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 ...

The aim of our protocol is to fractionate the biomass and extract lignin in a single step. Using this method, lignin can be recovered by simple filtration after the treatment without adjustment of pH, but simply by adding distilled water. The focus of this study is to evaluate the effect of this combined treatment of feedstock fractionation, its influence on lignin purity and yield, and its effect on the molecular weights and chemical functional groups in the extracted lignin.Deep eutectic solution microwave process is an ultra fast, efficient, and cost competitive technology for lignocellulosic biomass fractionation and lignin recovery with high purity. Prepare the deep eutectic solution in a 500 milliliter round bottom flask as described in the text manuscript. Then place five grams of feedstock, 50 milliliters of deep eutectic solution, and a stirring bar in a microwave in a closed polytetrafluoroethylene reactor.Close the microwave container with an appropriate cap and attach a temperature cap. Place it on the edge of the turntable, ensuring that it is constantly agitated and run the microwave for one minute. Using suitable gloves, take the container out of the microwave and let the mixture cool.Prepare a homogenous anti-solvent solution and add 50 milliliters of this solution to the treated feedstock. Centrifuge the mixture for five minutes at 3, 000 times G.Filter the supernatant using a glass filter crucible. Collect the remaining cellulose residue and wash it by adding 25 milliliters of anti-solvent solution and centrifuging.Add the filtered lignin-rich fraction and the filtered washes to a 500 milliliter round bottom flask. Evaporate the ethanol using a rotary evaporator at 50 degrees Celsius and 110 millibar. Then add 150 milliliters of deionized water to the concentrated liquor.Precipitate the lignin by centrifugation. Collect lignin as a pellet and wash it four times with 25 milliliters of distilled water. Then lyophilize the lignin or dry it in an oven at 40 degrees Celsius.Place the filter crucible in a muffle furnace at 550 degrees Celsius for four hours. When the oven cools to 150 degrees Celsius, remove the crucible and place it in a desiccator to cool. Then weigh it.Add approximately 30 milligrams of lignin into a borosilicate glass tube. Then add one milliliter of 72%sulfuric to the sample and place it in a 30 degrees Celsius bath for 60 minutes. Remove the sample and transfer it to a 100 milliliter glass bottle.Then add 28 milliliters of distilled water to dilute the acid to a concentration of 4%Put the glass bottle in an autoclave at 121 degrees Celsius for 60 minutes. Then remove the bottle from the autoclave and allow it to cool. To analyze acid insoluble lignin, filter the hydrolysate using a crucible under vacuum and collect the remaining solids in the glass bottle with deionized water.Dry the crucible containing the solids by placing it in an oven at 105 degrees Celsius for 16 hours. Then cool it in a desiccator and weigh the sample. Place the crucible in a muffle furnace at 550 degrees Celsius for four hours.Weigh the sample after drying it in a desiccator. For analysis of acid soluble lignin, measure the absorbance of the hydrolysate filtrate with a spectrophotometer at 205 nanometers using quartz cuvettes. To analyze chemical function of the extracted lignin, process the background single channel without sample.Then adjust the parameters and place one milligram of the sample on the crystal. Press sample single channel and process the obtained spectra. To determine the molecular weight of the extracted lignin, dissolve three milligrams of the lignin sample in three milliliters of DMF with 0.5%lithium chloride.Put the dissolved lignin in a vial and install the column proceeded by a guard column. Inject the sample into a high-performance liquid chromatography ultraviolet system. After analyzing the data, calculate the molecular weight of the extracted lignin as described in the text manuscript.Weigh a 50 milligram sample of lignin in a borosilicate glass tube and add three milliliters of one molar sulfuric acid. Then heat the mixture for three hours at 100 degrees Celsius and cool it. Add one milliliter of 15 molar ammonium hydroxide and check the pH to ensure that it is neutral or alkaline.Add one milliliter of 2-deoxyglucose to each sample as internal standard. Then add 400 microliters of this solution into special tubes containing 400 microliters of mixed solution. Add two milliliters of sodium borohydride dimethyl sulfoxide solution.Close the tubes and incubate for 90 minutes at 40 degrees Celsius in a water bath. Remove the tubes from the water bath and add 0.6 milliliters of glacial acetic acid, 0.4 milliliters of 1-methylimidazole and approximately four milliliters of acetic anhydride. After 15 minutes, add 10 milliliters of distilled water.Cool.And add approximately three milliliters of dichloromethane. After two hours, collect approximately one milliliter of the lower organic phase and inject it into a gas chromatograph equipped with a flame ionization detector capillary column. The lignin yield obtained with deep eutectic solution one oxalic acid was lower than the yields obtained with deep eutectic solution two lactic acid and deep eutectic solution three urea.Lignin purity exceeded 70%for the three pre-treatments of the biomasses, except for deep eutectic solution three urea pretreatment of alpha leaves, Aegagropila, and almond shells, which gave a lignin purity of 65%The highest lignin purity exceeded 90%It was obtained with the deep eutectic solution one treatment. Lignin purity and yield data were subjected to principal component analysis, which showed the deep eutectic solution one treatment to be positively correlated with lignin purity and confirmed it to be the purest lignin with the lowest yield. The sugar content in lignin extracted using deep eutectic solution three was the highest and followed by that obtained from solutions two and one.Similarly, the nitrogen content of deep eutectic solution one lignin extract was lower than that obtained from solutions two and three. The type of sugars in the extracted lignin were also characterized, depicting D-xylose and D-glucose to be the most abundant monosaccharides. The chemical functional groups present in the extracted lignans were investigated by FTIR spectroscopy.Infrared spectra of the different lignans between 3, 500 and 800 reciprocal centimeters are presented here. The spectra of lignin extracted with deep eutectic solutions one and two show the stretching vibrations of unconjugated and conjugated carbonyl groups, which were absent in the three commercial lignans:raw, soda processed, and alkali extracted lignans. The carboxylic acid signal, C double bond O, indicates possibility of the conjugation of some lignin functions with acids during its extraction and solubilization with the microwave-assisted deep eutectic solvent treatment.These results demonstrate the possibility of extracting value-added lignin of high purity from Mediterranean biomasses, which is presently undervalued and can help determine the optimal deep eutectic solvent while ensuring the purity of lignin.

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