This study introduced a pretreatment and enzymatic hydrolysis approach for poplar sawdust (PS), integrating sodium hydroxide (NaOH) with sodium dodecyl benzene sulfonate (SDBS), with the objective of maximizing biomass sugar outcomes. When synergistically applied with NaOH pretreatment, SDBS substantially enhanced the structural disintegration of PS. Under optimized conditions (10 % NaOH and 20 g/L SDBS), lignin and xylan removal achieved a rate of 97.8 % and 100.0 %, while glucan concentration soared to 93.0 %. The evaluations of cellulose accessibility, hydrophobic characteristics, crystallinity index, and surface morphology corroborated the highly effective separation of lignocellulosic constituents, thereby creating ideal substrate conditions for subsequent enzymatic hydrolysis. During the enzymatic hydrolysis phase, SDBS further augmented hydrolytic efficiency through its surfactant capabilities, culminating in a hydrolysis efficiency of 94.9 %. In-depth investigations revealed that SDBS mitigated the non-productive binding of lignin through electrostatic repulsion while simultaneously enhancing the conformational stability of enzyme molecules, ultimately resulting in a substantial enhancement of cellulase activity. This research revealed that SDBS greatly facilitated the fractionation of biomass constituents and significantly enhanced the efficiency of hydrolysis reactions, offering a promising and innovative pathway for biomass conversion.
Background The effective valorization of lignin and carbohydrates in lignocellulose matrix under the concept of biorefinery is a primary strategy to produce sustainable chemicals and fuels. Based on the reductive catalytic fractionation (RCF), lignin in lignocelluloses can be depolymerized into viscous oils, while the highly delignified pulps with high polysaccharides retention can be transformed into various chemicals. Results A biorefinery paradigm for sequentially valorization of the main components in poplar sawdust was constructed. In this process, the well-defined low-molecular-weight phenols and bioethanol were co-generated by tandem chemo-catalysis in the RCF stage and bio-catalysis in fermentation stage. In the RCF stage, hydrogen transfer reactions were conducted in one-pot process using Raney Ni as catalyst, while the isopropanol (2-PrOH) in the initial liquor was served as a hydrogen donor and the solvent for lignin dissolution. Results indicated the proportion of the 2-PrOH in the initial liquor of RCF influenced the chemical constitution and yield of the lignin oil, which also affected the characteristics of the pulps and the following bioethanol production. A 67.48 ± 0.44% delignification with 20.65 ± 0.31% of monolignols yield were realized when the 2-PrOH:H 2 O ratio in initial liquor was 7:3 (6.67 wt% of the catalyst loading, 200 °C for 3 h). The RCF pulp had higher carbohydrates retention (57.96 ± 2.78 wt%), which was converted to 21.61 ± 0.62 g/L of bioethanol with a yield of 0.429 ± 0.010 g/g in fermentation using an engineered S. cerevisiae strain. Based on the mass balance analysis, 104.4 g of ethanol and 206.5 g of lignin oil can be produced from 1000 g of the raw poplar sawdust. Conclusions The main chemical components in poplar sawdust can be effectively transformed into lignin oil and bioethanol. The attractive results from the biorefinery process exhibit great promise for the production of valuable biofuels and chemicals from abundant lignocellulosic materials.
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