Lignocellulosic Plant Biomass Research Articles

A genomic analysis reveals the diversity of cellulosome displaying bacteria.

Several species of cellulolytic bacteria display cellulosomes, massive multi-cellulase containing complexes that degrade lignocellulosic plant biomass (LCB). A greater understanding of cellulosome structure and enzyme content could facilitate the development of new microbial-based methods to produce renewable chemicals and materials. To identify novel cellulosome-displaying microbes we searched 305,693 sequenced bacterial genomes for genes encoding cellulosome proteins; dockerin-fused glycohydrolases (DocGHs) and cohesin domain containing scaffoldins. This analysis identified 33 bacterial species with the genomic capacity to produce cellulosomes, including 10 species not previously reported to produce these complexes, such as Acetivibrio mesophilus. Cellulosome-producing bacteria primarily originate from the Acetivibrio, Ruminococcus, Ruminiclostridium, and Clostridium genera. A rigorous analysis of their enzyme, scaffoldin, dockerin, and cohesin content reveals phylogenetically conserved features. Based on the presence of a high number of genes encoding both scaffoldins and dockerin-fused GHs, the cellulosomes in Acetivibrio and Ruminococcus bacteria possess complex architectures that are populated with a large number of distinct LCB degrading GH enzymes. Their complex cellulosomes are distinguishable by their mechanism of attachment to the cell wall, the structures of their primary scaffoldins, and by how they are transcriptionally regulated. In contrast, bacteria in the Ruminiclostridium and Clostridium genera produce 'simple' cellulosomes that are constructed from only a few types of scaffoldins that based on their distinct complement of GH enzymes are predicted to exhibit high and low cellulolytic activity, respectively. Collectively, the results of this study reveal conserved and divergent architectural features in bacterial cellulosomes that could be useful in guiding ongoing efforts to harness their cellulolytic activities for bio-based chemical and materials production.

Preparation and Compositional Analysis of Lignocellulosic Plant Biomass as a Precursor for Food Production During Food Crises.

In the event of a sunlight-blocking, temperature-lowering global catastrophe, such as a global nuclear war, super-volcano eruption or large asteroid strike, normal agricultural practices would be severely disrupted with a devastating impact on the global food supply. Despite the improbability of such an occurrence, it is prudent to consider how to sustain the surviving population following a global catastrophe until normal weather and climate patterns resume. Additionally, the ongoing challenges posed by climate change, droughts, flooding, soil salinization, and famine highlight the importance of developing food systems with resilient inputs such as lignocellulosic biomass. With its high proportion of cellulose, the abundant lignocellulosic biomass found across the Earth's land surfaces could be a source of energy and nutrition, but it would first need to be converted into foods. To understand the potential of lignocellulosic biomass to provide energy and nutrition to humans in post-catastrophic and other food crisis scenarios, compositional analyses should be completed to gauge the amount of energy (soluble sugars) and other macronutrients (protein and lipids) that might be available and the level of difficulty in extracting them. Suitable preparation of the lignocellulosic biomass is critical to achieve consistent and comparable results from these analyses. Here we describe a compilation of protocols to prepare lignocellulosic biomass and analyze its composition to understand its potential as a precursor to produce post-catastrophic foods which are those that could be foraged, grown, or produced under the new climate conditions to supplement reduced availability of traditional foods. These foods have sometimes been referred to in the literature as emergency, alternate, or resilient foods. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Convection oven drying (1 to 2 days) Alternate Protocol 1: Air-drying (2 to 3 days) Alternate Protocol 2: Lyophilization (1 to 4 days) Support Protocol 1: Milling plant biomass Support Protocol 2: Measuring moisture content Basic Protocol 2: Cellulose determination Basic Protocol 3: Lignin determination Basic Protocol 4: Crude protein content by total nitrogen Basic Protocol 5: Crude fat determination via soxtec extraction system Basic Protocol 6: Sugars by HPLC Basic Protocol 7: Ash content.

Controlling stabilization of oil‐in‐water emulsions with lignins through fractionation, functionalization, and formulation

AbstractLignins, heterogeneous assemblies of polyphenolic oligomers present in lignocellulosic plant biomass, are valorized mainly by combustion because of their low solubility in commonly used solvents. However, in addition to antioxidant, anti‐UV and antimicrobial properties, and marked interfacial properties are part of lignins physicochemical properties, thus making them good candidates for sustainable colloids. It is hypothesized that lignins solubility and emulsifying performances could be modulated by fractionation, functionalization, and formulation strategies. The importance of the solvent, and of the pH on lignins solubilization in aqueous phase was investigated. Accordingly, simple O/W emulsions stabilized by different lignins were designed and characterized. The whole results demonstrated that lignins solubility in water can be optimized using appropriate co‐solvent and pH readjustment resulting in a homogeneous dispersion with only 7.2 ± 1.8% wt/wt of insoluble lignins. Both fractionation and biocatalytic modification of lignins allowed increasing stabilization of the oil–water interface by limiting coalescence (23%–24% of relative increase of the D90) compared with non‐fractionated lignins (32%), thus advocating their potential use as multifunctional emulsion stabilizers. As a result, a direct link between the molar mass profile of lignins and their ability to stabilize the oil–water interface as well as to reduce emulsion's sedimentation could be established.

Metabolic engineering of Caldicellulosiruptor bescii for 2,3-butanediol production from unpretreated lignocellulosic biomass and metabolic strategies for improving yields and titers.

The platform chemical 2,3-butanediol (2,3-BDO) is used to derive products, such as 1,3-butadiene and methyl ethyl ketone, for the chemical and fuel production industries. Efficient microbial 2,3-BDO production at industrial scales has not been achieved yet for various reasons, including product inhibition to host organisms, mixed stereospecificity in product formation, and dependence on expensive substrates (i.e., glucose). In this study, we explore engineering of a 2,3-BDO pathway in Caldicellulosiruptor bescii, an extremely thermophilic (optimal growth temperature = 78°C) and anaerobic bacterium that can break down crystalline cellulose and hemicellulose into fermentable C5 and C6 sugars. In addition, C. bescii grows on unpretreated plant biomass, such as switchgrass. Biosynthesis of 2,3-BDO involves three steps: two molecules of pyruvate are condensed into acetolactate; acetolactate is decarboxylated to acetoin, and finally, acetoin is reduced to 2,3-BDO. C. bescii natively produces acetoin; therefore, in order to complete the 2,3-BDO biosynthetic pathway, C. bescii was engineered to produce a secondary alcohol dehydrogenase (sADH) to catalyze the final step. Two previously characterized, thermostable sADH enzymes with high affinity for acetoin, one from a bacterium and one from an archaeon, were tested independently. When either sADH was present in C. bescii, the recombinant strains were able to produce up to 2.5-mM 2,3-BDO from crystalline cellulose and xylan and 0.2-mM 2,3-BDO directly from unpretreated switchgrass. This serves as the basis for higher yields and productivities, and to this end, limiting factors and potential genetic targets for further optimization were assessed using the genome-scale metabolic model of C. bescii.IMPORTANCELignocellulosic plant biomass as the substrate for microbial synthesis of 2,3-butanediol is one of the major keys toward cost-effective bio-based production of this chemical at an industrial scale. However, deconstruction of biomass to release the sugars for microbial growth currently requires expensive thermochemical and enzymatic pretreatments. In this study, the thermo-cellulolytic bacterium Caldicellulosiruptor bescii was successfully engineered to produce 2,3-butanediol from cellulose, xylan, and directly from unpretreated switchgrass. Genome-scale metabolic modeling of C. bescii was applied to adjust carbon and redox fluxes to maximize productivity of 2,3-butanediol, thereby revealing bottlenecks that require genetic modifications.

Overexpression of REDUCED WALL ACETYLATION C increases xylan acetylation and biomass recalcitrance in Populus.

Plant lignocellulosic biomass, i.e. secondary cell walls of plants, is a vital alternative source for bioenergy. However, the acetylation of xylan in secondary cell walls impedes the conversion of biomass to biofuels. Previous studies have shown that REDUCED WALL ACETYLATION (RWA) proteins are directly involved in the acetylation of xylan but the regulatory mechanism of RWAs is not fully understood. In this study, we demonstrate that overexpression of a Populus trichocarpa PtRWA-C gene increases the level of xylan acetylation and increases the lignin content and S/G ratio, ultimately yielding poplar woody biomass with reduced saccharification efficiency. Furthermore, through gene coexpression network and expression quantitative trait loci (eQTL) analysis, we found that PtRWA-C was regulated not only by the secondary cell wall hierarchical regulatory network but also by an AP2 family transcription factor HARDY (HRD). Specifically, HRD activates PtRWA-C expression by directly binding to the PtRWA-C promoter, which is also the cis-eQTL for PtRWA-C. Taken together, our findings provide insights into the functional roles of PtRWA-C in xylan acetylation and consequently saccharification and shed light on synthetic biology approaches to manipulate this gene and alter cell wall properties. These findings have substantial implications for genetic engineering of woody species, which could be used as a sustainable source of biofuels, valuable biochemicals, and biomaterials.

Mechanism of Zn2+ regulation of cellulase production in Trichoderma reesei Rut-C30

BackgroundTrichoderma reesei Rut-C30 is a hypercellulolytic mutant strain that degrades abundant sources of lignocellulosic plant biomass, yielding renewable biofuels. Although Zn2+ is an activator of enzymes in almost all organisms, its effects on cellulase activity in T. reesei have yet to be reported.ResultsAlthough high concentrations of Zn2+ severely suppressed the extension of T. reesei mycelia, the application of 1–4 mM Zn2+ enhanced cellulase and xylanase production in the high-yielding cellulase-producing Rut-C30 strain of T. reesei. Expression of the major cellulase, xylanase, and two essential transcription activator genes (xyr1 and ace3) increased in response to Zn2+ stimulation. Transcriptome analysis revealed that the mRNA levels of plc-e encoding phospholipase C, which is involved in the calcium signaling pathway, were enhanced by Zn2+ application. The disruption of plc-e abolished the cellulase-positive influence of Zn2+ in the early phase of induction, indicating that plc-e is involved in Zn2+-induced cellulase production. Furthermore, treatment with LaCl3 (a plasma membrane Ca2+ channel blocker) and deletion of crz1 (calcineurin-responsive zinc finger transcription factor 1) indicated that calcium signaling is partially involved in this process. Moreover, we identified the zinc-responsive transcription factor zafA, the transcriptional levels of which declined in response to Zn2+ stress. Deletion of zafA indicates that this factor plays a prominent role in mediating the Zn2+-induced excessive production of cellulase.ConclusionsFor the first time, we have demonstrated that Zn2+ is toxic to T. reesei, although promotes a marked increase in cellulase production. This positive influence of Zn2+ is facilitated by the plc-e gene and zafA transcription factor. These findings provide insights into the role of Zn2+ in T. reesei and the mechanisms underlying signal transduction in cellulase synthesis.

AA16 Oxidoreductases Boost Cellulose-Active AA9 Lytic Polysaccharide Monooxygenases from Myceliophthora thermophila.

Copper-dependent lytic polysaccharide monooxygenases (LPMOs) classified in Auxiliary Activity (AA) families are considered indispensable as synergistic partners for cellulolytic enzymes to saccharify recalcitrant lignocellulosic plant biomass. In this study, we characterized two fungal oxidoreductases from the new AA16 family. We found that MtAA16A from Myceliophthora thermophila and AnAA16A from Aspergillus nidulans did not catalyze the oxidative cleavage of oligo- and polysaccharides. Indeed, the MtAA16A crystal structure showed a fairly LPMO-typical histidine brace active site, but the cellulose-acting LPMO-typical flat aromatic surface parallel to the histidine brace region was lacking. Further, we showed that both AA16 proteins are able to oxidize low-molecular-weight reductants to produce H2O2. The oxidase activity of the AA16s substantially boosted cellulose degradation by four AA9 LPMOs from M. thermophila (MtLPMO9s) but not by three AA9 LPMOs from Neurospora crassa (NcLPMO9s). The interplay with MtLPMO9s is explained by the H2O2-producing capability of the AA16s, which, in the presence of cellulose, allows the MtLPMO9s to optimally drive their peroxygenase activity. Replacement of MtAA16A by glucose oxidase (AnGOX) with the same H2O2-producing activity could only achieve less than 50% of the boosting effect achieved by MtAA16A, and earlier MtLPMO9B inactivation (6 h) was observed. To explain these results, we hypothesized that the delivery of AA16-produced H2O2 to the MtLPMO9s is facilitated by protein-protein interaction. Our findings provide new insights into the functions of copper-dependent enzymes and contribute to a further understanding of the interplay of oxidative enzymes within fungal systems to degrade lignocellulose.

Preassembled Cas9 Ribonucleoprotein-Mediated Gene Deletion Identifies the Carbon Catabolite Repressor and Its Target Genes in Coprinopsis cinerea.

Cre1 is an important transcription factor that regulates carbon catabolite repression (CCR) and is widely conserved across fungi. The cre1 gene has been extensively studied in several Ascomycota species, whereas its role in gene expression regulation in the Basidiomycota species remains poorly understood. Here, we identified and investigated the role of cre1 in Coprinopsis cinerea, a basidiomycete model mushroom that can efficiently degrade lignocellulosic plant wastes. We used a rapid and efficient gene deletion approach based on PCR-amplified split-marker DNA cassettes together with in vitro assembled Cas9-guide RNA ribonucleoproteins (Cas9 RNPs) to generate C. cinerea cre1 gene deletion strains. Gene expression profiling of two independent C. cinerea cre1 mutants showed significant deregulation of carbohydrate metabolism, plant cell wall degrading enzymes (PCWDEs), plasma membrane transporter-related and several transcription factor-encoding genes, among others. Our results support the notion that, like reports in the ascomycetes, Cre1 of C. cinerea orchestrates CCR through a combined regulation of diverse genes, including PCWDEs, transcription factors that positively regulate PCWDEs, and membrane transporters which could import simple sugars that can induce the expression of PWCDEs. Somewhat paradoxically, though in accordance with other Agaricomycetes, genes related to lignin degradation were mostly downregulated in cre1 mutants, indicating they fall under different regulation than other PCWDEs. The gene deletion approach and the data presented here will expand our knowledge of CCR in the Basidiomycota and provide functional hypotheses on genes related to plant biomass degradation. IMPORTANCE Mushroom-forming fungi include some of the most efficient lignocellulosic plant biomass degraders. They degrade dead plant materials by a battery of lignin-, cellulose-, hemicellulose-, and pectin-degrading enzymes, the encoding genes of which are under tight transcriptional control. One of the highest-level regulations of these metabolic enzymes is known as carbon catabolite repression, which is orchestrated by the transcription factor Cre1, and ensures that costly lignocellulose-degrading enzyme genes are expressed only when simple carbon sources (e.g., glucose) are not available. Here, we identified the Cre1 ortholog in a litter decomposer Agaricomycete, Coprinopsis cinerea, knocked it out, and characterized transcriptional changes in the mutants. We identified several dozen lignocellulolytic enzyme genes as well as membrane transporters and other transcription factors as putative target genes of C. cinerea cre1. These results extend knowledge on carbon catabolite repression to litter decomposer Basidiomycota.

Production, Properties and Applications of Xylooligosaccharides (XOS): A Review

Xylooligosaccharides derived from Xylan, significant component of hemicellulose in lignocellulosic plant biomass, are essential raw materials used in the food, pharmaceutical and agricultural industries. They find application in these industries due to their unique physicochemical properties such as pH stability, growth regulatory ability, and anti-allergic property. In addition, they have been shown to exhibit promising antimicrobial, anti-cancer, antioxidant and anti-inflammatory activities. Xylooligosaccharides convert waste into valuable foods, pharmaceuticals, and agricultural products, promoting health, the economy, and the environment.

Pretreatment of lignocellulosic biogas substrates by filamentous fungi

Decomposition of lignocellulosic plant biomass by four filamentous fungi was carried out to facilitate subsequent anaerobic degradation and biogas formation. Agricultural side products, wheat straw and corn stover and forestry energy plant willow chips were selected as plant biomass sources. The substrates were confronted by pure cultures of Penicillium aurantiogriseum (new isolate from rumen), Trichoderma reesei (DSM768), Gilbertella persicaria (SZMC11086) and Rhizomucor miehei (SZMC11005). In addition to total cellulolytic filter paper degradation activity, the production of endoglucanase, cellobiohydrolase, β-glucosidase enzymes were followed during the pretreatment period, which lasted for 10 days at 37 °C. The products of pretreatments were subsequently tested for mesophilic biogas production in batch reactors. All 4 strains effectively pretreated the lignocellulosic substrates albeit in varying degrees, which was related to the level of the tested hydrolytic enzyme activities. Penicillium aurantiogriseum showed outstanding hydrolytic enzyme production and highest biogas yield from the partially degraded substrates. Corn stover was the best substrate for biomass decomposition and biogas production. Scanning electron microscopy confirmed the deep penetration of fungal hyphae into the lignocellulosic substrate in all cases.

Establishment of the basidiomycete Fomes fomentarius for the production of composite materials

BackgroundFilamentous fungi of the phylum Basidiomycota are considered as an attractive source for the biotechnological production of composite materials. The ability of many basidiomycetes to accept residual lignocellulosic plant biomass from agriculture and forestry such as straw, shives and sawdust as substrates and to bind and glue together these otherwise loose but reinforcing substrate particles into their mycelial network, makes them ideal candidates to produce biological composites to replace petroleum-based synthetic plastics and foams in the near future.ResultsHere, we describe for the first time the application potential of the tinder fungus Fomes fomentarius for lab-scale production of mycelium composites. We used fine, medium and coarse particle fractions of hemp shives and rapeseed straw to produce a set of diverse composite materials and show that the mechanical materials properties are dependent on the nature and particle size of the substrates. Compression tests and scanning electron microscopy were used to characterize composite material properties and to model their compression behaviour by numerical simulations. Their properties were compared amongst each other and with the benchmark expanded polystyrene (EPS), a petroleum-based foam used for thermal isolation in the construction industry. Our analyses uncovered that EPS shows an elastic modulus of 2.37 ± 0.17 MPa which is 4-times higher compared to the F. fomentarius composite materials whereas the compressive strength of 0.09 ± 0.003 MPa is in the range of the fungal composite material. However, when comparing the ability to take up compressive forces at higher strain values, the fungal composites performed better than EPS. Hemp-shive based composites were able to resist a compressive force of 0.2 MPa at 50% compression, rapeseed composites 0.3 MPa but EPS only 0.15 MPa.ConclusionThe data obtained in this study suggest that F. fomentarius constitutes a promising cell factory for the future production of fungal composite materials with similar mechanical behaviour as synthetic foams such as EPS. Future work will focus on designing materials characteristics through optimizing substrate properties, cultivation conditions and by modulating growth and cell wall composition of F. fomentarius, i.e. factors that contribute on the meso- and microscale level to the composite behaviour.

Thermoxylanolytic and Thermosaccharolytic Potential of a Heat Adapted Bacterial Consortium Developed From Goat Rumen Contents

Thermoactive xylanases have important applications in the industrial deconstruction of lignocellulosic plant biomass, due to their sustained activity even at high temperature conditions of industrial bioreactors. We herein report the development of a thermoactive xylanolytic microbial consortium from the semi-digested contents of goat rumen and characterization of the xylanolytic enzyme cocktail produced by it. The consortium exhibited maximum endoxylanase activity at pH6 and at 60°C. Zymogram analysis revealed the production of multiple xylanases. The xylanase cocktail was stable over a pH range of 5–9 after pre-incubation for 3 h. It retained 74% activity after pre-incubation (60°C) for 50 min. It’s activity was enhanced in presence of β-mercaptoethanol, NH4+, Mg2⁺ and Ca2⁺, whereas Hg2⁺ had an inhibitory effect. The xylanolytic cocktail was further utilized for the saccharification of alkali pre-treated rice straw and mushroom spent rice straw. Saccharification was studied quantitatively using the dinitrosalicylic acid method and qualitatively using scanning electron microscopy. Results indicated the potential of the xylanolytic cocktail for the saccharification of rice straw and highlighted the significance of chemical and/or biological pre-treatment in improving the accessibility of the substrate towards the xylanase cocktail.

Cellobiose dehydrogenase from the agaricomycete Coprinellus aureogranulatus and its application for the synergistic conversion of rice straw

From the biotechnological viewpoint, the enzymatic disintegration of plant lignocellulosic biomass is a promising goal since it would deliver fermentable sugars for the chemical sector. Cellobiose dehydrogenase (CDH) is a vital component of the extracellular lignocellulose-degrading enzyme system of fungi and has a great potential to improve catalyst efficiency for biomass processing. In the present study, a CDH from a newly isolated strain of the agaricomycete Coprinellus aureogranulatus (CauCDH) was successfully purified with a specific activity of 28.9 U mg−1. This pure enzyme (MW = 109 kDa, pI = 5.4) displayed the high oxidative activity towards β-1–4-linked oligosaccharides. Not least, CauCDH was used for the enzymatic degradation of rice straw without chemical pretreatment. As main metabolites, glucose (up to 165.18 ± 3.19 mg g−1), xylose (64.21 ± 1.22 mg g−1), and gluconic acid (5.17 ± 0.13 mg g−1) could be identified during the synergistic conversion of this raw material with the fungal hydrolases (e.g., esterase, cellulase, and xylanase) and further optimization by using an RSM statistical approach.

Recent Advances in the Biosynthesis of Polyhydroxyalkanoates from Lignocellulosic Feedstocks.

Polyhydroxyalkanoates (PHA) are biodegradable polymers that are considered able to replace synthetic plastic because their biochemical characteristics are in some cases the same as other biodegradable polymers. However, due to the disadvantages of costly and non-renewable carbon sources, the production of PHA has been lower in the industrial sector against conventional plastics. At the same time, first-generation sugar-based cultivated feedstocks as substrates for PHA production threatens food security and considerably require other resources such as land and energy. Therefore, attempts have been made in pursuit of suitable sustainable and affordable sources of carbon to reduce production costs. Thus, in this review, we highlight utilising waste lignocellulosic feedstocks (LF) as a renewable and inexpensive carbon source to produce PHA. These waste feedstocks, second-generation plant lignocellulosic biomass, such as maize stoves, dedicated energy crops, rice straws, wood chips, are commonly available renewable biomass sources with a steady supply of about 150 billion tonnes per year of global yield. The generation of PHA from lignocellulose is still in its infancy, hence more screening of lignocellulosic materials and improvements in downstream processing and substrate pre-treatment are needed in the future to further advance the biopolymer sector.

Cover Feature: Acid Hydrotropic Fractionation of Lignocelluloses for Sustainable Biorefinery: Advantages, Opportunities, and Research Needs (ChemSusChem 15/2021)

The Cover Feature shows acid hydrotropic fractionation (AHF) of lignocellulosic plant biomass at atmospheric pressure, to result in cellulose-rich water-insoluble solids, a light colored and minimally condensed lignin, and a dissolved xylose sugar stream, using only a recyclable acid hydrotrope such as maleic acid. More information can be found in the Minireview by J. Zhu et al.

Ligninolytic valorization of agricultural residues by Aspergillus nomius and Trichoderma harzianum isolated from gut and comb of Odontotermes obesus (Termitidae)

Fungi produce enzymes that degrade the complex lignin thereby enabling the efficient utilization of plant lignocellulosic biomass in the production of biofuel and cellulose-based products. In the present study, the agricultural residues such as paddy straw, sugarcane bagasse, and coconut husk were used as substrates for the biodegradation by Aspergillus nomius (MN700028) and Trichoderma harzianum (MN700029) isolated from gut of the termite, Odontotermes obesus and fungus comb in the termite mound, respectively. The influence of varying concentrations of different carbon sources, pH, and temperature on ligninolytic enzyme production was examined under laboratory conditions. The highest activities of manganese peroxidase (0.24 U/mL), lignin peroxidase (10.38 U/mL) and laccase (0.05 U/mL) were observed under studied conditions. Fungal pretreatment of lignocellulosic biomass for 45 days showed that A. nomius and T. harzianum degraded 84.4% and 81.66% of hemicelluloses, 8.16% and 93.75% of cellulose, and 52.59% and 65% of lignin, respectively. The interaction of pH, temperature, and different carbon sources with fungal biomass and enzyme production was found significant (p ≤ 0.05). SEM analysis indicated alterations in the microstructures of degraded lignocellulosic substrates. A. nomius and T. harzianum were highly efficient in ligninolytic enzymes production and in vitro digestibility of agricultural residues. The study reports the production of laccase by A. nomius isolated from termite gut for the first time. The fungal isolates A. nomius and T. harzianum posses potential for ligninocellulosic waste degradation.

Shewanella baltica strain JD0705 isolated from the mangrove wetland soils in Thailand and characterization of its ligninolytic performance

Abstract. Chantarasiri A. 2021. Shewanella baltica strain JD0705 isolated from the mangrove wetland soils in Thailand and characterization of its ligninolytic performance. Biodiversitas 22: 354-361. Lignin is a complex biopolymer and the third component by mass of lignocellulosic plant biomass. Its recalcitrant property hampers the hydrolysis and utilization of cellulose and hemicellulose in the lignocellulosic biomass. Thus, the delignification of lignocellulosic biomass is an enormous challenge for emerging bio-based applications. This study presented a potential ligninolytic bacterium for potential use in the biological delignification process under mild conditions. This bacterium was isolated from the mangrove wetland soils in Thailand, characterized and identified as psychrotrophic Shewanella baltica strain JD0705. It was determined for ligninolytic activity and showed laccase activity at 5.23 ± 0.10 U/mL. The optimum temperature and pH for the laccase activity were observed to be 25°C at a pH of 7.0 respectively with a stability range of 20-30°C temperature and pH of 7.0-8.0. S. baltica strain JD0705 was used in the biological delignification of rice husk powder and promoted the hydrolysis of rice husk powder to obtain more liberating sugar content. The findings from this study indicated that feasibility of using this ligninolytic bacterium for the production of laccase and the delignification of lignocellulosic plant biomass.

Differentiation of Tracheary Elements in Sugarcane Suspension Cells Involves Changes in Secondary Wall Deposition and Extensive Transcriptional Reprogramming.

Plant lignocellulosic biomass, mostly composed of polysaccharide-rich secondary cell walls (SCWs), provides fermentable sugars that may be used to produce biofuels and biomaterials. However, the complex chemical composition and physical structure of SCWs hinder efficient processing of plant biomass. Understanding the molecular mechanisms underlying SCW deposition is, thus, essential to optimize bioenergy feedstocks. Here, we establish a xylogenic culture as a model system to study SCW deposition in sugarcane; the first of its kind in a C4 grass species. We used auxin and brassinolide to differentiate sugarcane suspension cells into tracheary elements, which showed metaxylem-like reticulate or pitted SCW patterning. The differentiation led to increased lignin levels, mainly caused by S-lignin units, and a rise in p-coumarate, leading to increased p-coumarate:ferulate ratios. RNAseq analysis revealed massive transcriptional reprogramming during differentiation, with upregulation of genes associated with cell wall biogenesis and phenylpropanoid metabolism and downregulation of genes related to cell division and primary metabolism. To better understand the differentiation process, we constructed regulatory networks of transcription factors and SCW-related genes based on co-expression analyses. Accordingly, we found multiple regulatory modules that may underpin SCW deposition in sugarcane. Our results provide important insights and resources to identify biotechnological strategies for sugarcane biomass optimization.

A thermostable bacterial lytic polysaccharide monooxygenase with high operational stability in a wide temperature range

BackgroundLytic polysaccharide monooxygenases (LPMOs) are oxidative, copper-dependent enzymes that function as powerful tools in the turnover of various biomasses, including lignocellulosic plant biomass. While LPMOs are considered to be of great importance for biorefineries, little is known about industrial relevant properties such as the ability to operate at high temperatures. Here, we describe a thermostable, cellulose-active LPMO from a high-temperature compost metagenome (called mgLPMO10).ResultsMgLPMO10 was found to have the highest apparent melting temperature (83 °C) reported for an LPMO to date, and is catalytically active up to temperatures of at least 80 °C. Generally, mgLPMO10 showed good activity and operational stability over a wide temperature range. The LPMO boosted cellulose saccharification by recombinantly produced GH48 and GH6 cellobiohydrolases derived from the same metagenome, albeit to a minor extent. Cellulose saccharification studies with a commercial cellulase cocktail (Celluclast®) showed that the performance of this thermostable bacterial LPMO is comparable with that of a frequently utilized fungal LPMO from Thermoascus aurantiacus (TaLPMO9A).ConclusionsThe high activity and operational stability of mgLPMO10 are of both fundamental and applied interest. The ability of mgLPMO10 to perform oxidative cleavage of cellulose at 80 °C and the clear synergy with Celluclast® make this enzyme an interesting candidate in the development of thermostable enzyme cocktails for use in lignocellulosic biorefineries.

A Review of Wood Biomass-Based Fatty Acids and Rosin Acids Use in Polymeric Materials.

In recent decades, vegetable oils as a potential replacement for petrochemical materials have been extensively studied. Tall oil (crude tall oil, distilled tall oil, tall oil fatty acids, and rosin acids) is a good source to be turned into polymeric materials. Unlike vegetable oils, tall oil is considered as lignocellulosic plant biomass waste and is considered to be the second-generation raw material, thus it is not competing with the food and feed chain. The main purpose of this review article is to identify in what kind of polymeric materials wood biomass-based fatty acids and rosin acids have been applied and their impact on the properties.