Name: ultrafast lignin extraction from unusual mediterranean lignocellulosic residues
Uploaded: 2021-03-09T12:30:00
Description: Watch this Scientific Journal Video about Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues at JoVE.com

MK and TB thanks Haitham Ayeb for statistical analyses and figure preparation, Walloon Region (European Regional Development-VERDIR) and Minister of Higher Education and Scientific Research (Taoufik Bettaieb) for funding.

1. Preparation of biomasses
<ol>
	<li>Biomass drying
	<ol>
		<li>Place the Posidonia leaves and aegagropile balls (Posidonia oceanica), harvested from Mediterranean beaches, in an oven at 40 &#176;C for 72 h.</li>
		<li>Place the almond shells (Prunus dulcis), generated from food industries, and olive pomace (Olea europaea L.), obtained from olive oil mills, in an oven at 40 &#176;C for 72 h.</li>
		<li>Place the pinecones (Pinus halepensis), collected from a forest, and alfa leaves ...

<ol>
	<li>Kammoun, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrothermal+dehydration+of+monosaccharides+promoted+by+seawater+fundamentals+on+the+catalytic+role+of+inorganic+salts.">Hydrothermal dehydration of monosaccharides promoted by seawater fundamentals on the catalytic role of inorganic salts.</a> Frontiers in Chemistry. 7, 132 (2019).</li><li>Kammoun, M., Ayeb, H., Bettaieb, T., Richel, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+characterisation+and+technical+assessment+of+agri-food+residues,+marine+matrices,+and+wild+grasses+in+the+South+Mediterranean+area:+A+considerable+inflow+for+biorefineries.">Chemical characterisation and technical assessment of agri-food residues, marine matrices, and wild grasses in the South Mediterranean area: A considerable inflow for biorefineries.</a> Waste Management. 118, 247-257 (2020).</li><li>Zhang, C. W., Xia, S. Q., Ma, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+pretreatment+of+lignocellulosic+biomass+using+deep+eutectic+solvents.">Facile pretreatment of lignocellulosic biomass using deep eutectic solvents.</a> Bioresource Technology. 219, 1-5 (2016).</li><li>Mora-Pale, M., Meli, L., Doherty, T. V., Linhardt, R. J., Dordick, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room+temperature+ionic+liquids+as+emerging+solvents+for+the+pretreatment+of+lignocellulosic+biomass.">Room temperature ionic liquids as emerging solvents for the pretreatment of lignocellulosic biomass.</a> Biotechnology and Bioengineering. 108 (6), 1229-1245 (2011).</li><li>Chen, Z., Wan, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+fractionation+of+lignocellulosic+biomass+by+microwave-assisted+deep+eutectic+solvent+pretreatment.">Ultrafast fractionation of lignocellulosic biomass by microwave-assisted deep eutectic solvent pretreatment.</a> Bioresource Technologie. 250, 532-537 (2018).</li><li>Francisco, M., Van Den Bruinhorst, A., Kroon, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+natural+and+renewable+low+transition+temperature+mixtures+(+LTTMs+):+screening+as+solvents+for+lignocellulosic+biomass+processing.">New natural and renewable low transition temperature mixtures ( LTTMs ): screening as solvents for lignocellulosic biomass processing.</a> Green Chemistry. 14 (8), 2153-2157 (2012).</li><li>Liu, Y. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+cleavage+of+lignin+-+carbohydrate+complexes+and+ultrafast+extraction+of+lignin+oligomers+from+wood+biomass+by+microwave-assisted+treatment+with+deep+eutectic+solvent.">Efficient cleavage of lignin - carbohydrate complexes and ultrafast extraction of lignin oligomers from wood biomass by microwave-assisted treatment with deep eutectic solvent.</a> Chem sus chem. 10, 1692-1700 (2017).</li><li>Xu, G. C., Ding, J. C., Han, R. Z., Dong, J. J., Ni, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancing+cellulose+accessibility+of+corn+stover+by+deep+eutectic+solvent+pretreatment+for+butanol+fermentation.">Enhancing cellulose accessibility of corn stover by deep eutectic solvent pretreatment for butanol fermentation.</a> Bioresource Technologie. 203, 364-369 (2016).</li><li>Jablonsk&#253;, M., Andrea, &. #. 3. 5. 2. ;., Kamensk&#225;, L., Vr&#353;ka, M., &#352;ima, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deep+eutectic+solvents+fractionation+of+wheat+straw+deep+eutectic+solvents+fractionation+of+wheat+straw.">Deep eutectic solvents fractionation of wheat straw deep eutectic solvents fractionation of wheat straw.</a> Bioresources. 10 (4), 8039-8047 (2015).</li><li>Shen, X. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+fractionation+of+lignocelluloses+by+biomass-derived+deep+eutectic+solvent+(DES)+pretreatment+for+cellulose+enzymatic+hydrolysis+and+lignin+valorization.">Facile fractionation of lignocelluloses by biomass-derived deep eutectic solvent (DES) pretreatment for cellulose enzymatic hydrolysis and lignin valorization.</a> Green Chemistry. 21, 275-283 (2019).</li><li>Alvarez-Vasco, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unique+low-molecular-weight+lignin+with+high+purity+extracted+from+wood+by+deep+eutectic+solvents+(DES):+a+source+of+lignin+for+valorization.">Unique low-molecular-weight lignin with high purity extracted from wood by deep eutectic solvents (DES): a source of lignin for valorization.</a> Green Chemistry. 18, 5133-5141 (2016).</li><li>Banu, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+on+biopolymer+production+via+lignin+valorization.">A review on biopolymer production via lignin valorization.</a> Bioresource Technologie. 290, 121790 (2019).</li><li>Gordobil, O., Olaizola, P., Banales, J. M., Labidi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lignins+from+agroindustrial+by-products+as+natural+ingredients+for+cosmetics+chemical+structure+and+in+vitro+sunscreen+and+cytotoxic+activities.">Lignins from agroindustrial by-products as natural ingredients for cosmetics chemical structure and in vitro sunscreen and cytotoxic activities.</a> Molecules. 25 (5), 1131 (2020).</li><li>Lee, C. S., Thu Tran, T. M., Weon Choi, J., Won, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lignin+for+white+natural+sunscreens.">Lignin for white natural sunscreens.</a> International Journal of Biological Macromolecules. 122, 549-554 (2019).</li><li>Widsten, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lignin-based+sunscreens-state-of-the-art,+prospects+and+challenges.">Lignin-based sunscreens-state-of-the-art, prospects and challenges.</a> Cosmetics. 7, 85 (2020).</li><li>Qian, Y., Qiu, X., Zhu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lignin:+a+nature-inspired+sun+blocker+for+broad-spectrum+sunscreens.">Lignin: a nature-inspired sun blocker for broad-spectrum sunscreens.</a> Royal Society of Chemistry. 17, 320-324 (2015).</li><li>Zijlstra, D. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+lignin+with+high+&#946;-O-4+content+by+mild+ethanol+extraction+and+its+effect+on+the+depolymerization+yield.">Extraction of lignin with high &#946;-O-4 content by mild ethanol extraction and its effect on the depolymerization yield.</a> Journal of Visualized Experiments. (143), e58575 (2019).</li></ol>

This study had many objectives; the first of which was to prepare and use low-cost green solvents with the characteristics of both ionic liquids and organic solvents. The second objective was to fractionate the biomass and extract lignin in a single step, without requiring preliminary steps such as the extraction of extractables using Soxhlet or hemicellulose using alkaline solvents, basic, or thermophysical techniques. The third aim was to recover lignin by simple filtration after the treatment, without adjustment of pH...

Sustainable biorefinery processes integrate biomass processing, its fractionation into molecules of interest, and their conversion to value-added products1. In second-generation biorefining, pretreatment is considered essential for fractionating biomass into its main components2. Traditional pretreatment methods utilizing chemical, physical, or biological strategies have been widely applied3. However, such pretreatment is considered the most expensive step in biorefining and has other disadvantages such as long processing time, high heat and power consumption, and solvent impurities4. Recently, DESs, whose properties are similar to those of ionic liquids3, have emerged as green solvents owing to advantages such as biodegradability, environmental-friendliness, ease of synthesis, and recovery after treatment5.
DESs are mixtures of at least one HBD, such as lactic acid, malic acid, or oxalic acid, and a hydrogen-bond acceptor (HBA) such as betaine or choline chloride (ChCl)6. HBA-HBD interactions enable a catalytic mechanism that permits cleavage of chemical bonds, causing biomass fractionation and lignin separation. Many researchers have reported the DES-based pretreatment of lignocellulosic feedstocks such as ChCl-glycerol on corn&#39;s cob and stover7,8, ChCl-urea, and ChCl-oxalic acid on wheat straw9, ChCl-lactic acid on Eucalyptus sawdust10, and ChCl-acetic acid11 and ChCl-ethylene glycol on wood11. To improve DES efficiency, the pretreatment should be combined with microwave treatment to accelerate biomass fractionation5. Many researchers have reported such a combined pretreatment (DES and microwave) of wood8 and of corn stover, switchgrass, and Miscanthus5, which provides new insight into the capacity of DESs for lignocellulosic fractionation and lignin extraction in one easy step over a short period.
Lignin is a phenolic macromolecule valorized as a raw material for the production of biopolymers and presents an alternative for the production of chemicals such as aromatic monomers and oligomers12. In addition, lignin has antioxidant and ultraviolet absorption activities13. Several studies have reported lignin applications in cosmetic products14,15. Its integration in commercial sunscreen products has improved the sun protection factor (SPF) of the product from SPF 15 to SPF 30 with the addition of only 2 wt % lignin and up to SPF 50 with the addition of 10 wt % lignin16. This paper describes an ultrafast approach for lignin-carbohydrate cleavage, assisted by combined DES-microwave pretreatment of Mediterranean biomasses. These biomasses consist of agri-food byproducts, particularly olive pomace and almond shells. Other biomasses that were investigated were those of a marine origin (Posidonia leaves and aegagropile) and those originating from a forest (pinecones and wild grasses). The focus of this study was to test low-cost green solvents to evaluate the effects of this combined pretreatment on feedstock fractionation, to investigate its influence on lignin purity and yield, and to study its effects on the molecular weights and chemical functional groups in the extracted lignin.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>HPLC Gel Permeation Chromatography</td>
			<td>Agilent 1200 series</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1 methylimadazole</td>
			<td>Acros organics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2-deoxy-D-glucose (internal standard)</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic anhydride</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Adjustables pipettors</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Alkali</td>
			<td></td>
			<td></td>
			<td>alkali-extracted lignin</td>
		</tr>
		<tr>
			<td>Arabinose (99%)</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Autoclave</td>
			<td>CERTO CLAV (Model CV-22-VAC-Pro)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Water Bath at 70 &#176;C</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bromocresol</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Catalyst</td>
			<td>CTQ (coded A22) (1.5 g K2SO4 + 0.045 g CuSO4.5 H2O + 0.045 g TiO2)</td>
			<td>Merck</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifugation container</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>BECKMAN COULTER</td>
			<td>Avanti J-E centrifuge</td>
			<td></td>
		</tr>
		<tr>
			<td>Ceramic crucibles</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Choline chloride 99%</td>
			<td>Acros organics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Column</td>
			<td>Agilent PLGel Mixed C (alpha 3,000 (4.6 &#215; 250 mm, 5 &#181;m) preceded by a guard column (TSK gel alpha guard column 4.6 mm &#215; 50 mm, 5 &#181;m)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Column</td>
			<td>HP1-methylsisoxane (30 m, 0.32 mm, 0.25 mm)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Crucible porosity N&#176;4 ( Filtering crucible)</td>
			<td>Shott Duran Germany</td>
			<td>boro 3.3</td>
			<td></td>
		</tr>
		<tr>
			<td>Deonized water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dessicator</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylformamide</td>
			<td>VWR BDH Chemicals</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylsulfoxide</td>
			<td>Acros organics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Erlenmeyer flask</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Merck (Darmstadtt, Germany)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Filtering crucibles, procelain</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Filtration flasks</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fourrier Transformed Inra- Red</td>
			<td>Vertex 70 Bruker apparatus 
			equipped with an attenuated total reflectance (ATR) module. 
			Spectra were recorded in the 4,000&#8211;400 cm&#8722;1 range with 32 scans 
			at a resolution of 4.0 cm&#8722;1</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Galactose (98%</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gaz Chromatography</td>
			<td>Agilent (7890 series)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass bottle 100 mL</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass tubes ( borosilicate) with teflon caps 10 mL</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose (98%</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Golves</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Graduated cylinder 50 mL /100 mL</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>H2SO4 Titrisol (0.1 N)</td>
			<td>Merck (Darmstadtt, Germany)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>H2SO4 (95-98%)</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td>BUCHI R-114)</td>
			<td></td>
		</tr>
		<tr>
			<td>Hummer cutter equiped with 1 mm and 0.5 mm sieve</td>
			<td>Mill Ttecator (Sweden)</td>
			<td>Cyclotec 1093</td>
			<td></td>
		</tr>
		<tr>
			<td>Indulin</td>
			<td></td>
			<td></td>
			<td>Raw lignin control</td>
		</tr>
		<tr>
			<td>Kjeldahl distiller</td>
			<td>Kjeltec 2300 (Foss)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kjeldahl tube</td>
			<td>FOSS</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kjeldhal rack</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kjeldhal digester</td>
			<td>Kjeltec 2300 (Foss)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kjeldhal suction system</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lab Chem station Software</td>
			<td></td>
			<td></td>
			<td>GC data analysis</td>
		</tr>
		<tr>
			<td>Lactic acid</td>
			<td>Merck (Darmstadtt, Germany)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lithium chloride LiCl</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mannose (98%)</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Methyl red</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave</td>
			<td>START SYNTH MILESTONE Microwave laboratory system</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave temperature probe</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave container</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Muffle Furnace</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Merck (Darmstadtt, Germany)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrogen free- paper</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Opus</td>
			<td></td>
			<td></td>
			<td>spectroscopy software</td>
		</tr>
		<tr>
			<td>Oven</td>
			<td>GmbH Memmert SNB100</td>
			<td>Memmert SNB100</td>
			<td></td>
		</tr>
		<tr>
			<td>Oxalic acid</td>
			<td>VWR BDH Chemicals</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>P 1000</td>
			<td></td>
			<td></td>
			<td>Soda-processed lignin</td>
		</tr>
		<tr>
			<td>pH paper</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>precision balance</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Infrared spectroscopy</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Quatz cuvette</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rhamnose (98%)</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rotary vacuum evaporator</td>
			<td>Bucher</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Round-bottom flask 500 mL</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>sodium borohydride NaBH4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Schott bottle</td>
			<td></td>
			<td></td>
			<td>glass bottle</td>
		</tr>
		<tr>
			<td>Sovirel tubes</td>
			<td>sovirel</td>
			<td></td>
			<td>Borosilicate glass tubes</td>
		</tr>
		<tr>
			<td>Spatule</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Special tube</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Spectophotometer</td>
			<td>UV-1800 Shimadzu</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilization indicator tape</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stir bar in teflon</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stirring plate</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Syringes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium borohydride</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Titrisol</td>
			<td>Merck</td>
			<td>Merck 109984</td>
			<td>0.1 N H2SO4</td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>VWR BDH Chemicals</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>VolumetriC flask 2.5 L /5 L</td>
			<td>Bucher</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Xylose (98%)</td>
			<td>Sigma Aldrich (St. Louis, USA)</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

ultrafast lignin extraction from unusual mediterranean lignocellulosic residues

Pretreatment is still the most expensive step in lignocellulosic biorefinery processes. It must be made cost-effective by minimizing chemical requirements as well as power and heat consumption and by using environment-friendly solvents. Deep eutectic solvents (DESs) are key, green, and low-cost solvents in sustainable biorefineries. They are transparent mixtures characterized by low freezing points resulting from at least one hydrogen bond donor and one hydrogen bond acceptor. Although DESs are promising solvents, it is necessary to combine them with an economic heating technology, such as microwave irradiation, for competitive profitability. Microwave irradiation is a promising strategy to shorten the heating time and boost fractionation because it can rapidly attain the appropriate temperature. The aim of this study was to develop a one-step, rapid method for biomass fractionation and lignin extraction using a low-cost and biodegradable solvent. 
In this study, a microwave-assisted DES pretreatment was conducted for 60 s at 800 W, using three kinds of DESs. The DES mixtures were facilely prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBDs): a monocarboxylic acid (lactic acid), a dicarboxylic acid (oxalic acid), and urea. This pretreatment was used for biomass fractionation and lignin recovery from marine residues (Posidonia leaves and aegagropile), agri-food byproducts (almond shells and olive pomace), forest residues (pinecones), and perennial lignocellulosic grasses (Stipa tenacissima). Further analyses were conducted to determine the yield, purity, and molecular weight distribution of the recovered lignin. In addition, the effect of DESs on the chemical functional groups in the extracted lignin was determined by Fourier-transform infrared (FTIR) spectroscopy. The results indicate that the ChCl-oxalic acid mixture affords the highest lignin purity and the lowest yield. The present study demonstrates that the DES-microwave process is an ultrafast, efficient, and cost-competitive technology for lignocellulosic biomass fractionation.

Figure 2A-C depict the lignin yield of extraction from the six feedstocks, shown in Figure 1A-F, after the combined microwave-DES pretreatment. The results show that the lignin yield obtained with DES1 (ChCl-oxalic acid) (Figure 2A) was lower than the yields obtained with DES2 (ChCl-lactic acid) and DES3 (ChCl-urea) (Figure 2B</...

Watch this Scientific Journal Video about Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues at JoVE.com

Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues

Deep eutectic solvent-based, microwave-assisted pretreatment is a green, fast, and efficient process for lignocellulosic fractionation and high-purity lignin recovery.

Pretreatment is still the most expensive step in lignocellulosic biorefinery processes. It must be made cost-effective by minimizing chemical requirements ...

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