Search Results (28)

Pretreatment of lignocellulosic biomass remains the primary obstacle to the profitable use of this type of biomass in biorefineries. The challenge lies in the recalcitrance of the lignin-carbohydrate complex to pretreatment, especially the difficulty in removing the lignin to access the carbohydrates (cellulose and hemicellulose). This study had two objectives: (i) to investigate the effect of reactive extrusion on lignocellulosic biomass in terms of delignification percentage and the structural characteristics of the resulting extrudates, and (ii) to propose a novel pretreatment approach involving extrusion technology based on the results of the first objective. Two types of biomasses were used: agricultural residue (corn stover) and forest residue (black spruce chips). By optimizing the extrusion conditions via response surface analysis (RSA), the delignification percentages were significantly improved. For corn stover, the delignification yield increased from 2.3% to 27.4%, while increasing from 1% to 25.3% for black spruce chips. The highest percentages were achieved without the use of sodium hydroxide and for temperatures below 65 °C. Furthermore, the optimized extrudates exhibited important structural changes without any formation of p-cresol, furfural, and 5-hydroxymethylfurfural (HMF) (enzymes and microbial growth-inhibiting compounds). Acetic acid however was detected in corn stover extrudate. The structural changes included the disorganization of the most recalcitrant functional groups, reduction of particle sizes, increase of specific surface areas, and the appearance of microscopic roughness on the particles. Analyzing all the data led to propose a new promising approach to the pretreatment of lignocellulosic biomasses. This approach involves combining extrusion and biodelignification with white rot fungi to improve the enzymatic hydrolysis of carbohydrates. Full article

The valorization of agri-food wastes can provide value-added products, enzymes and biofuels. For the second-generation ethanol (2G) production, pulps rich in cellulose are desirable in order to release fermentable sugars. This study investigated the homemade biosynthesis of cellulases and hemicellulases via solid-state fermentation (SSF) using sugarcane bagasse (SB) and wheat bran (WB) for the growth of endophytic fungi (Beauveria bassiana, Trichoderma asperellum, Metarhizium anisopliae and Pochonia chlamydosporia). Cocktails with high enzymatic levels were obtained, with an emphasis for M. anisopliae in the production of β-glucosidase (83.61 U/g after 288 h) and T. asperellum for xylanase (785.50 U/g after 144 h). This novel M. anisopliae β-glucosidase demonstrated acidophile and thermotolerant properties (optimum activity at pH 5.5 and 60 °C and stability in a wide pH range and up to 60 °C), which are suitable for lignocellulose saccharifications. Hence, the M. anisopliae multi-enzyme blend was selected for the hydrolysis of raw and organosolv-pretreated corn straw (CS) and corncob (CC) using 100 CBU/g cellulose. After the ethanol/water (1:1) pretreatment, solid fractions rich in cellulose (55.27 in CC and 50.70% in CS) and with low concentrations of hemicellulose and lignin were found. Pretreated CC and CS hydrolysates reached a maximum TRS release of 12.48 and 13.68 g/L, with increments of 100.80 and 73.82% in comparison to untreated biomass, respectively, emphasizing the fundamental role of a pretreatment in bioconversions. This is the first report on β-glucosidase biosynthesis using M. anisopliae and its use in biomass hydrolysis. These findings demonstrated a closed-loop strategy for internal enzyme biosynthesis integrated to reducing sugar release which would be applied for further usage in biorefineries. Full article

Extensive utilization of renewable biomass is crucial for the progress of carbon neutral and carbon peak implementation. Wheat straw, as an important by-product of crops, is hardly ever efficiently utilized by conventional processes. Here, we proposed a mild acid-coupled-with-enzymatic-treatment process to realize the utilization of lignin and hemicelluloses from pulping liquor on the basis of the chemical–mechanical pulping process. The pulping liquor was treated with acid first to precipitate lignin, and it was further hydrolyzed with xylanase to obtain XOSs. The recovered lignin was characterized by FT-IR, 2D-HSQC, GPC, etc. It was found that lignin undergoes depolymerization and condensation during acid treatment. Also, saccharide loss enhanced with the decrease in pH due to the presence of the LCC structure. As a result, an optimized pH of 4 for the acid treatment ensured that the removal rate of lignin and loss rate of polysaccharides achieved 77.15% and 6.13%, respectively. Moreover, further xylanase treatment of the pulping liquor attained a recovery rate of 51.87% for XOSs. The study presents a new insight for the efficient utilization of lignin and hemicellulose products from non-woody materials in the prevailing biorefinery concept. Full article

The aeronautical sector faces challenges in meeting its net-zero ambition by 2050. To achieve this target, much effort has been devoted to exploring sustainable aviation fuels (SAF). Accordingly, we evaluated the technical performance of potential SAF production in an integrated first- and second-generation sugarcane biorefinery focusing on Brazil. The CO₂ equivalent and the renewability exergy indexes were used to assess environmental performance and impact throughout the supply chain. In addition, exergy efficiency (η_B) and average unitary exergy costs (AUEC) were used as complementary metrics to carry out a multi-criteria approach to determine the overall performance of the biorefinery pathways. The production capacity assumed for this analysis covers 10% of the fuel demand in 2020 at the international Brazilian airports of São Paulo and Rio de Janeiro, leading to a base capacity of 210 kt jet fuel/y. The process design includes sugarcane bagasse and straw as the feedstock of the biochemical processes, including diverse pre-treatment methods to convert lignocellulosic resources to biojet fuel, and lignin upgrade alternatives (cogeneration, fast pyrolysis, and gasification Fischer-Tropsch). The environmental analysis for all scenarios shows a GHG reduction potential due to a decrease of up to 30% in the CO₂ equivalent exergy base emissions compared to fossil-based jet fuel. Full article

Posidonia oceanica balls (POB), a kind of seagrass, are a significant environmental issue since they are annually discharged onto beaches. Their current usefulness limits interest in their management and enhances the environmental problem. Therefore, in this research, the potential of this lignocellulosic biomass was studied from a holistic biorefinery point of view. To this end, an in-depth study was carried out to select the best pathway for the integral valorization of POBs. First, an autohydrolysis process was studied for the recovery of oligosaccharides. Then, a delignification stage was applied, where, in addition to studying different delignification methods, the influence of the autohydrolysis pre-treatment was also investigated. Finally, cellulose nanofibers (CNFs) were obtained through a chemo-mechanical treatment. The results showed that autohydrolysis not only improved the delignification process and its products, but also allowed the hemicelluloses to be valorized. Acetoformosolv delignification proved to be the most successful in terms of lignin and cellulose properties. However, alkaline delignification was able to extract the highest amount of lignin with low purity. CNFs were also successfully produced from bleached solids. Therefore, the potential of POB as a feedstock for a biorefinery was confirmed, and the pathway should be chosen according to the requirements of the desired end products. Full article

Corn cob is an abundant agricultural residue worldwide, with high potential and interesting composition, and its valorization still needs to be studied. Selectively fractionating its structural components (hemicellulose, cellulose, and lignin), value-added products can be produced, eliminating waste. In this work, integrated fractionation approaches were developed and evaluated. First, an organosolv process was optimized (ethanol:water, 50:50, w/w). Then, as a comparative method, alkaline delignification (using NaOH, 1–2%) was also studied. The organosolv process allowed a significant delignification of the material (79% delignification yield) and, at the same time, a liquid phase containing a relevant concentration (14.6 g/L) of xylooligosaccharides (XOS). The resulting solid fraction, rich in cellulose, showed an enzymatic digestibility of 90%. The alkaline process increased the delignification yield to 94%, producing a solid fraction with a cellulose enzymatic digestibility of 83%. The two later techniques were also used in a combined strategy of hydrothermal processing (autohydrolysis) followed by delignification. The first allowed the selective hydrolysis of hemicellulose to produce XOS-rich hydrolysates (26.8 g/L, 67.3 g/100 g initial xylan). The further delignification processes, alkaline or organosolv, led to global delignification yields of 76% and 93%, respectively. The solid residue, enriched in glucan (above 75% for both combined processes), also presented high enzymatic saccharification yields, 89% and 90%, respectively. The fractionation strategies proposed, and the results obtained are very promising, enabling the integrated upgrading of this material into a biorefinery framework. Full article

Utilization of lignin is among the most pressing problems for biorefineries that convert lignocellulosic biomass to fuels and chemicals. Recently “lignin-first” biomass fractionation has received increasing attention. In most biorefining concepts, carbohydrate portions of the biomass are separated, and their monomeric sugar components released, while the relatively chemically stable lignin rich byproduct remains underutilized. Conversely, in lignin-first processes, a one-pot fractionation and depolymerization is performed, leading to an oil rich in phenolic compounds and a cellulosic pulp. Usually, the pulp is considered as a fermentation feedstock to produce ethanol. Herein, the results of a study where various cellulosic pulps are tested for their potential to produce valuable products via pyrolysis processes, assessed via analytical pyrolysis (py-GC), are presented. Samples of herbaceous (switchgrass) and woody biomass (oak) were subjected to both an acid-catalyzed and a supported-metal-catalyzed reductive lignin-first depolymerization, and the pulps were compared. Fast pyrolysis of the pulps produced levoglucosan in yields of up to about 35 wt %. When normalized for the amount of biomass entering the entire process, performing the lignin-first reductive depolymerization resulted in 4.0–4.6 times the yield of levoglucosan than pyrolysis of raw biomass. Pulps derived from switchgrass were better feedstocks for levoglucosan production compared with pulps from oak, and pulps produced from metal-on-carbon catalyzed depolymerization produced more levoglucosan than those from acid-catalyzed depolymerization. Catalytic pyrolysis over HZSM-5 produced aromatic hydrocarbons from the pulps. In this case, the yields were similar from both feedstocks and catalyst types, suggesting that there is no advantage to lignin fractionation prior to zeolite-catalyzed catalytic pyrolysis for hydrocarbons. Full article

Apple wood waste (AWW), mainly tree trucks, is collectible lignocellulosic biomass from orchard rotation. The biorefinery of AWW is challenging because of the hard and dense structure. In the present work, chemical composition determination and microstructure observation was performed for the first time on AWW. Alkali-preimpregnation-assisted soda cooking (APSC) was developed to separate cellulose a pulp and lignin from AWW. APSC attained pulp yield of 34.2% at 23% NaOH, showing a 13.2% improvement compared to conventional soda cooking (SC). Fiber length analysis showed APSC-AWW pulp consisted mainly of medium and short fibers, which means blending with long-fibered pulp to enhance the physical strength of pulp sheets. A blend of APSC-AWW pulp and long-fibered pulp in the proportion of 80:20 attained comparable physical strength to hardwood kraft pulp. ASPC-AWW lignin was separated from spent liquor by acidification and then purified by dialysis desalination. The purified ASPC-AWW lignin showed a weight-average molecular weight of 4462 g/mol, similar to softwood kraft lignin but more uniform. Structural analysis revealed that ASPC-AWW lignin was composed of a syringyl unit (S), guaiacyl unit(G), and p-hydroxyphenyl unit (H), and an S unit was dominant with an S/G/H ratio of 74.5:18.2:7.3. It is believed the utilization of fruit tree wood waste as the feedstock of biorefinery is attractive to countries without sufficient forestry resources. Furthermore, the developed APSC is based on conventional SC, which ensures the feasibility of an industrial application. Full article

As a transition strategy towards sustainability, food packaging plays a crucial role in the current era. This, carried out in a biorefinery context of agricultural residues, involves not only obtaining desirable products but a comprehensive utilization of biomass that contributes to the circular bioeconomy. The present work proposes the preparation of bioactive absorbent food pads through a multi-product biorefinery approach from bay tree pruning waste (BTPW). In a first step, chitosan aerogels reinforced with lignocellulose and cellulose micro/nanofibers from BTPW were prepared, studying the effect of residual lignin on the material’s properties. The presence of micro/nanofibers improved the mechanical performance (up to 60%) in addition to increasing the water uptake (42%) when lignin was present. The second step was to make them bioactive by incorporating bay leaf extract. The residual lignin in the micro/nanofibers was decisive, since when present, the release profiles of the extract were faster, reaching an antioxidant power of more than 85% after only 30 min. Finally, these bioactive aerogels were used as absorbent pads for fresh meat. With the use of the bioactive aerogels (with ≥2% extract), the meat remained fresh for 10 days as a result of delayed oxidation of the food during storage (20% metmyoglobin proportion). Full article

Jerusalem artichoke (Helianthus tuberosus L.) is emerging as one of the energy plants considered for biofuel production. Alkali and alkali-involved pretreatment methods have been widely used for the bioconversion of cellulosic materials due to their high sugar yield and low inhibitor release. However, the recovery and treatment of wastewater (black liquor) have been poorly studied. Here, we present a novel two-stage pretreatment process design for recycling black liquor. Jerusalem artichoke stalk (JAS) was first treated with 2% (w/v) NaOH, after which lignin was recovered by H₂SO₄ at pH 2.0 from the black liquor. The recycled solutions were subsequently used to treat the NaOH-pretreated JAS for the second time to dissolve hemicellulose. CO-pretreated JAS, hydrolysates, and acid-insoluble lignin were obtained after the above-mentioned two-stage pretreatment. A reducing sugar yield of 809.98 mg/g Co-pretreated JAS was achieved after 48 h at 5% substrate concentration using a cellulase dosage of 25 FPU/g substrate. In addition, hydrolysates containing xylose and acid-insoluble lignin were obtained as byproducts. The pretreatment strategy described here using alkali and acid combined with wastewater recycling provides an alternative approach for cellulosic biorefinery. Full article

Driven by the excessive consumption of fossil resources and environmental pollution concerns, a large amount of biorefinery research efforts have been made for converting lignocellulosic biomass into fuels and chemicals. Recently, a strategy termed “lignin-first,” which allows for realizing high-yield and high-selectivity aromatic monomers, is regarded as one of the best prospective strategies. This review summarizes recent research advances in lignin-first biorefinery, starting from the raw lignocellulose through lignin-first processing and moving to downstream processing pathways for intermediate compounds. In particular, for the core purpose of producing liquid fuels, the corresponding downstream processing strategies are discussed in detail. These are based on the structural properties of the intermediates derived from lignin-first biorefinery, including the catalytic conversion of lignin and its derivatives (aqueous phase system and pyrolysis system) and the cascade utilization of carbohydrate residues (fermentation, pyrolysis, and hydrothermal liquefaction). We conclude with current problems and potential solutions, as well as future perspectives on lignin-first biorefinery, which may provide the basis and reference for the efficient utilization of lignocellulosic biomass. Full article

Novel environmentally friendly pretreatments have been developed in recent years to improve biomass fractionation. Solid-state fermentation (SSF) and treatment with ionic liquids show low environmental impact and can be used in biorefinery of biomass. In this work, these processes were assessed with brewery spent grain (BSG). First, BSG was used as a substrate to produce cellulases and xylanases by SSF with the fungi Aspergillus brasiliensis CECT 2700 and Trichoderma reesei CECT 2414. Then, BSG was pretreated with the ionic liquid [N₁₁₁₂OH][Gly] and hydrolyzed with the crude enzymatic extracts. Results showed that SSF of BSG with A. brasiliensis achieved the highest enzyme production; meanwhile, the pretreatment with ionic liquids allowed glucan and xylan fractions to increase and reduce the lignin content. In addition, a mixture of the extracts from both fungi in a ratio of 2.5:0.5 Aspergillus/Trichoderma (v/v) efficiently hydrolyzed the BSG previously treated with the ionic liquid [N₁₁₁₂OH][Gly], reaching saccharification percentages of 80.68%, 54.29%, and 19.58% for glucan, xylan, and arabinan, respectively. In conclusion, the results demonstrated that the BSG biorefinery process developed in this work is an effective way to obtain fermentable sugar-containing solutions, which can be used to produce value-added products. Full article

Reductive catalytic fractionation (RCF) has emerged as an effective lignin-first biorefinery strategy to depolymerize lignin into tractable fragments in high yields. Herein, we propose the RCF of spruce wood over a Ru/C bifunctional catalyst in the medium of ethanol and molecular hydrogen to produce monomeric phenolic compounds from lignin, polyols from hemicelluloses, and microcrystalline cellulose. This contribution attempts to elucidate the role of the Ru/C bifunctional catalysts characteristics. The results clarify the particular effect of the carbon support acidity, catalyst grain size, content and dispersion of Ru on the effectiveness of lignin and hemicelluloses extraction and the yields of liquid and gaseous products. The most efficient catalysts for RCF of spruce wood, providing high yields of the monomeric phenols, glycols, and solid product with content of cellulose up to 90 wt%, bear 3 wt% of Ru with a dispersion of 0.94 based on an acidic oxidized graphite-like carbon support Sibunit^®, and having a grain size of 56–94 μm. The Ru/C catalysts intensify the reactions of hydrodeoxygenation of liquid products from lignin. The main phenolic monomers are 4-propyl guaiacol, 4-propenyl guaiacol, and 4-propanol guaiacol. We explored the effect of the process temperature and time on the yield and composition of the liquid, solid, and gaseous products of spruce wood RCF. The optimal trade-off between the yields of phenolic monomers (30.0 wt%). polyols (18.6 wt%) and the solid product containing 84.4 wt% of cellulose is reached at 225 °C and 3 h over the most acidic Ru/C catalyst. Full article

Growing interest in sustainable sources of chemicals and energy from renewable and reliable sources has stimulated the design and synthesis of renewable Schiff-base (iminium) ionic liquids (ILs) to replace fossil-derived ILs. In this study, we report on the synthesis of three unique iminium-acetate ILs from lignin-derived aldehyde for a sustainable “future” lignocellulosic biorefinery. The synthesized ILs contained only imines or imines along with amines in their structure; the ILs with only imines group exhibited better pretreatment efficacy, achieving >89% sugar release. Various analytical and computational tools were employed to understand the pretreatment efficacy of these ILs. This is the first study to demonstrate the ease of synthesis of these renewable ILs, and therefore, opens the door for a new class of “Schiff-base ILs” for further investigation that could also be designed to be task specific. Full article

Lignin, a by-product of pulping and biorefinery, has great potential to replace petrochemical resources for wastewater purification. However, the defects of lignin, such as severe heterogeneity, inferior reactivity and poor solubility, characterize the production process of lignin-based products by high energy consumption and serious pollution. In this study, several lignin fractions with relatively homogeneous structure were first obtained by organic solvent fractionation, and their structures were fully deciphered by various characterization techniques. Subsequently, each lignin component was custom-valued for wastewater purification based on their structural characteristics. Benefiting from the high reactivity and reaction accessibility, the lignin fraction (lignin-1) refined by dissolving in ethanol and n-butanol could been used as a raw material to produce cationic lignin-based flocculant (LBF) in a copolymerization system using green, cheap and recyclable ethanol as solvent. The lignin fraction (lignin-2) extracted by methanol and dioxane showed low reactivity and high carbon content, which was used to produce lignin-based activated carbon (LAC) with phosphoric acid as activator. Moreover, the influences of synthetic factors on the purification capacity were discussed, and the LBF and LAC produced under the optimal conditions showed distinguished purification effect on kaolin suspension and heavy metal wastewater, respectively. Furthermore, the corresponding purification mechanism and external factors were also elaborated. It is believed that this cleaner production strategy is helpful for the valorization of lignin in wastewater resources. Full article