuel. The biochar Fourier-transform infrared (FTIR) spectra revealed that the functional groups were gradually lost, thus forming materials having merely polycyclic aromatic structures and high condensation rate. The biochar obtained at 600 and 700 °C proved having properties typical for microporous adsorbents, suitable for selective adsorption purposes. Based on the latest observations, another biochar application was proposed—as a catalyst. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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21 pages, 4160 KiB  
Article
Apricot Seed Shells and Walnut Shells as Unconventional Sugars and Lignin Sources
by Vita Halysh, Juan Miguel Romero-García, Alfonso M. Vidal, Tetiana Kulik, Borys Palianytsia, Minerva García and Eulogio Castro
Molecules 2023, 28(3), 1455; https://doi.org/10.3390/molecules28031455 - 02 Feb 2023
Cited by 3 | Viewed by 1856
Abstract
The present study focuses on using apricot seeds shells and walnut shells as a potential renewable material for biorefinery in Ukraine. The goal of the research work was to determine the relationship between the chemical composition of solid residues from biomass after acid [...] Read more.
The present study focuses on using apricot seeds shells and walnut shells as a potential renewable material for biorefinery in Ukraine. The goal of the research work was to determine the relationship between the chemical composition of solid residues from biomass after acid pretreatment with H2SO4, alkaline pretreatment with NaOH, and a steam explosion pretreatment and the recovery of sugars and lignin after further enzymatic hydrolysis with the application of an industrial cellulase Cellic CTec2. Apricot seeds shells and walnut shells consist of lots of cellulose (35.01 and 24.19%, respectively), lignin (44.55% and 44.63%, respectively), hemicelluloses (10.77% and 26.68%, respectively), and extractives (9.97% and 11.41%, respectively), which affect the efficiency of the bioconversion of polysaccharides to sugars. The alkaline pretreatment was found to be more efficient in terms of glucose yield in comparison with that of acid and steam explosion, and the maximum enzymatic conversions of cellulose reached were 99.7% and 94.6% for the solids from the apricot seeds shells and the walnut shells, respectively. The maximum amount of lignin (82%) in the residual solid was obtained during the processing of apricot seed shells submitted to the acid pretreatment. The amount of lignin in the solids interferes with the efficiency of enzymatic hydrolysis. The results pave the way for the efficient and perspective utilization of shells through the use of inexpensive, simple and affordable chemical technologies, obtaining value-added products, and thus, reducing the amount of environmental pollution (compared to the usual disposal practice of direct burning) and energy and material external dependency (by taking advantage of these renewable, low-cost materials). Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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25 pages, 1674 KiB  
Article
Analysis of Single-Step Pretreatments for Lignocellulosic Platform Isolation as the Basis of Biorefinery Design
by Jhonny Alejandro Poveda-Giraldo, Maria Camila Garcia-Vallejo and Carlos Ariel Cardona Alzate
Molecules 2023, 28(3), 1278; https://doi.org/10.3390/molecules28031278 - 28 Jan 2023
Cited by 5 | Viewed by 1378
Abstract
Biorefinery feasibility is highly influenced by the early design of the best feedstock transformation pathway to obtain value-added products. Pretreatment has been identified as the critical stage in biorefinery design since proper pretreatment influences subsequent reaction, separation, and purification processes. However, many pretreatment [...] Read more.
Biorefinery feasibility is highly influenced by the early design of the best feedstock transformation pathway to obtain value-added products. Pretreatment has been identified as the critical stage in biorefinery design since proper pretreatment influences subsequent reaction, separation, and purification processes. However, many pretreatment analyses have focused on preserving and valorizing six-carbon sugars for future use in bioconversion processes, leaving aside fractions such as hemicellulose and lignin. To date, there has been no pretreatment systematization for the removal of lignocellulosic fractions. This work defines pretreatment efficacy through operational, economic, environmental, and social indicators. Thus, using the data reported in the literature, as well as the results of the simulation schemes, a multi-criteria weighting of the best-performing schemes for the isolation or removal of cellulose, hemicellulose, and lignin was carried out. As a main result, it was concluded that dilute acid is the most effective for cellulose isolation and hemicellulose removal for producing platform products based on six- and five-carbon sugars, respectively. Additionally, the kraft process is the best methodology for lignin removal and its future use in biorefineries. The results of this work help to elucidate a methodological systematization of the pretreatment efficacy in the design of biorefineries as an early feasibility stage considering sustainability aspects. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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15 pages, 4942 KiB  
Article
Alkaline Modification of Arabica-Coffee and Theobroma-Cocoa Agroindustrial Waste for Effective Removal of Pb(II) from Aqueous Solutions
by Carmencita Lavado-Meza, Leonel De la Cruz-Cerrón, Yvan J.O. Asencios, Francielle Candian Firmino Marcos and Juan Z. Dávalos-Prado
Molecules 2023, 28(2), 683; https://doi.org/10.3390/molecules28020683 - 10 Jan 2023
Cited by 4 | Viewed by 1774
Abstract
Arabica-coffee and Theobroma-cocoa agroindustrial wastes were treated with NaOH and characterized to efficiently remove Pb(II) from the aqueous media. The maximum Pb(II) adsorption capacities, qmax, of Arabica-coffee (WCAM) and Theobroma-cocoa (WCTM) biosorbents (qmax = 303.0 and [...] Read more.
Arabica-coffee and Theobroma-cocoa agroindustrial wastes were treated with NaOH and characterized to efficiently remove Pb(II) from the aqueous media. The maximum Pb(II) adsorption capacities, qmax, of Arabica-coffee (WCAM) and Theobroma-cocoa (WCTM) biosorbents (qmax = 303.0 and 223.1 mg·g−1, respectively) were almost twice that of the corresponding untreated wastes and were higher than those of other similar agro-industrial biosorbents reported in the literature. Structural, chemical, and morphological characterization were performed by FT-IR, SEM/EDX, and point of zero charge (pHPZC) measurements. Both the WCAM and WCTM biosorbents showed typical uneven and rough cracked surfaces including the OH, C=O, COH, and C-O-C functional adsorbing groups. The optimal Pb(II) adsorption, reaching a high removal efficiency %R (>90%), occurred at a pH between 4 and 5 with a biosorbent dose of 2 g·L−1. The experimental data for Pb(II) adsorption on WACM and WCTM were well fitted with the Langmuir-isotherm and pseudo-second order kinetic models. These indicated that Pb(II) adsorption is a chemisorption process with the presence of a monolayer mechanism. In addition, the deduced thermodynamic parameters showed the endothermic (ΔH0 > 0), feasible, and spontaneous (ΔG0 < 0) nature of the adsorption processes studied. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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14 pages, 1411 KiB  
Article
Co-Fermentation of Glucose–Xylose Mixtures from Agroindustrial Residues by Ethanologenic Escherichia coli: A Study on the Lack of Carbon Catabolite Repression in Strain MS04
by Estefanía Sierra-Ibarra, Alejandra Vargas-Tah, Cessna L. Moss-Acosta, Berenice Trujillo-Martínez, Eliseo R. Molina-Vázquez, Alberto Rosas-Aburto, Ángeles Valdivia-López, Martín G. Hernández-Luna, Eduardo Vivaldo-Lima and Alfredo Martínez
Molecules 2022, 27(24), 8941; https://doi.org/10.3390/molecules27248941 - 15 Dec 2022
Cited by 4 | Viewed by 1606
Abstract
The production of biofuels, such as bioethanol from lignocellulosic biomass, is an important task within the sustainable energy concept. Understanding the metabolism of ethanologenic microorganisms for the consumption of sugar mixtures contained in lignocellulosic hydrolysates could allow the improvement of the fermentation process. [...] Read more.
The production of biofuels, such as bioethanol from lignocellulosic biomass, is an important task within the sustainable energy concept. Understanding the metabolism of ethanologenic microorganisms for the consumption of sugar mixtures contained in lignocellulosic hydrolysates could allow the improvement of the fermentation process. In this study, the ethanologenic strain Escherichia coli MS04 was used to ferment hydrolysates from five different lignocellulosic agroindustrial wastes, which contained different glucose and xylose concentrations. The volumetric rates of glucose and xylose consumption and ethanol production depend on the initial concentration of glucose and xylose, concentrations of inhibitors, and the positive effect of acetate in the fermentation to ethanol. Ethanol yields above 80% and productivities up to 1.85 gEtOH/Lh were obtained. Furthermore, in all evaluations, a simultaneous co-consumption of glucose and xylose was observed. The effect of deleting the xyIR regulator was studied, concluding that it plays an important role in the metabolism of monosaccharides and in xylose consumption. Moreover, the importance of acetate was confirmed for the ethanologenic strain, showing the positive effect of acetate on the co-consumption rates of glucose and xylose in cultivation media and hydrolysates containing sugar mixtures. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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23 pages, 2794 KiB  
Article
Fractionation of Raw and Parboiled Rice Husks with Deep Eutectic Solvents and Characterization of the Extracted Lignins towards a Circular Economy Perspective
by Chiara Allegretti, Emanuela Bellinetto, Paola D’Arrigo, Monica Ferro, Gianmarco Griffini, Letizia Anna Maria Rossato, Eleonora Ruffini, Luca Schiavi, Stefano Serra, Alberto Strini and Stefano Turri
Molecules 2022, 27(24), 8879; https://doi.org/10.3390/molecules27248879 - 14 Dec 2022
Cited by 5 | Viewed by 2115
Abstract
In the present work, rice husks (RHs), which, worldwide, represent one of the most abundant agricultural wastes in terms of their quantity, have been treated and fractionated in order to allow for their complete valorization. RHs coming from the raw and parboiled rice [...] Read more.
In the present work, rice husks (RHs), which, worldwide, represent one of the most abundant agricultural wastes in terms of their quantity, have been treated and fractionated in order to allow for their complete valorization. RHs coming from the raw and parboiled rice production have been submitted at first to a hydrothermal pretreatment followed by a deep eutectic solvent fractionation, allowing for the separation of the different components by means of an environmentally friendly process. The lignins obtained from raw and parboiled RHs have been thoroughly characterized and showed similar physico-chemical characteristics, indicating that the parboiling process does not introduce obvious lignin alterations. In addition, a preliminary evaluation of the potentiality of such lignin fractions as precursors of cement water reducers has provided encouraging results. A fermentation-based optional preprocess has also been investigated. However, both raw and parboiled RHs demonstrated a poor performance as a microbiological growth substrate, even in submerged fermentation using cellulose-degrading fungi. The described methodology appears to be a promising strategy for the valorization of these important waste biomasses coming from the rice industry towards a circular economy perspective. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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16 pages, 3088 KiB  
Article
Characterisation of a Novel Acetyl Xylan Esterase (BaAXE) Screened from the Gut Microbiota of the Common Black Slug (Arion ater)
by Henry Madubuike and Natalie Ferry
Molecules 2022, 27(9), 2999; https://doi.org/10.3390/molecules27092999 - 07 May 2022
Cited by 6 | Viewed by 2264
Abstract
Acetyl xylan esterases (AXEs) are enzymes capable of hydrolysing the acetyl bonds in acetylated xylan, allowing for enhanced activity of backbone-depolymerizing enzymes. Bioprospecting novel AXE is essential in designing enzyme cocktails with desired characteristics targeting the complete breakdown of lignocellulose. In this article, [...] Read more.
Acetyl xylan esterases (AXEs) are enzymes capable of hydrolysing the acetyl bonds in acetylated xylan, allowing for enhanced activity of backbone-depolymerizing enzymes. Bioprospecting novel AXE is essential in designing enzyme cocktails with desired characteristics targeting the complete breakdown of lignocellulose. In this article, we report the characterisation of a novel AXE identified as Gene_id_40363 in the metagenomic library analysed from the gut microbiota of the common black slug. The conserved domain description was identified with an NCBI BLASTp search using the translated nucleotide sequence as a query. The activity of the recombinant enzyme was tested on various synthetic substrates and acetylated substrates. The protein sequence matched the conserved domain described as putative hydrolase and aligned closely to an uncharacterized esterase from Buttiauxella agrestis, hence the designation as BaAXE. BaAXE showed low sequence similarity among characterized CE family proteins with an available 3D structure. BaAXE was active on 4-nitrophenyl acetate, reporting a specific activity of 78.12 U/mg and a Km value of 0.43 mM. The enzyme showed optimal activity at 40 °C and pH 8 and showed high thermal stability, retaining over 40% activity after 2 h of incubation from 40 °C to 100 °C. BaAXE hydrolysed acetyl bonds, releasing acetic acid from acetylated xylan and β-D-glucose pentaacetate. BaAXE has great potential for biotechnological applications harnessing its unique characteristics. In addition, this proves the possibility of bioprospecting novel enzymes from understudied environments. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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11 pages, 2077 KiB  
Article
Pressurized Solvent Extraction of Paulownia Bark Phenolics
by Paula Rodríguez-Seoane, Beatriz Díaz-Reinoso and Herminia Domínguez
Molecules 2022, 27(1), 254; https://doi.org/10.3390/molecules27010254 - 31 Dec 2021
Cited by 5 | Viewed by 1520
Abstract
Paulownia bark is mostly utilized jointly with wood, but the possibility of a separate valorization through the pressurized extraction of bark bioactives has been assessed. Subcritical water extraction and supercritical CO2 extraction are green technologies allowing shorter times than conventional solvent extraction [...] Read more.
Paulownia bark is mostly utilized jointly with wood, but the possibility of a separate valorization through the pressurized extraction of bark bioactives has been assessed. Subcritical water extraction and supercritical CO2 extraction are green technologies allowing shorter times than conventional solvent extraction under atmospheric shaken conditions. Subcritical water extraction was carried out at temperatures ranging from 140 to 240 °C and supercritical CO2 extraction was performed at different pressures (10, 20 and 30 MPa), temperatures (35, 45 and 55 °C) and ethanol concentrations (0, 10 and 15% (w/w)). Subcritical water extraction under a non-isothermal operation during heating up to 160 °C (19 min) provided extraction yields up to 30%, and the extracts contained up to 7% total phenolics with an ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) radical scavenging capacity equivalent to 35% the activity of Trolox, whereas at 240 °C, the yield decreased to 20%, but the phenolic content reached 21%, and the antiradical activity was equivalent to 85% of Trolox. Supercritical CO2 extraction at 30 MPa, 45 °C and 30 min reached a global yield of 2% after 180 min of extraction, but the product showed very low antiradical capacity. Gallic acid, vanillic acid, vanillin and apigenin were the major phenolic compounds found in the extracts. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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16 pages, 2944 KiB  
Article
Polish Varieties of Industrial Hemp and Their Utilisation in the Efficient Production of Lignocellulosic Ethanol
by Aleksandra Wawro, Jolanta Batog and Weronika Gieparda
Molecules 2021, 26(21), 6467; https://doi.org/10.3390/molecules26216467 - 26 Oct 2021
Cited by 7 | Viewed by 1582
Abstract
Nowadays, more and more attention is paid to the development and the intensification of the use of renewable energy sources. Hemp might be an alternative plant for bioenergy production. In this paper, four varieties of Polish industrial hemp (Białobrzeskie, Tygra, Henola, and Rajan) [...] Read more.
Nowadays, more and more attention is paid to the development and the intensification of the use of renewable energy sources. Hemp might be an alternative plant for bioenergy production. In this paper, four varieties of Polish industrial hemp (Białobrzeskie, Tygra, Henola, and Rajan) were investigated in order to determine which of them are the most advantageous raw materials for the effective production of bioethanol. At the beginning, physical and chemical pretreatment of hemp biomass was carried out. It was found that the most effective is the alkaline treatment with 2% NaOH, and the biomasses of the two varieties were selected for next stages of research: Tygra and Rajan. Hemp biomass before and after pretreatment was analyzed by FTIR and SEM, which confirmed the effectiveness of the pretreatment. Next, an enzymatic hydrolysis process was carried out on the previously selected parameters using the response surface methodology. Subsequently, the two approaches were analyzed: separated hydrolysis and fermentation (SHF) and a simultaneous saccharification and fermentation (SSF) process. For Tygra biomass in the SHF process, the ethanol concentration was 10.5 g∙L−1 (3.04 m3·ha−1), and for Rajan biomass at the SSF process, the ethanol concentration was 7.5 g∙L−1 (2.23 m3·ha−1). In conclusion, the biomass of Polish varieties of hemp, i.e., Tygra and Rajan, was found to be an interesting and promising raw material for bioethanol production. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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19 pages, 4727 KiB  
Article
Effect of the Micronization of Pulp Fibers on the Properties of Green Composites
by Bruno F. A. Valente, Armando J. D. Silvestre, Carlos Pascoal Neto, Carla Vilela and Carmen S. R. Freire
Molecules 2021, 26(18), 5594; https://doi.org/10.3390/molecules26185594 - 15 Sep 2021
Cited by 15 | Viewed by 2299
Abstract
Green composites, composed of bio-based matrices and natural fibers, are a sustainable alternative for composites based on conventional thermoplastics and glass fibers. In this work, micronized bleached Eucalyptus kraft pulp (BEKP) fibers were used as reinforcement in biopolymeric matrices, namely poly(lactic acid) (PLA) [...] Read more.
Green composites, composed of bio-based matrices and natural fibers, are a sustainable alternative for composites based on conventional thermoplastics and glass fibers. In this work, micronized bleached Eucalyptus kraft pulp (BEKP) fibers were used as reinforcement in biopolymeric matrices, namely poly(lactic acid) (PLA) and poly(hydroxybutyrate) (PHB). The influence of the load and aspect ratio of the mechanically treated microfibers on the morphology, water uptake, melt flowability, and mechanical and thermal properties of the green composites were investigated. Increasing fiber loads raised the tensile and flexural moduli as well as the tensile strength of the composites, while decreasing their elongation at the break and melt flow rate. The reduced aspect ratio of the micronized fibers (in the range from 11.0 to 28.9) improved their embedment in the matrices, particularly for PHB, leading to superior mechanical performance and lower water uptake when compared with the composites with non-micronized pulp fibers. The overall results show that micronization is a simple and sustainable alternative for conventional chemical treatments in the manufacturing of entirely bio-based composites. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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15 pages, 3161 KiB  
Article
Effective Utilisation of Halophyte Biomass from Saline Soils for Biorefinering Processes
by Jolanta Batog, Krzysztof Bujnowicz, Weronika Gieparda, Aleksandra Wawro and Szymon Rojewski
Molecules 2021, 26(17), 5393; https://doi.org/10.3390/molecules26175393 - 05 Sep 2021
Cited by 3 | Viewed by 1902
Abstract
The salinity of European soil is increasing every year, causing severe economic damage (estimated 1–3 million hectares in the enlarged EU). This study uses the biomass of halophytes—tall fescue (grass) and hemp of the Białobrzeskie variety from saline soils—for bioenergy, second generation biofuels [...] Read more.
The salinity of European soil is increasing every year, causing severe economic damage (estimated 1–3 million hectares in the enlarged EU). This study uses the biomass of halophytes—tall fescue (grass) and hemp of the Białobrzeskie variety from saline soils—for bioenergy, second generation biofuels and designing new materials—fillers for polymer composites. In the bioethanol obtaining process, in the first stage, the grass and hemp biomass were pretreated with 1.5% NaOH. Before and after the treatment, the chemical composition was determined and the FTIR spectra and SEM pictures were taken. Then, the process of simultaneous saccharification and fermentation (SSF) was carried out. The concentration of ethanol for both the grass and hemp biomass was approx. 7 g·L−1 (14 g·100 g−1 of raw material). In addition, trials of obtaining green composites with halophyte biomass using polymers (PP) and biopolymers (PLA) as a matrix were performed. The mechanical properties of the composites (tensile and flexural tests) were determined. It was found that the addition of a compatibilizer improved the adhesion at the interface of PP composites with a hemp filler. In conclusion, the grass and hemp biomass were found to be an interesting and promising source to be used for bioethanol and biocomposites production. The use of annually renewable plant biomass from saline soils for biorefinering processes opens up opportunities for the development of a new value chains and new approaches to sustainable agriculture. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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12 pages, 1028 KiB  
Article
Copper Adsorption on Lignin for the Removal of Hydrogen Sulfide
by Miroslav Nikolic, Marleny Cáceres Najarro, Ib Johannsen, Joseph Iruthayaraj, Marcel Ceccato and Anders Feilberg
Molecules 2020, 25(23), 5577; https://doi.org/10.3390/molecules25235577 - 27 Nov 2020
Cited by 8 | Viewed by 3065
Abstract
Lignin is currently an underutilized part of biomass; thus, further research into lignin could benefit both scientific and commercial endeavors. The present study investigated the potential of kraft lignin as a support material for the removal of hydrogen sulfide (H2S) from [...] Read more.
Lignin is currently an underutilized part of biomass; thus, further research into lignin could benefit both scientific and commercial endeavors. The present study investigated the potential of kraft lignin as a support material for the removal of hydrogen sulfide (H2S) from gaseous streams, such as biogas. The removal of H2S was enabled by copper ions that were previously adsorbed on kraft lignin. Copper adsorption was based on two different strategies: either directly on lignin particles or by precipitating lignin from a solution in the presence of copper. The H2S concentration after the adsorption column was studied using proton-transfer-reaction mass spectrometry, while the mechanisms involved in the H2S adsorption were studied with X-ray photoelectron spectroscopy. It was determined that elemental sulfur was obtained during the H2S adsorption in the presence of kraft lignin and the differences relative to the adsorption on porous silica as a control are discussed. For kraft lignin, only a relatively low removal capacity of 2 mg of H2S per gram was identified, but certain possibilities to increase the removal capacity are discussed. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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17 pages, 958 KiB  
Article
Micro-Fibrillated Cellulose in Adhesive Systems for the Production of Wood-Based Panels
by Emmanouil Karagiannidis, Charles Markessini and Eleftheria Athanassiadou
Molecules 2020, 25(20), 4846; https://doi.org/10.3390/molecules25204846 - 21 Oct 2020
Cited by 13 | Viewed by 2290
Abstract
Micro-Fibrillated Cellulose (MFC) is a new type of bio-based additive, coming from wood cellulose. It can compete and substitute oil derived chemicals in several application fields. In the present work, the use of micro-fibrillated cellulose, in waterborne adhesive systems applied in the manufacture [...] Read more.
Micro-Fibrillated Cellulose (MFC) is a new type of bio-based additive, coming from wood cellulose. It can compete and substitute oil derived chemicals in several application fields. In the present work, the use of micro-fibrillated cellulose, in waterborne adhesive systems applied in the manufacture of composite wood-based panels was evaluated. Research was conducted to test the potential of improving the performance of wood-based panel types such as particleboard, waferboard or randomly-oriented strand board and plywood, by the application of MFC and the substitution of conventional and non-renewable chemical compounds. The approaches followed to introduce MFC into the adhesive systems were three, i.e., MFC 2% suspension added during the adhesive resin synthesis, MFC 10% paste admixed with the already prepared adhesive resin and MFC 2% suspension admixed with the already prepared resin. It was found that MFC improves not only the performance of the final wood panel products but also the behaviour of the applied adhesive polymer colloids (e.g., rheology improvement), especially when admixed with the already prepared resins. Moreover, it was proven that when MFC is introduced into the adhesive resin system, there is a possibility of decreasing the resin consumption, by maintaining the board performance. MFC’s robustness to pH, shear and temperature makes it a highly interesting new additive for adhesive producers. In addition, its natural origin can give adhesive producers the opportunity to move over to more environmentally friendly product solutions. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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21 pages, 7464 KiB  
Article
Acquisition of Torrefied Biomass from Jerusalem Artichoke Grown in a Closed Circular System Using Biogas Plant Waste
by Szymon Szufa, Piotr Piersa, Łukasz Adrian, Jan Sielski, Mieczyslaw Grzesik, Zdzisława Romanowska-Duda, Krzysztof Piotrowski and Wiktoria Lewandowska
Molecules 2020, 25(17), 3862; https://doi.org/10.3390/molecules25173862 - 25 Aug 2020
Cited by 39 | Viewed by 2892
Abstract
The aim of the research was to investigate the effect of biogas plant waste on the physiological activity, growth, and yield of Jerusalem artichoke and the energetic usefulness of the biomass obtained in this way after the torrefaction process. The use of waste [...] Read more.
The aim of the research was to investigate the effect of biogas plant waste on the physiological activity, growth, and yield of Jerusalem artichoke and the energetic usefulness of the biomass obtained in this way after the torrefaction process. The use of waste from corn grain biodigestion to methane as a biofertilizer, used alone or supplemented with Apol-humus and Stymjod, caused increased the physiological activity, growth, and yield of Jerusalem artichoke plants and can limit the application of chemical fertilizers, whose production and use in agriculture is harmful for the environment. The experiment, using different equipment, exhibited the high potential of Jerusalem artichoke fertilized by the methods elaborated as a carbonized solid biofuel after the torrefaction process. The use of a special design of the batch reactor using nitrogen, Thermogravimetric analysis, Differential thermal analysis, and Fourier-transform infrared spectroscopy and combustion of Jerusalem artichoke using TG-MS showed a thermo-chemical conversion mass loss on a level of 30% with energy loss (torgas) on a level of 10%. Compared to research results on other energy crops and straw biomass, the isothermal temperature of 245 °C during torrefaction for the carbonized solid biofuel of Jerusalem artichoke biomass fertilized with biogas plant waste is relativlely low. An SEM-EDS analysis of ash from carbonized Jerusalem artichoke after torrefaction was performed after its combustion. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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19 pages, 1977 KiB  
Article
Optimization with Response Surface Methodology of Microwave-Assisted Conversion of Xylose to Furfural
by Carmen Padilla-Rascón, Juan Miguel Romero-García, Encarnación Ruiz and Eulogio Castro
Molecules 2020, 25(16), 3574; https://doi.org/10.3390/molecules25163574 - 06 Aug 2020
Cited by 13 | Viewed by 2994
Abstract
The production of furfural from renewable sources, such as lignocellulosic biomass, has gained great interest within the concept of biorefineries. In lignocellulosic materials, xylose is the most abundant pentose, which forms the hemicellulosic part. One of the key steps in the production of [...] Read more.
The production of furfural from renewable sources, such as lignocellulosic biomass, has gained great interest within the concept of biorefineries. In lignocellulosic materials, xylose is the most abundant pentose, which forms the hemicellulosic part. One of the key steps in the production of furfural from biomass is the dehydration reaction of the pentoses. The objective of this work was to assess the conditions under which the concentration of furfural is maximized from a synthetic, monophasic, and homogeneous xylose medium. The experiments were carried out in a microwave reactor. FeCl3 in different proportions and sulfuric acid were used as catalysts. A two-level, three-factor experimental design was developed for this purpose. The results were further analyzed through a second experimental design and optimization was performed by response surface methodology. The best operational conditions for the highest furfural yield (57%) turned out to be 210 °C, 0.5 min, and 0.05 M FeCl3. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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17 pages, 1405 KiB  
Article
Effects of Biosurfactants on Enzymatic Saccharification and Fermentation of Pretreated Softwood
by Alfredo Oliva-Taravilla, Cristhian Carrasco, Leif J. Jönsson and Carlos Martín
Molecules 2020, 25(16), 3559; https://doi.org/10.3390/molecules25163559 - 05 Aug 2020
Cited by 20 | Viewed by 3060
Abstract
The enzymatic hydrolysis of cellulose is inhibited by non-productive adsorption of cellulases to lignin, and that is particularly problematic with lignin-rich materials such as softwood. Although conventional surfactants alleviate non-productive adsorption, using biosurfactants in softwood hydrolysis has not been reported. In this study, [...] Read more.
The enzymatic hydrolysis of cellulose is inhibited by non-productive adsorption of cellulases to lignin, and that is particularly problematic with lignin-rich materials such as softwood. Although conventional surfactants alleviate non-productive adsorption, using biosurfactants in softwood hydrolysis has not been reported. In this study, the effects of four biosurfactants, namely horse-chestnut escin, Pseudomonas aeruginosa rhamnolipid, and saponins from red and white quinoa varieties, on the enzymatic saccharification of steam-pretreated spruce were investigated. The used biosurfactants improved hydrolysis, and the best-performing one was escin, which led to cellulose conversions above 90%, decreased by around two-thirds lignin inhibition of Avicel hydrolysis, and improved hydrolysis of pretreated spruce by 24%. Red quinoa saponins (RQS) addition resulted in cellulose conversions above 80%, which was around 16% higher than without biosurfactants, and it was more effective than adding rhamnolipid or white quinoa saponins. Cellulose conversion improved with the increase in RQS addition up to 6 g/100 g biomass, but no significant changes were observed above that dosage. Although saponins are known to inhibit yeast growth, no inhibition of Saccharomyces cerevisiae fermentation of hydrolysates produced with RQS addition was detected. This study shows the potential of biosurfactants for enhancing the enzymatic hydrolysis of steam-pretreated softwood. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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16 pages, 3171 KiB  
Article
Horticultural Plant Residues as New Source for Lignocellulose Nanofibers Isolation: Application on the Recycling Paperboard Process
by Isabel Bascón-Villegas, Eduardo Espinosa, Rafael Sánchez, Quim Tarrés, Fernando Pérez-Rodríguez and Alejandro Rodríguez
Molecules 2020, 25(14), 3275; https://doi.org/10.3390/molecules25143275 - 18 Jul 2020
Cited by 14 | Viewed by 2471
Abstract
Horticultural plant residues (tomato, pepper, and eggplant) were identified as new sources for lignocellulose nanofibers (LCNF). Cellulosic pulp was obtained from the different plant residues using an environmentally friendly process, energy-sustainable, simple, and with low-chemical reagent consumption. The chemical composition of the obtained [...] Read more.
Horticultural plant residues (tomato, pepper, and eggplant) were identified as new sources for lignocellulose nanofibers (LCNF). Cellulosic pulp was obtained from the different plant residues using an environmentally friendly process, energy-sustainable, simple, and with low-chemical reagent consumption. The chemical composition of the obtained pulps was analyzed in order to study its influence in the nanofibrillation process. Cellulosic fibers were subjected to two different pretreatments, mechanical and TEMPO(2,2,6,6-Tetramethyl-piperidin-1-oxyl)-mediated oxidation, followed by high-pressure homogenization to produce different lignocellulose nanofibers. Then, LCNF were deeply characterized in terms of nanofibrillation yield, cationic demand, carboxyl content, morphology, crystallinity, and thermal stability. The suitability of each raw material to produce lignocellulose nanofibers was analyzed from the point of view of each pretreatment. TEMPO-mediated oxidation was identified as a more effective pretreatment to produce LCNF, however, it produces a decrease in the thermal stability of the LCNF. The different LCNF were added as reinforcing agent on recycled paperboard and compared with the improving produced by the industrial mechanical beating. The analysis of the papersheets’ mechanical properties shows that the addition of LCNF as a reinforcing agent in the paperboard recycling process is a viable alternative to mechanical beating, achieving greater reinforcing effect and increasing the products’ life cycles. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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12 pages, 2244 KiB  
Article
A Direct Silanization Protocol for Dialdehyde Cellulose
by Arianna Lucia, Markus Bacher, Hendrikus W. G. van Herwijnen and Thomas Rosenau
Molecules 2020, 25(10), 2458; https://doi.org/10.3390/molecules25102458 - 25 May 2020
Cited by 22 | Viewed by 4761
Abstract
Cellulose derivatives have many potential applications in the field of biomaterials and composites, in addition to several ways of modification leading to them. Silanization in aqueous media is one of the most promising routes to create multipurpose and organic–inorganic hybrid materials. Silanization has [...] Read more.
Cellulose derivatives have many potential applications in the field of biomaterials and composites, in addition to several ways of modification leading to them. Silanization in aqueous media is one of the most promising routes to create multipurpose and organic–inorganic hybrid materials. Silanization has been widely used for cellulosic and nano-structured celluloses, but was a problem so far if to be applied to the common cellulose derivative “dialdehyde cellulose” (DAC), i.e., highly periodate-oxidized celluloses. In this work, a straightforward silanization protocol for dialdehyde cellulose is proposed, which can be readily modified with (3-aminopropyl)triethoxysilane. After thermal treatment and freeze-drying, the resulting product showed condensation and cross-linking, which was studied with infrared spectroscopy and 13C and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy. The cross-linking involves both links of the hydroxyl group of the oxidized cellulose with the silanol groups (Si-O-C) and imine-type bonds between the amino group and keto functions of the DAC (-HC=N-). The modification was achieved in aqueous medium under mild reaction conditions. Different treatments cause different levels of hydrolysis of the organosilane compound, which resulted in diverse condensed silica networks in the modified dialdehyde cellulose structure. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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18 pages, 4213 KiB  
Article
Production and Mechanical Characterisation of TEMPO-Oxidised Cellulose Nanofibrils/β-Cyclodextrin Films and Cryogels
by Bastien Michel, Julien Bras, Alain Dufresne, Ellinor B. Heggset and Kristin Syverud
Molecules 2020, 25(10), 2381; https://doi.org/10.3390/molecules25102381 - 20 May 2020
Cited by 9 | Viewed by 3013
Abstract
Wood-based TEMPO-oxidised cellulose nanofibrils (toCNF) are promising materials for biomedical applications. Cyclodextrins have ability to form inclusion complexes with hydrophobic molecules and are considered as a method to bring new functionalities to these materials. Water sorption and mechanical properties are also key properties [...] Read more.
Wood-based TEMPO-oxidised cellulose nanofibrils (toCNF) are promising materials for biomedical applications. Cyclodextrins have ability to form inclusion complexes with hydrophobic molecules and are considered as a method to bring new functionalities to these materials. Water sorption and mechanical properties are also key properties for biomedical applications such as drug delivery and tissue engineering. In this work, we report the modification with β-cyclodextrin (βCD) of toCNF samples with different carboxyl contents viz. 756 ± 4 µmol/g and 1048 ± 32 µmol/g. The modification was carried out at neutral and acidic pH (2.5) to study the effect of dissociation of the carboxylic acid group. Films processed by casting/evaporation at 40 °C and cryogels processed by freeze-drying were prepared from βCD modified toCNF suspensions and compared with reference samples of unmodified toCNF. The impact of modification on water sorption and mechanical properties was assessed. It was shown that the water sorption behaviour for films is driven by adsorption, with a clear impact of the chemical makeup of the fibres (charge content, pH, and adsorption of cyclodextrin). Modified toCNF cryogels (acidic pH and addition of cyclodextrins) displayed lower mechanical properties linked to the modification of the cell wall porosity structure. Esterification between βCD and toCNF under acidic conditions was performed by freeze-drying, and such cryogels exhibited a lower decrease in mechanical properties in the swollen state. These results are promising for the development of scaffold and films with controlled mechanical properties and added value due to the ability of cyclodextrin to form an inclusion complex with active principle ingredient (API) or growth factor (GF) for biomedical applications. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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16 pages, 3545 KiB  
Article
Feasibility of Barley Straw Fibers as Reinforcement in Fully Biobased Polyethylene Composites: Macro and Micro Mechanics of the Flexural Strength
by Ferran Serra-Parareda, Fernando Julián, Eduardo Espinosa, Alejandro Rodríguez, Francesc X. Espinach and Fabiola Vilaseca
Molecules 2020, 25(9), 2242; https://doi.org/10.3390/molecules25092242 - 10 May 2020
Cited by 15 | Viewed by 3601
Abstract
Awareness on deforestation, forest degradation, and its impact on biodiversity and global warming, is giving rise to the use of alternative fiber sources in replacement of wood feedstock for some applications such as composite materials and energy production. In this category, barley straw [...] Read more.
Awareness on deforestation, forest degradation, and its impact on biodiversity and global warming, is giving rise to the use of alternative fiber sources in replacement of wood feedstock for some applications such as composite materials and energy production. In this category, barley straw is an important agricultural crop, due to its abundance and availability. In the current investigation, the residue was submitted to thermomechanical process for fiber extraction and individualization. The high content of holocellulose combined with their relatively high aspect ratio inspires the potential use of these fibers as reinforcement in plastic composites. Therefore, fully biobased composites were fabricated using barley fibers and a biobased polyethylene (BioPE) as polymer matrix. BioPE is completely biobased and 100% recyclable. As for material performance, the flexural properties of the materials were studied. A good dispersion of the reinforcement inside the plastic was achieved contributing to the elevate increments in the flexural strength. At a 45 wt.% of reinforcement, an increment in the flexural strength of about 147% was attained. The mean contribution of the fibers to the flexural strength was assessed by means of a fiber flexural strength factor, reaching a value of 91.4. The micromechanical analysis allowed the prediction of the intrinsic flexural strength of the fibers, arriving up to around 700 MPa, and coupling factors between 0.18 and 0.19, which are in line with other natural fiber composites. Overall, the investigation brightness on the potential use of barley straw residues as reinforcement in fully biobased polymer composites. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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16 pages, 4609 KiB  
Article
Biocomposites of Bio-Polyethylene Reinforced with a Hydrothermal-Alkaline Sugarcane Bagasse Pulp and Coupled with a Bio-Based Compatibilizer
by Nanci Vanesa Ehman, Diana Ita-Nagy, Fernando Esteban Felissia, María Evangelina Vallejos, Isabel Quispe, María Cristina Area and Gary Chinga-Carrasco
Molecules 2020, 25(9), 2158; https://doi.org/10.3390/molecules25092158 - 05 May 2020
Cited by 20 | Viewed by 4099
Abstract
Bio-polyethylene (BioPE, derived from sugarcane), sugarcane bagasse pulp, and two compatibilizers (fossil and bio-based), were used to manufacture biocomposite filaments for 3D printing. Biocomposite filaments were manufactured and characterized in detail, including measurement of water absorption, mechanical properties, thermal stability and decomposition temperature [...] Read more.
Bio-polyethylene (BioPE, derived from sugarcane), sugarcane bagasse pulp, and two compatibilizers (fossil and bio-based), were used to manufacture biocomposite filaments for 3D printing. Biocomposite filaments were manufactured and characterized in detail, including measurement of water absorption, mechanical properties, thermal stability and decomposition temperature (thermo-gravimetric analysis (TGA)). Differential scanning calorimetry (DSC) was performed to measure the glass transition temperature (Tg). Scanning electron microscopy (SEM) was applied to assess the fracture area of the filaments after mechanical testing. Increases of up to 10% in water absorption were measured for the samples with 40 wt% fibers and the fossil compatibilizer. The mechanical properties were improved by increasing the fraction of bagasse fibers from 0% to 20% and 40%. The suitability of the biocomposite filaments was tested for 3D printing, and some shapes were printed as demonstrators. Importantly, in a cradle-to-gate life cycle analysis of the biocomposites, we demonstrated that replacing fossil compatibilizer with a bio-based compatibilizer contributes to a reduction in CO2-eq emissions, and an increase in CO2 capture, achieving a CO2-eq storage of 2.12 kg CO2 eq/kg for the biocomposite containing 40% bagasse fibers and 6% bio-based compatibilizer. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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11 pages, 1839 KiB  
Article
Fully Biobased Epoxy Resins from Fatty Acids and Lignin
by Pablo Ortiz, Richard Vendamme and Walter Eevers
Molecules 2020, 25(5), 1158; https://doi.org/10.3390/molecules25051158 - 05 Mar 2020
Cited by 35 | Viewed by 8170
Abstract
The use of renewable resources for plastic production is an imperious need for the reduction of the carbon footprint and the transition towards a circular economy. With that goal in mind, fully biobased epoxy resins have been designed and prepared by combining epoxidized [...] Read more.
The use of renewable resources for plastic production is an imperious need for the reduction of the carbon footprint and the transition towards a circular economy. With that goal in mind, fully biobased epoxy resins have been designed and prepared by combining epoxidized linseed oil, lignin, and a biobased diamine derived from fatty acid dimers. The aromatic structures in lignin provide hardness and strength to an otherwise flexible and breakable epoxy resin. The curing of the system was investigated by infrared spectroscopy and differential scanning calorimetry (DSC). The influence of the different components on the thermo-mechanical properties of the epoxy resins was analyzed by DSC, thermal gravimetric analysis (TGA), and tensile tests. As the content of lignin in the resin increases, so does the glass transition, the Young’s modulus, and the onset of thermal degradation. This correlation is non-linear, and the higher the percentage of lignin, the more pronounced the effect. All the components of the epoxy resin being commodity chemicals, the present system provides a realistic opportunity for the preparation of fully biorenewable resins at an industrial scale. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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13 pages, 2906 KiB  
Article
Optimized Bioproduction of Itaconic and Fumaric Acids Based on Solid-State Fermentation of Lignocellulosic Biomass
by Amparo Jiménez-Quero, Eric Pollet, Luc Avérous and Vincent Phalip
Molecules 2020, 25(5), 1070; https://doi.org/10.3390/molecules25051070 - 27 Feb 2020
Cited by 25 | Viewed by 3561
Abstract
The bioproduction of high-value chemicals such as itaconic and fumaric acids (IA and FA, respectively) from renewable resources via solid-state fermentation (SSF) represents an alternative to the current bioprocesses of submerged fermentation using refined sugars. Both acids are excellent platform chemicals with a [...] Read more.
The bioproduction of high-value chemicals such as itaconic and fumaric acids (IA and FA, respectively) from renewable resources via solid-state fermentation (SSF) represents an alternative to the current bioprocesses of submerged fermentation using refined sugars. Both acids are excellent platform chemicals with a wide range of applications in different market, such as plastics, coating, or cosmetics. The use of lignocellulosic biomass instead of food resources (starch or grains) in the frame of a sustainable development for IA and FA bioproduction is of prime importance. Filamentous fungi, especially belonging to the Aspergillus genus, have shown a great capacity to produce these organic dicarboxylic acids. This study attempts to develop and optimize the SSF conditions with lignocellulosic biomasses using A. terreus and A. oryzae to produce IA and FA. First, a kinetic study of SSF was performed with non-food resources (wheat bran and corn cobs) and a panel of pH and moisture conditions was studied during fermentation. Next, a new process using an enzymatic cocktail simultaneously with SSF was investigated in order to facilitate the use of the biomass as microbial substrate. Finally, a large-scale fermentation process was developed for SSF using corn cobs with A. oryzae; this specific condition showed the best yield in acid production. The yields achieved were 0.05 mg of IA and 0.16 mg of FA per gram of biomass after 48 h. These values currently represent the highest reported productions for SSF from raw lignocellulosic biomass. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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Review

Jump to: Editorial, Research

27 pages, 3213 KiB  
Review
Bioethanol Production from Lignocellulosic Biomass—Challenges and Solutions
by Magdalena Broda, Daniel J. Yelle and Katarzyna Serwańska
Molecules 2022, 27(24), 8717; https://doi.org/10.3390/molecules27248717 - 09 Dec 2022
Cited by 63 | Viewed by 11036
Abstract
Regarding the limited resources for fossil fuels and increasing global energy demands, greenhouse gas emissions, and climate change, there is a need to find alternative energy sources that are sustainable, environmentally friendly, renewable, and economically viable. In the last several decades, interest in [...] Read more.
Regarding the limited resources for fossil fuels and increasing global energy demands, greenhouse gas emissions, and climate change, there is a need to find alternative energy sources that are sustainable, environmentally friendly, renewable, and economically viable. In the last several decades, interest in second-generation bioethanol production from non-food lignocellulosic biomass in the form of organic residues rapidly increased because of its abundance, renewability, and low cost. Bioethanol production fits into the strategy of a circular economy and zero waste plans, and using ethanol as an alternative fuel gives the world economy a chance to become independent of the petrochemical industry, providing energy security and environmental safety. However, the conversion of biomass into ethanol is a challenging and multi-stage process because of the variation in the biochemical composition of biomass and the recalcitrance of lignin, the aromatic component of lignocellulose. Therefore, the commercial production of cellulosic ethanol has not yet become well-received commercially, being hampered by high research and production costs, and substantial effort is needed to make it more widespread and profitable. This review summarises the state of the art in bioethanol production from lignocellulosic biomass, highlights the most challenging steps of the process, including pretreatment stages required to fragment biomass components and further enzymatic hydrolysis and fermentation, presents the most recent technological advances to overcome the challenges and high costs, and discusses future perspectives of second-generation biorefineries. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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28 pages, 1393 KiB  
Review
Processing of Biomass Prior to Hydrogen Fermentation and Post-Fermentative Broth Management
by Zhila Honarmandrad, Karolina Kucharska and Jacek Gębicki
Molecules 2022, 27(21), 7658; https://doi.org/10.3390/molecules27217658 - 07 Nov 2022
Cited by 5 | Viewed by 2360
Abstract
Using bioconversion and simultaneous value-added product generation requires purification of the gaseous and the liquid streams before, during, and after the bioconversion process. The effect of diversified process parameters on the efficiency of biohydrogen generation via biological processes is a broad object of [...] Read more.
Using bioconversion and simultaneous value-added product generation requires purification of the gaseous and the liquid streams before, during, and after the bioconversion process. The effect of diversified process parameters on the efficiency of biohydrogen generation via biological processes is a broad object of research. Biomass-based raw materials are often applied in investigations regarding biohydrogen generation using dark fermentation and photo fermentation microorganisms. The literature lacks information regarding model mixtures of lignocellulose and starch-based biomass, while the research is carried out based on a single type of raw material. The utilization of lignocellulosic and starch biomasses as the substrates for bioconversion processes requires the decomposition of lignocellulosic polymers into hexoses and pentoses. Among the components of lignocelluloses, mainly lignin is responsible for biomass recalcitrance. The natural carbohydrate-lignin shields must be disrupted to enable lignin removal before biomass hydrolysis and fermentation. The matrix of chemical compounds resulting from this kind of pretreatment may significantly affect the efficiency of biotransformation processes. Therefore, the actual state of knowledge on the factors affecting the culture of dark fermentation and photo fermentation microorganisms and their adaptation to fermentation of hydrolysates obtained from biomass requires to be monitored and a state of the art regarding this topic shall become a contribution to the field of bioconversion processes and the management of liquid streams after fermentation. The future research direction should be recognized as striving to simplification of the procedure, applying the assumptions of the circular economy and the responsible generation of liquid and gas streams that can be used and purified without large energy expenditure. The optimization of pre-treatment steps is crucial for the latter stages of the procedure. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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23 pages, 5892 KiB  
Review
Durability of Cellulosic-Fiber-Reinforced Geopolymers: A Review
by Jie Liu and Chun Lv
Molecules 2022, 27(3), 796; https://doi.org/10.3390/molecules27030796 - 25 Jan 2022
Cited by 22 | Viewed by 3445
Abstract
Geopolymers have high early strength, fast hardening speed and wide sources of raw materials, and have good durability properties such as high temperature resistance and corrosion resistance. On the other hand, there are abundant sources of plant or cellulose fibers, and it has [...] Read more.
Geopolymers have high early strength, fast hardening speed and wide sources of raw materials, and have good durability properties such as high temperature resistance and corrosion resistance. On the other hand, there are abundant sources of plant or cellulose fibers, and it has the advantages of having a low cost, a light weight, strong adhesion and biodegradability. In this context, the geopolymer sector is considering cellulose fibers as a sustainable reinforcement for developing composites. Cellulosic-fiber-reinforced geopolymer composites have broad development prospects. This paper presents a review of the literature research on the durability of cellulosic-fiber-reinforced geopolymer composites in recent years. In this paper, the typical properties of cellulose fibers are summarized, and the polymerization mechanism of geopolymers is briefly discussed. The factors influencing the durability of cellulosic-fiber-reinforced geopolymer composites were summarized and analyzed, including the degradation of fibers in a geopolymer matrix, the toughness of fiber against matrix cracking, the acid resistance, and resistance to chloride ion penetration, high temperature resistance, etc. Finally, the influence of nanomaterials on the properties of geopolymer composites and the chemical modification of fibers are analyzed, and the research on cellulosic-fiber-reinforced geopolymer composites is summarized. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass II)
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13 pages, 2646 KiB  
Review
Biorefinery of Biomass of Agro-Industrial Banana Waste to Obtain High-Value Biopolymers
by Carlos Redondo-Gómez, Maricruz Rodríguez Quesada, Silvia Vallejo Astúa, José Pablo Murillo Zamora, Mary Lopretti and José Roberto Vega-Baudrit
Molecules 2020, 25(17), 3829; https://doi.org/10.3390/molecules25173829 - 23 Aug 2020
Cited by 43 | Viewed by 7860
Abstract
On a worldwide scale, food demand is increasing as a consequence of global population growth. This makes companies push their food supply chains’ limits with a consequent increase in generation of large amounts of untreated waste that are considered of no value to [...] Read more.
On a worldwide scale, food demand is increasing as a consequence of global population growth. This makes companies push their food supply chains’ limits with a consequent increase in generation of large amounts of untreated waste that are considered of no value to them. Biorefinery technologies offer a suitable alternative for obtaining high-value products by using unconventional raw materials, such as agro-industrial waste. Currently, most biorefineries aim to take advantage of specific residues (by either chemical, biotechnological, or physical treatments) provided by agro-industry in order to develop high-value products for either in-house use or for sale purposes. This article reviews the currently explored possibilities to apply biorefinery-known processes to banana agro-industrial waste in order to generate high-value products out of this residual biomass source. Firstly, the Central and Latin American context regarding biomass and banana residues is presented, followed by advantages of using banana residues as raw materials for the production of distinct biofuels, nanocellulose fibers, different bioplastics, and other high-value products Lastly, additional uses of banana biomass residues are presented, including energy generation and water treatment. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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37 pages, 8285 KiB  
Review
Electrosynthesis of Biobased Chemicals Using Carbohydrates as a Feedstock
by Vincent Vedovato, Karolien Vanbroekhoven, Deepak Pant and Joost Helsen
Molecules 2020, 25(16), 3712; https://doi.org/10.3390/molecules25163712 - 14 Aug 2020
Cited by 20 | Viewed by 5663
Abstract
The current climate awareness coupled with increased focus on renewable energy and biobased chemicals have led to an increased demand for such biomass derived products. Electrosynthesis is a relatively new approach that allows a shift from conventional fossil-based chemistry towards a new model [...] Read more.
The current climate awareness coupled with increased focus on renewable energy and biobased chemicals have led to an increased demand for such biomass derived products. Electrosynthesis is a relatively new approach that allows a shift from conventional fossil-based chemistry towards a new model of a real sustainable chemistry that allows to use the excess renewable electricity to convert biobased feedstock into base and commodity chemicals. The electrosynthesis approach is expected to increase the production efficiency and minimize negative health for the workers and environmental impact all along the value chain. In this review, we discuss the various electrosynthesis approaches that have been applied on carbohydrate biomass specifically to produce valuable chemicals. The studies on the electro-oxidation of saccharides have mostly targeted the oxidation of the primary alcohol groups to form the corresponding uronic acids, with Au or TEMPO as the active electrocatalysts. The investigations on electroreduction of saccharides focused on the reduction of the aldehyde groups to the corresponding alcohols, using a variety of metal electrodes. Both oxidation and reduction pathways are elaborated here with most recent examples. Further recommendations have been made about the research needs, choice of electrocatalyst and electrolyte as well as upscaling the technology. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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22 pages, 7671 KiB  
Review
Development of ‘Lignin-First’ Approaches for the Valorization of Lignocellulosic Biomass
by Tamás I. Korányi, Bálint Fridrich, Antonio Pineda and Katalin Barta
Molecules 2020, 25(12), 2815; https://doi.org/10.3390/molecules25122815 - 18 Jun 2020
Cited by 81 | Viewed by 10742
Abstract
Currently, valorization of lignocellulosic biomass almost exclusively focuses on the production of pulp, paper, and bioethanol from its holocellulose constituent, while the remaining lignin part that comprises the highest carbon content, is burned and treated as waste. Lignin has a complex structure built [...] Read more.
Currently, valorization of lignocellulosic biomass almost exclusively focuses on the production of pulp, paper, and bioethanol from its holocellulose constituent, while the remaining lignin part that comprises the highest carbon content, is burned and treated as waste. Lignin has a complex structure built up from propylphenolic subunits; therefore, its valorization to value-added products (aromatics, phenolics, biogasoline, etc.) is highly desirable. However, during the pulping processes, the original structure of native lignin changes to technical lignin. Due to this extensive structural modification, involving the cleavage of the β-O-4 moieties and the formation of recalcitrant C-C bonds, its catalytic depolymerization requires harsh reaction conditions. In order to apply mild conditions and to gain fewer and uniform products, a new strategy has emerged in the past few years, named ‘lignin-first’ or ‘reductive catalytic fractionation’ (RCF). This signifies lignin disassembly prior to carbohydrate valorization. The aim of the present work is to follow historically, year-by-year, the development of ‘lignin-first’ approach. A compact summary of reached achievements, future perspectives and remaining challenges is also given at the end of the review. Full article
(This article belongs to the Special Issue Lignocellulosic Biomass)
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