Hot water extraction of inner and outer bark of Norway Spruce (Picea abies)

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1 Hot water extraction of inner and outer bark of Norway Spruce (Picea abies) Jens Krogell COST FP0901 meeting

2 Spruce bark Inner bark (~90 vol-%) and outer bark (~10 vol-%) Huge valuable side stream in wood industry Chemical composition not completely known, differs from wood Known composition of bark better utilisation 2

3 Accelerated Solvent Extraction (ASE) Automated extraction with different times and pressures Sequential extractions with different solvents possible 3

4 Hexane (90 C) Acetone/Water (100 C) Extraction scheme Water (100, 160 C) Spruce bark Pre-extracted bark Bark residue Cellulose Extractives Monomeric sugars Hemicelluloses Monomeric sugars Tannins? Lignin 4

5 Totally dissolved solids (TDS) mg/g bark Gravimetrically determined Hot water extract components ( C) Hydrophilics Lipophilics 0 Inner bark Outer bark 5

6 Hexane (90 C) Acetone/Water (100 C) Water (100, 160 C) Spruce bark Pre-extracted bark Bark residue Cellulose Extractives Hemicelluloses Lignin Acid hydrolysis Monomeric sugars HP-SEC Monomeric sugars Acid methanolysis Klason-lignin determination GC GC GC TMAH-GC-MS 6

7 Extractives Lipophilic and hydrophilic compounds extracted with hexane and acetone/water GC results gives both quantitative and qualitative results Long or short column GC 7

8 Lipophilics 8 Steryl esters Diglycerides Triglycerides Fatty acids Resin acids Sterols Aliphatic alcohols Diterpenoids mg/g Inner bark Long column Outer bark Short column

9 mg/g Long column Hydrophilics Inner bark Outer bark 40 Short column Flavonoids Stilbenes Sugar monomers Steryl esters* Stilbene glucosides Triglycerides* * Components that eluates at the same time as steryl esters and triglycerides

10 Hemicelluloses and monomers Mild depolymerization of hemicelluloses Adding 2 M HCl in methanol to freeze-dried sample and in 105 C for 3 hours cleaves hemicelluloses but not cellulose Samples are further silylated with HMDS and TMCS Good method for uronic acids determination (mild conditions) Gives hemicellulose content in monomeric form Methanolysis can be done on both solid and liquid samples Monomers determined after direct silylation 10

11 Chromatogram of sugar units in bark extract Inner bark, 160 C Std Ara Glc Man Gal Xyl Rha GalA 11

12 mg/ bark Bark water extract Inner bark 160 C, 60 min Total hemicelluloses ~150 mg/g bark Total extracts ~400 mg/g bark Hemicelluloses and pectins Monomers 10 0 Ara Xyl 4-O- MeGlcA GlcA Gal Man Glc Rha GalA 12

13 Cellulose Two step acid hydrolysis 72 % sulfuric acid, 2 hours, room temp Dilute with water, over night, autoclave 125 C 90 min Cleaves cellulose to glucose cellulose content in sample 13

14 Klason-lignin Improved Klason-lignin method (gravimetrically) + TMAH*-GC-MS Py-TMAH-GC-MS milder conditions than py-gc-ms Not all Klason-lignin is lignin, lot of long chained fatty acids probably originated from suberin 32% in inner bark, 45% in outer bark * tetramethylammonium hydroxide Ref: Scwanninger, M., Hinterstoisser, B., 2002, Klason Lignin: Modifications to Improve the Precision of the Standardized Determination, Holzforshung

15 TMAH-GC-MS chromatogram Reference (lignin sample) Unextracted outer bark min

16 Metals by ICP-MS Gives a detailed picture of the amount of inorganic elements in the bark mg/kg bark mg/kg < 10 mg/kg Zn Al Na B Fe 0 Pb Mo Cu Ni Cr Cd Inner bark Outer bark Ca K Mg Mn P S Zn Al Na B Fe Pb Mo Cu Ni Cr Cd 16

17 Inner bark Outer bark Lipophilics Hydrophilics Lipophilics Hydrophilics Monosaccharides "Klason-lignin" Monosaccharides Polysaccharides, extractable (160 C, 60 min) Polysaccharides nonextractable Cellulose Polysaccharides, nonextractable Polysaccharides, extractable (160 C, 60 min) "Klason-lignin" Cellulose Silylation + GC Methanolysis + silylation + GC Hydrolysis + silylation + GC Klason method + TMAH-GC-MS 17

18 Conclusions 15% of total weight of bark is extractable hemicelluloses and pectins 91 % of dried inner bark characterized 86 % of dried outer bark characterized Important to get as much knowledge as possible of bark (valuable side chain) We need good extraction and analytical methods 18

19 The future Purify the bark hemicelluloses (arabinans?) Improve the extraction More work needed on industrial bark Develop existing and new analytical methods 19

20 Applications Platform chemicals Animal feed Specialty sugars Bioethanol? 20