Pretreatment Liquor Research Articles

Utilization of pretreated green liquor dregs as an activator for blast furnace slag: Effect on hydration, phase assemblage, and rheology

This study explores the utilization of calcium- and magnesium-rich pulp mill residues, i.e., green liquor dregs (GLDs), as an activator for ground granulated blast furnace slag (BFS). The aim of this study is to examine the potential of this unutilized residue when used as a part of alkali-activated materials (AAMs) and in this way enhance the exploitation of GLD. This study focuses on the fresh- and hardened-state properties of the produced paste and mortar samples, where 70% of BFS and 30% of GLD have been incorporated. Two different-sourced and thermally pretreated (105 °C, 300 °C, and 525 °C) GLDs have been used. The effect of thermal treatment on the utilization possibility of GLDs with respect to viscosity, setting times, reactivity, mineralogy, and microstructure is analyzed using the paste samples, while its effect on workability, and strength gain is measured using the mortar samples. Results show that both GLDs enhance the hydration of BFS and that the early-age hydration and strength increase when the GLDs have undergone pretreatment at the highest temperature (525 °C). However, at the later age (28 days), the samples activated with the GLDs treated at 300 °C achieve the highest strength. The addition of both GLDs treated at any temperature increases the viscosity of the composite samples and reduces their workability; however, it should be noted that optimization of water to binder ratio was not the objective of this study. The results of this study show that GLD, previously considered unreactive, can potentially become a reactive component of AAMs.

Efficient binary diol-based deep eutectic solvent pretreatment for enhancing enzymatic saccharification and lignin fractionation from eucalyptus

An innovative binary biol-based deep eutectic solvent (DES), specifically ethylamine hydrochloride-ethylene glycol (EaCl-EG), was developed for efficient pretreatment of eucalyptus biomass. This DES exhibited superior performance in achieving high delignification (85.0%) and xylan removal (80.0%), while preserving a significant amount of cellulose (94.5%) compared to choline chloride-based DES. Notably, the pretreated eucalyptus residues showed a remarkable glucose yield of over 92.5%, representing a substantial enhancement of up to 15 times compared to untreated eucalyptus. Furthermore, the pretreated liquor yielded high-purity lignin with a yield of 97.8%, characterized by well-preserved β-O-4 structure and nanoscale dimensions. These lignin nanoparticles (LNPs) were subsequently self-assembled into lignin nanobottles (LNBs), adding further value to the pretreatment process. The proposed novel binary EaCl-EG DES presented great potential as an efficient pretreatment solvent for future biomass fractionation processes.

Comparative analysis of bioenergy and mycoprotein production from apple pomace: Strategies for enhancement and environmental benefits

Apple pomace constitutes a major waste stream of the food processing industry that is characterized by high concentrations of free sugars and structural carbohydrates. This study comparatively explored alternative apple pomace valorization strategies. To this regard, the integration of hydrothermal and organic acid pretreatment as a strategy to enhance anaerobic digestion biomethane yield and alternative production of mycoprotein as a valuable secondary product via the use of Aspergillus oryzae and Neurospora intermedia edible fungi were investigated. In scenario 1, both pretreatment liquors and solid residues underwent anaerobic digestion to produce biomethane. In scenario 2, pretreatment liquors and solid residues underwent fungal cultivation and anaerobic digestion, respectively. Additionally, to optimize bioenergy yield and minimize wastewater generation in scenario 2, the fungal growth effluent was also subjected to anaerobic digestion. In scenario 1, employing methane for transportation showed the potential to decrease GHG by 314.8 kt CO2 eq, translating to US$72.4 million in social cost savings. Similarly, in scenario 2, replacing edible fungal biomass in the food market could lead to a substantial reduction in emissions by 824.2 kt CO2 eq and a corresponding US$227.0 million in social cost savings.

Holistic investigation of structural evolution in corn stover lignin under pretreatment with varying γ-valerolactone concentrations

Until now, research on green and sustainable γ-valerolactone (GVL) pretreatment has predominantly centered on component separation efficiency, with limited attention given to the lignin structure. Nonetheless, the lignin's structure is considerably affected by the fractionation, consequently influencing its potential valorization. Herein, we conducted a holistic investigation of the structural evolution of two fractions of lignin in corn stover, obtained under pretreatment with varying GVL concentrations: GVL lignin (GVLL) originated from pretreatment liquor and cellulolytic enzyme lignin (CEL) separated from pretreated residue. Our findings indicated a general positive correlation between the molecular weight and polydispersity index of both GVLL and CEL with the increasing GVL concentration. This phenomenon is attributed to the enhanced lignin dissolution and relocation as the GVL concentration increases. Moreover, higher GVL concentrations also increased the acidity of reaction system, leading to degradation of β-O-4 linkages from 45.2 to 34.9 and 57.6 to 37.9 per 100 aromatic units in GVLL and CEL, respectively. Compared to CEL, GVLL exhibited a more remarkable phenolics yield (33.7% vs. 22.2%) during hydrodeoxygenation due to its superior purity and lower degree of polymerization. Recycling studies demonstrated the stability of GVL at lower concentrations. These findings provide valuable insights for optimizing GVL pretreatment systems.

Valorization of straw biomass into lignin bio-ink, bacterial cellulose and activated nanocarbon through the trade-off alkali-catalyzed glycerol organosolv biorefinery

Integrated lignocellulosic biorefinery that transforms low-value lignocellulose into multiple value-added products is crucial for a low-carbon sustainable development. Herein, a one-pot alkali-catalyzed glycerol organosolv (ALGO) pretreatment-based integrated biorefinery process to directionally produce lignin bio-inks, bacterial celluloses (BCs), and activated nanocarbons (ANCs) was proposed. ALGO pretreatment could modify the structure of dissolved lignins by glycerolysis. The extracted lignin fragments with high-purity (>90 %), uniform with low molecular weight (2500–4000 of Mw), and abundant hydrophilic aliphatic –OH were promising candidates in 3D-printable inks preparation. The glycerolysis reaction during ALGO process also enabled pretreated substrates toward high hydrolyzability and protected pretreatment liquor from generating fermentable inhibitors, making the solid fractions more liable for enzymatic deconstruction and microbial fermentation. Without any detoxification treatments, hydrolysates from ALGO pretreated substrates were used directly as carbon sources for BCs production, resulting in the BC yields were 56 % higher than that of the commercial glucose. The enzymatic hydrolysis residue and BC fermentation waste liquid were synthesized into ANCs via a facile carbonization process, which could further increase the value of ALGO biorefinery. Calculations showed that this ALGO integrated strategy rendered the conversion of ∼75 % lignins in pretreatment liquor to bio-inks and nearly 100 % solid fractions to BCs and ANCs. Unlike the conventional “lignin-first” route to obtain high-purity cellulose by sacrificing the value-adding conversion ability of by-products, the designed technical route in this work achieved a good trade-off between fractionation ability and subsequent conversion potential, inspiring further exploration of the technical correlation between biomass fractionation and bioproduct processing.

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.

Lignocellulosic biomass pretreatment with a lignin stabilization strategy and valorization toward multipurpose fractionation

Lignocellulosic biomass has emerged as a promising alternative with sustainable advantages for the production of a wide range of renewable products and value-added chemicals. In this study, a pretreatment strategy that use a fully recyclable acid hydrotrope (p-TsOH aqueous solution) to extract lignin and employ glyoxylic acid (GA) to stabilize lignin was proposed for biomass valorization toward multipurpose fractionation. 83.0 % of lignin was dissolved out by p-TsOH hydrotrope (80 wt%) with GA addition to form GA-stabilized product at 80 o C for 15 min. The stabilized lignin was subsequently used as an additive in the preparation of lignin-based suncream. Notably, the incorporation of 4 wt% lignin nanospheres into an SPF15 sunscreen yielded a measured SPF of 59.94. Furthermore, the depolymerization of uncondensed lignin into aromatic monomers yielded a high lignin-oil yield of 84.2 %. Additionally, direct heating of the pretreatment liquor facilitated the conversion of monosaccharides into furfural, achieving a desired yield of 53.7 % without the addition of any acid catalyst. The pretreatment also enhanced the enzymatic hydrolysis of glucan, resulting in a saccharification yield of 98.4 %. Moreover, short-term ultrasonication of the pretreated substrate yielded pulp suitable for papermaking. Incorporating 15 wt% fibers into the produced paper sheets led to a 5.3 % increase in tear index and a 25.4 % increase in tensile index. This study presents a viable pretreatment strategy for the multipurpose fractionation of lignocellulosic biomass, offering potential avenues for biomass valorization.

The use of xylose from elephant grass liquor and coproduction of organic acids by wild‐type bacteria isolated from food waste

AbstractDuring the normal production of ethanol from pretreated lignocellulosic biomass, only the solid fraction containing C6 sugars is generally used by unmodified yeasts in the fermentation process – the remaining liquid fraction, rich in xylose, is used almost exclusively by genetically modified organisms (GMOs) or for other purposes. As the liquor can be used in the manufacture of a series of chemical inputs, microorganisms that metabolize C5 sugars from different sources were initially isolated with the aim of converting these sugars into acetic acid (AA) and lactic acid (LA). Experiments were carried out with pretreated elephant grass liquor, evaluating the effect of adding commonly referenced nutrients through experimental design. Thus, the present work involves the isolation, screening, and molecular characterization of bacteria, easily found in nature, with the potential to metabolize xylose and produce AA and LA, with yields similar or superior to those shown in studies employing GMOs. Using wild‐type strains, high yields were obtained with Acetobacter cerevisiae (0.96 g LA and 0.71 g AA per g total sugars) and Levilactobacillus brevis (0.77 g LA and 0.61 g AA per g total sugars) in relation to the organic acids of interest, highlighting the total conversion of the sugar blend (xylose, glucose, and arabinose) in 24 h. Ammonium citrate also significantly influenced the final yields, being responsible for the increase in production. The results are useful for biorefinery platforms and may contribute to the full use of sugars released in the lignocellulosic pretreatment of raw materials.

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.

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

Pretreatment is a prerequisite to tackle the issue of biomass recalcitrance, which is the major hindrance of lignocellulose-to-sugars routes. In the present study, a novel combination of dilute sulfuric acid (dilute-H2SO4) with Tween 80 pretreatment of corn stover (CS) was developed to significantly enhance the enzyme digestibility. Strong synergistic effects of H2SO4 and Tween 80 for simultaneously eliminating hemicellulose and lignin and significantly promoting saccharification yield were observed. A response surface optimization realized the maximum monomeric sugar yield of 95.06% at 120 °C for 1.4 h with 0.75 wt% of H2SO4 and 73.92 wt% of Tween 80. The excellent enzyme susceptibility of pretreated CS was explained by their physical and chemical characteristics via SEM, XRD, and FITR. The repeatedly recovered pretreatment liquor exerted highly-effective reusability in the subsequent pretreatments for at least four cycles. This strategy offers a highly-efficient and practical pretreatment strategy, which provides valuable information for the lignocellulose-to-sugars routes.

Recovery of mixture of hydroxyethylammonium carboxylate protic ionic liquids from sugarcane pretreatment liquor using activated carbon in a fixed bed column

Integrated strategies using fixed bed columns can facilitate the recovery of protic ionic liquids (PILs) used in the pretreatment of lignocellulosic biomass. In this study, we investigated the adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] on activated carbon in a fixed bed column for recovering the PILs mixture present in the liquor of the pretreatment. Breakthrough curves were determined experimentally. Breakthrough time (tb), exhaustion time (te), difference between tb and te, adsorption efficiency (ϕads), column efficiency (ϕcol) and qe equilibrium capacity were evaluated as a function of simultaneous variations in superficial velocity (vs) and temperature (T) using a central composite rotatable design. The optimum conditions for PIL purification were vs = 1.66 cm/min (Q = 1.3 mL/min) and T = 20 °C. After selection of optimum operating conditions, PILs separation was evaluated in a model solution and sugarcane pretreatment liquor, with similar intervals for recover of PILs. This is the first study to develop a successful proof of concept of mixture PILs [Mea][Ac]/[Mea][Hex] recovery from sugarcane straw pretreatment liquor in a fixed-bed column of activated carbon. The results indicate that the method has great potential for industrial application.

A novel integrated biorefinery approach for apple pomace valorization with significant socioeconomic benefits

Ethanolic organosolv pretreatment was used to enhance the yield of ethanol production from apple pomace through a biorefinery. The pretreatment was conducted at various conditions (100, 150, and 180 °C; 30 and 60 min; 50 and 85% ethanol) in the absence or presence of 0.5% sulfuric acid. Then, pectin was extracted from the pretreatment liquor, the solvent (i.e., ethanol) was recovered by distillation, lignin was separated, and the pretreated solid was subjected to simultaneous saccharification and fermentation for ethanol production. The highest ethanol yield was achieved when the pretreatment was performed at 100 °C for 30 min with 50% ethanol in the absence of sulfuric acid, giving an overall yield of 173.3 g ethanol per 1 kg of untreated pomace. Besides, under these conditions, the amounts of extracted pectin and lignin were 76 g and 3 g per each kg of the untreated pomace, respectively. The study of socioeconomic impacts of the optimized biorefinery indicated that a total of 59.3 million liters of ethanol could potentially be generated from collectible apple pomace in Iran per annum, leading to a significant reduction in well-to-wheel greenhouse gas emissions of 84.9 and 85.6 (kt CO2 equivalent) using apple-pomace-ethanol-blended fuels of E85 and E10, respectively.

Chemical-free production of multiple high-value bioproducts from metabolically engineered transgenic sugarcane ‘oilcane’ bagasse and their recovery using nanofiltration

Bioenergy crops have potential for being a sustainable and renewable feedstock for biofuels and various value-added bioproducts. The study utilizes recently developed transgenic sugarcane (‘oilcane’) bagasse for chemical-free coproduction of high-value bioproducts, i.e., furfurals, HMF, acetic acid, cellulosic sugars, and vegetative lipids. Hydrothermal pretreatment was optimized at 210 °C for 5 min to coproduce 6.91%, 2.67%, 5.07%, 2.42% and 37.82% (w/w) furfurals, HMF, acetic acid, vegetative lipids, and cellulosic sugars, respectively from lignocellulosic biomass. Additionally, nanofiltration system in-series was successfully established to recover sugars, furfurals, HMF, and acetic acid from the pretreatment liquor. 1st nanofiltration with Duracid NF membrane rejected ∼99% sugars. Concentrated sugars with significantly reduced inhibitory products were obtained in retentate for fermentation. 2nd nanofiltration with NF90 membrane used permeate of 1st nanofiltration as feed and rejected ∼ 86% furfurals. The work demonstrates the feasibility of coproducing and recovering multiple biochemicals from lignocellulosic biomass.

Construction of anhydrous two-step organosolv pretreatment of lignocellulosic biomass for efficient lignin membrane-extraction and solvent recovery

Glycerol organosolv (GO) pretreatment has been revealed to be potent in selectively deconstructing the lignocellulosic biomass and effectively enhancing its enzymatic hydrolysis, but the conventional solid washing and GO lignin extraction processes frequently consume large amounts of water, resulting additionally in difficulty recycling the glycerol. In this study, an anhydrous two-step organosolv pretreatment process was explored, followed by the membrane ultrafiltration of glycerol lignin. The results showed that the solid washing of the residual glycerol after the atmospheric glycerol organosolv (AGO) pretreatment was necessary for the subsequent operation of high-solid enzymatic hydrolysis. Washing with ethanol was desirable as an alternative to water as only a low glycerol content of 5.2% resided in the substrate. Membrane ultrafiltration was helpful in extracting the AGO lignin from the pretreatment liquor, in which a high lignin extraction of 81.5% was made with a regenerated cellulose membrane (cut-off for 1 kDa) under selected ultrafiltration conditions. With the characterization of membrane-extracted lignin, it was observed for the first time that the AGO lignin has a well-preserved structure of G/S type. Moreover, the lignin was enriched with reactive groups, i.e. β-O-4′ linkages and aliphatic hydroxyl groups, which was very likely due to the glycerol grafting onto the lignin via α-etherification reaction. The two-step organosolv pretreatment process allowed 86% of glycerol and 92% of the ethanol recovery with ∼78% of distillation energy savings, which was applicable for extraction of organosolv lignin and recycling use of organic solvents.

Fungal-Modified Lignin-Enhanced Physicochemical Properties of Collagen-Based Composite Films.

Renewable and biodegradable materials have attracted broad attention as alternatives to existing conventional plastics, which have caused serious environmental problems. Collagen is a potential material for developing versatile film due to its biosafety, renewability, and biodegradability. However, it is still critical to overcome the low mechanical, antibacterial and antioxidant properties of the collagen film for food packaging applications. To address these limitations, we developed a new technology to prepare composite film by using collagen and fungal-modified APL (alkali pretreatment liquor). In this study, five edible and medical fungi, Cunninghamella echinulata FR3, Pleurotus ostreatus BP3, Ganoderma lucidum EN2, Schizophyllum commune DS1 and Xylariaceae sp. XY were used to modify the APL, and that showed that the modified APL significantly improved the mechanical, antibacterial and antioxidant properties of APL/Collagen composite films. Particularly, the APL modified by BP3, EN2 and XY showed preferable performance in enhancing the properties of the composite films. The tensile strength of the film was increased by 1.5-fold in the presence of the APL modified by EN2. To further understand the effect of fungal-biomodified APL on the properties of the composite films, a correlation analysis between the components of APL and the properties of composite films was conducted and indicated that the content of aromatic functional groups and lignin had a positive correlation with the enhanced mechanical and antioxidant properties of the composite films. In summary, composite films prepared from collagen and fungal biomodified APL showed elevated mechanical, antibacterial and antioxidant properties, and the herein-reported novel technology prospectively possesses great potential application in the food packaging industry.

An integrated process for co-producing fermentable sugars and xylonate from sugarcane bagasse based on xylonic acid assisted pretreatment

In this study, a renewable organic acid (xylonic acid), which can be prepared by the biooxidation of xylose, is used for pretreating sugarcane bagasse. The effects of reaction temperature and time on the release of fermentable xylose and glucose were investigated. On the basis of guaranteeing the good enzymatic hydrolysis efficiency and minimizing the effects of inhibitors, the pretreatment with 1 % xylnoic acid at 190 °C for 30 min was selected after optimization. In this case, 70 % xylose was released, while enzymatic hydrolysis yield was also up to 86.5 %. Meanwhile, the pretreated hydrolysate liquor was proved that it could be used for producing xylonate by biooxidation of Gluconobacter oxydans. Finally, the sequential process of the xylonic acid pretreatment and saccharification also clear the path for recycling the lignin as value-added bioproducts. Overall, this study presents a green-like strategy for fully exploiting sugarcane bagasse.

Multienzymatic conversion of monosaccharides from birch biomass after pretreatment

This study presents proof-of-concept validation of a multi enzymatic biocatalytic system, capable of producing monosaccharides from a birch biomass pretreated liquor with simultaneous cofactor regeneration. To improve the stability of the proposed biocatalyst, co-immobilization of NAD + -dependent xylose dehydrogenases, glucose dehydrogenase, and NADH-dependent 3-hydroxybutyrate dehydrogenase was performed on mesoporous silica SBA-15. The results of the physicochemical analysis confirmed the effectiveness of enzymes deposition on the support material and changes in the surface area and porous structure of silica before and after the process. Process conditions in which the three-enzymes system allowed to achieve the highest efficiency of the conducted reactions were optimized at 20 °C, pH 7, 90 min of process duration, 400 mM of levulinic acid addition and ratio of NAD + :NADH 1:5. Results from this study demonstrate excellent xylonic acid, gluconic acid and 4-hydroxyvaleric acid production at conversion rate of 98.7%, 95.6% and 99.2%, respectively. In addition, the high stability and reusability of the developed biocatalytic system was confirmed based on tests in ten successive catalytic cycles and the storage time of 10 days at 4 °C. At the end of the tests, co-immobilized enzymes were capable of catalyzing the process with >70% efficiency. The presented data confirmed the effectiveness of co-immobilization, improvement of enzyme properties including their high reusability, as well as indicated the application potential of the proposed multienzymatic system in the conversion of components of pretreated biomass solutions. • Three types of dehydrogenases have been successfully co-immobilized using silica SBA-15. • Monosaccharides from the birch biomass pretreated liquor were effectively converted. • Addition of levulinic acid ensured the creation of a cofactor regeneration system. • The production of three organic acids was carried out with over 95% of efficiency. • Co-immobilized enzymes retained 70% of acids productivity after 10 catalytic cycles.

Carbonate pre-treatment of wood for transformative structural applications through densification

This study investigated carbonate pre-treatment of wood followed by densification for producing advanced wood structural materials. Poplar wood blocks of 100 mm long and 20 mm wide with thickness of 10 mm were treated with sodium carbonate with and without sulfide at different carbonate loadings at 150 ºC for 30 min. Carbonate effectively removed lignin and hemicelluloses which facilitated subsequent wood densification for improving wood mechanical properties . Comparing with wood pre-treatment using sodium hydroxide, carbonate pre-treatment improved wood yield but achieved similar level of wood mechanical strength. Considering sodium carbonate is the key ingredient of commercial pulping process liquors such as spent pulping liquor (black liquor) and green liquor (an aqueous solution of the dissolved inorganic smelt from the combustion of concentrated pulping spent liquor), the present study indicated that low cost, effective, and cleaner wood pre-treatment can be achieved using spent process liquors rather than fresh and expensive sodium hydroxide (white liquor). Laboratory black liquor was used to pretreat the same poplar wood blocks, the good wood mechanical properties of the treated wood after densification confirmed this hypothesis. The practical significance of the present study is the utilization the residue alkali in spent process liquors rather than fresh NaOH for wood pre-treatment to reduce environmental impact. Furthermore, the spent liquor after wood-pretreatment can be directly feed into commercial pulp mill chemical recovery system to reduce capital and operation cost. • Carbonate wood pre-treatment for subsequent wood densification. • Carbonate is effective in delignification and dissolve hemicelluloses. • Pulping spent liquor and green liquor for wood pre-treatment for densification. • Carbonate and pulping liquor pre-treatment improved wood mechanical properties after densification.

Ethanol organosolv pretreatment of sugarcane bagasse assisted by organic acids and supercritical carbon dioxide

The scCO2-assisted organosolv pretreatment of sugarcane bagasse was carried out using aqueous ethanol and organic acid catalysts. Variables involved were temperature (150–190 °C), time (0–60 min), type of catalyst (acetic, citric, and oxalic acids), amount of CO2 (25–50 g), ethanol titer in water (0–80 vol%), and catalyst concentration (0.5 to 1.5 % w·v−1). The best delignification (86 wt%) and glucan retention (89 wt%) were achieved at 170 °C for 15 min using 60 vol% ethanol in water, 1 wt% oxalic acid, and 25 g CO2. Organic acid esterification was a limitation for pretreatment operations using ethanol titers above 60 vol%. Enzymatic hydrolysis of pretreated materials at 1 % (w·v−1) glucans released 74.3 ± 0.2 % glucose in 96 h using Cellic CTec3 (Novozymes) at 9.89 FPU·gglucans−1. The concentrated pretreatment liquor allowed lignin recovery by water precipitation in high yields, while the aqueous supernatant contained low levels of fermentation inhibitors.

A multi-product strategy for the fractionation of corn stover based on peracetic acid and maleic acid processing

As an efficient lignocellulose fractionation process, peracetic acid and maleic acid (PAM) pretreatment is integrated into a multi-product platform for the simultaneous manufacture of cellulose, lignin, and xylose. Employing such strategy, 100 g corn stover (dry basis) yielded 39.63 g cellulose-rich solids along with 11.88 g xylose and 12.00 g lignin recovered from the pretreatment liquor. The recovery of xylose and lignin was assessed with various organic solvents, of which 2-methyltetrahydrofuran (2-MeTHF) showed superior performance, giving high lignin yield (75.23%) and xylose yield (67.32%). The recovered lignin (2-MeTHF-L) was characterized by high purity, relatively low molecular weight, and large numbers of carboxyl group. Besides, 2D-HSQC NMR analysis revealed that the 2-MeTHF-L was esterified with maleic acid during PAM pretreatment, partly responsible for its enhanced antioxidant ability. This strategy maximizes feedstock utilization and improves the processability in downstream valorization, offering a prospect for sustainable and efficient biorefineries.