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Editorial

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4 pages, 218 KiB

Open AccessEditorial

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

Cited by 1 | Viewed by 1224

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)

Research

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22 pages, 2592 KiB

Open AccessArticle

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 6 | Viewed by 4801

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

Open AccessArticle

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 6 | Viewed by 2047

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

Open AccessArticle

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 - 2 Feb 2023

Cited by 9 | Viewed by 2526

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

Open AccessArticle

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 1888

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

Open AccessArticle

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 5 | Viewed by 2334

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, q_max, of Arabica-coffee (WCAM) and Theobroma-cocoa (WCTM) biosorbents (q_max = 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, q_max, of Arabica-coffee (WCAM) and Theobroma-cocoa (WCTM) biosorbents (q_max = 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 (pH_PZC) 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

Open AccessArticle

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 2151

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 g_EtOH/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

Open AccessFeature PaperArticle

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 6 | Viewed by 2812

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

Open AccessArticle

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 - 7 May 2022

Cited by 6 | Viewed by 2932

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

Open AccessArticle

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 6 | Viewed by 1886

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

Open AccessArticle

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 8 | Viewed by 2005

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

Open AccessArticle

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 18 | Viewed by 2820

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

Open AccessArticle

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 - 5 Sep 2021

Cited by 5 | Viewed by 2284

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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Review

Jump to: Editorial, Research

27 pages, 3213 KiB

Open AccessReview

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 - 9 Dec 2022

Cited by 107 | Viewed by 17032

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

Open AccessReview

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 - 7 Nov 2022

Cited by 7 | Viewed by 3022

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

Open AccessReview

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 31 | Viewed by 4172

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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