Ethanol Organosolv Pretreatment Research Articles

Enhanced biobutanol production with sustainable Co-substrates synergy from paper waste and garden waste with municipal biowaste

Synergy in the co-processing of lignocellulosic wastes and municipal biowaste (MB) can unlock their potential for biobutanol production. This study assessed the potential for biobutanol production through the co-processing of lignocellulosic waste and MB. Specifically, it compared the co-processing of paper waste with MB to that of garden waste and MB. Ethanol organosolv pretreatment served as a dual-function process for both pretreatment and detoxification purposes. Initial fermentation of hydrolysates from untreated paper waste using Clostridium acetobutylicum produced 0.9 g/L of acetone and ethanol but no detectable butanol. Organosolv pretreatment led to a significant increase in acetone and ethanol production but did not yield butanol. Co-processing paper waste with MB using organosolv pretreatment resulted in the production of 2.8–3.2 g/L butanol, along with increased acetone and ethanol production. Furthermore, co-processing a 1:1 (w/w) mixture of paper waste and MB under mild and severe pretreatment conditions produced 45.5 g and 43.4 g butanol, respectively, compared to 34.8 g and 14.4 g butanol when processing these waste streams separately. The study also explored the positive impact of co-processing garden waste with MB, a distinct lignocellulosic source, enhancing acetone-butanol-ethanol (ABE) yield by 27–40%. These findings highlight the potential of synergistic waste co-processing for achieving a more suitable balance of nutrients to enhance biobutanol and ABE production from biowastes. Additionally, the simultaneous treatment of lignocellulosic waste and municipal biowaste offers a simplified approach to waste processing, contributing to advancements in sustainable biomass utilization and bioenergy production.

Sustainable biorefinery development for valorizing all wastes from date palm agroindustry

This study examined how various residues from date palm agroindustrial can be utilized in a biorefinery platform to produce ethanol, methane, and lignin. Liquid hot water, ethanol organosolv, and catalyzed ethanol organosolv (CEO) pretreatments were applied to trunk, leaves, leaf sheath, pedicels, date cake, and seeds. The process included extracting lignin from the liquid fraction, followed by converting the pretreated solid material into ethanol. The fermentation residues were also utilized to produce biomethane through anaerobic digestion. Two different scenarios were employed for the biorefining, i.e., (Ⅰ) maximum lignin production and (Ⅱ) maximum biofuel production. The best results for the first scenario were obtained when CEO was employed in the pretreatment of date palm wastes, where 806.9 mL ethanol, 902.8 L methane, and 528.0 g lignin were produced from each kg of each residue. In energetic terms, the biofuel products (i.e., ethanol and methane) were determined to have a combined energy content equivalent to 1553.1 mL of gasoline. Likewise, the most favorable outcomes of the second scenario were obtained by incorporating CEO pretreatment of trunk, leaf sheath, leaves, and pedicels in the valorization of untreated date cake and seeds. Furthermore, for the second scenario, the resulting products were 967.5 mL ethanol, 1605.3 L methane, and 341.0 g lignin, with the biofuel products having a combined energetic content equivalent to 2452.0 mL of gasoline. These findings indicate that the biorefining of date palm agroindustrial wastes has significant potential for bioenergy production.

Comparative study of acid- and alkali-catalyzed 1,4-butanediol pretreatment for co-production of fermentable sugars and value-added lignin compounds

BackgroundOrganosolv pretreatment is one of the most efficient methods for delignification and boosting biomass saccharification. As compared to typical ethanol organosolv pretreatments, 1,4-butanediol (BDO) organosolv pretreatment is a high-boiling-point solvent pretreatment, which can generate low pressure in the reactor during high temperature cooking that improves the operation safety. Although several studies showed that organosolv pretreatment can lead to effective delignification and enhancement in glucan hydrolysis, there has been no studies on acid- and alkali-catalyzed BDO pretreatment, as well as their comparison on promoting biomass saccharification and lignin utilization.ResultsIt was shown that BDO organosolv pretreatment was more effective in removing lignin from poplar as compared with typical ethanol organosolv pretreatment under the same pretreatment conditions. HCl-BDO pretreatment with 40 mM acid loading led to 82.04% of original lignin removed from biomass, as compared to the lignin removal of 59.66% in HCl-Ethanol pretreatment. Besides, acid-catalyzed BDO pretreatment was more effective in improving the enzymatic digestibility of poplar than alkali-catalyzed BDO pretreatment. As a result, HCl-BDO with acid loading of 40 mM provided a good enzymatic digestibility of cellulose (91.16%) and the maximum sugar yield of 79.41% from original woody biomass. The linear correlations between physicochemical structure (e.g., fiber swelling, cellulose crystallinity, crystallite size, surface lignin coverage and cellulose accessibility) changes of BDO pretreated poplar and enzymatic hydrolysis were plotted to figure out the main factors that influenced biomass saccharification. Moreover, acid-catalyzed BDO pretreatment mainly brought about the phenolic hydroxyl (PhOH) groups formation in lignin structure, while alkali-catalyzed BDO pretreatment mostly led to the lower molecular weight of lignin.ConclusionsResults indicated that the acid-catalyzed BDO organosolv pretreatment could significantly improve enzymatic digestibility of the highly recalcitrant woody biomass. The great enzymatic hydrolysis of glucan resulted from increased cellulose accessibility, which mostly associated with the higher degree of delignification and hemicellulose solubilization, as well as the more increase in fiber swelling. Besides, lignin was recovered from the organic solvent, which could be used as natural antioxidants. The formation of phenolic hydroxyl groups in lignin structure and the lower molecular weight of lignin contributed to its greater radical scavenging capacity.

High Temperature Lignin Separation for Improved Yields in Ethanol Organosolv Pre-Treatment

The full utilization of renewable raw materials is necessary for a sustainable economy. Lignin is an abundant biopolymer, but is currently mainly used for energy production. Ethanol organosolv pre-treatment produces high-quality lignin, but still faces substantial economic challenges. Lignin solubility increases with temperature, and previous studies have shown that it reprecipitates during cooling after the pre-treatment. Thus, a possibility for the optimization of lignin production with this process can be the separation of extract and residual biomass at high temperatures. In this work, lignin was extracted from wheat straw at 180 °C, and the extract was separated from the remaining solids at several temperatures after the pre-treatment. The results show that 10.1 g/kg of lignin and 2.2 g/kg of carbohydrates are dissolved at the pre-treatment temperature of 180 °C, which is reduced to 8.6 g/kg of lignin and 1.2 g/kg of carbohydrates after cooling. The precipitation of lignin separated from the extracts at 180 °C showed that a higher lignin concentration at high temperatures results in a 46% improvement in the yield of solid lignin, while there was no significant impact on the lignin purity.

Conversion of Glucose and Xylose to 5-Hydroxymethyl furfural, Furfural, and Levulinic Acid Using Ethanol Organosolv Pretreatment under Various Conditions

The objective of this study was to understand the conversion characteristics of glucose and xylose using the major monosaccharide standards for lignocellulosic biomass. The acid-catalyzed organosolv pretreatment conducted using ethanol was significantly different from the acid-catalyzed process conducted in an aqueous medium. 5-hydroxymethylfurfural (5-HMF), levulinic acid and furfural were produced from glucose conversion. The maximum yield of 5-HMF was 5.5%, at 200°C, when 0.5% sulfuric acid was used. The maximum yield of levulinic acid was 21.5%, at 220°C, when 1.0% sulfuric acid was used. Furfural was produced from xylose conversion and under 0.5% sulfuric acid, furfural reached the maximum yield 48.5% at 210°C. Ethyl levulinate and methyl levulinate were also formed from the glucose standard following the esterification reaction conducted under conditions of the combined conversion method, which proceeded under both ethanol-rich and water-rich conditions.

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.

Influence of Acetic Acid as a Catalyst in Ethanol Organosolv Pretreatment of Wheat Straw for the Production of Colloidal Lignin Particles and Enzymatic Hydrolysis

influence of Acetic Acid as a Catalyst in Ethanol Organosolv Pretreatment of Wheat Straw for the Production of Colloidal Lignin Particles and Enzymatic Hydrolysis

Aqueous ethanol organosolv process for the valorization of Brewer’s spent grain (BSG)

Brewers spent grain (BSG), the main solid byproduct of brewing, is annually generated by ca 37 million tons worldwide, which due to limited application, mostly ends up in landfills. This study aims to separate BSG’s fractions (lignin, cellulose, and hemicellulose) by ethanol organosolv pretreatment. Lignin-rich fractions were recovered using a two-step separation technique. The effects of temperature, retention time, and ethanol concentration on the quantity and quality of fractions were studied. The temperature considerably impacted the quality and quantity of obtained fractions, while other parameter effects greatly depended on the temperature. Substantial hemicellulose removal (90 %) along with lignin removal (56 %) and recovery (57 %) were obtained at 180 °C. The highest lignin purity (95 %) was obtained at the pretreatment conditions of 180 °C, 120 min, and 50 % ethanol concentration. This work provides an alternative route for BSG utilization, mitigating its environmental impact while enhancing the economy of a brewery.

Combined Extraction and Ethanol Organosolv Fractionation of Exhausted Olive Pomace for Bioactive Compounds

AbstractThe olive pomace oil extracting industry generates large amounts of exhausted olive pomace (EOP), a lignocellulosic waste that needs to be managed according to sustainable criteria. The aim of this work is to devise an integrated strategy to valorize EOP by applying two‐step extraction, and to evaluate the effect of an ethanol organosolv pretreatment on the delignification and enzymatic hydrolysis of the extracted EOP. Once the extraction and organosolv pretreatment conditions are selected, solubilized lignin is recovered from the pretreatment liquor using different methods. In addition to those organosolv lignin samples, a lignin‐rich solid is obtained after enzymatic saccharification of the pretreated solid. All the lignin samples are fully characterized aiming at further valorization. The selected two‐step aqueous extraction (85 °C, 90 min, 10% biomass) removes 89% of the extractives content in raw EOP and achieves the full recovery of phenols and mannitol content in that fraction, 4.7 mg gallic acid equivalents per g EOP and 4.5 mg g−1 EOP, respectively. The organosolv pretreatment (50% ethanol catalyzed with 1% H2SO4, 140 °C, 60 min, 15% biomass) results in a delignified solid with 81% of enzymatic digestibility and a high purity organosolv lignin (>71%), rich in guaiacyl units.

Characteristic of oil palm empty fruit bunch after ethanol-organosolv pretreatment catalyzed by acid

The increasing growth of palm oil industry results in an increase in the accumulation of waste generated from the industry, such as oil palm empty fruit bunches (OPEFB). OPEFB is a good source of renewable raw materials if a pretreatment process can overcome the recalcitrance of OPEFB and allows the fractionation of all carbohydrates and lignin. In this work, the effectiveness of organosolv pretreatment to deconstruct OPEFB and to recover high purity of lignin and glucan was studied. The pretreatment experiments were carried out at 210 °C for 90 minutes with a solid to liquid ratio of 1/10. Ethanol 50% (v/v) was used as solvent. The effect of H2SO4 0.07% (w/w) as catalyst was also studied. The results showed that organosolv pretreatment with the addition of acid increased the purity of glucan and lignin by 36 and 5%, respectively. A total of 65% lignin was recovered, which was 3.6 times higher than lignin from pretreatment without acid catalyst. After organosolv pretreatment with an acid catalyst, the crystallinity index (CRI) decreased by 54%, while the decrease in CRI was only 14.4% after pretreatment without an acid catalyst. The water retention value of the pretreated OPEFB with acid catalyst increased by 8%. It can be concluded that organosolv pretreatment using ethanol as a solvent with the addition of acid catalyst succeeded in fractionating OPEFB with high purity and reducing recalcitrant OPEFB.

Enhanced Enzymatic Saccharification of Mixed Sawdust Wastes: Comparison of SPORL, Dilute Acid, Formic Acid, and Ethanol Organosolv Pretreatments

Abstract. Utilization of the huge quantity of sawdust wastes is urgent. In this study, SPORL, dilute acid pretreatment (DA), formic acid pretreatment (FA), ethanol pretreatment (EtOH/H2O), and sulfuric acid catalyzed ethanol pretreatment (EtOH/H2O/H2SO4), on improving enzymatic hydrolysis of mixed sawdust wastes were comprehensively compared. EtOH/H2O/H2SO4 was the most effective pretreatment in lignin removal from sawdust fiber cell wall, while FA was much more effective in hemicellulose removal. After the pretreatments, the crystallinity of cellulose increased because of the removal of amorphous hemicellulose and lignin. Moreover, the fiber surface became coarse and porous, especially after EtOH/H2O/H2SO4, the structure was destroyed into fragments, which enhanced the cellulase accessibility of cellulose. Therefore, the glucose yield of EtOH/H2O/H2SO4 pretreated substrate was highest among these five pretreatments, achieved at 91.4% with a cellulase loading of only 10 FPU/g glucan.
 
 Resumen. Es urgente aprovechar la gran cantidad de residuos de aserrín. En este estudio, SPORL, pretratamiento con ácido diluido (DA), pretratamiento con ácido fórmico (FA), pretratamiento con etanol (EtOH/H2O) y pretratamiento con etanol catalizado con ácido sulfúrico (EtOH/H2O/H2SO4), sobre la mejora de la hidrólisis enzimática de residuos de aserrín mezclado fueron comparados de manera integral. EtOH/H2O/H2SO4 fue el pretratamiento más eficaz para eliminar la lignina de la pared celular de la fibra de aserrín, mientras que el FA fue mucho más eficaz para eliminar la hemicelulosa. Después de los pretratamientos, la cristalinidad de la celulosa aumentó debido a la eliminación de hemicelulosa amorfa y lignina. Además, la superficie de la fibra se volvió gruesa y porosa, especialmente después de EtOH/H2O/H2SO4, la estructura se destruyó en fragmentos, lo que mejoró la accesibilidad de celulasa de la celulosa. Por lo tanto, el rendimiento de glucosa del sustrato pretratado con EtOH/H2O/H2SO4 fue el más alto entre estos cinco pretratamientos, alcanzado al 91,4% con una carga de celulasa de solo 10 FPU / g de glucano.

The effects of mild Lewis acids-catalyzed ethanol pretreatment on the structural variations of lignin and cellulose conversion in balsa wood

Ethanol organosolv pretreatment is a green and effective deconstruction process for main components in lignocellulose biomass. Herein, balsa wood was firstly subjected to a modified ethanol/water solution (EWS) pretreatment with different Lewis acids catalysts (AlCl3, CuCl2, FeCl3) at 140–180 °C. The delignification ratios and structural characteristics of the dissociated lignin, enzymatic hydrolysis of cellulose in the pretreated substrates as well as the degradation products from hemicellulose during the pretreatment process were comprehensively investigated. Results showed that dissociation and depolymerization of lignin fragments was robust in AlCl3-catalyzed pretreatment than those by CuCl2 and FeCl3-catalyzed pretreatment. In detail, the results showed that the optimal delignification ratio and removal of the hemicelluloses occurred in AlCl3-catalyzed pretreatment. Moreover, the structural characterizations of lignin fractions by 2D-HSQC, 31P NMR and GPC also revealed that the obtained lignin has the advantages of small and homogeneous molecules as well as abundant functional groups. As a result of adequate removal of hemicellulose and lignin, the enzymatic digestibility of cellulose in the pretreated residue was significantly elevated. In short, the above findings are also in line with the concept of maximizing the utilization of bioresources, which will be beneficial for value-added applications of balsa wood in the biorefinery.

Production and Properties of Lignin Nanoparticles from Ethanol Organosolv Liquors-Influence of Origin and Pretreatment Conditions.

Despite major efforts in recent years, lignin as an abundant biopolymer is still underutilized in material applications. The production of lignin nanoparticles with improved properties through a high specific surface area enables easier applicability and higher value applications. Current precipitation processes often show poor yields, as a portion of the lignin stays in solution. In the present work, lignin was extracted from wheat straw, spruce, and beech using ethanol organosolv pretreatment at temperatures from 160–220 °C. The resulting extracts were standardized to the lowest lignin content and precipitated by solvent-shifting to produce lignin micro- and nanoparticles with mean hydrodynamic diameters from 67.8 to 1156.4 nm. Extracts, particles and supernatant were analyzed on molecular weight, revealing that large lignin molecules are precipitated while small lignin molecules stay in solution. The particles were purified by dialysis and characterized on their color and antioxidant activity, reaching ASC equivalents between 19.1 and 50.4 mg/mg. This work gives detailed insight into the precipitation process with respect to different raw materials and pretreatment severities, enabling better understanding and optimization of lignin nanoparticle precipitation.

Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment

Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4′ linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.

Sustainable biofuels and bioplastic production from the organic fraction of municipal solid waste

Municipal solid waste is an environmental threat worldwide; however, the organic fraction of municipal solid waste (OF-MSW) has a great potential for the generation of fuels and high-value products. In the current study, OF-MSW was utilized for the production of ethanol, hydrogen, as well as 2,3-butanediol, an octane booster, by using Enterobacter aerogenes. Furthermore, a promising alternative to non-biodegradable petrochemical-based polymers, polyhydroxyalkanoates (PHAs), was produced. The OF-MSW was first pretreated by an acetic acid catalyzed ethanol organosolv pretreatment at 120 and 160 °C followed by enzymatic hydrolysis of the residual solids. The residual unhydrolyzed solids resulting from enzymatic hydrolysis were further anaerobically digested for methane production. The enzymatic hydrolysis of the solids prepared at 120 °C for 60 min led to the production of hydrolysate with the highest glucose production yield of 498.5 g/kg dry untreated OF-MSW, which was fermented to 139.1 g 2,3-butanediol, 98.3 g ethanol, 28.6 g acetic acid, 71.4 L biohydrogen, and 40 g PHAs. Moreover, 23.1 L biomethane was produced through the anaerobic digestion of the enzymatic hydrolysis residue solids. Thus, appreciable amounts of energy (8236.9 kJ) and an eco-friendly bioplastic were produced by the valorization of carbon sources available in OF-MSW.

Efficient biobutanol production from potato peel wastes by separate and simultaneous inhibitors removal and pretreatment

Abstract Potato peel waste (PPW) is a carbohydrate-rich waste from potato industries, which is an environmental threat worldwide. In this study, it was evaluated for biobutanol production via acetone-butanol-ethanol fermentation by Clostridium acetobutylicum. The results showed that PPW contained a considerable amount of glycoalkaloids, severe inhibitors for the bacterium. Thus, three processes, i.e., dilute acid pretreatment (Process I), the inhibitors extraction followed by dilute acid hydrolysis (Process II) and ethanol organosolv pretreatment (Process III), were employed before hydrolysis and fermentation to produce ABE. The extraction of glycoalkaloids with ethanol, dilute acid hydrolysis at 180 °C for 60 min, and enzymatic hydrolysis led to a hydrolysate with 36 g/L glucose, which was successfully fermented to 11.6 g/L ABE. In process II, the organosolv pretreatment led to the removal of the major fraction of inhibitors, in the range of 77–88% of glycoalkaloids. The enzymatic hydrolysis of PPW pretreated with 75% ethanol at 180 °C for 60 min resulted in a fermentable hydrolysate with 38 g/L glucose. The fermentation of overall hydrolysate resulted in a high ABE concentration of 24.8 g/L, indicating that PPW is an appropriate substrate for butanol production after the removal of its bacterial inhibitors.

Ammonia-ethanol-water pretreatment of wheat straw for facilitating enzymatic saccharification integrated with the preparation of submicron lignin spheres

Ammonia-ethanol-water (AEW) pretreatment was adopted to treat wheat straw for ameliorating saccharification with the integrated preparation of submicron lignin spheres (SLS). Results showed that AEW pretreatment could remove 77% of lignin and 90% of extractives, thus increasing specific surface area and porosity of the substrate and finally enhancing the release of fermentable sugars in saccharification. Under the optimal pretreatment conditions (170 °C for 2 h, ethanol concentration 55% (v/v), ammonia concentration 7.5 wt%), the final total sugar yield reached 81.7% after pretreatment and saccharification, which was 2.25 times higher compared to the conventional ethanol organosolv pretreatment. Moreover, washing could be excluded for AEW-pretreated wheat straw before saccharification, and both ethanol and ammonia could be readily recovered and reused, making the AEW pretreatment clean and sustainable. In addition, SLS with hollow structure and average diameter of 161.2 ± 53.6 nm were fabricated using the fractionated lignin, which could offset the overall cost of AEW pretreatment.

Conversion of rubber wood waste to methane by ethanol organosolv pretreatment

The restricted bioavailability of structurally complex carbohydrates for digestion has hitherto resulted in a low methane potential from rubber wood waste (RW). The effects of hydrothermal (HT) and ethanol organosolv (OS) pretreatments on the methane produced by anaerobic digestion of RW were investigated in the study reported. HT with temperatures above 190 °C significantly enhanced the anaerobic digestibility of RW mainly due to the degradation of hemicellulose. On the other hand, OS with 75% ethanol provided a potential methane gas yield of 165.1 L CH4/kg-VS, which was higher than that for HT at 210 and 230 °C by 39 and 7%, respectively. This was due to intensive delignification during OS pretreatment which led to a reduction in the non-productive adsorption of cellulolytic enzymes by lignin. A first-order kinetic model showed that OS had a higher hydrolysis rate (k = 0.073 ± 0.003 day−1) resulting in a higher methane yield when lower pretreatment temperatures were applied. The anaerobic degradation of the pretreated RW in this study was a result of simultaneous CH4 production through the symbiosis of anaerobic bacteria and methanogens using a combination of the aceticlastic and hydrogenothrophic bioconversion pathways. The recovery and use of the phenolic compounds remaining in the process water would be a way of adding value to this process and the feasibility of producing methane from RW should be further investigated.

Biorefining Oat Husks into High-Quality Lignin and Enzymatically Digestible Cellulose with Acid-Catalyzed Ethanol Organosolv Pretreatment

Oat husks are low-value lignocellulosic residues of oat processing that carry an environmental impact. Their polymers (cellulose, hemicellulose, and lignin) can be converted into a wide variety of value-added products; however, efficient pretreatment methods are needed that allow their fine separation for further tailored valorization. This study pioneered the use of milling-free and low acid-catalyzed ethanol organosolv for the delignification of oat husks, allowing their conversion into three high-quality streams, namely, glucan-rich, lignin-rich, and hemicellulosic compound-rich streams. Temperature, retention time, and solid-to-liquid ratio were found to impact the delignification of oat husks when using a one-factor-at-a-time strategy. The ideal conditions that were found (210 °C, 90 min, and solid-to-liquid ratio of 1:2) culminated into glucan and lignin fractions containing 74.5% ± 11.4% glucan and 74.9% ± 7.6% lignin, respectively. These high-purity lignin fractions open the possibility for higher value applications by lignin, potentially impacting the feasibility of second generation biorefineries. The glucan fraction showed 90% digestibility after 48 h of hydrolysis with 10 filter paper units of enzyme cocktail per gram of glucan. Considering the absence of size reduction and high solid loading, together with the quality of the obtained streams, organosolv pretreatment could be a potential strategy for the valorization of oat lignocellulosic residues.

Effects of the advanced organosolv pretreatment strategies on structural properties of woody biomass

Plants have evolved their lignocellulosic cell walls through complex structural and chemical mechanisms to protect itself against microbial attacks, which makes native lignocellulosic biomass recalcitrant to enzymatic deconstruction. Pretreatment is a crucial step in the biological conversion of biomass as it can render structural changes in the plant cell wall to reduce the biomass recalcitrance, thus enhancing its sugar release performance. There have been many efforts to develop effective pretreatment technologies to overcome the biomass recalcitrance with a primary focus on the efficient conversion of biomass carbohydrates to liquid fuels, while lignin is significantly underutilized despite its bulk amount and high-value opportunities. In this study, the effects of two recent organosolv pretreatment strategies, co-solvent enhanced lignocellulosic fractionation (CELF) and γ-Valerolactone (GVL) pretreatments, on physicochemical properties of poplar were investigated and compared with the effects of conventional ethanol organosolv pretreatment. Diverse physicochemical properties of biomass including chemical compositions, molecular weights of cellulose and lignin, aromatics and inter-unit linkages of lignin, lignin hydroxyl group contents, cellulose crystallinity, and accessible surface area of cellulose were analyzed before and after pretreatments. The results revealed how each organic solvent pretreatment system affected biomass structural characteristics and recalcitrance.