Phenolic Lignin Research Articles

An Engineered Laccase from Fomitiporia mediterranea Accelerates Lignocellulose Degradation.

Laccases from white-rot fungi catalyze lignin depolymerization, a critical first step to upgrading lignin to valuable biodiesel fuels and chemicals. In this study, a wildtype laccase from the basidiomycete Fomitiporia mediterranea (Fom_lac) and a variant engineered to have a carbohydrate-binding module (Fom_CBM) were studied for their ability to catalyze cleavage of β-O-4' ether and C-C bonds in phenolic and non-phenolic lignin dimers using a nanostructure-initiator mass spectrometry-based assay. Fom_lac and Fom_CBM catalyze β-O-4' ether and C-C bond breaking, with higher activity under acidic conditions (pH < 6). The potential of Fom_lac and Fom_CBM to enhance saccharification yields from untreated and ionic liquid pretreated pine was also investigated. Adding Fom_CBM to mixtures of cellulases and hemicellulases improved sugar yields by 140% on untreated pine and 32% on cholinium lysinate pretreated pine when compared to the inclusion of Fom_lac to the same mixtures. Adding either Fom_lac or Fom_CBM to mixtures of cellulases and hemicellulases effectively accelerates enzymatic hydrolysis, demonstrating its potential applications for lignocellulose valorization. We postulate that additional increases in sugar yields for the Fom_CBM enzyme mixtures were due to Fom_CBM being brought more proximal to lignin through binding to either cellulose or lignin itself.

Engineered Ru on HY zeolite catalyst for continuous and selective hydrodeoxygenation of lignin phenolics to cycloalkanes under moderate conditions

We report a continuous selective hydrodeoxygenation (HDO) process of guaiacol conversion to cycloalkanes under 180 °C/1 MPa, which results in improved HDO chemistry for lignin-based jet fuel production. The incipient wetness impregnation method was modified to prepare an HY zeolite-supported Ru catalyst with better metal dispersion and acid site uniformity, which overcomes the low conversion and selectivity of previous literature. The modified catalyst (Ru-HY-60-MI) was tested in a continuous fixed bed reactor, resulting in increased HDO conversion of guaiacol to cycloalkanes compared to the unmodified catalyst. Pressure, temperature, and weight hourly space velocity-dependent tests validate guaiacol HDO over Ru-HY-60-MI catalyzed ring hydrogenation of guaiacol to 2-methoxycyclohexanol, acid-catalyzed demethoxylation and dehydration to cyclohexene, and further hydrogenation of cyclohexene to cyclohexane. These experiments enable exploring a continuous HDO process, demonstrate effectiveness for other β-β and α-O-4 lignin representatives and real lignin bio-oil, and pave the way towards commercialization of lignin-based jet fuel.

Phenolic Compounds and Antioxidant Capacity Comparison of Wild-Type and Yellow-Leaf gl1 Mutant of Lagerstroemia indica.

The yellow-leaf gl1 mutant of Lagerstroemia indica exhibits an altered phenylpropanoid metabolism pathway compared to wild-type (WT). However, details on the metabolites associated with leaf color variation, including color-specific metabolites with bioactive constituents, are not fully understood. Chemical and metabolomics approaches were used to compare metabolite composition and antioxidant capacity between the gl1 mutant and WT leaves. The mutant exhibited an irregular xylem structure with a significantly lower phenolic polymer lignin content and higher soluble phenolic compounds. Untargeted metabolomics analysis identified phenolic compounds, particularly lignans, as key differential metabolites between gl1 and WT, with a significant increase in the mutant. The neolignan derivative balanophonin-4-O-D-glu was identified as a characteristic metabolite in the gl1 mutant. The soluble phenolic compounds of the gl1 mutant exhibited higher FRAP, ABTS, DPPH, and hydroxyl radical scavenging activity than in WT. Correlation analysis showed a positive relationship between antioxidant capacity and phenolic compounds in L. indica. Metabolites associated with leaf color variation in the L. indica yellow-leaf gl1 mutant demonstrated high antioxidant capacity, particularly in scavenging hydroxyl radicals.

Long-term biogas slurry application increases microbial necromass but not plant lignin contribution to soil organic carbon in paddy soils as regulated by fungal community

Biogas slurry (BS) is widely considered as a source of organic matter and nutrients for improving soil organic carbon (SOC) sequestration and crop production in agroecosystems. Microbial necromass C (MNC) is considered one of the major precursors of SOC sequestration, which is regulated by soil microbial anabolism and catabolism. However, the microbial mechanisms through which BS application increases SOC accumulation in paddy soils have not yet been elucidated. A 12-year field experiment with four treatments (CK, no fertilizers; CF, chemical fertilizer application; BS1 and BS2, biogas slurry application at two nitrogen rates from BS) was conducted in rice paddy fields. The results showed that long-term BS application had no effect on lignin phenols proportion in SOC relative to CF. In contrast, BS application elevated the MNC contribution to SOC by 15.5–20.5 % compared with the CF treatment. The proportion of fungal necromass C (FNC) to SOC increased by 16.0 % under BS1 and by 25.8 % under BS2 compared with the CF treatment, while no significant difference in bacterial necromass C (BNC) contribution to SOC was observed between the BS and CF treatments. The MNC was more closely correlated with fungal community structures than with bacterial community structures. We further found that fungal genera, Mortierella and Ciliophora, mainly regulated the MNC, FNC and BNC accumulation. Collectively, our results highlighted that fungi play a vital role in SOC storage in paddy soils by regulating MNC formation and accumulation under long-term BS application.

Intercropping regulates plant- and microbe-derived carbon accumulation by influencing soil physicochemical and microbial physiological properties

Intercropping can increase soil carbon (C) sequestration and utilization by planting a variety of plants on a same land. However, the main plant and microbial-driven pathways leading to the increased C sequestration in intercropping soils are rarely studied. Therefore, it is important to reveal the distinct contributions of plant- and microbe-derived C to soil organic C (SOC) for understanding the regulation of intercropping in global C storage. Herein, two widely accepted sets of bio-markers, namely, amino sugars and lignin phenols, were employed to compare the distribution of plant- and microbe-derived C as well as their contributions to SOC in maize monoculture and intercropping systems, based on a field experiment established in 2013; meanwhile, the associations of soil physicochemical properties and microbial physiological traits with plant- and microbe-derived residues were disclosed via correlation and model analysis. Compared with the monoculture, maize intercropping significantly increased soil amino sugar and microbial necromass C contents as well as their contributions to SOC in maize mature stage; maize inter-planted with gingelly or soybean significantly increased these variables in the elongation stage; meanwhile, maize inter-planted with gingelly significantly increased soil lignin phenol content and its contribution to SOC in the mature stage. In all treatments and growth stages, microbial necromass C contributed more to SOC than lignin phenols, and fungal necromass C contributed more to SOC than bacterial necromass. The contribution of microbial necromass C to SOC was mainly influenced by amino sugar content, microbial C use efficiency, dissolved organic C content, and microbial biomass C content. The contribution of plant-derived C to SOC was mainly influenced by lignin phenol content, pH, and NH4+-N content. These results demonstrate the distinct regulations of maize intercropping on plant- and microbe-derived C to soil C pool by influencing soil physicochemical properties and microbial physiological traits, and meanwhile, highlight the potential of intercropping in global C storage.

Enhancement of disease resistance against Alternaria alternata in winter jujube fruit by phenyllactic acid through regulating Ca2+ signaling transduction and mitogen-activated protein kinase cascades

Alternaria rot caused by Alternaria alternata is one of destructive fungal diseases of postharvest winter jujubes. This study performed to evaluate the potential mechanisms participated in the enhancement disease resistance of winter jujubes by phenyllactic acid (PLA). Results demonstrated that PLA reduced the lesion diameter of A. alternata-inoculated winter jujubes. Additionally, PLA treatment led to an up-regulation in the transcription levels of ZjCML23/28, ZjCIPK11/12/20, ZjCDPK1/3/5, ZjMAPKKK18, ZjMAPKK6, and ZjMAPK7/19 as well as ZjNPR1 and ZjWRKY14/22/44/55/64 in fruit. Conversely, the transcription levels of ZjMAPK15 and ZjMAPKKK17 were down-regulated. Simultaneously, PLA enhanced the gene transcription levels and enzymatic activities of peroxidase, β-1,3-glucanase, and chitinase in winter jujubes, while facilitating the deposition of lignin, flavonoids, and total phenolics. Overall, these findings suggest that PLA enhances the resistance of winter jujube fruit via positively modulating the transcription of key Ca2+ receptor protein, activating the mitogen-activated protein kinase cascades, and potentially involving NPR1 and WRKY transcription factors.

Polypropylene packaging alleviates the quality deterioration of Lentinus edodes through antioxidant system and phenylpropane pathway

Lentinus edodes (L. edodes) is a popular edible mushroom, which is very easy to rot and deteriorate after harvest. The quality of L. edodes were significantly affected by different packaging materials. Hence, polypropylene (PP) or polyethylene (PE) packaging were employed to explore the effects and underlying mechanisms on the post-harvested quality of L. edodes. Compared with PE packaging, PP packaging could maintain good storage quality and membrane integrity of L. edodes by reducing oxidative damage, which might be related to the significantly decreased relative electrolyte leakage and malondialdehyde content at the later stage of storage. Also, PP packaging could improve the antioxidant ability and inhibit the production of H2O2 by the decreased catalase and increased superoxide dismutase content. Phenylalanine ammonia lyase, phenylalanine ammonia lyase and cinnamaldehyde dehydrogenase, as the key enzymes in the metabolic pathway of phenylpropane, increased at the later storage of PP-packaged L. edodes. It helped the synthesis of phenolic substances and lignin accumulation. These results indicated PP packaging could be an effective material for maintaining the postharvest storage quality of L. edodes, which might be related to the antioxidant system and phenylpropane pathway.

Bioaugmentation with Advenella kashmirensis for the treatment of a kraft pulp effluent by aerated lagoon

Brazil is considered a world leader in paper production. It is estimated that the sector contributes 46.5% of the national gross domestic product, and its effluents have high concentrations of organic matter and recalcitrant compounds which can cause coloration and ecotoxicity, generating impact if not properly treated. A potential strategy for the treatment of this wastewater is bioaugmentation with native bacteria isolated from the industrial sludge and effluent, which, due to their potential metabolism adapted to adverse environmental conditions, may favor the removal of specific compounds. When associated with immobilization techniques, the inoculum can develop as a biofilm adhered to a support medium, which provides surfaces for adhesion, growth and survival of bacteria. We therefore investigated the treatment of Kraft pulp effluent by bioaugmentation with the autochthonous bacterium Advenella kashmirensis both immobilized in a spongy support medium - Aqua Porous Gel (APG) - and in free-swimming (planktonic) form, denominated Phase I and II, respectively. The investigation was performed in a bench-scale aerated lagoon system with untreated industrial effluent. The effect of the use of bacteria in bioaugmentation was assessed by the removal parameters of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Color, Total Phenolic Compounds (TPC) and Lignin Compounds (LC). The results indicate that both Phases I and II were efficient for the treatment of COD, BOD5 and color parameters. However, the biofilm form provided better stability to the biological system in the treatment of the Kraft pulp effluent.&#x0D; Keywords: adhered, kraft effluent, SEM, suspended solids.

Contributions of plant‐ and microbial‐derived residuals to mangrove soil carbon stocks: Implications for blue carbon sequestration

Abstract Coastal blue carbon ecosystems, particularly mangroves, are becoming increasingly recognised for their importance in mitigating climate change. Still, the specific patterns and drivers of plant lignin components and microbial necromass accumulation in these ecosystems are unclear. In response, we carried out a study along a 40‐year mangrove restoration chronosequence, measuring lignin phenol and amino sugar concentrations in soil profiles (0–100 cm) as indicators of plant‐based and microbial‐derived residues, respectively. Our results showed that restoration significantly increased plant lignin phenol and amino sugar concentrations, with mature mangroves having much higher concentrations than tidal flats. During restoration, the fungal necromass was greater than the bacterial necromass. The factors influencing the lignin phenols were tree biomass, total nitrogen, pH and salinity, while those influencing the formation of amino sugars were total biomass, soil C: N ratio and pH. While the amino sugars decreased, the lignin phenols increased with the content of SOC, providing evidence of the important role lignin phenol components play in the formation of SOC in mangrove. Synthesis: By separating soil carbon into plant‐based and microbial‐derived components, our results demonstrate that the carbon stock in mangrove sediments is vulnerable to disturbances and that changes from anaerobic to aerobic conditions cause significant carbon mineralisation. The precise identification of soil carbon sources in blue carbon ecosystems could aid in elucidating the mechanisms of soil carbon sequestration and their responses to environmental changes. Read the free Plain Language Summary for this article on the Journal blog.

Comparative analyses reveal a phenylalanine ammonia lyase dependent and salicylic acid mediated host resistance in Zingiber zerumbet against the necrotrophic soft rot pathogen Pythium myriotylum

Little is known about the molecular basis of host defense in resistant wild species Zingiber zerumbet (L.) Smith against the soil-borne, necrotrophic oomycete pathogen Pythium myriotylum Drechsler, which causes the devastating soft rot disease in the spice crop ginger (Zingiber officinale Roscoe). We investigated the pattern of host defense between Z. zerumbet and ginger in response to P. myriotylum inoculation. Analysis of gene expression microarray data revealed enrichment of phenylpropanoid biosynthetic genes, particularly lignin biosynthesis genes, in pathogen-inoculated Z. zerumbet compared to ginger. RT-qPCR analysis showed the robust activation of phenylpropanoid biosynthesis genes in Z. zerumbet, including the core genes PAL, C4H, 4CL, and the monolignol biosynthesis and polymerization genes such as CCR, CAD, C3H, CCoAOMT, F5H, COMT, and LAC. Additionally, Z. zerumbet exhibited the accumulation of the phenolic acids including p-coumaric acid, sinapic acid, and ferulic acid that are characteristic of the cell walls of commelinoid monocots like Zingiberaceae and are involved in cell wall strengthening by cross linking with lignin. Z. zerumbet also had higher total lignin and total phenolics content compared to pathogen-inoculated ginger. Phloroglucinol staining revealed the enhanced fortification of cell walls in Z. zerumbet, specifically in xylem vessels and surrounding cells. The trypan blue staining indicated inhibition of pathogen growth in Z. zerumbet at the first leaf whorl, while ginger showed complete colonization of the pith within 36 h post inoculation (hpi). Accumulation of salicylic acid (SA) and induction of SA regulator NPR1 and the signaling marker PR1 were observed in Z. zerumbet. Silencing of PAL in Z. zerumbet through VIGS suppressed downstream genes, leading to reduced phenylpropanoid accumulation and SA level, resulting in the susceptibility of plants to P. myriotylum. These findings highlight the essential role of PAL-dependent mechanisms in resistance against P. myriotylum in Z. zerumbet. Moreover, our results suggest an unconventional role for SA in mediating host resistance against a necrotroph. Targeting the phenylpropanoid pathway could be a promising strategy for the effective management of P. myriotylum in ginger.

N-fixing tree species promote the chemical stability of soil organic carbon in subtropical plantations through increasing the relative contribution of plant-derived lipids

Biodiversity experiments have shown that soil organic carbon (SOC) is not only a function of plant diversity, but is also closely related to the nitrogen (N) -fixing plants. However, the effect of N-fixing trees on SOC chemical stability is still little known, especially with the compounding effects of tree species diversity. An experimental field manipulation was established in subtropical plantations of southern China to explore the impacts of tree species richness (i.e., one, two, four and six tree species) and with/without N-fixing trees on SOC chemical stability, as indicated by the ratio of easily oxidized organic carbon to SOC (EOC/SOC). Plant-derived C components in terms of hydrolysable plant lipids and lignin phenols were isolated from soils for evaluating their relative contributions to SOC chemical stability. The results showed that N-fixing tree species rather than tree species richness had a significant effect on EOC/SOC. Hydrolysable plant lipids and lignin phenols were negatively correlated with EOC/SOC, while hydrolysable plant lipids contributed more to EOC/SOC than lignin phenols, especially in the occurrence of N-fixing trees. The presence of N-fixing tree species led to an increase in soil N availability and a decrease in fungal abundance, promoting the selective retention of certain key components of hydrolysable plant lipids, thus enhancing SOC chemical stability. These findings underpin the crucial role of N-fixing trees in shaping SOC chemical stability, and therefore, preferential selection of N-fixing tree species in mixed plantations is an appropriate silvicultural strategy to improve SOC chemical stability in subtropical plantations.

Selective Sorting and Degradation of Permafrost Organic Matter in the Nearshore Zone of Herschel Island (Yukon, Canada)

AbstractErosion of permafrost coasts due to climate warming releases large quantities of organic carbon (OC) into the Arctic Ocean. While burial of permafrost OC in marine sediments potentially limits degradation, resuspension of sediments in the nearshore zone potentially enhances degradation and greenhouse gas production, adding to the “permafrost carbon feedback.” Recent studies, focusing on bulk sediments, suggest that permafrost OC derived from coastal erosion is predominantly deposited close to shore. However, bulk approaches disregard sorting processes in the coastal zone, which strongly influence the OC distribution and fate. We studied soils and sediments along a transect from the fast‐eroding shoreline of Herschel Island—Qikiqtaruk (Yukon, Canada) to a depositional basin offshore. Sample material was fractionated by density (1.8 g cm−3) and size (63 μm), separating loose OC from mineral‐associated OC. Each fraction was analyzed for element content (TOC, TN), carbon isotopes (δ13C, Δ14C), molecular biomarkers (n‐alkanes, n‐alkanoic acids, lignin phenols, cutin acids), and mineral surface area. The OC partitioning between fractions changes considerably along the transect, highlighting the importance of hydrodynamic sorting in the nearshore zone. Additionally, OC and biomarker loadings decrease along the land‐ocean transect, indicating significant loss of OC during transport. However, molecular proxies for degradation show contrasting trends, suggesting that OC losses are not always well reflected in its degradation state. This study, using fraction partitioning that crosses land‐ocean boundaries in a way not done before, aids to disentangle sorting processes from degradation patterns, and provides quantitative insight into losses of thawed and eroded permafrost OC.

Identification and expression analysis of whole gene family of Isatis indigotica 4-coumarate: CoA ligase

The 4-coumarate: CoA ligase(4CL) is a key enzyme in the upstream pathway of phenylpropanoids such as flavonoids, soluble phenolic esters, lignans, and lignins in plants. In this study, 13 4CL family members of Arabidopsis thaliana were used as reference sequences to identify the 4CL gene family candidate members of Isatis indigotica from the reported I. indigotica genome. Further bioinformatics analysis and analysis of the expression pattern of 4CL genes and the accumulation pattern of flavonoids were carried out. Thirteen 4CL genes were obtained, named Ii4CL1-Ii4CL13, which were distributed on chromosomes 1, 2, 3, 4, and 6. The analysis of the gene structure and conserved structural domains revealed the intron number of I. indigotica 4CL genes was between 1 and 12 and the protein structural domains were highly conserved. Cis-acting element analysis showed that there were multiple response elements in the promoter sequence of I. indigotica 4CL gene family, and jasmonic acid had the largest number of reaction elements. The collinearity analysis showed that there was a close relationship between the 4CL gene family members of I. indigotica and A. thaliana. As revealed by qPCR results, the expression analysis of the 4CL gene family showed that 10 4CL genes had higher expression levels in the aboveground part of I. indigotica. The content assay of flavonoids in different parts of I. indigotica showed that flavonoids were mainly accumulated in the aboveground part of plants. This study provides a basis for further investigating the roles of the 4CL gene family involved in the biosynthesis of flavonoids in I. indigotica.

Palladium-catalyzed conversion of phenols into tetrahydroacridines

A drug and medicinal skeleton, tetrahydroacridines (including tacrine), were synthesized from phenolic lignin monomers and 2-aminoarylketones via palladium catalysis.

Pathways for vanillin production through alkaline aerobic oxidation of a phenolic lignin model compound, guaiacylglycerol-β-guaiacyl ether, in concentrated aqueous alkali

There are at least two plausible pathways for vanillin production in the alkaline aerobic oxidation of lignin, as suggested by the degradation of model compounds.

Phenolation, amination and cross-linking of lignin: synthesis and characterization of functionalized lignin

Phenolation, amination and cross-linking of lignin: synthesis and characterization of functionalized lignin

Plant- and microbial-mediated soil organic carbon accumulation in Spartina alterniflora salt marshes

Coastal wetlands play a crucial role in the global carbon (C) cycle; however, they have been affected by the invasive plant Spartina alterniflora. The impacts of S. alterniflora invasions on soil organic carbon (SOC) source and composition in wetlands are poorly understood compared to SOC stocks. This hinders the accurate estimation of blue C budgets owing to the long-term effects of S. alterniflora invasions. Here, a space-for-time substitution method was applied to investigate SOC accumulation in invasive 5-, 10-, 15-, 18-, and 21-year-old S. alterniflora communities. This was compared with bare flat in the topsoil (0–10 cm) and subsoil (30–60 cm) of coastal wetlands. Biomarkers (lignin phenols and amino sugars) and Fourier transform infrared spectroscopy were used to describe the accumulation patterns of plant- and microbial-derived C across varying S. alterniflora invasion times, as well as associated stabilization mechanisms. Plant-derived C dominated the SOC content compared to microbial-derived C during S. alterniflora invasions, while microbial-derived C played a more critical role in SOC stability than that of plant-derived C. At both soil depths, microbial-derived C gradually increased with increasing invasion time, whereas plant-derived C initially increased and then decreased, consistent with changes in SOC content. The variation in inundation conditions, influenced by tides, emerged as a significant factor affecting the accumulation of plant- and microbial-derived C, as well as SOC stability. Decreased inundation frequency and increased oxygen exposure, driven by tides, may lead to a rapid rise in SOC mineralization and the enrichment of microbial-derived C at the expense of plant-derived C. Consequently, this process improved SOC stability. These findings hold substantial implications for potential C loss resulting from the long-term impacts of S. alterniflora invasions. Furthermore, they may help predict the long-term effects of S. alterniflora invasions on blue C budgets within the context of global change scenarios.

Size-fractionated distribution of glycerol dialkyl glycerol tetraether core lipids in surface sediments of a large-river delta-front estuary

Glycerol dialkyl glycerol tetraether core lipids (GDGTs) are microbial biomarkers ubiquitously distributed in terrestrial and marine environments. Dispersal and fate of GDGTs in an estuary largely depends on sediment grain size, however, their size distribution patterns remain poorly understood. Here, surface sediments collected from the Changjiang Estuary were separated into <20, 20–32, 32–63, 63–125 and >125 μm fractions, and analyzed for GDGTs as well as total organic carbon (TOC), stable isotopic composition (δ13C) of TOC and lignin phenols, to investigate the size and spatial distributions of GDGTs and the particle size effects on GDGTs proxies in this large river delta-front estuary. The concentrations of isoprenoidal GDGTs (isoGDGTs) were higher in the finest fractions and in off-estuary sites. On the contrary, branched GDGTs (brGDGTs) were high not only in the finest fractions but in coarser fractions (>32 μm fractions), and thus at both near- and off-estuary sites. The branched and isoprenoid tetraether (BIT) index increased with increasing grain size, and decreased sharply from the estuary (~0.52) to the shelf (~0.16). BrGDGTs were positively correlated with crenarcheaol in both high and low BIT regions. The brGDGTIIIa/IIa ratios in all size fractions were <0.59, further indicating that the brGDGTs were mainly derived from terrestrial input with minimum in-situ production. Fractional TOC source assignments derived from the BIT index was significantly positively correlated with the fractions of terrestrial OC from a mixing model based on δ13C-TOC and lignin contents, indicating that BIT may track a broader pool of terrestrial OC than just soil OC. This work provides novel, yet preliminary insights into the size fractionated distribution characteristics of GDGTs and the applicability of BIT as a proxy for OC sources in estuarine sediments. More work is needed to further clarify the particle size effects on other GDGTs proxies in estuarine systems.

Cascade disassembling of spent coffee grounds into phenols, lignin and fermentable sugars en route to a green active packaging

Coffee is one of the most popular beverages worldwide, whose consumption generates spent coffee grounds (SCGs) as one of the major by-products. A new biorefinery flowchart aimed at the integral valorization of SCGs in view of the possible implementation of a sustainable active packaging is proposed in this work. The cascade approach started with a delipidization step to get coffee oil (13.0 g/100 g SCGs). Then, a hydroalcoholic extraction followed by a treatment with a deep eutectic solvent (composed of choline chloride and lactic acid) allowed to recover low molecular weight phenolic compounds (9.6 g/100 g SCGs) and lignin (6.2 g/100 g SCGs), respectively. Both fractions were found to display promising antioxidant properties in chemical assays. The residual solid material was then submitted to saccharification through a statistical approach, enabling the optimization of the enzymatic cocktail needed to address biomass structural and compositional complexity. The process resulted in 57 % and 73 % saccharification yields for cellulose and hemicellulose respectively, corresponding to the recovery of 11.6 g of fermentable sugars per 100 g of SCGs, and led to a homogeneous residual solid (4.3 g/100 g SCGs) still endowed with antioxidant properties. Finally, the possible use of the inhibitory-free saccharification extract for the microbial production of polyhydroxybutyrate was demonstrated using a proper engineered Escherichia coli strain, achieving about 0.7 g/L of biopolymer (1.2 g/100 g SCGs). Overall, the combination of the sequential processes applied in this work allowed to recover functional compounds accounting for ca. 45 % w/w of the starting biomass, paving the way to the development of a coffee-biorefinery aimed at the designing of fully biobased materials composed of polyhydroxyalkanoates and active additives, i.e. phenols and lignin.

Lignin demethylation enabled robust and reprocessable bio-polyurethane elastomer with adaptable cross-linking network

The development of sustainable bio-polyurethanes (bio-PU) from nonfood lignin has been attracting extensive attention owing to the abundant reserves, stable aromatic structures, and rich hydroxyls of lignin. However, exploiting a high-performance lignin-based PU integrating excellent mechanical properties with reprocessability is still a challenge. Herein, we proposed a dynamic phenolic-carbamates to construct robust and reprocessable bio-PU elastomers based on the reaction of phenolic lignin (PL) with isocyanate. Benefiting from the low Mw of 1692 Da and the abundant phenolic hydroxyls of 8.3 mmol/g, the adaptable cross-linking network consisting of dynamic hydrogen bonds and phenolic-carbamates were formed by PL. The synthesized phenolic lignin-based PU (PLPU) displayed tunable mechanical properties via adjusting PL substitution amount. The tensile strength, modulus and toughness of PLPU reached 58.8 MPa, 1350.3 MPa, and 57 MJ/m3 when the substitution amount of PL was 70%, respectively. Importantly, the reversible cross-linking structure endowed PLPU with excellent multi-reprocessability. After 5 reprocessing cycles, the retention ratio of strength, breaking elongation, modulus and toughness was 87.6%, 58.9%, 218.1% and 63.3%, respectively, which were 1.6, 1.1, 3.5, 2.2 times higher than those of commercial lignin-based polyurethane (CLPU). Therefore, this work not only presents a robust and multi-reprocessable lignin-based PU elastomer with high substitution amount, but also provides a promising sustainable alternative to replace petroleum-based plastic.