Using Undigested Biomass Solid Leftovers from the Saccharification Process to Integrate Lignosulfonate Production in a Sugarcane Bagasse Biorefinery

Abstract

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 °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 β-O-4′ alkyl−aryl ether substructures were α-sulfonated. The combined chemical characteristics of the prepared lignosulfonate suggested its suitability for use in several lignosulfonate applications.

Xylan, Xylooligosaccharides, and Aromatic Structures With Antioxidant Activity Released by Xylanase Treatment of Alkaline-Sulfite–Pretreated Sugarcane Bagasse

“…Previous work demonstrated that GAX extraction also benefits subsequent saccharification of remaining solids by commercial enzyme cocktails once the residual polysaccharides became more accessible to cellulolytic enzymes ( Sporck et al, 2017 ). After completing this biorefinery schedule, residual lignin from the final saccharification step can be converted into marketable lignosulfonates, as recently reported in Heinz et al (2022) .…”

Lignin Modification for Enhanced Performance of Polymer Composites

“…Lignosulfonates are highly dependent on NaOH (13% w/w) at 159 °C and 4% H 2 SO 4 at 121 °C for 1 h whenever the reslufonation reaction is enhanced. 68 The process of adding sulfuric acid to lignin, known as the sulfite procedure, can make it hydrophilic and improve its ability to allow water to pass through. Lignosulfonate, a type of lignin, has a higher molecular weight sulfonate group that ranges per unit of phenyl propane, between 0.4 and 0.7.…”

“…Because of the environment’s acidity, predominantly α-sulfonated β-O-4′alkyl-aryl ether bridge is broken via a quinone methide intermediate or through nucleophilic substitution. Lignosulfonates are highly dependent on NaOH (13% w/w) at 159 °C and 4% H 2 SO 4 at 121 °C for 1 h whenever the reslufonation reaction is enhanced . The process of adding sulfuric acid to lignin, known as the sulfite procedure, can make it hydrophilic and improve its ability to allow water to pass through.…”

Impact of Product Diversification on the Economic Sustainability of Second-Generation Ethanol Biorefineries: A Critical Review

“…Still on the valorization of black liquor and the residual solid fraction from enzymatic hydrolysis, Heinz et al [144] conducted a study on utilizing these two streams for lignosulfonate production from SCB. The combined stream obtained from the union of these side-streams was re-sulfonated to enhance the concentration of lignosulfonate in the liquid stream.…”