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1 Supporting information for: Quantification of lignin and its structural features in plant biomass using 13 C lignin as internal standard for pyrolysis-gc-sim-ms Gijs van Erven a, Ries de Visser b, Donny W.H. Merkx a,c, Willem Strolenberg a, Peter de Gijsel a, Harry Gruppen a, Mirjam A. Kabel a, * a Wageningen University & Research, Laboratory of Food Chemistry, Bornse Weilanden 9, 6708 WG, Wageningen, The Netherlands. b IsoLife bv, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands. c Unilever R&D Vlaardingen, livier van Noortlaan 120, 3133 AT, Vlaardingen, The Netherlands *Corresponding author. Tel: address: mirjam.kabel@wur.nl Supporting Information contents: page S-2: Detailed experimental procedures for preparation of non-labelled and 13 C-labelled wheat straw and compositional analysis of total biomass and lignin isolates page S-4: HSQC-NMR spectra (Figure S-1) page S-5: Annotated structures by HSQC-NMR (Figure S-2) page S-6: Py-GC/MS pyrograms of 12 C-LIGpure and 13 C-LIGpure (Figure S-3) page S-7: 13 C lignin EI-MS library (Figure S-4) page S-13: Comparison of lignin quantification in poaceous biomass via 12 C lignin external standard and 13 C lignin internal standard based py-gc-sim-ms page S-14: Impact of RRF application on 13 C-IS lignin quantification in poaceous biomass page S-15: Composition of poaceous biomasses analyzed (Table S-1 and S-2) S-1

2 1. Detailed experimental procedures Preparation of non-labelled and 13 C-labelled wheat straw Non-labelled ( 12 C ) and uniformly 13 C-labelled (97 atom % 13 C, 13 C ) spring wheat plants (Triticum aestivum L. cv. Baldus ) (WS) were produced under identical growth conditions in the custom designed, air-tight, highirradiance labelling chambers of the facility ESPAS (Experimental Soil Plant Atmosphere System, IsoLife, Wageningen, The Netherlands). 1 The environmental and atmospheric conditions were fully controlled. Plants were grown hydroponically at a photosynthetic photon flux density (PPFD) of 900 µmol m 2 s 1 (top of plants) at a 16 h day length, a day/night temperature of 24/16 C and RH of 75 %, in a closed atmosphere containing either regular C2 (1.1 atom % 13 C; 12C ) or 98 atom % 13 C2 (C2 labelled with the stable isotope 13 C; from pressurized cylinders, Sigma-Aldrich, St Louis, USA; U- 13 C ) from the seedling stage until fully mature and ripened (Haun, Feeke s and Zadoks scales 16.0, 11.4 and 92, respectively). 2-4 The 13 C abundance of the C2 in the chamber was continuously monitored by analysis both 12 C2 and 13 C2 using Non- Dispersive Infrared (NDIR) throughout the culturing time (IsoLife). Minerals were supplied as Hoagland-type nutrient solutions with micronutrients and iron, maintaining ph between 5 and 6. 5,6 After 14 weeks of culture, plants were harvested. Immediately after removing the plants from the labelling facility, plants were dissected and stems cut to 3-6 cm pieces, weighed, packaged in food-grade PE pouches and stored at -30 C till freeze-drying (lyophilization at 0.6 mbar). The final dried material was stored in a dry place in the dark till analysis. After freezedrying, subsamples were prepared for analysis of atom % 13 C by high-abundance Isotope-ratio Mass Spectrometry (IRMS) (Sigma-Aldrich, St Louis, USA and Stable Isotope Facility, UC- Davis, CA, USA) and were equal to 1.1 at% 13 C and 97.6 at% 13 C for 12 C and 13 C WS, respectively. Two spring wheat plants were used with a total of approximately 80 stalks for the non-labelled as well as 13 C labelled straw. From the total material a randomly selected sample of 3 grams (approx. 4% of total material) was taken for the isolation of the lignins. Compositional analysis of total biomass and lignin isolates Carbohydrate content and composition Carbohydrate content and composition was determined in duplicate as constituent monosaccharides after acid hydrolysis by a modified method reported by Englyst & Cummings. 7 Samples were treated with 72% (w/w) H2S4 for 2 h at 30 C followed by 1 M H2S4 for 4 h at 100 C and diluted (20x) before analysis. Degradation of monosaccharides during hydrolysis was corrected for by including monosaccharide standard mixtures in hydrolysis. Analysis was S-2

3 performed on a High Performance Anion Exchange Chromatography (HPAEC) Dionex ICS system (Thermo Scientific, Synnyvale, CA, USA). The system was equipped with a CarboPac PA-1 column (250 mm x 2 mm ID) in combination with a CarboPac guard column (50 mm x 2 mm ID) with pulsed amperometric detection (PAD) (all Dionex). 10 µl of sample was injected and eluted at a flow rate of 0.4 ml min -1 using a combination of three mobile phases: A) 0.1 M NaH, B) 1 M NaAc in 0.1 M NaH and C) H2. The elution profile used was as follows: 0-35 min isocratic on 100% C; min linearly from 100% A to 40% B; min isocratic on 100% B; min isocratic on 100%A; min isocratic on 100% C. Postcolumn addition of 0.5 M NaH at 0.1 ml min -1 was performed between 0-35 min and min. Protein content Nitrogen content was analyzed in duplicate using the combustion method (DUMAS) on a Flash EA 1112 Nitrogen Analyzer (Thermo Scientific, Synnyvale, CA, USA). Methionine (Acros rganics, Geel, Belgium) was used as calibration standard. A nitrogen to protein conversion factor of 6.25 was used. 8 Ash content Ash content of oven dried samples (40 C, 8 h) was determined gravimetrically after burning samples at 550 C for 16 h. Analyses were performed in triplicate. Lignin content Extrative-free (aceton) wheat straw (WS) and corn stover (CS) and unextracted barley straw (BS) and sugarcane bagasse (SCB) were milled in a Mixer Mill MM 400 (Retsch, Haan, Germany) and passed through a 0.25 mm sieve. Water unextractable solids (WUS) were obtained by extracting as explained in the section Isolation of lignin from 12 C and 13 C wheat straw. Final residues were freeze-dried. Acid insoluble (Klason) lignin corrected for ash and protein and acid soluble lignin contents of biomass WUS samples were determined in duplicate according to Jurak et al. 9 Protein content of acid insoluble residues was determined as described above. S-3

4 2. HSQC NMR spectra Figure S-1 Representative HSQC-NMR spectra of 12 C-LIGpure (A,B) and 13 C-LIGpure (C, D). A, C: aliphatic (δ C/δ H 50-90/ ) region, B,D: aromatic/unsaturated (δ C/δ H / ) region. Structures of annotated correlation peaks are presented in Figure S5. Annotated structures D and F are not visible at this zoom level. Note that in the aromatic region of the 13 C spectrum (D) significant 13 C- 13 C coupling is observed. S-4

5 3. Structures interunit linkages R H H H 4' CH 3 H 4' CH 3 4' CH 3 H 5' CH 3 CH 3 CH 3 CH 3 A A' A ox CH3 B CH 3 5' 5'' CH 3 ' ' ' 4' 4'' H 3 C CH 3 H H ' 1' ' ' H Ar CH 3 CH 3 CH 3 C D F CH 3 H 2' 3' 4' H ' 6' 5' CH CH 3 CH 3 H T I H pca H FA H H H CH 3 H 3 C CH 3 H G S Figure S-2 Structures annotated by HSQC-NMR. A: --4 alkyl-aryl ether; A : --4 alkyl-aryl ether -acetylated; Aox: --4 alkyl-aryl ether C -oxidized; B: phenylcoumaran; C: resinol; D: dibenzodioxocins; F: spirodienone; I: cinnamyl alcohol end-group; pca: p-coumarate; FA: ferulate; T: tricin; H: p-hydroxyphenyl unit; G: guaiacyl unit; S: syringyl unit. Dotted line represents H or CH 3.,-diarylether, and cinammaldehyde end group structures were not detected. S-5

6 4. 12 C-LIGpure and 13 C-LIGpure pyrograms A Relative intensity Relative intensity B Time (min) Figure S-3 Representative py-gc/ms pyrograms (TIC) of 12 C-LIGpure (A) and 13 C-LIGpure (B). Peak annotation according to Table 1 in main article. S-6

7 5. 13 C MS library Figure S-4 EI-MS (70 ev) spectra of 13 C-labelled lignin-derived pyrolysis products. Compounds were identified on the basis of retention time, fragmentation spectra and carbon number of 12 C analogues. Average mass spectrum across the chromatographic peak with noise subtraction at two sides. Indicated masses are >10% relative abundance, where the highest fragment is put at 100%. CAS numbers of corresponding 12 C compounds are specified in Table 1. S-7

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13 6. Comparison of lignin quantification in poaceous biomass via 12 C lignin external standard and 13 C lignin internal standard based py-gc-sim-ms Lignin content (% w/w) BS CS SCB WS Klason (AILcorr + ASL) 12C external RRF 13C internal RRF Figure S-5: Lignin content determination via Klason (duplicate) (Acid-insoluble lignin corrected for ash and protein (AIL corr) + Acid-soluble lignin (ASL)), 12 C external standard with RRF correction via py-gc-sim-ms (triplicate) and 13 C internal standard with RRF correction via py-gc-sim-ms (triplicate). WS: wheat straw, CS: corn stover, BS: barley straw, SCB: sugar cane bagasse. S-13

14 7. Impact of RRF application on 13 C-IS lignin quantification in poaceous biomass 50 Lignin content (% w/w) WS CS BS SCB Klason AILcorr+ASL 13C-IS RRF 13C-IS N RRF Figure S-6: Lignin content determination via Klason (duplicate) (Acid-insoluble lignin corrected for ash and protein (AIL corr) + Acid-soluble lignin (ASL)) and 13 C-IS based py-gc-sim-ms (triplicate) with and without application of relative response factors (RRF) for lignin-derived pyrolysis products. WS: wheat straw, CS: corn stover, BS: barley straw, SCB: sugar cane bagasse, AIL: acid-insoluble, AS: acid-soluble. S-14

15 8. Composition of poaceous biomasses Table S-1 Composition of poaceous biomasses (% dry weight) determined in duplicate, except for ash in triplicate. WS: wheat straw, CS: corn stover, BS: barley straw, SCB: sugarcane bagasse, AI: acid-insoluble, AS: acid soluble. carbohydrate a protein ash AI lignin b AS lignin WS 64.72± ± ± ± ±0.3 CS 63.53± ± ± ± ±0.9 BS 68.60± ± ± ± ±0.8 SCB 60.71± ± ± ± ±0.3 a presented as anhydrosugars, b corrected for ash and protein Table S-2 Molar composition of carbohydrates herbaceous biomasses (% mol) determined in duplicate. BS: barley straw, WS: wheat straw, CS: corn stover, BS: barley straw, SCB: sugarcane bagasse arabinose galactose glucose xylose uronic acid WS 3.84± ± ± ± ±0.19 CS 4.90± ± ± ± ±0.10 BS 3.39± ± ± ± ±0.04 SCB 0.78± ± ± ± ±0.01 S-15

16 References (1) Gorissen, A.; Kraut, N. U.; de Visser, R.; de Vries, M.; Roelofsen, H.; Vonk, R. J. Food Chem. 2011, 127, (2) Haun, J. Agron. J. 1973, 65, (3) Large, E. C. Plant Pathol. 1954, 3, (4) Zadoks, J. C.; Chang, T. T.; Konzak, C. F. Weed research 1974, 14, (5) Smakman, G. Physiol. Plant. 1982, 56, (6) Visser, R. D.; Vianden, H.; Schnyder, H. Plant, Cell Environ. 1997, 20, (7) Englyst, H. N.; Cummings, J. H. Analyst 1984, 109, (8) Jones, D. B. US Agric. Circ 1931, (9) Jurak, E.; Punt, A. M.; Arts, W.; Kabel, M. A.; Gruppen, H. PLoS NE 2015, 10, e S-16

Caroline Vanderghem, Nicolas Jacquet, Christophe Blecker, Michel Paquot

Pretreatments and enzymatic hydrolysis of Miscanthus x giganteus for oligosaccharides production: delignification degree and characterisation of the hydrolysis products Caroline Vanderghem, Nicolas Jacquet,