Combined dilute sulfuric acid and Tween 80 pretreatment of corn stover significantly improves the enzyme digestibility: synergistic removal of hemicellulose and lignin

Efficient and facile biphasic pretreatment for corn stover fractionation with comprehensive utilization of cellulose, xylan and lignin

Developing a mild and efficient pretreatment technique to fully utilize lignocellulosic biomass remains a challenge. In this work, a biphasic system with 2-phenoxyethanol (EPH) organic solvent and phosphotungstic acid (PTA) aqueous solution was employed to pretreat corn stover. The prominent synergistic effect between EPH and PTA was revealed to play a key role in the fractionation of corn stover. The excellent separation efficiency with 88.55 % cellulose retention, 85.02 % xylan removal, and 86.68 % lignin removal was achieved under mild pretreatment conditions. The 62.18 % of xylose in aqueous phase, and 83.44 % of lignin from organic phase were recovered after the EPH/PTA biphasic pretreatment. Furthermore, the solid residue was digested with high enzymatic glucose yield of 92.69 %, and the xylose was oxidated with xylonic acid yield of 50.06 %. Meanwhile, the high-performance lignin-based films were manufactured by using the recovered lignin. This study presented a promising way for high-value utilization of lignocellulosic biomass.

Establishment of efficient system for bagasse bargaining: Combining fractionation of saccharides, recycling of high-viscosity solvent and dismantling

Sugarcane bagasse (SCB) has a recalcitrant structure, which hinders its component dismantling and subsequent high value utilization. Some organic solvents are favorable to dismantle lignocellulose, but their high viscosity prevents separation of components and reuse of solvents. Herein, ethylene glycol phenyl ether (EGPE)-acid system is used as an example to develop green and efficient methods to dismantle SCB, purify polysaccharides and lignin, and reuse solvents. Results show that dismantling SCB at 130 °C, 0.5 % H2SO4, and 100 min can obtain 85.5 % cellulose recovery, 94.1 % hemicellulose removal and 83.7 % lignin removal. Different molecular weight saccharides are separated by membranes filtration and centrifugation, and lignin recovered by antisolvent precipitation. The solvent recovered by distillation, achieving high dismantling efficiency of 89.2 % cellulose recovery, 94.1 % hemicellulose removal and 94.4 % lignin removal after four recycles. Results show a promising approach for the closed-loop process of dismantling lignocellulose, fractionating saccharides, and reusing solvents in high-viscosity systems.

High-solids saccharification of non-pretreated citrus peels through tailored cellulase

Citrus peels, characterized by their low lignin and high sugar content, have been drawing increasing attention as a valuable lignocellulosic biomass with significant potential in biorefinery. Notably, in this study, the citrus waste was found to be enzymatically accessible without any pretreatment. Moreover, to promote the high-solids saccharification of the citrus peels, a tailored cellulase cocktail was formulated by response surface methodology (RSM), along with a fed-batch strategy aiming to obtain a high substrate loading. The study resulted in an optimized cellulase cocktail (7.08 U/g DM of β-glucosidase, 164.17 U/g DM of hemicellulase, 47.38 mg/g DM of sophorolipid, and 64.68 mg/g DM of Tween 80) and achieved solids loading of 22 % with a total sugar concentration of 123.84 g/L, corresponding to a yield of 93.12 % (65.28 % in batch operation). These findings provided essential validation for the efficient utilization of citrus waste, ensuring them promising potential as feedstock for sugar platforms.

Highly Efficient Production of Cellulosic Ethanol from Poplar Using an Optimal C6/C5 Co-Fermentation Strain of Saccharomyces cerevisiae

Cellulosic ethanol is the key technology to alleviate the pressure of energy supply and climate change. However, the ethanol production process, which is close to industrial production and has a high saccharification rate and ethanol yield, still needs to be developed. This study demonstrates the effective conversion of poplar wood waste into fuel-grade ethanol. By employing a two-step pretreatment using sodium chlorite (SC)-dilute sulfuric acid (DSA), the raw material achieved a sugar conversion rate exceeding 85% of the theoretical value. Under optimized conditions, brewing yeast co-utilizing C6/C5 enabled a yield of 35 g/L ethanol from 10% solid loading delignified poplar hydrolysate. We increased the solid loading to enhance the final ethanol concentration and optimized both the hydrolysis and fermentation stages. With 20% solid loading delignified poplar hydrolysate, the final ethanol concentration reached 60 g/L, a 71.4% increase from the 10% solid loading. Our work incorporates the pretreatment, enzymatic hydrolysis, and fermentation stages to establish a simple, crude poplar waste fuel ethanol process, expanding the range of feedstocks for second-generation fuel ethanol production.

Improving saccharification efficiency of corn stover through ferric chloride-deep eutectic solvent pretreatment

An effective deep eutectic solvent (DES) and Iron(III) chloride (FeCl3) combination pretreatment system was developed to improve the removal efficiency of lignin and hemicellulose from corn stover (CS) and enhance its saccharification. N-(2-hydroxyethyl)ethylenediamine (NE) was selected as the hydrogen-bond-donor for preparing ChCl-based DES (ChCl:NE), and a mixture of ChCl:NE (60 wt%) and FeCl3 (0.5 wt%) was utilized for combination pretreatment of CS at 110 ℃ for 50 min. FeCl3/ChCl:NE effectively removed lignin (87.0 %) and xylan (55.9 %) and the enzymatic hydrolysis activity of FeCl3/ChCl:NE-treated CS was 5.5 times that of CS. The reducing sugar yield of pretreated CS was 98.6 %. FeCl3/ChCl:NE significantly disrupted the crystal structure of cellulose in CS and improved the removal of lignin and hemicellulose, enhancing the conversion of cellulose and hemicellulose into monomeric sugars. Overall, this combination of FeCl3 and DES pretreatment methods has high application potential for the biological refining of lignocellulose.

Selective Removal of Hemicellulose by Diluted Sulfuric Acid Assisted by Aluminum Sulfate

Hemicellulose can be selectively removed by acid pretreatment. In this study, selective removal of hemicellulose was achieved using dilute sulfuric acid assisted by aluminum sulfate pretreatment. The optimal pretreatment conditions were 160 °C, 1.5 wt% aluminum sulfate, 0.7 wt% dilute sulfuric acid, and 40 min. A component analysis showed that the removal rate of hemicellulose and lignin reached 98.05% and 9.01%, respectively, which indicated that hemicellulose was removed with high selectivity by dilute sulfuric acid assisted by aluminum sulfate pretreatment. Structural characterizations (SEM, FTIR, BET, TGA, and XRD) showed that pretreatment changed the roughness, crystallinity, pore size, and functional groups of corn straw, which was beneficial to improve the efficiency of enzymatic hydrolysis. This study provides a new approach for the high-selectivity separation of hemicellulose, thereby offering novel insights for its subsequent high-value utilization.

Combination of alkaline biodiesel-derived crude glycerol pretreated corn stover with dilute acid pretreated water hyacinth for highly-efficient single cell oil production by oleaginous yeast Cutaneotrichosporon oleaginosum

Single cell oil (SCO) prepared from biodiesel-derived crude glycerol (BCG) and lignocellulosic biomass (LCB) via oleaginous yeasts is an intriguing alternative precursor of biodiesel. Here, a novel strategy combining alkaline BCG pretreated corn stover and dilute acid pretreated water hyacinth for SCO overproduction was developed. The mixed pretreatment liquors (MPLs) were naturally neutralized and adjusted to a proper carbon-to-nitrogen ratio beneficial for SCO overproduction by Cutaneotrichosporon oleaginosum. The toxicity of inhibitors was relieved by dilution detoxification. The enzymatic hydrolysate of solid fractions was suitable for SCO production either separately or simultaneously with MPLs. Fed-batch fermentation of the MPLs resulted in high cell mass, SCO content, and SCO titer of 80.7 g/L, 75.7 %, and 61.1 g/L, respectively. The fatty acid profiles of SCOs implied high-quality biodiesel characteristics. This study offers a novel BCG&LCB-to-SCO route integrating BCG-based pretreatment and BCG/LCB hydrolysates co-utilization, which provides a cost-effective technical route for micro-biodiesel production.

Highly-efficient lipid production from hydrolysate of Radix paeoniae alba residue by oleaginous yeast Cutaneotrichosporon oleaginosum

Valorization of herbal extraction residues (HERs) into value-added products is pivotal for the sustainability of Chinese medicine industry. Here, seven different enzymatic hydrolysates of dilute acid pretreated HERs were evaluated for lipid production by Cutaneotrichosporon oleaginosum. Among them, the highest sugar yield via hydrolysis and the maximum lipid production were obtained from Radix paeoniae alba residue (RPAR). More interestingly, high proportion of sugar polymers was disintegrated into fermentable sugars during the pretreatment step, allowing a cheap non-enzymatic route for producing sugars from RPAR. A repeated dilute acid pretreatment gained a high sugar concentration of 241.6 g/L through reusing the pretreatment liquor (PL) for four times. Biomass, lipid concentration, and lipid content achieved 49.5 g/L, 35.7 g/L and 72.2 %, respectively, using fed-batch culture of PL. The biodiesel parameters indicated lipids produced from HERs were suitable for biodiesel production. This study offers a cost-effective way to upgrade the HERs waste into micro-biodiesel.