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Additional file 1: Figure S1. Time course of the enzymatic glucan and xylan conversion of sugarcane bagasse after chemithermomechanical pretreatment with increasing alkaline-sulfite loads. A reference chlorite-delignified sugarcane bagasse sample is also included in the dataset.

Additional file 3: Figure S2. Processes diagram, main process steps and transformations, and mass balances for sugarcane bagasse and total pCAs and FAs by treatment and analytical procedure. The photomicrography of the untreated sugarcane bagasse was obtained after toluidine blue staining.

Additional file 2: Table S1. Assignments of 1H/13C correlation signals in the 2D HSQC spectra from untreated and pretreated sugarcane (Saccharum spp.) bagasse in DMSO-d6.

Chemithermomechanical (CTMP) processing of lignocellulosic materials can be used as an efficient pretreatment of lignocellulosic materials. This type of process has been largely used in the mechanical pulping industry with currently available equipment and robust technology. The use of alkaline sulfite in this process provides selective lignin removal up to 50% delignification, which has been proved efficient to decrease recalcitrance of the pretreated materials. The current work evaluates sugarcane bagasse pretreatment by alkaline sulfite CTMP processing. Solids yield after processing with increasingly chemical loads (from 1.25% to 10% sulfite) were in the range of 87% to 82%, respectively. The most severe pretreated sample was completely hydrolyzed by 10 FPU cellulases (Cellic CtecII)/g of substrate within 24 h hydrolysis. Lower chemical doses in the pretreatment provided substrates with higher recalcitrance. Mass balance of sugarcane bagasse components at the most severe condition indicated 49% and 28% of lignin and xylan removal, respectively. Under this condition, the glucan loss was limited to 4%. Besides delignification, the residual lignins appeared sulfonated after CTMP pretreatment. Both delignification and sulfonation of residual lignins resulted in significant increases in the water retention values of the pretreated material (from 134% to 244% in the untreated and severely pretreated material, respectively). 2D-NMR evaluation of the pretreated materials corroborated intense delignification with increasingly sulfite loads. Xylan side groups were progressively removed, whereas part of the original p-coumaric acid (PCA), acylating gama-OH of the lignin side chain, resisted to the most severe pretreatment condition. Direct correlations were observed for lignin removal, WRV, sulfonation of residual lignins and digestibility of the polysaccharides fraction., FAPESP 2014/06923-6

Additional file 2: Table S1. Assignment of the carbohydrate and lignin 13C/1H correlation signals in the 2D HSQC NMR spectra of the GAX samples.

Additional file 1: Figure S1. Mass balance for sugarcane bagasse components during alkaline-sulfite chemothermomechanical pretreatment followed by GAX extraction based on the enzymatic method and enzymatic hydrolysis of unwashed pretreated solids. Figure S2. Mass balance for sugarcane bagasse components during alkaline-sulfite chemothermomechanical pretreatment followed by GAX extraction based on the De Lopez method and enzymatic hydrolysis of unwashed pretreated solids. Figure S3. Mass balance for sugarcane bagasse components during alkaline-sulfite chemothermomechanical pretreatment followed by GAX extraction based on the Hoijemethod and enzymatic hydrolysis of unwashed pretreated solids. Figure S4. Mass balance for sugarcane bagasse components during alkaline-sulfite chemothermomechanical pretreatment followed by enzymatic hydrolysis of unwashed pretreated solids. Figure S5. Mass balance for sugarcane bagasse components during alkaline-sulfite chemothermomechanical pretreatment followed by extensive washing and enzymatic hydrolysis of pretreated solids.

Additional file 5: Figure S4. Time dependence of the enzymatic conversion of xylan to xylose in internode fractions from six different sugarcane hybrids.

Additional file 1: Table S1. Chemical composition and processing yield of sugarcane bagasse pretreated by an alkaline-sulfite process using 5 % NaOH and 10 % Na2SO3.

Additional file 4: Figure S3. Time dependence of the enzymatic conversion of glucan to glucose in internode fractions from six different sugarcane hybrids.

Additional file 1: Table S1. Monomeric sugars released from internode fractions from six different sugarcane hybrids after mild hydrolysis with 2 mol/L trifluoroacetic acid (TFA). TFA hydrolysis barely hydrolyzes crystalline cellulose allowing for the evaluation of non-cellulosic monosaccharides. Xylose, followed by glucose and arabinose was the most abundant monosaccharides.

Additional file 6: Figure S5. Time dependence of the enzymatic conversion of barley MLG to glucose monomers with commercial enzymes.

Additional file 3: Figure S2. Illustrative X-ray diffraction spectra of the rind (red) and pith (green) regions of the sugarcane hybrid 58. The minimum between the peaks at approximately 19 degrees 2θ is assigned to amorphous cellulose, whereas the intense peaks at 22 degrees 2θ is assigned to one of the crystalline forms of cellulose.

10 páginas.- 5 figuras.- 2 tablas.- 50 referencias.- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acssuschemeng.2c01274, Innovative schemes for lignocellulosic biomass refining could optimize the chemical use and biomass conversion efficiency, providing diversified biorefinery products. A new biorefinery scheme used mild alkaline-sulfite chemithermomechanical processing to pretreat sugarcane bagasse, producing highly digestible solids and diluted lignosulfonates in the black pretreatment liquor. Most of the glucan and xylan contained in the pretreated solids were converted into monosaccharides by saccharification with commercial enzymes. The undigested biomass solids remaining from the saccharification process were recycled with the existing alkaline-sulfite black pretreatment liquor. The optimized reaction conditions (159 degrees C and 13% NaOH amendment in the liquor) enhanced the lignosulfonate concentration from 7.1 +/- 0.3 to 33.5 +/- 0.7 g/L. Mass balance for the process indicates that most of the original sugarcane bagasse lignin were split into lignosulfonates contained in the resulfonation liquor (57.3%) and in the enzymatic hydrolysate (16.2%). 2D-NMR analysis of a lignosulfonate fraction recovered by ultrafiltration confirmed that approximately 9-10% of all beta-O-4' alkyl-aryl ether substructures were alpha-sulfonated. The combined chemical characteristics of the prepared lignosulfonate suggested its suitability for use in several lignosulfonate applications., This work was supported by FAPESP (grant number 2019/25867-3), CNPq (grant number 308570/2017-0), and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (CAPES)-Finance Code 001. J.R. and J.C.d.R. were funded by MCIN/AEI/10.13039/501100011033, by "ERDF A way of making Europe" (project PID2020-118968RB-I00), and by the Regional Andalusian Government, Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades/FEDER (project P20-00017).