Optimized Organosolv Pretreatment of Biomass Residues Using 2-Methyltetrahydrofuran and n-Butanol

The Covalent Linking of Organophosphorus Heterocycles to Date Palm Wood-Derived Lignin: Hunting for New Materials with Flame-Retardant Potential

Environmentally acceptable and renewably sourced flame retardants are in demand. Recent studies have shown that the incorporation of the biopolymer lignin into a polymer can improve its ability to form a char layer upon heating to a high temperature. Char layer formation is a central component of flame-retardant activity. The covalent modification of lignin is an established technique that is being applied to the development of potential flame retardants. In this study, four novel modified lignins were prepared, and their char-forming abilities were assessed using thermogravimetric analysis. The lignin was obtained from date palm wood using a butanosolv pretreatment. The removal of the majority of the ester groups from this heavily acylated lignin was achieved via alkaline hydrolysis. The subsequent modification of the lignin involved the incorporation of an azide functional group and copper-catalysed azide-alkyne cycloaddition reactions. These reactions enabled novel organophosphorus heterocycles to be linked to the lignin. Our preliminary results suggest that the modified lignins had improved char-forming activity compared to the controls. 31P and HSQC NMR and small-molecule X-ray crystallography were used to analyse the prepared compounds and lignins.

Combined sulfuric acid and choline chloride/glycerol pretreatment for efficiently enhancing enzymatic saccharification of reed stalk

In this study, an efficient combination of pretreatment solvents involving Choline chloride/Glycerol (ChCl/Gly) and H2SO4 was firstly developed to assess the pretreatment performance and determine optimal pretreatment conditions. The results illustrated that the H2SO4-[ChCl/Gly] combination efficiently removed lignin (52.6%) and xylan (80.5%) from the pretreated reed stalk, and subsequent enzymatic hydrolysis yielded 91.1% of glucose. Furthermore, several characterizations were conducted to examine the structural and morphological changes of the reed stalk, revealing apparently enhanced accessibility (128.4 to 522.6 mg/g), reduced lignin surface area (357.9 to 229.5 m2/g), and substantial changes on biomass surface. Based on the aforementioned study, possible mechanisms for the H2SO4-[ChCl/Gly] pretreatment of reed stalks were proposed. The comprehensive understanding of combined H2SO4-[ChCl/Gly] pretreatment system for enhancing the saccharification of the reed stalk was interpreted in this work. Overall, this novel approach could be efficiently applied to pretreat and saccharify reed stalks, empowering the biomass refining industry.

Organosolv pretreatment: an in-depth purview of mechanics of the system

The concept of biorefinery has been advancing globally and organosolv pretreatment strategy has seen an upsurge in research due to its efficiency in removing the recalcitrant lignin and dissolution of cellulose. The high-performance organosolv system uses green solvents and its reusability contributes concurrently to the biorefinery sector and sustainability. The major advantage of the current system involves the continuous removal of lignin to enhance cellulose accessibility, thereby easing the later biorefinery steps, which were immensely restricted due to the recalcitrant lignin. The current system process can be further explored and enhanced via the amalgamation of new technologies, which is still a work in progress. Thus, the current review summarizes organosolv pretreatment and the range of solvents used, along with a detailed mechanistic approach that results in efficient pretreatment of LCB. The latest developments for designing high-performance pretreatment systems, their pitfalls, and advanced assessments such as Life Cycle Assessment along with Techno-Economic Assessment have also been deliberated to allow an insight into its diverse potential applicability towards a sustainable future.

Advances on Cellulose Manufacture in Biphasic Reaction Media

Cellulose is produced industrially by the kraft and sulfite processes. The evolution of these technologies in biorefineries is driven by the need to obtain greater added value through the efficient use of raw materials and energy. In this field, organosolv technologies (and within them, those using liquid phases made up of water and one partly miscible organic solvent, known as "biphasic fractionation" in reference to the number of liquid phases) represent an alternative that is receiving increasing interest. This study considers basic aspects of the composition of lignocellulosic materials, describes the fundamentals of industrial cellulose pulp production processes, introduces the organosolv methods, and comprehensively reviews published results on organosolv fractionation based on the use of media containing water and an immiscible solvent (1-butanol, 1-pentanol or 2-methyltetrahydrofuran). Special attention is devoted to aspects related to cellulose recovery and fractionation selectivity, measured through the amount and composition of the treated solids.

Enhancing enzymatic saccharification of sunflower straw through optimal tartaric acid hydrothermal pretreatment

Sunflower straw, a usually neglected and abundant agricultural waste, has great potential for contributing to environmental protection realizing its high-value of valorization if utilizing properly. Because hemicellulose contains amorphous polysaccharide chains, relatively mild organic acid pretreatment can effectively reduce its resistance. Through hydrothermal pretreatment, sunflower straw was pretreated in tartaric acid (1 wt%) at 180 ^oC for 60 min to enhance its reducing sugar recovery. After tartaric acid-assisted hydrothermal pretreatment, 39.9% of lignin and 90.2% of hemicellulose were eliminated. The reducing sugar recovery increased threefold, while the solution could be effectively reused for four cycles. The properties of more porous surface, improved accessibility, and decreased surface lignin area of sunflower straw were observed through various characterizations, which explained the improved saccharide recovery and provided a basis for the mechanism of tartaric acid-assisted hydrothermal pretreatment. Overall, this tartaric acid hydrothermal pretreatment strategy greatly provided new impetus for the biomass refinery.

A fractionation strategy of cellulose, hemicellulose, and lignin from wheat straw via the biphasic pretreatment for biomass valorization

Developing an environmentally friendly and efficient pretreatment to utilize wheat straw is essential to a sustainable future. An acid biphasic system with 2-methyltetrahydrofuran (2-MeTHF) organic solvent and dilute p-toluenesulfonic acid (p-TsOH) were employed for the simultaneous fractionation of three components. Results showed that the biphasic system had excellent cellulose protection and high removal of hemicellulose and lignin. In detail, Under the optimal conditions (0.1 M p-TsOH, 2-MeTHF: H₂O = 1:1 (v:v), 140 °C, 3 h), mostly cellulose retained in the residues (95.69%), 57.18% of lignin was removed and high yield of hemicellulose-based C5 sugars was achieved (77.49%). In the further process of dehydration of pre-hydrolysate dichloromethane (DCM) as an organic phase, the yield of furfural was 80.07% (170 °C-80 min). The saccharification of residue reached 95.82%. p-TsOH/2-MeTHF/H₂O pretreatment was desirable for high selectivity fractionation. Important chemicals for bioenergy including furfural, monosaccharides and lignin are obtained.

Isolation of Pure Lignin and Highly Digestible Cellulose from Defatted and Steam-Exploded Cynara cardunculus

In this work, a three-step approach to isolate the main components of lignocellulosic cardoon, lignin and cellulose, was investigated. The raw defatted biomass, Cynara cardunculus, after steam explosion was subjected to a mild organosolv treatment to extract soluble lignin (L1). Then, enzymatic hydrolysis was performed to achieve decomposition of the saccharidic portion into monosaccharides and isolate residual lignin (L2). The fractionation conditions were optimized to obtain a lignin as less degraded as possible and to maximize the yield of enzymatic hydrolysis. Furthermore, the effect of the use of aqueous ammonia as an extraction catalyst on both fractions was studied. Each fraction was characterized by advanced techniques, such as elemental analysis and ³¹P nuclear magnetic resonance (NMR), ¹³C-¹H two-dimensional (2D)-NMR, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and UV-vis spectroscopies for lignin and X-ray diffraction (XRD), Klason compositional analysis, elemental analysis, and ATR-FTIR spectroscopy for cellulose-rich fractions. The impact of the cellulose-rich fraction composition and crystallinity was also correlated to the efficiency of the hydrolysis step, performed using the enzymatic complex Cellic CTec3.

Organosolv pretreatment for biorefineries: Current status, perspectives, and challenges

Biorefineries integrate processes for the sustainable conversion of biomass into chemicals, materials, and bioenergy so that resources are optimized and effluents are minimized. Despite the vast potential of lignocellulosic biorefineries, their success depends heavily on effective, economically viable, and sustainable biomass fractionation. Although efficient, organosolv pretreatment still faces challenges that must be overcome for its widespread utilization, mainly related to solvent type and recycling, robustness regarding biomass type and integration of hemicellulose recovery and use. This review shows the recent advances and state-of-the-art of organosolv pretreatment, discussing the advances, such as the use of biobased solvents, whilst also shedding light on the perspectives of using the streams - cellulose, hemicellulose, and lignin - to produce biofuels and products of high added value. In addition, it presents an overview of the existing industrial implementations of organosolv processes and, lastly, shows the main scientific and industrial challenges and opportunities for this process.

Advances in organosolv modified components occurring during the organosolv pretreatment of lignocellulosic biomass

The valorization of organosolv pretreatment (OP) is a required approach to the industrialization of the current enzyme-mediated lignocellulosic biorefinery. Recent literature has demonstrated that the solvolysis happening in the OP can modify the soluble components into value-added active compounds, namely organosolv modified lignin (OML) and organosolv modified sugars (OMSs), in addition to protecting them against excessive degradation. Among them, the OML is coincidental with the "lignin-first" strategy that should render a highly reactive lignin enriched with β-O-4 linkages and less condensed structure by organosolv grafting, which is desirable for the transformation into phenolic compounds. The OMSs are valuable glycosidic compounds mainly synthesized by trans-glycosylation, which can find potential applications in cosmetics, foods, and healthcare. Therefore, a state-of-the-art OP holds a big promise of lowering the process cost by the valorization of these active compounds. Recent advances in organosolv modified components are reviewed, and perspectives are made for addressing future challenges.

An insight into the principles of lignocellulosic biomass-based zero-waste biorefineries: a green leap towards imperishable energy-based future

Lignocellulosic biomass (LCB) is an energy source that has a huge impact in today's world. The depletion of fossil fuels, increased pollution, climatic changes, etc. have led the public and private sectors to move towards sustainability i.e. using LCB for the production of biofuels and value-added compounds. A major bottleneck of the process is the recalcitrant nature of LCB. This can be overcome by using various pretreatment strategies like physical, chemical, biological, physicochemical, etc. Further, the pretreated biomass is made to undergo various steps like hydrolysis, saccharification, etc. for the conversion of value-added products and the remaining waste residues can be further utilized for the synthesis of secondary products thus favouring the zero-waste biorefinery concept. Currently, microorganisms are being explored for their use in biorefinery but the unavailability of commercial strains is a major limitation. Thus, the use of metagenomics can be used to overcome the limitation which is both cost-effective and environmentally friendly. The review deliberates the composition of LCBs, and their recalcitrance nature, followed by the structural changes caused by various pretreatment methods. The further steps in biorefineries, strategies for the development of zero-waste refineries, bottlenecks, and suggestions are also discussed. Special emphasis is given to the use of metagenomics for the discovery of microorganisms efficient for zero-waste biorefineries.

Effective Mild Ethanol-Based Organosolv Pre-Treatment for the Selective Valorization of Polysaccharides and Lignin from Agricultural and Forestry Residues

Organosolv pre-treatments aiming to selectively remove and depolymerise lignin and hemicellulose and yield an easily digestible cellulose fraction are one of the potential options for industrial implementation within the biorefinery concept. However, the use of high temperatures and/or high catalyst concentrations is still hindering its wide adoption. In this work, mild temperature organosolv processes (140 °C) that were either non-catalysed or catalysed with sulphuric or acetic acid were compared to standard similar conditions using ethanol-based organosolv for both wheat straw (WS) and eucalyptus wood residues (ERs) as agricultural and forestry-derived model raw materials, respectively. The experimental results demonstrated that high cellulose purities could be obtained for the catalysed ethanol-based processing of the WS, which resulted in high saccharification yields (>80%), conversely to the non-catalysed process, which only reached values close to 70%. For eucalyptus residues (ERs), the pulp yields obtained were lower than the values obtained for the WS, suggesting that the ERs were a more reactive material. Cellulose purity was higher than that obtained for the corresponding treatment for the WS, with the highest cellulose purity being obtained for the ethanol-based process catalysed with sulphuric acid. Both materials presented high lignin yield recovery in the liquid stream.