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Volume 73 Issue 1 - Special Issue: Advances in biorefinery research \ Issue Editor: Thomas Rosenau

Issue of Holzforschung

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Contents
Journal Overview

Publicly Available December 19, 2018

Editorial

Publicly Available December 13, 2018

Advances in biorefinery research

Thomas Rosenau

Page range: 1-2

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Original Articles

Publicly Available November 17, 2018

Techno-economic feasibility of bioethanol production via biorefinery of olive tree prunings (OTP): optimization of the pretreatment stage

Juan C. Solarte-Toro, Juan M. Romero-García, Ana Susmozas, Encarnación Ruiz, Eulogio Castro, Carlos A. Cardona-Alzate

Page range: 3-13

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Abstract

The aim of this work was to evaluate the economic feasibility of the bioethanol production (BEP) based on olive tree pruning (OTP) as a biomass feedstock with optimization of the dilute acid pretreatment in focus. For this, the BEP was simulated taking into account the influence of the operating conditions of the pretreatment stage. Then, the techno-economic results were analyzed by means of the response surface methodology (RSM). The results show that lowest price of BE was 1.94 USD l −1 with a yield of 174.12 l t −1 OTP under optimal conditions. As a conclusion, the raw material cost has a strong influence in the economic feasibility of the BEP from OTP. The inclusion of other processing lines into the process would improve the process economy.

October 25, 2018

Designing an olive tree pruning biorefinery for the production of bioethanol, xylitol and antioxidants: a techno-economic assessment

Ana Susmozas, Antonio D. Moreno, Juan M. Romero-García, Paloma Manzanares, Mercedes Ballesteros

Page range: 15-23

Abstract

Olive tree crops, extensively cultivated in Southern European countries, yield large amounts of olive tree pruning (OTP) biomass. This could be used within the framework of a bio-based economy that maximizes the utilization of biomass resources in a sustainable way. In the present work, the techno-economic feasibility of an OTP-based integrated biorefinery is evaluated by the process simulation software Aspen Plus, while the process is aimed at the production of ethanol, xylitol, antioxidants and electricity. Overall, the proposed plant could perform economically, and it is self-sufficient from an energy resource point of view. The plant as designed yields around 109 l of ethanol, 27 kg of xylitol and 43 kg of antioxidants per ton of OTP biomass, with an estimated production cost of 0.24 € l −1 , 1.48 € kg −1 and 5.12 € kg −1 , respectively. In a 10-year period, the economic profitability of the biorefinery plant is within a positive investment balance, with a net present value (NPV) of 32.1 M€ and a payback period of 5–6 years. These figures point out the opportunities for placing in the market several OTP-based products. Based on these data, the construction of small-scale OTP-based lignocellulosic biorefineries seems to be a realistic scenario.

Publicly Available October 13, 2018

Structural characteristics of lignin in pruning residues of olive tree (Olea europaea L.)

Jorge Rencoret, Ana Gutiérrez, Eulogio Castro, José C. del Río

Page range: 25-34

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Abstract

Olive tree pruning (OTP) is an abundant and inexpensive agricultural lignocellulosic residue that is an interesting feedstock for producing bioethanol and other bio-products in the context of lignocellulosic biorefineries. However, the presence of lignin in OTP hinders the transformation processes as it limits the access to cell wall polysaccharides. On the other hand, the aromatic/phenolic structure of the lignin polymer makes it an interesting raw material for producing chemicals, fuels and other commodities that are nowadays produced from fossil fuels. Thus, the knowledge of the OTP lignin structure is crucial to develop tailor-made pretreatments for their removal as well as for additional valorization of the lignin polymer. In this work, the OTP lignin was isolated as milled wood lignin (MWL), a lignin preparation that is considered representative of the native lignin, and characterized by two-dimensional nuclear magnetic resonance (2D-NMR) and thioacidolysis. The results demonstrated that the lignin is mainly composed of guaiacyl (G) and syringyl (S) lignin units in similar abundances (S/G ratio of ~1), with minor amounts of p -hydroxyphenyl (H) units. The most abundant lignin inter-unit linkages are β- O -4′ alkyl-aryl ethers (75% of all linkages), followed by the condensed phenylcoumarans (12%) and resinols (8%), and with lower amounts of dibenzodioxocins (2%) and spirodienones (3%). The analysis of the thioacidolysis dimers gave additional information regarding the distribution of the lignin units involved in condensed interunit linkages, including 5-5′, 4- O -5′, β-5′, β-1′ and β-β′. The high lignin content (25%), together with the relatively low S/G ratio and the abundance of condensed (carbon-carbon linked) structures, points to a low reactivity of OTP lignin during delignification pretreatments.

October 25, 2018

Production of xylooligosaccharides and cellulosic ethanol from steam-exploded barley straw

Cristina Álvarez, Felicia Sáez, Alberto González, Ignacio Ballesteros, José Miguel Oliva, María José Negro

Page range: 35-44

Abstract

Agricultural residues, such as barley straw (BS), are attractive sources for the production of chemicals and fuels based on the biorefinery principle. In the present paper, BS was steam exploded at 180°C/30 min and then 90% of the cellulose and 60% of the hemicellulose were recovered in solid and liquid fractions respectively, which were used for ethanol and xylooligosaccharides (XOS) production. In the course of enzymatic hydrolysis (EH), different solid loading (SL) (10–20% w/v) and enzyme doses (15 and 30 FPU g −1 glucan) were applied to optimize the yield of glucose concentrations, while 92 g l −1 glucose was released at 20% SL and 30 FPU g −1 glucan enzyme dosage. For ethanol production, two different process configurations were compared: separate hydrolysis and fermentation (SHF) or prehydrolysis with simultaneous saccharification and fermentation (PSSF). To transform the soluble hemicellulose into xylooligomers, two glycoside hydrolases (GH) families 10 and 11 endoxylanases were used. Reaction times, enzyme dose and several combinations of enzymes were optimized to maximize the conversion into XOS. Under the pretreatment conditions indicated above, 14 g of ethanol was obtained via the PSSF approach and 11.1 g of XOS (with DP2–DP6) was obtained per 100 g of raw material.

October 20, 2018

A commercial laccase-mediator system to delignify and improve saccharification of the fast-growing Paulownia fortunei (Seem.) Hemsl.

Jorge Rencoret, Antonio Pereira, Gisela Marques, José Carlos del Río, Ángel T. Martínez, Ana Gutiérrez

Page range: 45-54

Abstract

It was demonstrated for the first time that a laccase-based enzymatic pretreatment is able to delignify fast-growing paulownia species. The treatment was performed with a commercial low-redox potential laccase isolated from Myceliophthora thermophila (Apinis) Oorschot and methyl syringate (MeS) as a natural phenolic mediator. Up to 24% lignin removal was attained by the laccase-MeS treatment (L/MeS), followed by alkaline peroxide extraction in a multistage sequence. The reduction in lignin content was accompanied by a significant improvement in the subsequent enzymatic saccharification, with increases of up to 38% glucose and 34% xylose yields. The structural modifications of the lignin were analyzed in situ by two dimensional-nuclear magnetic resonance (2D-NMR) spectroscopy. A considerable removal of guaiacyl and syringyl lignin units with respect to the carbohydrate signals was visible as well as the cleavage of β- O -4′, β-5′ and β-β′ linkages leading to elevated amounts of C α -oxidized guaiacyl and syringyl units. The presence of oxidized lignin compounds in the filtrates of the enzymatic treatments – such as vanillin, vanillic acid, syringaldehyde and syringic acid – conclusively demonstrates the ability of L/MeS treatment to oxidize and depolymerize the lignin in paulownia wood.

November 8, 2018

Organosolv pretreated beech wood as a substrate for acetone butanol ethanol extractive fermentation

Helena González-Peñas, Thelmo A. Lú-Chau, Nicolás Botana, María Teresa Moreira, Juan M. Lema, Gemma Eibes

Page range: 55-64

Abstract

Acetone-butanol-ethanol (ABE) fermentation has a high potential for industrial application in lignocellulose-based biorefinery. Nevertheless, strong end-product inhibition is a severe limitation of this process, which can be partially solved by in situ product recovery techniques, such as extractive fermentation. In this work, the hydrolyzed cellulose from organosolv pre-treated beech wood ( Fagus sylvatica L.) was fermented by Clostridium beijerinckii CECT 508 and compared with synthetic P2 medium in conventional and extractive fermentation processes. The conventional control fermentation yielded 9.12 g l −1 of ABE with C. beijerinckii CECT 508, while ABE overproduction of 40% was observed with cellulose hydrolysate as a substrate. After extractive batch fermentation based on 2-butyl-1-octanol as extractant, the final ABE titer was doubled in the P2 control medium over the conventional batch, with respective increases of 50, 190, and 140% for butanol (B), acetone (A) and ethanol (E). In the case of ABE as a hydrolysate medium, the total production increased by 10% with liquid extraction, while mainly B was responsible for this improvement. The total productivity was nevertheless gradually decreased in extractive fermentation, with a significantly slower production rate and the microbial growth compared to conventional fermentation. Moreover, solvent production and sugar consumption stopped, although the aqueous B concentration was below the inhibition threshold. The mid-term toxicity of the extraction solvent 2-butyl-1-octanol seems responsible for these results and this issue should be considered in future research.

December 13, 2018

Fine-fibrous cellulose II aerogels of high specific surface from pulp solutions in TBAF·H₂O/DMSO

Christian B. Schimper, Paul Pachschwoell, Martin Wendland, Ena Smid, Marie-Alexandra Neouze, Jean-Marie Nedelec, Ute Henniges, Thomas Rosenau, Falk Liebner

Page range: 65-81

Abstract

Lightweight cellulose II aerogels featuring densities of about 40–70 mg cm −3 were prepared from 1 to 3% solutions of different pulps in hot (60°C) tetra-n-butylammonium fluoride (TBAF)·H 2 O/dimethyl sulfoxide (DMSO) by (i) the coagulation of cellulose with EtOH to afford self-standing, transparent and homogeneous gels, (ii) gel ripening and washing, (iii) solvent exchange and (iv) supercritical carbon dioxide (scCO 2 ) drying. Size exclusion chromatography (SEC) analyses confirmed that the chemical integrity of cellulose is largely preserved at short dissolution times. Dissolution of more than 2% of cellulose at a sufficiently low viscosity for solution, casting was achieved after the water content of TBAF was reduced to a value equaling that of the monohydrate. Intriguingly, the obtained aerogels featured higher specific surfaces (≤470 m 2 g −1 ) than comparable materials prepared from other cellulose solvents. This is due to the particular morphology of TBAF aerogels, which is supposedly formed by spinodal decomposition of the cellulose/solvent mixture upon exposure to the cellulose antisolvent. As a result, largely homogeneous three-dimensional (3D) networks of agglomerated cellulose spheres were formed, which simultaneously acted as supporting scaffolds for interconnected micron-size voids. As cellulose spheres are composed of very small interwoven nanofibers, TBAF-derived aerogels contain a high portion of micropores and small amounts of mesopores, too.

October 17, 2018

Oil-absorbing porous cellulosic material from sized wood pulp fines

Jérôme Colson, Hassan Amer, Falk Liebner, Wolfgang Gindl-Altmutter

Page range: 83-92

Abstract

Fine fibres (fines) occur at various stages of the papermaking process. The high specific surface of fines may be of special interest in applications beyond papermaking. In the present study, foamy water suspensions of fines were freeze-dried, and in this way their porous structure was maintained. The density and porosity of these foams could be governed by varying the water content of the suspensions. The obtained matrices were highly hydrophobic because of the sizing applied during the papermaking process. Consequently, a high oil sorption capacity of the fines was observed. Up to a porosity of 98%, more than 80% of the overall volume of the foam-like material could be soaked with liquid. At higher porosities, the absorbed volume decreased. Mechanical reinforcement of the foams with poly(methyl methacrylate) (PMMA) as accomplished by dip-coating had no negative impact on the sorption behaviour. However, the performance of reinforced samples suffered from strong shrinkage upon drying, especially for high porosity matrices.

October 17, 2018

Novel protein-repellent and antimicrobial polysaccharide multilayer thin films

Matea Korica, Lidija Fras Zemljič, Matej Bračič, Rupert Kargl, Stefan Spirk, David Reishofer, Katarina Mihajlovski, Mirjana Kostić

Page range: 93-103

Abstract

Nanostructured and bio-active polysaccharide-based thin films were manufactured by means of subsequent spin-coated deposition of a regenerated cellulose (RC) layer and a 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) oxidised cellulose nanofibril (TOCN) layer. The bio-activity of the bilayer was achieved by addition of chitosan (CS). The chitosan was either mixed with the TOCN (TOCN+CS) and deposited on the RC layer by spin-coating, or deposited on the RC and TOCN bilayer by pumping its aqueous solution with various pH over the surface of the bilayer. The water content of the thin films and the CS interactions with the bilayer during deposition were studied in situ by means of a quartz crystal microbalance with dissipation (QCM-D). The pH dependent charging behaviour of the TOCN, TOCN+CS and CS dispersions was evaluated by pH-potentiometric titrations. The surface morphology of the thin films was characterised by atomic force microscopy (AFM). The bio-activity of the thin films was evaluated by studying their protein-repellent properties in situ with a continuous flow of bovine serum albumin (BSA) by means of QCM-D and by evaluating their antibacterial properties in vitro against Staphylococcus aureus and Escherichia coli . These polysaccharide-based thin films are high value-added products because of their multifunctionality, high water absorbance capacity, protein-repellence and antimicrobial activity, and have the potential for medical application as a wound dressing material.

October 17, 2018

Environmental sustainability assessment of HMF and FDCA production from lignocellulosic biomass through life cycle assessment (LCA)

Sara Bello, Iana Salim, Pedro Méndez-Trelles, Eva Rodil, Gumersindo Feijoo, Maria Teresa Moreira

Page range: 105-115

Abstract

2,5-Furandicarboxylic acid (FDCA) and 5-hydroxymethylfurfural (HMF) are top biomass-based platform chemicals with promising potential and an essential part of the future of green chemistry. HMF can be obtained mainly from fructose or glucose. Lignocellulosic glucose has a high production potential from not edible biomass. In the present paper life cycle assessment (LCA) was performed aiming at a better understanding of the environmental performance of the production of FDCA and HMF from lignocellulosic feedstock. Two case studies from the literature were modeled to obtain the life cycle inventory data. The production routes to FDCA comprise seven different process sections: hydrolysis, HMF synthesis, HMF recovery, FDCA synthesis, FDCA flash separation, FDCA purification and HMF boiler. By means of the LCA methodology, solvents such as dimethyl sulfoxide (DMSO) and dichloromethane (DCM), together with the energy demand, were found to be clear critical points in the process. Two scenarios were in focus: Scenario 1 considered the purification of FDCA through crystallization, whereas in Scenario 2 purification was performed through distillation.

Review

December 8, 2018

Lignin-based foams as insulation materials: a review

Vebi Mimini, Vasken Kabrelian, Karin Fackler, Hubert Hettegger, Antje Potthast, Thomas Rosenau

Page range: 117-130

Abstract

The bulk use of renewable polymers is currently largely limited to cellulose and, less significantly, hemicelluloses. Technical lignins are only applied in novel materials to a rather limited extent, although bulk lignin utilization is a worldwide research object. Native lignins, which belong to the second or third most abundant biopolymers of terrestrial plants, are mostly used in the form of technical lignins from wood pulping processes; they are employed in low-performance sectors or simply burnt for the generation of energy. Technical lignins are available in huge quantities and have a large application potential, mainly in areas where their aromatic nature is of relevance. This review presents the state of the art of foamed lignin-based polymers (lignofoams) as high-performance insulation materials. In the focus of this presentation are the fundamental foaming principles and influential agents that have an improvement potential concerning the matrix interactions between technical lignins (including lignosulfonates) and a copolymer in foam composites. The different approaches for foam preparation are critically compared. In general, the reviewed papers disclose that the lignin part in foams should be less than 37%. There are significant difficulties to improve the properties of lignofoams, and thus intensive research is needed to find better formulations and new technologies.

About this journal

Objective
Holzforschung (HF) is an international scholarly journal that publishes cutting-edge research on the biology, chemistry, physics and technology of wood and wood components. High quality papers about biotechnology and tree genetics are also welcome. Rated year after year as one of the top scientific journals in the category of Pulp and Paper (ISI Journal Citation Index), Holzforschung represents innovative, high quality basic and applied research. The German title reflects the journal's origins in a long scientific tradition, but all articles are published in English to stimulate and promote cooperation between experts all over the world. Ahead-of-print publishing ensures fastest possible knowledge transfer.

Topics

Biology, chemistry, physics and technology of wood and wood components
Biotechnology and tree genetics

Article formats
Original articles, Reviews, Short notes

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Volume 73 Issue 1 - Special Issue: Advances in biorefinery research \ Issue Editor: Thomas Rosenau

Issue of Holzforschung

Frontmatter

Advances in biorefinery research

Techno-economic feasibility of bioethanol production via biorefinery of olive tree prunings (OTP): optimization of the pretreatment stage

Abstract

Designing an olive tree pruning biorefinery for the production of bioethanol, xylitol and antioxidants: a techno-economic assessment

Abstract

Structural characteristics of lignin in pruning residues of olive tree (Olea europaea L.)

Abstract

Production of xylooligosaccharides and cellulosic ethanol from steam-exploded barley straw

Abstract

A commercial laccase-mediator system to delignify and improve saccharification of the fast-growing Paulownia fortunei (Seem.) Hemsl.

Abstract

Organosolv pretreated beech wood as a substrate for acetone butanol ethanol extractive fermentation

Abstract

Fine-fibrous cellulose II aerogels of high specific surface from pulp solutions in TBAF·H2O/DMSO

Abstract

Oil-absorbing porous cellulosic material from sized wood pulp fines

Abstract

Novel protein-repellent and antimicrobial polysaccharide multilayer thin films

Abstract

Environmental sustainability assessment of HMF and FDCA production from lignocellulosic biomass through life cycle assessment (LCA)

Abstract

Lignin-based foams as insulation materials: a review

Abstract

Fine-fibrous cellulose II aerogels of high specific surface from pulp solutions in TBAF·H₂O/DMSO