Lignin-First Fractionation of Softwood Lignocellulose Using a Mild Dimethyl Carbonate and Ethylene Glycol Organosolv Process

The contemporary nexus of medicines security and bioprospecting: a future perspective for prioritizing the patient

Reacting to the challenges presented by the evolving nexus of environmental change, defossilization, and diversified natural product bioprospecting is vitally important for advancing global healthcare and placing patient benefit as the most important consideration. This overview emphasizes the importance of natural and synthetic medicines security and proposes areas for global research action to enhance the quality, safety, and effectiveness of sustainable natural medicines. Following a discussion of some contemporary factors influencing natural products, a rethinking of the paradigms in natural products research is presented in the interwoven contexts of the Fourth and Fifth Industrial Revolutions and based on the optimization of the valuable assets of Earth. Following COP28, bioprospecting is necessary to seek new classes of bioactive metabolites and enzymes for chemoenzymatic synthesis. Focus is placed on those performance and practice modifications which, in a sustainable manner, establish the patient, and the maintenance of their prophylactic and treatment needs, as the priority. Forty initiatives for natural products in healthcare are offered for the patient and the practitioner promoting global action to address issues of sustainability, environmental change, defossilization, quality control, product consistency, and neglected diseases to assure that quality natural medicinal agents will be accessible for future generations.

Clean Synthetic Strategies to Biologically Active Molecules from Lignin: A Green Path to Drug Discovery

Deriving active pharmaceutical agents from renewable resources is crucial to increasing the economic feasibility of modern biorefineries and promises to alleviate critical supply-chain dependencies in pharma manufacturing. Our multidisciplinary approach combines research in lignin-first biorefining, sustainable catalysis, and alternative solvents with bioactivity screening, an in vivo efficacy study, and a structural-similarity search. The resulting sustainable path to novel anti-infective, anti-inflammatory, and anticancer molecules enabled the rapid identification of frontrunners for key therapeutic indications, including an anti-infective against the priority pathogen Streptococcus pneumoniae with efficacy in vivo and promising plasma and metabolic stability. Our catalytic methods provided straightforward access, inspired by the innate structural features of lignin, to synthetically challenging biologically active molecules with the core structure of dopamine, namely, tetrahydroisoquinolines, quinazolinones, 3-arylindoles and the natural product tetrahydropapaveroline. Our diverse array of atom-economic transformations produces only harmless side products and uses benign reaction media, such as tunable deep eutectic solvents for modulating reactivity in challenging cyclization steps.

Unleashing the capacity of Rhodococcus for converting lignin into lipids

Bioconversion of bioresources/wastes (e.g., lignin, chemical pulping byproducts) represents a promising approach for developing a bioeconomy to help address growing energy and materials demands. Rhodococcus, a promising microbial strain, utilizes numerous carbon sources to produce lipids, which are precursors for synthesizing biodiesel and aviation fuels. However, compared to chemical conversion, bioconversion involves living cells, which is a more complex system that needs further understanding and upgrading. Various wastes amenable to bioconversion are reviewed herein to highlight the potential of Rhodococci for producing lipid-derived bioproducts. In light of the abundant availability of these substrates, Rhodococcus' metabolic pathways converting them to lipids are analyzed from a "beginning-to-end" view. Based on an in-depth understanding of microbial metabolic routes, genetic modifications of Rhodococcus by employing emerging tools (e.g., multiplex genome editing, biosensors, and genome-scale metabolic models) are presented for promoting the bioconversion. Co-solvent enhanced lignocellulose fractionation (CELF) strategy facilitates the generation of a lignin-derived aromatic stream suitable for the Rhodococcus' utilization. Novel alkali sterilization (AS) and elimination of thermal sterilization (ETS) approaches can significantly enhance the bioaccessibility of lignin and its derived aromatics in aqueous fermentation media, which promotes lipid titer significantly. In order to achieve value-added utilization of lignin, biodiesel and aviation fuel synthesis from lignin and lipids are further discussed. The possible directions for unleashing the capacity of Rhodococcus through synergistically modifying microbial strains, substrates, and fermentation processes are proposed toward a sustainable biological lignin valorization.

Sustainable production of dopamine hydrochloride from softwood lignin

Dopamine is not only a widely used commodity pharmaceutical for treating neurological diseases but also a highly attractive base for advanced carbon materials. Lignin, the waste from the lignocellulosic biomass industry, is the richest source of renewable aromatics on earth. Efficient production of dopamine direct from lignin is a highly desirable target but extremely challenging. Here, we report an innovative strategy for the sustainable production of dopamine hydrochloride from softwood lignin with a mass yield of 6.4 wt.%. Significantly, the solid dopamine hydrochloride is obtained by a simple filtration process in purity of 98.0%, which avoids the tedious separation and purification steps. The approach begins with the acid-catalyzed depolymerization, followed by deprotection, hydrogen-borrowing amination, and hydrolysis of methoxy group, transforming lignin into dopamine hydrochloride. The technical economic analysis predicts that this process is an economically competitive production process. This study fulfills the unexplored potential of dopamine hydrochloride synthesis from lignin.

Chemoenzymatic Cascade Reaction for the Valorization of the Lignin Depolymerization Product G-C2-Dioxolane Phenol

Combining solid acid catalysts with enzyme reactions in aqueous environments is challenging because either very acidic conditions inactivate the enzymes, or the solid acid catalyst is neutralized. In this study, Amberlyst-15 encapsulated in polydimethylsiloxane (Amb-15@PDMS) is used to deprotect the lignin depolymerization product G-C2 dioxolane phenol in a buffered system at pH 6.0. This reaction is directly coupled with the biocatalytic reduction of the released homovanillin to homovanillyl alcohol by recombinant horse liver alcohol dehydrogenase, which is subsequently acylated by the promiscuous acyltransferase/hydrolase PestE_I208A_L209F_N288A in a one-pot system. The deprotection catalyzed with Amb-15@PDMS attains up to 97 % conversion. Overall, this cascade enables conversions of up to 57 %.

Physicochemical Properties, Thermal Stability, and Pyrolysis Behavior of Antioxidative Lignin from Water Chestnut Shell Obtained with Ternary Deep Eutectic Solvents

The molecular weight of lignin extracted from lignocellulosic biomass is an important factor in determining its valorization in industrial processes. Herein, this work aims to explore the extraction of high molecular weight and bioactive lignin from water chestnut shells under mild conditions. Five kinds of deep eutectic solvents were prepared and applied to isolate lignin from water chestnut shells. The extracted lignin was further characterized with element analysis, gel permeation chromatography, and Ultraviolet-visible and Fourier-transform infrared spectroscopy. The distribution of pyrolysis products was identified and quantified with thermogravimetric analysis-Fourier-transform infrared spectroscopy and pyrolysis-gas chromatograph-mass spectrometry. The results showed that choline chloride/ethylene glycol/p-toluenesulfonic acid (1:1.8:0.2 molar ratio) exhibited the highest fractionation efficiency for lignin (84.17% yield) at 100 °C for 2 h. Simultaneously, the lignin showed high purity (90.4%), high relative molecular weight (37,077 g/mol), and excellent uniformity. Furthermore, the aromatic ring structure of lignin remained intact, consisting mainly of p-hydroxyphenyl, syringl, and guaiacyl subunits. The lignin generated a large number of volatile organic compounds during the depolymerization process, mainly composed of ketones, phenols, syringols, guaiacols, esters, and aromatic compounds. Finally, the antioxidant activity of the lignin sample was evaluated with the 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay; the lignin from water chestnut shells showed excellent antioxidant activity. These findings confirm that lignin from water chestnut shells has a broad application prospect in valuable chemicals, biofuels and bio-functional materials.

Highly effective fractionation chemistry to overcome the recalcitrance of softwood lignocellulose

The efficient fractionation and thus production of individual biomass components are pivotal processes in the biorefinery concept. However, the recalcitrant nature of lignocellulose biomass, especially in the case of softwood, is one of the main obstacles to the wider application of biomass-based chemicals and materials. In this study, the use of aqueous acidic systems in the presence of thiourea was studied for the fractionation of softwood in mild conditions. Despite relatively low temperature (100 °C) and treatment times (30-90 min), notable high lignin removal efficiency (approximately 90 %) was obtained. Chemical characterization and the isolation of minor fraction of cationic, water-soluble lignin indicated that the fractionation proceed via nucleophilic addition of thiourea to lignin, resulting in dissolution of lignin in acidic water in relatively mild conditions. Besides high fractionation efficiency, both fiber and lignin fractions were obtained with bright color, significantly elevating their usability in material applications.

Lignocellulosic Biorefinery Technologies: A Perception into Recent Advances in Biomass Fractionation, Biorefineries, Economic Hurdles and Market Outlook

Lignocellulosic biomasses (LCB) are sustainable and abundantly available feedstocks for the production of biofuel and biochemicals via suitable bioconversion processing. The main aim of this review is to focus on strategies needed for the progression of viable lignocellulosic biomass-based biorefineries (integrated approaches) to generate biofuels and biochemicals. Processing biomass in a sustainable manner is a major challenge that demands the accomplishment of basic requirements relating to cost effectiveness and environmental sustainability. The challenges associated with biomass availability and the bioconversion process have been explained in detail in this review. Limitations associated with biomass structural composition can obstruct the feasibility of biofuel production, especially in mono-process approaches. In such cases, biorefinery approaches and integrated systems certainly lead to improved biofuel conversion. This review paper provides a summary of mono and integrated approaches, their limitations and advantages in LCB bioconversion to biofuel and biochemicals.

High value valorization of lignin as environmental benign antimicrobial

Lignin is a natural aromatic polymer of p-hydroxyphenylpropanoids with various biological activities. Noticeably, plants have made use of lignin as biocides to defend themselves from pathogen microbial invasions. Thus, the use of isolated lignin as environmentally benign antimicrobial is believed to be a promising high value approach for lignin valorization. On the other hand, as green and sustainable product of plant photosynthesis, lignin should be beneficial to reduce the carbon footprint of antimicrobial industry. There have been many reports that make use of lignin to prepare antimicrobials for different applications. However, lignin is highly heterogeneous polymers different in their monomers, linkages, molecular weight, and functional groups. The structure and property relationship, and the mechanism of action of lignin as antimicrobial remains ambiguous. To show light on these issues, we reviewed the publications on lignin chemistry, antimicrobial activity of lignin models and isolated lignin and associated mechanism of actions, approaches in synthesis of lignin with improved antimicrobial activity, and the applications of lignin as antimicrobial in different fields. Hopefully, this review will help and inspire researchers in the preparation of lignin antimicrobial for their applications.

Structural elucidation and targeted valorization of poplar lignin from the synergistic hydrothermal-deep eutectic solvent pretreatment

Elucidating the structural variations of lignin during the pretreatment is very important for lignin valorization. Herein, poplar wood was pretreated with an integrated process, which was composed of AlCl₃-catalyzed hydrothermal pretreatment (HTP, 130-150 °C, 1.0 h) and mild deep-eutectic solvents (DES, 100 °C, 10 min) delignification for recycling lignin fractions. Confocal Raman Microscopy (CRM) was developed to visually monitor the delignification process during the HTP-DES pretreatment. NMR characterizations (2D-HSQC and ³¹P NMR) and elemental analysis demonstrated that the lignin fractions had undergone the following structural changes, such as dehydration, depolymerization, condensation. Molecular weights (GPC), microstructure (SEM and TEM), and antioxidant activity (DPPH analysis) of the lignins revealed that the DES delignification resulted in homogeneous lignin fragments (1.32 < PDI < 1.58) and facilitated the rapid assemblage of lignin nanoparticles (LNPs) with controllable nanoscale sizes (30-210 nm) and excellent antioxidant activity. These findings will enhance the understanding of structural transformations of the lignin during the integrated process and maximize the lignin valorization in a current biorefinery process.

Lignin-First Monomers to Catechol: Rational Cleavage of C-O and C-C Bonds over Zeolites

A catalytic route is developed to synthesize bio-renewable catechol from softwood-derived lignin-first monomers. This process concept consists of two steps: 1) O-demethylation of 4-n-propylguaiacol (4-PG) over acidic beta zeolites in hot pressurized liquid water delivering 4-n-propylcatechol (4-PC); 2) gas-phase C-dealkylation of 4-PC providing catechol and propylene over acidic ZSM-5 zeolites in the presence of water. With large pore sized beta-19 zeolite as catalyst, 4-PC is formed with more than 93 % selectivity at nearly full conversion of 4-PG. The acid-catalyzed C-dealkylation over ZSM-5 zeolite with medium pore size gives a catechol yield of 75 %. Overall, around 70 % catechol yield is obtained from pure 4-PG, or 56 % when starting from crude 4-PG monomers obtained from softwood by lignin-first RCF biorefinery. The selective cleavage of functional groups from biobased platform molecules through a green and sustainable process highlights the potential to shift feedstock from fossil oil to biomass, providing drop ins for the chemicals industry.

A review on physico-chemical delignification as a pretreatment of lignocellulosic biomass for enhanced bioconversion

Effective pretreatment of lignocellulosic biomass (LCB) is one of the most important steps in biorefinery, ensuring the quality and commercial viability of the overall bioprocess. Lignin recalcitrance in LCB is a major bottleneck in biological conversion as the polymerization of lignin with hemicellulose hinders enzyme accessibility and further bioconversion to fuels and chemicals. Therefore, there is a need to delignify LCB to ease further bioprocessing. The efficiency of delignification, quality and quantity of the desired products, and generation of inhibitors depend upon the type of pretreatment employed. This review summarizes different single and integrated physicochemical pretreatments for delignification. Additionally, conditions required for effective delignification and the advantages and drawbacks of each method were evaluated. Advances in overcoming the recalcitrance of residual lignin to saccharification and the methods to recover lignin after delignification are also discussed. Efficient lignin recovery and valorization strategies provide an avenue for the sustainable lignocellulose biorefinery.

A one-step deconstruction-separation organosolv fractionation of lignocellulosic biomass using acetone/phenoxyethanol/water ternary solvent system

A novel ternary solvent system for organosolv fractionation of lignocellulosic biomass, named APW process, which is composed of acetone, phenoxyethanol and water with the advantages of monophasic deconstruction and biphasic separation of components was developed. Through fractionation of amorpha as a case study, a monophasic APW solution (acetone/phenoxyethanol/water = 5:11:4, volume ratio) with the best lignin affinity was constructed based on Hansen solubility parameters. According to Taguchi experimental design, the optimal conditions were 130 °C, 70 min, 0.15 M sulfuric acid and 20 LSR. Under optimal conditions, removal of lignin and hemicellulose reached 95.60% and 98.39%, respectively. While 80.48% of cellulose was retained in residue and its digestibility was 80.36%. Then, 83.74% of hemicellulose was recovered from aqueous as sugars, and 35.64% of lignin was recovered by precipitation. Moreover, APW process also have effective fractionation of sugarcane bagasse, corn cob and pine, cellulose and hemicellulose recovery were both over 80%.

Tunable and functional deep eutectic solvents for lignocellulose valorization

Stabilization of reactive intermediates is an enabling concept in biomass fractionation and depolymerization. Deep eutectic solvents (DES) are intriguing green reaction media for biomass processing; however undesired lignin condensation is a typical drawback for most acid-based DES fractionation processes. Here we describe ternary DES systems composed of choline chloride and oxalic acid, additionally incorporating ethylene glycol (or other diols) that provide the desired 'stabilization' function for efficient lignocellulose fractionation, preserving the quality of all lignocellulose constituents. The obtained ethylene-glycol protected lignin displays high β-O-4 content (up to 53 per 100 aromatic units) and can be readily depolymerized to distinct monophenolic products. The cellulose residues, free from condensed lignin particles, deliver up to 95.9 ± 2.12% glucose yield upon enzymatic digestion. The DES can be recovered with high yield and purity and re-used with good efficiency. Notably, we have shown that the reactivity of the β-O-4 linkage in model compounds can be steered towards either cleavage or stabilization, depending on DES composition, demonstrating the advantage of the modular DES composition.

Advances in Versatile Nanoscale Catalyst for the Reductive Catalytic Fractionation of Lignin

In the past five years, biomass-derived biofuels and biochemicals were widely studied both in academia and industry as promising alternatives to petroleum. In this Review, the latest progress of the synthesis and fabrication of porous nanocatalysts that are used in catalytic transformations involving hydrogenolysis of lignin is reviewed in terms of their textural properties, catalytic activities, and stabilities. A particular emphasis is made with regard to the catalyst design for the hydrogenolysis of lignin and/or lignin model compounds. Furthermore, the effects of different supports on the lignin hydrogenolysis/hydrogenation are discussed in detail. Finally, the challenges and future opportunities of lignin hydrogenolysis over nanomaterial-supported catalysts are also presented.

Highly Efficient Semi-Continuous Extraction and In-Line Purification of High β-O-4 Butanosolv Lignin

Innovative biomass fractionation is of major importance for economically competitive biorefineries. Lignin is currently severely underutilized due to the use of high severity fractionation methodologies that yield complex condensed lignin that limits high-value applicability. Mild lignin fractionation conditions can lead to lignin with a more regular C-O bonded structure that has increased potential for higher value applications. Nevertheless, such extraction methodologies typically suffer from inadequate lignin extraction efficiencies and yield. (Semi)-continuous flow extractions are a promising method to achieve improved extraction efficiency of such C-O linked lignin. Here we show that optimized organosolv extraction in a flow-through setup resulted in 93-96% delignification of 40 g walnut shells (40 wt% lignin content) by applying mild organosolv extraction conditions with a 2 g/min flowrate of a 9:1 n-butanol/water mixture with 0.18 M H2SO4 at 120°C in 2.5 h. 85 wt% of the lignin (corrected for alcohol incorporation, moisture content and carbohydrate impurities) was isolated as a powder with a high retention of the β-aryl ether (β-O-4) content of 63 linking motifs per 100 C9 units. Close examination of the isolated lignin showed that the main carbohydrate contamination in the recovered lignin was butyl-xyloside and other butoxylate carbohydrates. The work-up and purification procedure were investigated and improved by the implementation of a caustic soda treatment step and phase separation with a continuous integrated mixer/separator (CINC). This led to a combined 75 wt% yield of the lignin in 3 separate fractions with 3% carbohydrate impurities and a very high β-O-4 content of 67 linking motifs per 100 C9 units. Analysis of all the mass flows showed that 98% of the carbohydrate content was removed with the inline purification step, which is a significant improvement to the 88% carbohydrate removal for the traditional lignin precipitation work-up procedure. Overall we show a convenient method for inline extraction and purification to obtain high β-O-4 butanosolv lignin in excellent yields.

Recent advances in the valorization of plant biomass

Plant biomass is a highly abundant renewable resource that can be converted into several types of high-value-added products, including chemicals, biofuels and advanced materials. In the last few decades, an increasing number of biomass species and processing techniques have been developed to enhance the application of plant biomass followed by the industrial application of some of the products, during which varied technologies have been successfully developed. In this review, we summarize the different sources of plant biomass, the evolving technologies for treating it, and the various products derived from plant biomass. Moreover, the challenges inherent in the valorization of plant biomass used in high-value-added products are also discussed. Overall, with the increased use of plant biomass, the development of treatment technologies, and the solution of the challenges raised during plant biomass valorization, the value-added products derived from plant biomass will become greater in number and more valuable.

Facilitating enzymatic hydrolysis with a novel guaiacol-based deep eutectic solvent pretreatment

Herein, we established a novel deep eutectic solvent (DES) using lignin-derived guaiacol as hydrogen bond donor (HBD). The sole ChCl/guaiacol system was found to be inefficient for the fractionation of wheat straw (WS), while the incorporation of trace AlCl₃ significantly facilitated the degradation of hemicellulose and lignin, resulting in a complete enzymatic digestibility of the pretreated WS. Further, this study revealed that the DES-degraded lignin was readily precipitated during the washing process, and thus hindered the enzymatic hydrolysis of poplar and bamboo (with hydrolysis yield of 42.03% and 71.67%, respectively). Alkali washing offers a possible approach to remove the precipitated lignin, after which a near 100% hydrolysis yield was also obtained for poplar and bamboo.

New Mechanistic Insights into the Lignin β-O-4 Linkage Acidolysis with Ethylene Glycol Stabilization Aided by Multilevel Computational Chemistry

Acidolysis in conjunction with stabilization of reactive intermediates has emerged as one of the most powerful methods of lignin depolymerization that leads to high aromatic monomer yields. In particular, stabilization of reactive aldehydes using ethylene glycol results in the selective formation of the corresponding cyclic acetals (1,3-dioxolane derivatives) from model compounds, lignin, and even from softwood lignocellulose. Given the high practical utility of this method for future biorefineries, a deeper understanding of the method is desired. Here, we aim to elucidate key mechanistic questions utilizing a combination of experimental and multilevel computational approaches. The multiscale computational protocol used, based on ReaxFF molecular dynamics, represents a realistic scenario, where a typical experimental setup can be reproduced confidently given the explicit molecules of the solute, catalyst, and reagent. The nudged elastic band (NEB) approach allowed us to characterize the key intermolecular interactions involved in the reaction paths leading to crucial intermediates and products. The high level of detail obtained clearly revealed for the first time the unique role of sulfuric acid as a proton donor and acceptor in lignin β-O-4 acidolysis as well as the reaction pathways for ethylene glycol stabilization, and the difference in reactivity between compounds with different methoxy substituents.

Reductive catalytic fractionation of pine wood: elucidating and quantifying the molecular structures in the lignin oil

In-depth structural analysis of biorefined lignin is imperative to understand its physicochemical properties, essential for its efficient valorization to renewable materials and chemicals. Up to now, research on Reductive Catalytic Fractionation (RCF) of lignocellulose biomass, an emerging biorefinery technology, has strongly focused on the formation, separation and quantitative analysis of the abundant lignin-derived phenolic monomers. However, detailed structural information on the linkages in RCF lignin oligomers, constituting up to 50 wt% of RCF lignin, and their quantification, is currently lacking. This study discloses new detailed insights into the pine wood RCF lignin oil's molecular structure through the combination of fractionation and systematic analysis, resulting in the first assignment of the major RCF-derived structural units in the 1H-13C HSQC NMR spectrum of the RCF oligomers. Specifically, β-5 γ-OH, β-5 ethyl, β-1 γ-OH, β-1 ethyl, β-β 2x γ-OH, β-β THF, and 5-5 inter-unit linkages were assigned unambiguously, resulting in the quantification of over 80% of the lignin inter-unit linkages and end-units. Detailed inspection of the native lignin inter-unit linkages and their conversion reveals the occurring hydrogenolysis chemistry and the unambiguous proof of absence of lignin fragment condensation during proper RCF processing. Overall, the study offers an advanced analytical toolbox for future RCF lignin conversion and lignin structural analysis research, and valuable insights for lignin oil valorization purposes.

Toward a Consolidated Lignin Biorefinery: Preserving the Lignin Structure through Additive-Free Protection Strategies

As part of the continuing efforts in lignin-first biorefinery concepts, this study concerns a consolidated green processing approach to obtain high yields of hemicelluloses and lignin with a close to native molecular structure, leaving a fiber fraction enriched in crystalline cellulose. This is done by subcritical water extraction of hemicelluloses followed by organosolv lignin extraction. This initial report focuses on a detailed characterization of the lignin component, with the aim of unravelling processing strategies for the preservation of the native linkages while still obtaining good yields and high purity. To this effect, a static cycle process is developed as a physical protection strategy for lignin, and advanced NMR analysis is applied to study structural changes in lignin. Chemical protection mechanisms in the cyclic method are also reported and contrasted with the mechanisms in a reference batch extraction process where the role of homolytic cleavage in subsequent repolymerization reactions is elucidated.

Development of 'Lignin-First' Approaches for the Valorization of Lignocellulosic Biomass

Currently, valorization of lignocellulosic biomass almost exclusively focuses on the production of pulp, paper, and bioethanol from its holocellulose constituent, while the remaining lignin part that comprises the highest carbon content, is burned and treated as waste. Lignin has a complex structure built up from propylphenolic subunits; therefore, its valorization to value-added products (aromatics, phenolics, biogasoline, etc.) is highly desirable. However, during the pulping processes, the original structure of native lignin changes to technical lignin. Due to this extensive structural modification, involving the cleavage of the β-O-4 moieties and the formation of recalcitrant C-C bonds, its catalytic depolymerization requires harsh reaction conditions. In order to apply mild conditions and to gain fewer and uniform products, a new strategy has emerged in the past few years, named 'lignin-first' or 'reductive catalytic fractionation' (RCF). This signifies lignin disassembly prior to carbohydrate valorization. The aim of the present work is to follow historically, year-by-year, the development of 'lignin-first' approach. A compact summary of reached achievements, future perspectives and remaining challenges is also given at the end of the review.

Stabilization strategies in biomass depolymerization using chemical functionalization

A central feature of most lignocellulosic-biomass-valorization strategies is the depolymerization of all its three major constituents: cellulose and hemicellulose to simple sugars, and lignin to phenolic monomers. However, reactive intermediates, generally resulting from dehydration reactions, can participate in undesirable condensation pathways during biomass deconstruction, which have posed fundamental challenges to commercial biomass valorization. Thus, new strategies specifically aim to suppress condensations of reactive intermediates, either avoiding their formation by functionalizing the native structure or intermediates or selectively transforming these intermediates into stable derivatives. These strategies have provided unforeseen upgrading pathways, products and process solutions. In this Review, we outline the molecular driving forces that shape the deconstruction landscape and describe the strategies for chemical functionalization. We then offer an outlook on further developments and the potential of these strategies to sustainably produce renewable-platform chemicals.