Recovery and Utilization of Lignin Monomers as Part of the Biorefinery Approach

Lignin is a substantial component of lignocellulosic biomass but is under-utilized relative to the cellulose and hemicellulose components. Historically, lignin has been burned as a source of process heat, but this heat is usually in excess of the process energy demands. Current models indicate that development of an economically competitive biorefinery system requires adding value to lignin beyond process heat. This addition of value, also known as lignin valorization, requires economically viable processes for separating the lignin from the other biomass components, depolymerizing the lignin into monomeric subunits, and then upgrading these monomers to a value-added product. The fact that lignin’s biological role is to provide biomass with structural integrity means that this heteropolymer can be difficult to depolymerize. However, there are chemical and biological routes to upgrade lignin from its native form to compounds of industrial value. Here we review the historical background and current technology of (thermo) chemical depolymerization of lignin; the natural ability of microbial enzymes and pathways to utilize lignin, the current prospecting work to find novel microbial routes to lignin degradation, and some applications of these microbial enzymes and pathways; and the current chemical and biological technologies to upgrade lignin-derived monomers

Heterogeneously catalyzed lignin depolymerization

Biomass offers a unique resource for the sustainable production of bio-derived chemical and fuels as drop-in replacements for the current fossil fuel products. Lignin represents a major component of lignocellulosic biomass, but is particularly recalcitrant for valorization by existing chemical technologies due to its complex cross-linking polymeric network. Here, we highlight a range of catalytic approaches to lignin depolymerisation for the production of aromatic bio-oil and monomeric oxygenates

Valorisation of lignin by depolymerisation and fractionation using supercritical fluids and conventional solvents

A procedure for Lignosulphonate valorisation is investigated. An attempt has been made to obtain diverse value-added products maximizing the atom economy. This procedure is carried in sequential steps starting with an oxidative depolymerization in supercritical water. Next, the reaction mixture is fractionated according to its solubility in water and in ethyl acetate. Several analytical methods - CHN elemental analysis, aqueous GPC and 31P-NMR - were used to determine the composition of these fractions and to assess their suitability for different applications. Water-insoluble fractions were converted to a lignin-derived hydrochar for the synthesis of active carbon of superior quality. Monomers were recovered from bio-oil fraction by supercritical carbon dioxide extraction and the remaining oil is proposed as a potential starting material for the synthesis of polyurethane foams

Obtaining lignin nanoparticles by sonication

Lignin, the main natural aromatic polymer was always aroused researchers interest. Currently around 90% of this biomaterial is burned for energy. It has a very complex and complicated structure which depends on the separation method and plant species, what determine difficulties to use as a raw material widely. This research presents a physical method to modify lignin by ultrasonic irradiation in order to obtain nanoparticles. The nanoparticles synthesized were dimensionally and morphologically characterized. At the same time the preoccupations were to determine the structural and compositional changes that occurred after sonication. To achieve this, two types of commercial lignins (wheat straw and Sarkanda grass) were used and the modifications were analyzed by FTIR-spectroscopy, GPC-chromatography, (31)P-NMR-spectroscopy and HSQC0. The results confirm that the compositional and structural changes of nanoparticles obtained are not significantly modified at the intensity applied but depend on the nature of lignin

Aplicação de abordagens químicas e biológicas para valorização da lignina

Orientador: Fabio Marcio SquinaTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: As atividades voltadas para a produção comercial de etanol a partir de materiais lignocelulósicos criaram a oportunidade de desenvolver novas tecnologias utilizando correntes de processos com alto conteúdo de lignina. Encontrar aplicações para a lignina que possam agregar maior valor, em comparação com a queima para produção de energia, torna-se imprescindível para viabilizar estes processos no contexto de biorefinarias. A lignina é um polímero aromático com características singulares. Devido à sua estrutura molecular heterogênea, a lignina ainda é um polímero inexplorado em tecnologias de bioconversão. As estratégias emergentes para as transformações de ligninas são focadas em catálises inorgânicas, orgânicas ou na combinação de ambas. Sob esta perspectiva, este trabalho buscou desenvolver estratégias químicas e biológicas para valorizar correntes de lignina geradas no processamento do bagaço de cana-de-açúcar. Neste contexto, como estratégia química, fragmentos de lignina derivadas de tratamento alcalino de bagaço de cana-de-açúcar, depois de processo de explosão a vapor, foram submetidas a um processo de acidificação. As frações solúveis produzidas em diferentes valores de pH foram caracterizadas quimicamente e a capacidade antioxidante in vitro contra espécies reativas de oxigênio e nitrogênio foram avaliadas. Em comparação com as outras frações obtidas neste trabalho, a fração solúvel obtida em pH 2 apresentou as melhores capacidades de eliminação contra todas as espécies de radicais testadas (10,2 ± 0,7 mmol Trolox equivalente g-1 para ROO?, IC30 = 14,9 ?g mL-1 para H2O2 e IC50 = 2,3 ?g mL-1 para ONOO-), bem como apresentou a menor polidispersidade (1,2). Dados biofísicos mostraram que as moléculas presentes nas frações solúveis obtidas em pH 4 e 2 consistiam estruturalmente em pequenos discos com raio e espessura média de 0,31 nm e polifenóis de baixo peso molecular (~ 400 Da), enquanto que frações solúveis obtidas em pH elevados predominavam nanopartículas de lignina (discos com raio maiores que 1,1 nm e espessura em torno de 0,7 nm) e agregados com dimensão fractal em torno de 2,8 nm. Em todas as frações solúveis foram identificados compostos fenólicos e não fenólicos conhecidos como eficientes antioxidantes na literatura. Estes resultados demostraram que o tratamento de acidificação é uma estratégia simples e promissora para valorizar correntes heterogêneas de ligninas provenientes do processamento do bagaço, obtendo-se preparações com composições com reduzida polidispersidade e alta capacidade antioxidante. Neste trabalho de doutorado também foram avaliados processos enzimáticos para valorização da lignina. Foi explorado o potencial de duas lacases fúngicas juntamente com um mediador para isolar ligninas de baixo peso molecular a partir da biomassa lignocelulósica. As ligninas isoladas foram utilizadas como doadores de elétrons para a ativação de monooxigenases de polissacarídeos líticas (LPMOs). Uma correlação direta entre a lignina de baixo peso molecular obtida com o sistema mediador-lacase e o aumento na atividade de um coquetel celulolítico comercial contendo LPMOs foi encontrada quando a celulose pura foi hidrolisada. Nas condições testadas no trabalho, a co-incubação das lacases com com o coquetel contendo LPMOs resultou em uma competição pelo substrato oxigênio, inibindo as LPMOs. O tratamento com lacases podem ter causado outras modificações na presença de celulose, tornando o material mais recalcitrante para a sacarificação enzimática. Finalmente, visando a descoberta e aplicação de novos biocatalizadores envolvidos na desconstrução e valorização de material lignocelulósico, o basidiomiceto derivado do mar Peniophora sp. CBMAI 1063 cultivado em condições salinas teve seu genoma sequenciado, os genes anotados e o conteúdo proteico do secretoma analisado. Os estudos mostraram que o fungo possui um espectro enzimático ligninolítico completo e versátil, produzindo especialmente enzimas envolvidas na degradação da lignina. A principal lacase secretada pelo fungo mostrou potencial em tecnologias de bioconversão, promovendo modificação, despolimerização e solubilização de ligninas do bagaçoAbstract: The development of commercial production of ethanol from lignocellulosic materials has created the opportunity to increase the transformation of lignin streams into high added-value applications. Finding applications for lignin valorization instead of combustion for energy production is essential to make biorefineries an element of sustainable development. Lignin is a complex aromatic polymer with unique characteristics. However, due to its molecular structure, lignin is an untapped resource in bioconversion technologies. Emerging strategies for lignin transformations focus on inorganic or organic catalysis or a combination of both. This thesis focuses on chemical and biological strategies to add value to lignin from sugarcane bagasse. Lignin obtained from alkaline treatment of steam-exploded sugarcane bagasse was submitted to an acidification process. The soluble fractions produced at different pH were comprehensively characterized, and in vitro antioxidant capacity against reactive oxygen and nitrogen species was evaluated. The soluble fraction obtained at pH 2 exhibited the highest scavenging capacities against all tested species (10.2 ± 0.7 mmol Trolox equivalent g?1 for ROO?, IC30 = 14.9 ?g mL?1 for H2O2 and IC50 = 2.3 ?g mL?1 for ONOO?) and the lowest polydispersity value (1.2). Biophysical data showed that the soluble fractions obtained at pH 4 and pH 2 consisted of small nanometer-sized discs with average radius and thickness of 0.31 nm made from low molecular weight polyphenolics (~400 Da). In the soluble fractions obtained at high pH larger lignin nanoparticles (average disk radius higher than 1.1 nm and disk thickness around 0.7 nm) and larger aggregates with fractal dimension of 2.8 nm were found. Phenolic and non-phenolic compounds, well-known as efficient antioxidants, were identified in all soluble fractions. The results provided, further demonstrates that acidification treatment is a promising strategy to upgrade heterogeneous lignin-enriched stream from sugarcane bagasse, such as preparations with homogeneous compositions and high antioxidant capacity. Furthermore, the potential of two fungal laccases together with a mediator to isolate low molecular weight lignin from lignocellulosic biomass was explored. These lignins were used as electron donors for activation of lytic polysaccharide monooxygenases (LPMOs). For cellulose hydrolysis a direct correlation between the low molecular weight lignin obtained with laccases and the activity of a cellulolytic cocktail containing LPMOs was found. Under the conditions tested, the co-incubation of laccases with LPMOs showed a substrate competition towards LPMOs inhibition by oxygen. Also laccase treatment may cause other modifications in presence of cellulose, rendering the material more recalcitrant for enzymatic saccharification. Finally, regarding the discovery of new enzymes for lignin deconstruction, the genome sequencing, annotation and secretome analysis of the marine-derived basidiomycete Peniophora sp. CBMAI 1063 grown under saline optimal conditions were performed. Omics studies showed that this fungus possesses a complete and versatile enzymatic spectrum, especially enzymes involved in lignin degradation. In addition, the major secreted laccase exhibited potential to lignocellulose bioconversion new technologies, promoting lignin modification, depolymerization and solubilizationDoutoradoBioquimicaDoutora em Biologia Funcional e Molecular2013/03061-0FAPES

Added-value chemicals from lignin oxidation

Lignin is the second most abundant component, next to cellulose, in lignocellulosic biomass. Large amounts of this polymer are produced annually in the pulp and paper industries as a coproduct from the cooking process-most of it burned as fuel for energy. Strategies regarding lignin valorization have attracted significant attention over the recent decades due to lignin’s aromatic structure. Oxidative depolymerization allows converting lignin into added-value compounds, as phenolic monomers and/or dicarboxylic acids, which could be an excellent alternative to aromatic petrochemicals. However, the major challenge is to enhance the reactivity and selectivity of the lignin structure towards depolymerization and prevent condensation reactions. This review includes a comprehensive overview of the main contributions of lignin valorization through oxidative depolymerization to produce added-value compounds (vanillin and syringaldehyde) that have been developed over the recent decades in the LSRE group. An evaluation of the valuable products obtained from oxidation in an alkaline medium with oxygen of lignins and liquors from different sources and delignification processes is also provided. A review of C4 dicarboxylic acids obtained from lignin oxidation is also included, emphasizing catalytic conversion by O2 or H2O2 oxidation.This work was financially supported by Base Funding—UIDB/50020/2020 and Programmatic- UIDP/50020/2020 Funding of the Associate Laboratory LSRE-LCM—funded by national funds through FCT/MCTES (PIDDAC) and Base Funding—UIDB/00690/2020 of CIMO— Centro de Investigação de Montanha—funded by national funds through FCT/MCTES (PIDDAC). COST Action LignoCOST (CA17128). Carlos Vega-Aguilar thanks the Costa Rican Science, Technology and Telecommunications Ministry for the PhD. Scholarship MICITT-PINN-CON-2-1-4-17-1-002.info:eu-repo/semantics/publishedVersio

Guiding stars to the field of dreams: Metabolically engineered pathways and microbial platforms for a sustainable lignin-based industry

Lignin is an important structural component of terrestrial plants and is readily generated during biomass fractionation in lignocellulose processing facilities. Due to lacking alternatives the majority of technical lignins is industrially simply burned into heat and energy. However, considering its vast abundance and a chemically interesting richness in aromatics, lignin is presently regarded both as the most under-utilized and promising feedstock for value-added applications. Notably, microbes have evolved powerful enzymes and pathways that break down lignin and metabolize its various aromatic components. This natural pathway atlas meanwhile serves as a guiding star for metabolic engineers to breed designed cell factories and efficiently upgrade this global waste stream. The metabolism of aromatic compounds, in combination with success stories from systems metabolic engineering, as reviewed here, promises a sustainable product portfolio from lignin, comprising bulk and specialty chemicals, biomaterials, and fuels

Recent advances on the utilization of layered double hydroxides (LDHs) and related heterogeneous catalysts in a lignocellulosic-feedstock biorefinery scheme

Layered double hydroxides (LDHs) and derived materials have been widely used as heterogeneous catalysts for different types of reactions either in gas or in liquid phase. Among these processes, the valorization/upgrading of lignocellulosic biomass and derived molecules have attracted enormous attention because it constitutes a pivotal axis in the transition from an economic model based on fossil resources to one based on renewable biomass resources with preference for biomass waste streams. Proof of this is the increasing amount of literature reports regarding the rational design and implementation of LDHs and related materials in catalytic processes such as: depolymerization, hydrogenation, selective oxidations, and C-C coupling reactions, among others, where biomass-derived compounds are used. The major aim of this contribution is to situate the most recent advances on the implementation of these types of catalysts into a lignocellulosic-feedstock biorefinery scheme, highlighting the versatility of LDHs and derived materials as multifunctional, tunable, cheap and easy to produce heterogeneous catalysts

Redefining biorefinery: the search for unconventional building blocks for materials

This review discusses different strategies for the upgrading of biomass into sustainable monomers and building blocks as scaffolds for the preparation of green polymers and materials