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The most abundant natural renewable resource in the world, lignocellulosic biomass (LCB), has the potential to be exploited as a substitute green feedstock for the synthesis of various chemicals, materials, and biofuels. The annual global production of 13 billion tonnes of LCB offers an opportunity to cater to the increasing energy and materials requirement of process industries and also restricts the discharge of greenhouse gases. Although LCB is enriched with valuable ingredients such as cellulose, lignin, and hemicellulose, its recalcitrant nature limits its efficient utilisation. These components of LCB are strongly interlinked with each other, which resists their isolation and conversion valorisation into useful products. To disrupt the complicated structure of LCB and to isolate the lignocellulosic components in pure form, pretreatment is a crucial process in the bio-refinery, ensuring the economic feasibility of downstream processes. This review provides an outline of the structure, composition, and various sources of LCB; and the necessity of the pretreatment. Moreover, this article provides an in-depth analysis of the underlying mechanisms, advantages, and limitations of various pretreatment methods, such as physical, chemical, biological, and physicochemical. Further, the impact of chemical pretreatment techniques on the physicochemical characteristics of the material that is extracted from the biomass is also covered in detail through the rigorous evaluation of performance metrics, including substrate digestibility, sugar yield, inhibitor production, and energy requirements. This review provides a balanced and comprehensive overview of the state-of-the-art pretreatment strategies and their impact on biomass valorisation that will be useful to the scientists, engineers, and policy makers interested in biomass conversion technologies., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The Poaceae family of plants provides cereal crops that are critical for human and animal nutrition, and also, they are an important source of biomass. Interacting plant cell wall components give rise to recalcitrance to digestion; thus, understanding the wall molecular architecture is important to improve biomass properties. Xylan is the main hemicellulose in grass cell walls. Recently, we reported structural variation in grass xylans, suggesting functional specialisation and distinct interactions with cellulose and lignin. Here, we investigated the functions of these xylans by perturbing the biosynthesis of specific xylan types. We generated CRISPR/Cas9 knockout mutants in Brachypodium distachyon XAX1 and GUX2 genes involved in xylan substitution. Using carbohydrate gel electrophoresis, we identified biochemical changes in different xylan types. Saccharification, cryo-SEM, subcritical water extraction and ssNMR were used to study wall architecture. BdXAX1A and BdGUX2 enzymes modify different types of grass xylan. Brachypodium mutant walls are likely more porous, suggesting the xylan substitutions directed by both BdXAX1A and GUX2 enzymes influence xylan-xylan and/or xylan-lignin interactions. Since xylan substitutions influence wall architecture and digestibility, our findings open new avenues to improve cereals for food and to use grass biomass for feed and the production of bioenergy and biomaterials., (© 2024 The Authors New Phytologist © 2024 New Phytologist Foundation.)

Lytic polysaccharide monooxygenases (LPMOs) are one of the emerging classes of copper metalloenzymes that have received considerable attention due to their ability to boost the enzymatic conversion of intractable polysaccharides such as plant cell walls and chitin polymers. LPMOs catalyze the oxidative cleavage of β-1,4-glycosidic bonds using molecular O 2 or H 2 O 2 in the presence of an external electron donor. LPMOs have been classified as an auxiliary active (AA) class of enzymes and, further based on substrate specificity, divided into eight families. Until now, multiple LPMOs from AA9 and AA10 families, mostly from microbial sources, have been investigated; the exact mechanism and structure-function are elusive to date, and recently discovered AA families of LPMOs are just scratched. This review highlights the origin and discovery of the enzyme, nomenclature, three-dimensional protein structure, substrate specificity, copper-dependent reaction mechanism, and different techniques used to determine the product formation through analytical and biochemical methods. Moreover, the diverse functions of proteins in various biological activities such as plant-pathogen/pest interactions, cell wall remodeling, antibiotic sensitivity of biofilms, and production of nanocellulose along with certain obstacles in deconstructing the complex polysaccharides have also been summarized, while highlighting the innovative and creative ways to overcome the limitations of LPMOs in hydrolyzing the biomass., (© 2024 Federation of European Biochemical Societies.)

Background: The ability of lignocellulose degradation for filamentous fungi is always attributed to their efficient CAZymes system with broader applications in bioenergy development. ADP-ribosylation factor GTPase-activating proteins (Arf-GAPs), pivotal in fungal morphogenesis, lack comprehensive studies on their regulatory mechanisms in lignocellulose utilization. Results: Here, the orthologs (TgGlo3 and TgGcs1) of Arf-GAPs in S. cerevisiae were characterized in Trichoderma guizhouense NJAU4742. The results indicated that overexpression of Tggcs1 (OE-Tggcs1) enhanced the lignocellulose utilization, whereas increased expression of Tgglo3 (OE-Tgglo3) elicited antithetical responses. On the fourth day of fermentation with rice straw as the sole carbon source, the activities of endoglucanase, cellobiohydrolase, xylanase, and filter paper of the wild-type strain (WT) reached 8.20 U mL−1, 4.42 U mL−1, 14.10 U mL−1, and 3.56 U mL−1, respectively. Compared to WT, the four enzymes activities of OE-Tggcs1 increased by 7.93%, 6.11%, 9.08%, and 12.92%, respectively, while those decreased to varying degrees of OE-Tgglo3. During the nutritional growth, OE-Tgglo3 resulted in the hyphal morphology characterized by sparsity and constriction, while OE-Tggcs1 led to a notable increase in vacuole volume. In addition, OE-Tggcs1 exhibited higher transport efficiencies for glucose and cellobiose thereby sustaining robust cellular metabolic rates. Further investigations revealed that Tgglo3 and Tggcs1 differentially regulated the transcription level of a dynamin-like GTPase gene (Tggtp), eliciting distinct redox states and apoptotic reaction, thus orchestrating the cellular response to lignocellulose utilization. Conclusions: Overall, these findings underscored the significance of TgArf-GAPs as pivotal regulators in lignocellulose utilization and provided initial insights into their differential modulation of downstream targets. [ABSTRACT FROM AUTHOR]

Efficient pretreatment of wheat straw (WS) under mild conditions facilitates its further enzymatic hydrolysis and conversion. Three pretreatment processes with mild conditions including formic acid pretreatment (FAP), sodium chlorite pretreatment (SCP), and alkaline hydrogen peroxide (AHP) pretreatment were investigated in this study. The chemical components of WS before and after pretreatment were compared, and the samples were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The lignin removal by FAP, SCP, and AHP pretreatment was 55.79%, 99.33%, and 94.97%, and the enzymatic hydrolysis yields (EHY) were 68.03%, 75.52%, and 90.76%, respectively. The results showed that AHP pretreatment had a better performance on enzyme accessibility thus improving the EHY. Meanwhile, lignin can be separated from the AHP pretreatment liquid, which helps to improve the economics of the process. The effects of enzymes and additives on enzymatic hydrolysis were further optimized by response surface methodology. Under the conditions of 20.37 FPU/g cellulase, 32.14 IU/g xylanases, and 19.15 mg/g Tween 80, the experimental result showed that the maximum EHY was 94.15%, which was close to the predicted EHY (96.19%). The experiments on fed-batch mode after AHP pretreatment with high-solid loadings (20% w/v) were conducted, and the EHY reached 86.05%. These results contributed to improving the economic feasibility of WS pretreatment and enzymatic hydrolysis process. [ABSTRACT FROM AUTHOR]

Cellulose is the major renewable feedstock used in a variety of industrial processes. However, its native state, organizing itself in microfibrils and interacting with other components of the cell wall complex, forms a highly recalcitrant structure. Expansin proteins may facilitate the enzymatic saccharification stage by affecting non-covalent bonds between the wall polymers. In the current study, the expression profile of five selected Expansin genes from sugarcane, an important crop in the supply of biomass lignocellulose for the ethanol industry, was analyzed in leaves, roots, and young culms. The SacEXP32 and SacEXP39 genes, potentially associated with the cell wall architecture modification in sugarcane culm, were selected for functional characterization studies in Nicotiana benthamiana using the agroinfiltration assay. Heterologous expression of SacEXP32 and SacEXP39 revealed that N. benthamiana cellulose synthase gene was positively regulated at the transcript level in transformed tissue. However, only SacEXP32 expression increased cell area and enzymatic saccharification efficiency. SacEXP32 overexpression may have influenced the network of all cell wall polymers, indicating that this gene is a potential target for biotechnological approaches to improve plant biomass industrial processing. [ABSTRACT FROM AUTHOR]

This work reports the degradation of cellulosic material, i.e., paper, under different environmental conditions (soil and hydrolytic). Models were developed using central composite design (CCD) within the framework of response surface methodology (RSM) and artificial neural network (ANN) techniques. It is done as part of a solid waste management system to eliminate the waste produced by excessive paper usage and obtain optimized degradation conditions of paper. In view of the real environments where paper-based solid wastes are usually exposed, soil degradation and hydrolytic degradation of paper were investigated. The factors pH (4–10), compost ratio (2–5), CaCl2 (5–15 ppm), and time (7–20 days) were independent factors that varied for the study, and degradation conversion was measured as the dependent variable for soil degradation of paper. The factors pH (4–10), CaCl2 (2–5 ppm), tripotassium phosphate (TPP, 2–5 ppm), and time (6–16 days) were independent variables that varied for the study, and degradation conversion was the dependent variable for hydrolytic degradation of paper. The optimal conditions for soil degradation were determined to be a pH of 4, a compost ratio of 5, a salt (CaCl2) addition of 5 ppm, and a duration of 20 days, resulting in the highest observed conversion rate. The coefficient of regression (R2) for CCD is 87.24%, whereas it is 94.82% for ANN. The optimal conditions for achieving maximum conversion in hydrolytic degradation include a pH of 10, a CaCl2 salt concentration of 5 ppm, a TPP salt concentration of 2 ppm, and a duration of 16 days. The coefficient of regression for CCD is 75.15%, while the coefficient of regression for ANN is 93.91%. In both deterioration scenarios, the data exhibited a higher degree of fit when modeled using ANN compared to CCD (RSM). [ABSTRACT FROM AUTHOR]

Purpose: Herein, the extraction of lignin from rubber tree residues (Hevea brasiliensis Müll. Arg), particularly from the seed shell, is reported with the aim of providing added value to this plantation. Methods: The protocol employed consisted of an organosolv extraction using formic or acetic acids and p-TsOH as catalyst assisted by ultrasound, avoiding the use of high temperatures and mineral acids. Results: 22% yield of lignin was obtained from the dried rubber seed shell using the formic acid/p-TsOH combination in comparison with 13% yield obtained with acetic acid/p-TsOH. The extracted lignin was oxidized isolating typical fragments derived from syringyl, guaiacyl and p-hydroxyphenyl units. The lignin was characterized by IR, UV, NMR, TGA and DSC. Moreover, total phenol content and antioxidant activity were also evaluated. Conclusion: The results exhibited the presence of typical lignin aromatic composition. The lignin obtained by the seed shell could be effectively employed in numerous future applications and the method could be considered as a low-cost acid catalysed process. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) has garnered attention among biomaterial scientists for its unique physicochemical features and biocompatibility; however, the lack of bioactivity has limited its biomedical applications. Thus, this study describes the in situ preparation of BC/hydroxyapatite (HA) nanocomposite membranes using static and agitated fermentation to enhance the bioactivity of BC. The incorporation of HA increased BC production from 2.31 g/L without HA to 4.10 and 3.26 g/L under static and agitated fermentation, respectively, although the SEM observation indicates the formation of a fibrous structure in BC mesh under both fermentations. It was also observed that the content of HA nanoparticles in BC obtained from agitated fermentation was higher than that obtained from static fermentation. In addition, the average fiber diameter was increased from 56 ± 17 nm for agitated nanocomposites (BC/HA-A) to 145 ± 48 nm for static BC/HA nanocomposites (BC/HA-S) and 122 ± 26 nm for BC. In conclusion, the in situ formation of BC/HA nanocomposite under agitated fermentation appears more convenient in term of BC yield, HA content and distribution, and cytotoxicity against fibroblast cells (BJ1). This strategy will inspire new ways to prepare BC-based materials for medical applications. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment has great potential for the separation of biomass components. In this study, taking bamboo and cotton stalk as raw materials, two-stage alkaline pretreatment was designed for evaluating the components fractionation. The chemical structure of isolated xylan from bamboo and cotton stalk have a backbone of (1 → 4)-β-D-Xylp units attached with 4-O-Me-α-D-GlcpA and/or α-L-Araf units as the branched chain, characterized by Fourier transform infrared spectroscopy and Heteronuclear Single Quantum Coherence Nuclear Magnetic Resonance. Its excellent pretreatment performance was mainly due to the alkali solution weakening the hydrogen bond between cellulose and hemicellulose and saponifying the ester bond between hemicellulose and lignin, thus increasing the fiber porosity. The cellulose enzymatic hydrolysis yield of two-stage alkaline pretreatments cotton stalks and bamboo could reach to 74.2% and 82.1%. The recovery of xylan and lignin of two-stage alkaline pretreatments cotton stalks and bamboo was 85.4% and 84.5%, and 85.1% and 85.1%. This technology was a great potential to promote the efficiency of the component separation of nonwood biomass. [ABSTRACT FROM AUTHOR]

Using lignocellulosic materials as a feedstock to produce ethanol is an alternative to cleaner energy production. The pretreatment and enzymatic hydrolysis steps play a role in breaking down the lignocellulosic structure and making the sugars available for fermentation. Non-ionic surfactants have been included in the cellulosic ethanol production process to increase ethanol titers. Non-ionic surfactants commonly contribute to the enzymatic digestion of lignocelluloses, but there are doubts about whether they are beneficial or harmful in the pretreatment and ethanol fermentation steps. This study evaluated Tween 80 (polysorbate 80) in pretreatment, enzymatic hydrolysis, and fermentation with Saccharomyces cerevisiae PE2 to obtain ethanol from green coconut fiber (GCF). To reduce the GCF's recalcitrance and to increase enzyme accessibility, the material was pretreated using steam explosion (severity factor of 3.71 and 4.24), alkaline (sodium hydroxide), and sequential steam explosion/alkaline pretreatment in the presence of the surfactant. The surfactant did not increase delignification in steam explosion pretreatment, but it increased the sugar release when compared to the pretreatments without Tween 80. The addition of the surfactant during enzymatic hydrolysis increased glucose production in all experiments. Adsorption experiments showed that Tween 80 increased enzymatic activity. The highest glucose production was 20.31 ± 0.48 g/L and cellulosic conversion of 65.12% after adding 1.0% (w/v) Tween 80 in sequential steam explosion/alkaline pretreatment and enzymatic hydrolysis. Simultaneous saccharification and fermentation (SSF) and semi-simultaneous saccharification and fermentation (SSSF) strategies were investigated with the surfactant addition. When 2.0% (w/v) Tween 80 was added in all fermentations, it hindered ethanol production. A fed-batch SSSF and nonisothermal-fed-batch-SSSF were also performed, along with an enzyme fed-batch strategy. The highest ethanol concentration achieved was 48.21 ± 1.13 g/L by adding 1.0% (w/v) Tween 80 to the nonisothermal-fed-SSSF with 30% (w/v) solid loading. [ABSTRACT FROM AUTHOR]

Cellulosic materials are attracting increasing research interest because of their abundance, biocompatibility, and biodegradability, making them suitable in multiple industrial and medical applications. Functionalization of cellulose is usually required to improve or expand its properties to meet the requirements of different applications. Cellulose-binding domains (CBDs) found in various proteins have been shown to be powerful tools in the functionalization of cellulose materials. In this review, we firstly introduce the structural characteristics of commonly used CBDs belonging to carbohydrate-binding module families 1, 2 and 3. Then, we summarize four main kinds of methodologies for employing CBDs to modify cellulosic materials (i.e., CBD only, genetic fusion, non-covalent linkage and covalent linkage). Via different approaches, CBDs have been used to improve the material properties of cellulose, immobilize enzymes for biocatalysis, and design various detection tools. To achieve industrial applications, researches for lowering the production cost of CBDs, improving their performance (e.g., stability), and expanding their application scenarios are still in need. [ABSTRACT FROM AUTHOR]

The biological valorization of cork depends mainly on the weakening of cell wall recalcitrance. As a typical softwood, Chinese fir is more resistant to enzyme and microbial invasion than most biomass. This study compared the efficiency of two single-step pretreatments (dilute sulfuric acid pretreatment (DSA) and acidic sodium chlorite pretreatment (SC)) and their interaction effects on the pretreatment process. Two single pretreatments could selectively remove hemicellulose and some lignin from Chinese fir sawdust (CFS). Combined pretreatments resulted in a remarkable synergistic enhancement in delignification. The hemicellulose-removal-first strategy is favored by softwood delignification, the destruction of fiber morphology, and the redistribution of lignin. Using DSA-SC, more than 90% of lignin and hemicellulose were removed, and complete hydrolysis (99.3%) was obtained. Based on DSA-SC, the CFS biorefinery recovered 41.6% lignin and 52.8% hemicellulose sugar, and 306.1 g lactic acid was produced from 1000.0 g CFS. The integrated pretreatment process with a stepwise separation feature could be effectively applied in softwood destruction and provide more opportunities for softwood waste whole-component utilization. [ABSTRACT FROM AUTHOR]

The production of high-value commodities from sugarcane bagasse and harvest residues could be integrated into existing sugarcane mills to create sugarcane biorefineries. Three distinctly different domains of operating conditions were optimised for autocatalyzed steam pretreatment and enzymatic hydrolysis of these lignocelluloses, to provide sugars according to biorefinery priorities, i.e. (i) maximum digestibility of the solids for glucose only, (ii) maximum hemicellulose recovery in the prehydrolysate for xylose only, or (iii) maximum combined sugar yield (CSY; glucose plus xylose). Bagasse pretreatment showed isolated optima for each response at (i) 215 °C, 15 min; (ii) 202.2 °C, 5 min; and (iii) 215 °C, 5 min. For the harvest residues, the three domains of optimum conditions overlapped within temperatures of 198 and 200 °C, and times of 8 and 12°min, allowing for a single pretreatment condition that meets all three criteria. The practicality and robustness of the preferred pretreatment conditions were demonstrated with a mixed stream of both feedstocks. [ABSTRACT FROM AUTHOR]

Background: The phenolic polymer lignin is one of the primary chemical constituents of the plant secondary cell wall. Due to the inherent plasticity of lignin biosynthesis, several phenolic monomers have been shown to be incorporated into the polymer, as long as the monomer can undergo radicalization so it can participate in coupling reactions. In this study, we significantly enhance the level of incorporation of monolignol ferulate conjugates into the lignin polymer to improve the digestibility of lignocellulosic biomass. Results: Overexpression of a rice Feruloyl-CoA Monolignol Transferase (FMT), OsFMT1, in hybrid poplar (Populus alba x grandidentata) produced transgenic trees clearly displaying increased cell wall-bound ester-linked ferulate, p-hydroxybenzoate, and p-coumarate, all of which are in the lignin cell wall fraction, as shown by NMR and DFRC. We also demonstrate the use of a novel UV–Vis spectroscopic technique to rapidly screen plants for the presence of both ferulate and p-hydroxybenzoate esters. Lastly we show, via saccharification assays, that the OsFMT1 transgenic p oplars have significantly improved processing efficiency compared to wild-type and Angelica sinensis-FMT-expressing poplars. Conclusions: The findings demonstrate that OsFMT1 has a broad substrate specificity and a higher catalytic efficiency compared to the previously published FMT from Angelica sinensis (AsFMT). Importantly, enhanced wood processability makes OsFMT1 a promising gene to optimize the composition of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

In the present study, cleaner technologies, viz. microwave (MW) and microwave-assisted chimeric enzyme treatments (MWEC), were applied for extracting pectin from mango and pomegranate peels, and their impact was compared with the conventional citric acid extraction (CA) in terms of yield, structural features, physico-chemical characteristics and techno-functional properties of the isolated pectins. Chimeric enzymes [bi-chimera: endo-mannanase and endo-xylanase (ManB-XynB); tri-chimera: endo-mannanase, endo-xylanase, and cellulase (ManB-XynB-CelB)] connected by flexible linkers (5–15 amino acids) were generated using overlap extension PCR. ManB-XynB expressed extracellularly (Mw ~ 59 kDa) and was optimally active at 50 °C, pH 6, while ManB-XynB-CelB expressed intracellularly (Mw ~ 112 kDa) and exhibited optimum activities at 50–55 °C, pH 5–7. MWEC of mango and pomegranate peels showed the maximum yield of pectin. Scanning electron micrographs of MWEC treated peels revealed a synergistic action between chimeric enzymes and microwave for extracting pectin as distinguishable physical modifications (cracks, pores and erosion) of the peel surface were observed. ATR/FT-IR spectra of MWEC extracted pectins suggested that considerable portion (> 50%) of galacturonic acid residues was non-esterified. This was corroborated by the degree of esterification present in MWEC extracted pectins. Arabinose and galactose were the predominant neutral sugars found in the extracted pectins. MWEC extracted peel pectin had high protein and ferulic acid content, low particle size, good water holding capacity and low molecular weight, but only MWEC extracted mango peel pectin exhibited good emulsion activity and stability when compared to either MW or CA extraction methods. Rheological measurements suggested that pectins extracted using MW and MWEC exhibit low viscosities and Newtonian behaviour. [ABSTRACT FROM AUTHOR]

Lignin is an inexpensive bio-adsorbent and has many applications in the adsorption of heavy metals. The structure and size of the lignin molecular chain affect its properties. Introducing of amino functional groups to the structure of lignin can improve its physical and chemical properties and increase its reactivity and adsorption power. Lignin cross-linking also improves its performance and adsorption characteristics. In the first step, lignin as a black liquor was extracted and purified from the waste of the wood factory. The lignin was then reacted with phenol to obtain lignophenol. The obtained lignophenol was then aminated via reacting with the ethylene diamine. Finally, in order to increase the strength of the adsorbent structure and prevent the dissolution of the adsorbent at low pHs (suitable for adsorption), 37% aqueous formaldehyde was added to the aminated lignin, from which aminated and cross-linked lignophenol was then obtained. Different types of lignins including lignin, lignophenol and amine-functionalized (branched or cross-linked) lignophenol were well synthesized and identified. The results of FT-IR spectrum showed that the amine functional groups were well attached to the lignophenol branches and the lignophenol was converted to the amino-containing lignophenol. Also, the results of acid–base titration and 11HNMR show that phenol was successfully bonded onto the lignin and amine functional groups were observed in lignin structure. The results of acid–base titration, elemental analysis and zeta potential tests also confirmed amination of lignophenol. [ABSTRACT FROM AUTHOR]

Thin coating layers of cross-linked polydimethylsiloxane (PDMS) and inorganic particles including glass spheres (GS), colloidal and fumed silica (aero and N20), montmorillonite (MMT), and kaolin (K) were attached onto Grade 1 Whatman filter paper (WFP) substrates using the spraycoating procedure to achieve superhydrophobic hybrid paper sheets. Coating formulations were varied in terms of their PDMS molecular masses and inorganic particles to prepare different samples. The effect of PDMS molecular weight and change in inorganic particle composition on the optical properties, surface roughness, barrier properties, surface chemistry, and topography was investigated. Hybrid paper sheets with ΔE00 values lower than 1 could be achieved, the surface roughness of which could be decreased by increasing the PDMS molecular weight in the coating formulation. Scanning electron microscopy studies revealed a homogeneous coating distribution, resulting in significant improvements in both the air and water barrier properties of the hybrid paper sheets. Spectroscopic investigations revealed the presence of interactions between the coating layer and the underlying paper substrate. Moreover, the distribution behavior of the inorganic particles on the spraycoated surfaces using the proposed method was also investigated using model compounds. [ABSTRACT FROM AUTHOR]

The combination of ball milling (BM), microwave irradiation (MI), and deep eutectic solvents (DES) results synergistic for an efficient, selective, and very rapid (10 min) delignification of materials with high lignin content (ca. 50 wt%) such as walnut shells (WS). Lignin is dissolved in the DES, whereas the polysaccharide fractions remain suspended with limited degradation, due to the rapid pretreatment. After ball milling procedure (3 h), biomass loadings in the range of 100–200 g L−1 are selectively delignified in 10 min at 150 °C by using choline chloride:formic acid DES (1:2 molar ratio), rendering lignin yields of 60–80% (ca. ~ 40–60 g lignin L−1). Ball milling, microwave irradiation, and DES systems are much more efficient than ball milling, conventional heating, and DES system. The obtained lignins exhibited similar Fourier-transform infrared spectroscopy (FTIR) profile to that of milled wood lignin (MWL), indicating minimal functional group changes. [ABSTRACT FROM AUTHOR]

To reduce the cost of pretreatment, an advanced formic acid pretreatment directly using spent liquor was developed for corn cob valorisation in this work. The spent liquor pretreatment showed a satisfactory lignocellulose fractionation effect, and a high enzymatic hydrolysis efficiency over 95% was achieved even when the spent liquor was recycled 5 times. Based on this result, the direct recycling of the spent liquor for pretreatment could lead to a threefold increase in the amount of corn cob processed and reduce energy consumption on the recovery unit by 80%. Meanwhile, the recycling strategy of spent liquor also could bring an enrichment of xylooligosaccharides (XOS) in the spent liquor. A total of 56.0 g/L XOS was obtained with a high proportion of XOS in spent liquor, which favoured XOS separation and purification during the downstream process of XOS production. The developed strategy shows a good potential on the industrialization of formic acid pretreatment for biorefineries. [ABSTRACT FROM AUTHOR]

Background: Manganese peroxidases (MnPs) are, together with lignin peroxidases and versatile peroxidases, key elements of the enzymatic machineries secreted by white-rot fungi to degrade lignin, thus providing access to cellulose and hemicellulose in plant cell walls. A recent genomic analysis of 52 Agaricomycetes species revealed the existence of novel MnP subfamilies differing in the amino-acid residues that constitute the manganese oxidation site. Following this in silico analysis, a comprehensive structure–function study is needed to understand how these enzymes work and contribute to transform the lignin macromolecule. Results: Two MnPs belonging to the subfamilies recently classified as MnP-DGD and MnP-ESD—referred to as Ape-MnP1 and Cst-MnP1, respectively—were identified as the primary peroxidases secreted by the Agaricales species Agrocybe pediades and Cyathus striatus when growing on lignocellulosic substrates. Following heterologous expression and in vitro activation, their biochemical characterization confirmed that these enzymes are active MnPs. However, crystal structure and mutagenesis studies revealed manganese coordination spheres different from those expected after their initial classification. Specifically, a glutamine residue (Gln333) in the C-terminal tail of Ape-MnP1 was found to be involved in manganese binding, along with Asp35 and Asp177, while Cst-MnP1 counts only two amino acids (Glu36 and Asp176), instead of three, to function as a MnP. These findings led to the renaming of these subfamilies as MnP-DDQ and MnP-ED and to re-evaluate their evolutionary origin. Both enzymes were also able to directly oxidize lignin-derived phenolic compounds, as seen for other short MnPs. Importantly, size-exclusion chromatography analyses showed that both enzymes cause changes in polymeric lignin in the presence of manganese, suggesting their relevance in lignocellulose transformation. Conclusions: Understanding the mechanisms used by basidiomycetes to degrade lignin is of particular relevance to comprehend carbon cycle in nature and to design biotechnological tools for the industrial use of plant biomass. Here, we provide the first structure–function characterization of two novel MnP subfamilies present in Agaricales mushrooms, elucidating the main residues involved in catalysis and demonstrating their ability to modify the lignin macromolecule. [ABSTRACT FROM AUTHOR]

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Areca fruit husk fibers are generally consisting of hemicellulose, lignin, wax and some of the inorganic components. Present study concentrates on the extraction and characterization of hemicellulose and lignin from these areca fruit husk fibers which shall be used in composite preparation. In order to extract hemicellulose and lignin, different molar concentrations (such as 1, 2, 3, 4 and 5 Molar concentrations) of alkali were used. From the present work it is found that the graded ethanol with 4 volumes has depicted the improved hemicellulose yield as compared to hemicellulose precipitate and 0.2 volume alkali-soluble hemicellulose. And highest hemicellulose precipitate yield was found at temperatures of 40 °C and alkali concentrations of 3 M. Fourier transform infrared spectroscopy analyses demonstrate hemicellulose precipitates and alkali-soluble hemicellulose (0.2 volumes and 4 volumes), noted in the range of 450–4000 cm−1, as the percentage transmittance versus wavenumber graph is plotted. Finally, the thermogravimetric analysis performed to study the effect of alkali treatment on thermal stability of empty areca fruit bunches. And it is concluded that alkali treatment is the best suited method in the process of hemicellulose and lignin extraction from the areca fruit husk fibers. After this, these treated fibers can be used in the different composite preparation processes. [ABSTRACT FROM AUTHOR]

Background: Bacterial nanocellulose (BNC), a natural polymer material, gained significant popularity among researchers and industry. It has great potential in areas, such as textile manufacturing, fiber-based paper, and packaging products, food industry, biomedical materials, and advanced functional bionanocomposites. The main current fermentation methods for BNC involved static culture, as the agitated culture methods had lower raw material conversion rates and resulted in non-uniform product formation. Currently, studies have shown that the production of BNC can be enhanced by incorporating specific additives into the culture medium. These additives included organic acids or polysaccharides. γ-Polyglutamic acid (γ-PGA), known for its high polymerization, excellent biodegradability, and environmental friendliness, has found extensive application in various industries including daily chemicals, medicine, food, and agriculture. Results: In this particular study, 0.15 g/L of γ-PGA was incorporated as a medium additive to cultivate BNC under agitated culture conditions of 120 rpm and 30 ℃. The BNC production increased remarkably by 209% in the medium with 0.15 g/L γ-PGA and initial pH of 5.0 compared to that in the standard medium, and BNC production increased by 7.3% in the medium with 0.06 g/L γ-PGA. The addition of γ-PGA as a medium additive resulted in significant improvements in BNC production. Similarly, at initial pH levels of 4.0 and 6.0, the BNC production also increased by 39.3% and 102.3%, respectively. To assess the characteristics of the BNC products, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis were used. The average diameter of BNC fibers, which was prepared from the medium adding 0.15 g/L γ-PGA, was twice thicker than that of BNC fibers prepared from the control culture medium. That might be because that polyglutamic acid relieved the BNC synthesis from the shear stress from the agitation. Conclusions: This experiment held great significance as it explored the use of a novel medium additive, γ-PGA, to improve the production and the glucose conversion rate in BNC fermentation. And the BNC fibers became thicker, with better thermal stability, higher crystallinity, and higher degree of polymerization (DPv). These findings lay a solid foundation for future large-scale fermentation production of BNC using bioreactors. [ABSTRACT FROM AUTHOR]

In this study, an attempt has been made to recover the lignin and enhance the sugar yield from the de-oiled Jatropha curcas waste (DJW) through alkaline hydrolysis and saccharification. The alkaline hydrolysis process was performed using sodium hydroxide (NaOH) for a solid loading rate of 10% w/v. The process parameters considered for the optimization study using RSM were — time (6.36–73.63 min), NaOH concentration (0.6137–12.38%), and temperature (85.68–156.3°C). The maximum kraft lignin (KL) recovered at the optimum conditions for the response was found to be 93.4%. The functional groups in the treated and untreated Jatropha curcas seed cake and the recovered lignin were studied using FTIR. The recovered kraft lignin has been characterized using 1H-NMR and FTIR. The enzymatic saccharification efficiency was estimated based on the release of glucose. Maximum glucose yield (%) was found to be 92.45% for NaOH pretreated DJW compared to the untreated biomass, for which the glucose yield was only 46.64%. [ABSTRACT FROM AUTHOR]

Exploring sustainable energy and chemical sources based on biomass has increased global interest. This study was focused on produce second-generation bioethanol using a new pretreatment process. The effectiveness of sodium hydroxide (NaOH) pretreatment on oil palm empty fruit bunch (OPEFB) for lignin removal, reducing sugar, and bioethanol production at low temperature and pressure was investigated using batch and continuous processes. Response surface methodology (RSM) was used to optimize the NaOH concentration and solid to liquor ratio (SL) at a maximum temperature of 100 °C and atmospheric pressure. The mathematical formula derived from RSM was based on 11 runs of the batch treatment. In the batch treatment process, 2 M NaOH, the temperature of 80 °C, and SL ratio of 8 have resulted in lignin removal of 38.7%, reducing sugars of 8.3%, and bioethanol concentration of 4.1%. The validation of formula has been calculated from calculation and experiment values. Moreover, at the same retention time, continuous pretreatment showed a reducing sugar content of 5.9% and a bioethanol concentration by 2.5%. The results show that the continuous process can be employed in effective bioethanol production from OPEFB. [ABSTRACT FROM AUTHOR]

Subterranean termites primarily use decaying wood as both nest material and food, and the worker caste is responsible for searching for new wood. Because brown-rotted wood contains (Z,Z,E)-3,6,8-dodecatrien-1-ol, which is a trail pheromone component in Reticulitermes termites, it is considered that this compound attracts termite workers. However, while the trail pheromone allows passing workers to continue to move along it, it is unlikely to attract them from a distance. Therefore, workers should use other attractants derived from decaying wood as cues to locate it. In this study, we found that an aromatic abietane diterpenoid in termite culture medium made from brown-rotted Japanese red pine (Pinus densiflora) attracted workers of the Japanese subterranean termite Reticulitermes speratus (Kolbe) (Isoptera: Rhinotermitidae). Gas chromatography analyses and behavioral assays revealed that the n-hexane extract of the medium contains dehydroabietic acid, which is a resin component of various conifers, and this compound attracts workers. These results strongly suggest that R. speratus workers mainly use this compound as a cue to locate brown-rotted pinewood in nature. Our study contributes to the understanding of the mechanisms of wood detection in termites. [ABSTRACT FROM AUTHOR]

Multi-product biorefineries are up-and-coming industries to diversify the economy of countries since they have a productive matrix with a biological characteristic capable of processing various types of biomass with applications in pharmaceutical, renewable energy, and other industries. In this context, this research analyzes the literature on biorefineries and the methods of assessing social impacts that consider quality of life, employment, and stakeholders, among other metrics, as guided by the United Nations—UN. A systematic review combined with bibliometric, semantic, and content analysis was carried out by searching scientific documents in the Scopus and Web of Science databases. A total of 116 articles were located, of which three researchers selected twenty-three to compose the research. The Fleiss Kappa Index was applied to verify the agreement of the evaluators' decision regarding the inclusion and exclusion of articles, whose result was K = 0.43 above the tolerable limit defined for the inclusion of articles, which is K ≥ 0.21. Therefore, all twenty-three articles were included. The results indicate that authors showed greater interest in the topic of this research in the period from 2017 to 2019, representing 70% of the total scientific findings in the reviewed literature. It was observed that the types of research that predominate in the studies are empirical, with 52% of the articles. The qualitative approach, however, obtained a variation of 400% in the studied period. Another important fact is that 93% of all authors published only 1, and not 61% as expected by Lotka law. Social impact studies show greater adherence to second-generation lignocellulosic biorefineries, which use the fractionation of inedible materials and projects whose methods consider Social Life Cycle and Multicriteria are more consistent for assessing the social impacts of biorefineries, as they allow an analysis of qualitative and quantitative information. [ABSTRACT FROM AUTHOR]

Background: Microbial expansins (EXLXs) are non-lytic proteins homologous to plant expansins involved in plant cell wall formation. Due to their non-lytic cell wall loosening properties and potential to disaggregate cellulosic structures, there is considerable interest in exploring the ability of microbial expansins (EXLX) to assist the processing of cellulosic biomass for broader biotechnological applications. Herein, EXLXs with different modular structure and from diverse phylogenetic origin were compared in terms of ability to bind cellulosic, xylosic, and chitinous substrates, to structurally modify cellulosic fibrils, and to boost enzymatic deconstruction of hardwood pulp. Results: Five heterogeneously produced EXLXs (Clavibacter michiganensis; CmiEXLX2, Dickeya aquatica; DaqEXLX1, Xanthomonas sacchari; XsaEXLX1, Nothophytophthora sp.; NspEXLX1 and Phytophthora cactorum; PcaEXLX1) were shown to bind xylan and hardwood pulp at pH 5.5 and CmiEXLX2 (harboring a family-2 carbohydrate-binding module) also bound well to crystalline cellulose. Small-angle X-ray scattering revealed a 20–25% increase in interfibrillar distance between neighboring cellulose microfibrils following treatment with CmiEXLX2, DaqEXLX1, or NspEXLX1. Correspondingly, combining xylanase with CmiEXLX2 and DaqEXLX1 increased product yield from hardwood pulp by ~ 25%, while supplementing the TrAA9A LPMO from Trichoderma reesei with CmiEXLX2, DaqEXLX1, and NspEXLX1 increased total product yield by over 35%. Conclusion: This direct comparison of diverse EXLXs revealed consistent impacts on interfibrillar spacing of cellulose microfibers and performance of carbohydrate-active enzymes predicted to act on fiber surfaces. These findings uncover new possibilities to employ EXLXs in the creation of value-added materials from cellulosic biomass. [ABSTRACT FROM AUTHOR]

High starch sweetpotatoes (HSSPs) are renewable feedstocks with the potential to support industrially relevant chemical production. Here, three HSSP genotypes (NC-413, NCPUR06-020, and NCDM02-180) and a table-stock variety (Covington) were tested for butanol production by Clostridium beijerinckii NCIMB 8052 in two process configurations, separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). Results indicated that sweetpotato genotype, preparation (fresh vs flour), and system configuration significantly affected acetone-butanol-ethanol (ABE) fermentation efficiency. Particularly, conversion using the Covington variety showed the highest product yields and robust results with both preparations (0.137 and 0.094 g butanol/g initial starch for fresh and flour preparations, respectively) without requiring pre-processing for phenolic removal with polyvinylpyrrolidone (PVP). On the other hand, cultures with purple varieties NC-413 and NCPUR06-020, with the exception of NCPUR06-020 fresh preparations, required anthocyanin removal to achieve 0.103 g butanol/g initial starch, which represented more than a 1.6-fold increase in butanol concentration compared to purple sweetpotato hydrolysates without PVP phenolic pretreatment. Conversions with the white genotype (NCDM02-180) showed the lowest performance and largest variability under a SHF configuration (0.012 to 0.034 g butanol/g initial starch for fresh and flour, respectively), while butanol yields under SSF conditions (0.069 g butanol/g initial starch) were similar to the other genotypes examined. This study establishes the feasibility of using regionally relevant sweetpotato feedstocks (e.g., non-food-intended varieties as well as table-stock residues or culls) as a source of crude sugars for butanol fermentation and some of the key processing conditions that influence C. beijerinckii culture performance. [ABSTRACT FROM AUTHOR]

The isolation of nanocellulose materials by means of enzymatic hydrolysis offers advantages in terms of their properties and operational conditions, but there is still a lack of enzymatic cocktails specifically designed for this application. The present work investigates the use of a thermostable endoglucanase-rich enzymatic cocktail from Myceliophthora thermophila for nanocellulose production. An initial set of experiments was conducted to determine the optimal conditions for enzyme production under solid-state cultivation in small-scale polypropylene plastic bags. A full factorial experimental design was used as a statistical tool to evaluate the effects of the solid substrate and moisture content on the production of endoglucanase and β-glucosidase. Solid-state cultivations in a multilayer packed-bed bioreactor were then carried out under the selected conditions to obtain a larger volume of an enzymatic extract with high endoglucanase selectivity, given by the ratio of endoglucanase (203 ± 6 U/g-substrate) to β-glucosidase activity (1.6 ± 0.1 U/g-substrate). The enzymatic hydrolysis of eucalyptus cellulose pulp at different temperatures, with this endoglucanase-rich cocktail at a loading of 10 mg-protein/g-pulp, resulted in higher glucose release (11 ± 2 g-glucose/L) at 60 °C, with 61 ± 9% cellulose conversion and 16.2% nanocellulose yield. The isolated nanomaterial with average diameter of 36.65 nm and length of 156.63 nm, presented a crystallinity index of 77.4% and thermal stability temperature of 316 °C. These results show the potential to isolate nanocellulose using a thermostable endoglucanase-rich enzymatic cocktail produced locally by solid-state cultivation in a packed-bed bioreactor, in accordance to the biorefinery concept. [ABSTRACT FROM AUTHOR]

Loops are small secondary structural elements that play a crucial role in the emergence of new enzyme functions. However, the evolutionary molecular mechanisms how proteins acquire these loop elements and obtain new function is poorly understood. To address this question, we study glycoside hydrolase family 19 (GH19) chitinase—an essential enzyme family for pathogen degradation in plants. By revealing the evolutionary history and loops appearance of GH19 chitinase, we discover that one loop which is remote from the catalytic site, is necessary to acquire the new antifungal activity. We demonstrate that this remote loop directly accesses the fungal cell wall, and surprisingly, it needs to adopt a defined structure supported by long-range intramolecular interactions to perform its function. Our findings prove that nature applies this strategy at the molecular level to achieve a complex biological function while maintaining the original activity in the catalytic pocket, suggesting an alternative way to design new enzyme function. Loop regions play a key role in protein evolution. Herein the authors demonstrate how GH19 chitinase acquired additional antifungal activity by introducing remote loops, without compromising its original function. This work offers an innovative approach to expand enzyme function. [ABSTRACT FROM AUTHOR]

Samples of Eucalyptus globulus wood were processed in a reaction media made up of 1-pentanol, water, and diluted acid catalyst. The effects of selected variables (proportion of 1-pentanol in the reaction media, catalyst charge and temperature) on wood solubilization and on the composition of the various phases from treatments (solids containing cellulose, pentanol-rich phase containing depolymerized lignin, and the aqueous phase concentrating the hemicellulose-derived products) were assessed by Response Surface Methodology. Numerical optimization based on the statistical models allowed the identification of the best operational conditions, under which extensive removal of both lignin and hemicelluloses was reached at good selectivity toward cellulose solubilization. The treated solids achieved near stoichiometric conversion upon enzymatic hydrolysis performed under diverse operational conditions, and the lignin structural analysis provided data typical for hardwoods. The experimental results confirmed the potential of 1-pentanol as a solvent for Eucalyptus globulus wood-based biorefineries. [ABSTRACT FROM AUTHOR]

Glycerol-assisted instant catapult steam explosion (ICSE) of lignocellulose is an effective pretreatment method for enhancing sugar production compared to glycerol-free ICSE. In this study, glycerol-assisted ICSE of corn stover was studied in order to understand the reaction mechanisms and further optimize the process. Results showed that water extraction of corn stover prior to ICSE reduced pseudo-lignin formation. The combination of water extraction and glycerol-assisted ICSE led to the formation of lignin with a lower molecular weight (Mw) of 2851 g/mol than 3521 g/mole of that from the combination of water extraction and glycerol-free ICSE. 1H-13C NMR analysis revealed that glycerol likely reacted with lignin carboxylic OHs through esterification while etherification of aliphatic OHs was not observed in ICSE. These lignin analyses indicated that glycerol protected lignin from condensation/repolymerization during glycerol-assisted ICSE. Enzymatic hydrolysis results showed that without water extraction increasing glycerol usage from 0.2 kg/kg stover to 0.4 kg/kg stover improved glucan digestibility to 78% but further increase to 0.5 kg/kg stover reduced glucan digestibility. In addition, at the glycerol usage of 0.2–0.4 kg/kg stover, washing of pretreated stover for removal of glycerol and other biomass-derived compounds did not improve glucan digestibility compared to unwashed ones. Combination of water extraction and glycerol-assisted ICSE led to a high glucan digestibility of 89.7% and a total glucose yield of 25.5 g glucose/100 g stover, which were 30.1% and 7.5 g/100 g stover higher than those derived from glycerol-free ICSE of stover, respectively. Since glycerol is a low-cost carbon source, the resulting enzymatic hydrolysate that contained both glucose and glycerol may be directly used to produce bioproducts by microbial fermentation. Highlights: Glycerol-assisted ICSE of corn stover improved enzymatic glucose production. Water extraction prior to ICSE further enhanced sugar production. Enzymatic hydrolysis was not affected by glycerol from glycerol-assisted ICSE. Sequential water extraction and ICSE led to a high glucan digestibility of 89.7%. Glycerol likely had a multiple role in ICSE and enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Background: The main challenge for large-scale production of bacterial cellulose (BC) includes high production costs interlinked with raw materials, and low production rates. The valorization of renewable nutrient sources could improve the economic effectiveness of BC fermentation while their direct bioconversion into sustainable biopolymers addresses environmental pollution and/or resource depletion challenges. Herein a green bioprocess was developed to produce BC in high amounts with the rather unexplored bacterial strain Komagataeibacter rhaeticus, using waste streams such as wine distillery effluents (WDE) and biodiesel-derived glycerol. Also, BC was evaluated as a bio-adsorbent for phenolics, dyes and metals removal to enlarge its market diversification. Results: BC production was significantly affected by the WDE mixing ratio (0–100%), glycerol concentration (20–45 g/L), type of glycerol and media-sterilization method. A maximum BC concentration of 9.0 g/L, with a productivity of 0.90 g/L/day and a water holding capacity of 60.1 g water/g dry BC, was achieved at 100% WDE and ≈30 g/L crude glycerol. BC samples showed typical cellulose vibration bands and average fiber diameters between 37.2 and 89.6 nm. The BC capacity to dephenolize WDE and adsorb phenolics during fermentation reached respectively, up to 50.7% and 26.96 mg gallic acid equivalents/g dry BC (in-situ process). The produced BC was also investigated for dye and metal removal. The highest removal of dye acid yellow 17 (54.3%) was recorded when 5% of BC was applied as the bio-adsorbent. Experiments performed in a multi-metal synthetic wastewater showed that BC could remove up to 96% of Zn and 97% of Cd. Conclusions: This work demonstrated a low-carbon approach to produce low-cost, green and biodegradable BC-based bio-adsorbents, without any chemical modification. Their potential in wastewater-treatment-applications was highlighted, promoting closed-loop systems within the circular economy era. This study may serve as an orientation for future research towards competitive or targeted adsorption technologies for wastewater treatment or resources recovery. [ABSTRACT FROM AUTHOR]

Almond pruning biomass is an important agricultural residue that has been scarcely studied for the co-production of sugars and solid biofuels. In this work, the production of monosaccharides from almond prunings was optimised by a two-step process scheme: pretreatment with dilute sulphuric acid (0.025 M, at 185.9–214.1 ℃ for 0.8–9.2 min) followed by enzyme saccharification of the pretreated cellulose. The application of a response surface methodology enabled the mathematical modelling of the process, establishing pretreatment conditions to maximise both the amount of sugar in the acid prehydrolysate (23.4 kg/100 kg raw material, at 195.7 ℃ for 3.5 min) and the enzymatic digestibility of the pretreated cellulose (45.4%, at 210.0 ℃ for 8.0 min). The highest overall sugar yield (36.8 kg/100 kg raw material, equivalent to 64.3% of all sugars in the feedstock) was obtained with a pretreatment carried out at 197.0 ℃ for 4.0 min. Under these conditions, moreover, the final solids showed better properties for thermochemical utilisation (22.0 MJ/kg heating value, 0.87% ash content, and 72.1 mg/g moisture adsorption capacity) compared to those of the original prunings. [ABSTRACT FROM AUTHOR]

Background: EnZolv is a novel enzyme-based, eco-friendly biomass pretreatment process that has shown great potential in the field of textile engineering and biotechnology. It employs laccase from Hexagonia hirta MSF2 and 2% ethanol in the process of delignification. The process is designed to evaluate optimal conditions to remove lignin and other impurities from cotton spinning mill waste (CSMW), without compromising the quality and strength of the fibers. CSMW is a low-cost and readily available source of cellulose, making it an ideal candidate for delignification using EnZolv. By optimizing the pretreatment conditions and harnessing the potential of enzymatic delignification, this research aims to contribute to more sustainable and efficient ways of utilizing lignocellulosic biomass in various industries for the production of biochemical and bioproducts. Results: The present study emphasizes the EnZolv pretreatment in the delignification of cotton spinning mill wastes irrespective of the cellulose content. EnZolv process parameters such as, moisture content, enzyme load, incubation time, incubation temperature, and shaking speed were optimized. Under pre-optimized conditions, the percent lignin reduction was 61.34%, 61.64%, 41.85%, 35.34%, and 35.83% in blowroom droppings (BD), flat strips (FS), lickerin fly (LF), microdust (MD) and comber noils (CN), respectively. Using response surface methodology (RSM), the statistically optimized EnZolv pretreatment conditions showed lignin reduction of 59.16%, 62.88%, 48.26%, 34.64%, and 45.99% in BD, FS, LF, MD, and CN, respectively. Conclusion: Traditional chemical-based pretreatment methods often involve harsh chemicals and high energy consumption, which can have detrimental effects on the environment. In contrast, EnZolv offers a greener approach by utilizing enzymes that are biodegradable and more environmentally friendly. The resulting fibers from EnZolv treatment exhibit improved properties that make them suitable for various applications. Some of the key properties include enhanced cellulose recovery, reduced lignin content, and improved biophysical and structural characteristics. These improvements can contribute to the fiber's performance and processability in different industries and future thrust for the production of cellulose-derived and lignin-derived bioproducts. [ABSTRACT FROM AUTHOR]

Background: The polysaccharides in lignocellulosic biomass hold potential for production of biofuels and biochemicals. However, achieving efficient conversion of this resource into fermentable sugars faces challenges, especially when operating at industrially relevant high solid loadings. While it is clear that combining classical hydrolytic enzymes and lytic polysaccharide monooxygenases (LPMOs) is necessary to achieve high saccharification yields, exactly how these enzymes synergize at high solid loadings remains unclear. Results: An LPMO-poor cellulase cocktail, Celluclast 1.5 L, was spiked with one or both of two fungal LPMOs from Thermothielavioides terrestris and Thermoascus aurantiacus, TtAA9E and TaAA9A, respectively, to assess their impact on cellulose saccharification efficiency at high dry matter loading, using Avicel and steam-exploded wheat straw as substrates. The results demonstrate that LPMOs can mitigate the reduction in saccharification efficiency associated with high dry matter contents. The positive effect of LPMO inclusion depends on the type of feedstock and the type of LPMO and increases with the increasing dry matter content and reaction time. Furthermore, our results show that chelating free copper, which may leak out of the active site of inactivated LPMOs during saccharification, with EDTA prevents side reactions with in situ generated H2O2 and the reductant (ascorbic acid). Conclusions: This study shows that sustaining LPMO activity is vital for efficient cellulose solubilization at high substrate loadings. LPMO cleavage of cellulose at high dry matter loadings results in new chain ends and thus increased water accessibility leading to decrystallization of the substrate, all factors making the substrate more accessible to cellulase action. Additionally, this work highlights the importance of preventing LPMO inactivation and its potential detrimental impact on all enzymes in the reaction. [ABSTRACT FROM AUTHOR]

In the quest for alternative renewable energy sources, a new self-assembled hybrid configuration of cellulose-coated oil-in-water emulsion particles with yeast was formed. In this research, the addition of yeasts (S. cerevisiae) to the micro-particle emulsion revealed a novel self-assembly configuration in which the yeast cell is connected to surrounding cellulose-coated micro-particles. This hybrid configuration may enhance the simultaneous saccharification and fermentation process by substrate channeling. Glucose produced by hydrolysis of the cellulose shells coating the micro-particles, catalyzed by cellulytic enzymes attached to their coating, is directly fermented to ethanol by the yeasts to which the particles are connected. The results indicate ethanol yield of 62%, based on the cellulose content of the emulsion, achieved by the yeast/micro-particle hybrids. The functionality of this hybrid configuration is expected to serve as a micro-reactor for a cascade of biochemical reactions in a "one-pot" consolidated process transforming cellulose to valuable chemicals, such as biodiesel. [ABSTRACT FROM AUTHOR]

The biofuel yield from lignocellulose biomass depends strongly on the fermentable sugar yield from the hydrolysis step. Enzymatic hydrolysis, the preferable hydrolysis method, gives low sugar yield due to the lignin existence and the cellulose crystallinity. To increase the sugar yield, pretreatment is required to breakdown the recalcitrant nature of lignocellulose biomass. This review paper presents a comprehensive critical review of the lignocellulosic biomass (LCB) pretreatment methods for enhanced fermentable sugar yield. There is a need for an effective and cost-efficient pretreatment method that curbs inhibitory products and reduces the use of chemicals and energy. This paper highlighted recent advances in agricultural-based LCB pretreatment; discussed current challenges, advantages, and disadvantages; and suggested future solutions for agricultural-based biofuel production. Examined methods include pulsed electric energy (PEE), ionic liquid, co-solvent enhanced lignocellulosic fractionation pretreatment, and deep eutectic solvent. Each method was reviewed by its conditions (indicate the use of energy and chemicals), sugar yield, and inhibitory products. The review also researched the synergistic effect of combining more than one pretreatment method as a potential approach to overcome the drawbacks of the individual methods. In addition, the paper suggested improvement for each method and identified the research gaps to be bridged. Also, a comparison, summary, and research perspectives were provided. [ABSTRACT FROM AUTHOR]

Biomass as a green renewable energy source has the potential to become a significant energy source in the future due to the depletion of fossil fuels. Herein, carbon dioxide was employed to enhance the acidic pretreatment of corn cobs with lithium bromide trihydrate (LBTH) system to extract low molecular weight lignin with high antioxidant activity. The main factors that have an influence on the degradation of carbohydrates and lignin in corn cobs were examined, such as the amount of CO2 and the reaction temperature during the treatment with the CO2/LBTH system. The results showed that the extraction yield rate of low molecular weight lignin and the total conversion of corn cobs were 81.6% and 83.5%, respectively, under the operating conditions of 76.2 g CO2 concentration at 100 °C for 4 h during the treatment of CO2/LBTH system. Specifically, the CO2/LBTH system promoted the breakdown of the β-O-4 aryl ether bond of lignin, resulting in the production of low molecular weight lignin with improved hydroxyl content and antioxidant activity. To transform inexpensive biomass resources into lignin with a high value-added, the CO2/LBTH system is thus of strategic and practical relevance. [ABSTRACT FROM AUTHOR]

Primary cell walls and middle lamella of higher plants include homogalacturonan, the substrate for polygalacturonases. Seeking to enhance lignocellulose saccharification, chimeras between the endopolygalacturonase I from Chondrostereum (Stereum) purpureum (EndoPG-I) and family 3, 44, and 77 carbohydrate-binding modules (CBMs) from Hungateiclostridium thermocellum (Ht) or Ruminococcus flavefaciens (Rf) were constructed, expressed, and characterized. Chimeras presented similar KM values and pH/temperature optima as unfused EndoPG-I against citrus pectin, kcat/KM values 1.6, 1.7, and 1.3-fold higher for the HtCBM3-EndoPG, HtCBM44-EndoPG, and RtCBM77-EndoPG, respectively. Commercial enzyme cocktail supplementation with HtCBM44-EndoPG and RtCBM77-EndoPG increased reducing sugar release from untreated sugarcane bagasse by 35 and 25%, respectively. All chimeras increased reducing sugar release by 20–25% against orange bagasse compared with EndoPG-I or equimolar EndoPG-I/CBM mixtures. These results show that proximity between plant cell wall components in situ influences CBM-enzyme chimera activity and improves saccharification of lignocellulosic materials. [ABSTRACT FROM AUTHOR]

The nature of a sweet sorghum cultivar influences the recovery of sugars from the bagasse during pretreatment. The sugars recovered are used in applications for conversion to high-value products such as alcohols, organic acids, and other fuels and chemicals. The severity of the pretreatment used plays a crucial role in the yield and quality of the sugars that can be recovered. Therefore, a strategic approach was taken to lower the severity of the pretreatment process to a combined severity factor (CSF) value of 0.48, whilst maintaining a high level of total-sugar recovery (i.e. 68% (w/w) and higher). This was achieved by screening 23 sweet sorghum cultivars for high-performance characteristics at low-severity conditions and optimizing the pretreatment process conditions. The pretreatment conditions included time, temperature, and acid concentration ranges of 5 to 60 min, 150 to 210 oC, and 0.00–0.96% (w/w) H2SO4, respectively. Cultivar AP6 was identified as the best performer, producing the highest total sugar yield of 78.17%. A reduction in total by-product formation from 4.79 to 2.79 g/100 g biomass was also observed. Three preferred cultivars selected for pilot scale pretreatment using steam explosion resulted in maximum total sugar recoveries that exceeded 80% (w/w). Cultivar selection provides an opportunity to utilize sweet sorghum bagasse that will liberate sugars at desired yields while reducing the generation of by-products by implementing low severity pretreatments. [ABSTRACT FROM AUTHOR]

In order to improve the biogas production from sweet sorghum bagasse (SSB) pretreated with alkaline hydrogen peroxide and reveal the influence of zeolite dosage and TE on the anaerobic digestion performance, as well as the synergistic effect of zeolite dosage and TE, three dosages of zeolite and trace elements (TE) were used as additives for batched biogas production from pretreated sweet sorghum bagasse slurry (PSSBS). The results showed that the maximum methane production of 274.5 mL/g volatile solid (VS) from the group of PSSBS + 5 g/L zeolite + 1 mL TE could be obtained and 58.4% higher than that of untreated sweet sorghum bagasse. Modified Gompertz model estimation demonstrated that the PSSBS + 5 g/L zeolite + 1 mL TE group caused the highest methane production rate to improve by up to 41.6% from SSB and by at least 39.9% from PSSBS. Moreover, with the zeolite and TE addition, activities of cellulase and dehydrogenase of the digestate analysis indicated a positive influence on biogas production and the high alkalinity maintained the stability of the system. This work will provide experimental reference for biogas production from sweet sorghum bagasse. [ABSTRACT FROM AUTHOR]

Botryosphaeriaceae (Botryosphaeriales, Dothideomycetes, Ascomycota) encompasses commonly encountered opportunistic pathogens that cause stem cankers on woody plants. Lifestyles of Botryosphaeriaceae species could vary as endophytes, pathogens and saprobes and one species can have one or more lifestyles. Therefore, this family is an excellent candidate to study the relationships among lifestyles and lifestyle changes. It is postulated that this family has saprobic ancestors, and the mechanisms by which they evolved from nonpathogenic ancestors to woody pathogens remain unclear. Here, we present an analysis of 18 Botryosphaeriaceae genomes, including four newly generated high-quality genomes of Botryosphaeriaceae strains. We compared Botryosphaeriaceae genomes with phylogenetically closely related Dothideomycetes taxa including plant pathogens and saprobes which revealed significant net gene family expansion in Botryosphaeriaceae. This gene expansion is prominent in the early ancestors before the divergence of genera of Botryosphaeriaceae. This expansion affected the pathogenicity-related genes and detoxification genes. Furthermore, we analysed horizontal gene transfer, which is a mechanism of transfer to genetic material between organisms that are not in a parent–offspring relationship and identified widespread putative intra-kingdom horizontal gene transfer events in this family. Most were transferred during the evolution of ancient ancestors of Botryosphaeriaceae, before the divergence of the modern genera and were enriched in pathogenicity-related genes and detoxification genes. Furthermore, The RNA sequencing analysis of the Botryosphaeriaceae species Lasiodiplodia theobromae revealed that pathogenicity-related genes and detoxification genes, including those obtained through gene family expansion and horizontal gene transfers, were significantly induced after the infection of plant hosts rather than before infection. These insights reveal critical roles for gene family expansion and horizontal gene transfers in the evolutionary adaptation of Botryosphaeriaceae in the infection of woody plants. We postulate that the pathogenic lifestyle of Botryosphaeriaceae species evolved from saprobic or endophytic lifestyles in the early divergence of this family. However, there are few endophytic genomes available for closely related species of Botryosphaeriaceae, thus further studies are necessary to clarify the evolutionary relationships of the endophytes. [ABSTRACT FROM AUTHOR]

Excessive mining and utilization fossil fuels has led to drastic environmental consequences, which will contribute to global warming and cause further climate change with severe consequences for the human population. The magnitude of these challenges requires several approaches to develop sustainable alternatives for chemicals and fuels production. In this context, biological processes, mainly microbial fermentation, have gained particular interest. For example, autotrophic gas-fermenting acetogenic bacteria are capable of converting CO, CO2 and H2 into biomass and multiple metabolites through Wood-Ljungdahl pathway, which can be exploited for large-scale fermentation processes to sustainably produce bulk biochemicals and biofuels (e.g. acetate and ethanol) from syngas. Clostridium autoethanogenum is one representative of these chemoautotrophic bacteria and considered as the model for the gas fermentation. Recently, the development of synthetic biology toolbox for this strain has enabled us to study and genetically improve their metabolic capability in gas fermentation. In this review, we will summarize the recent progress involved in the understanding of physiological mechanism and strain engineering for C. autoethanogenum, and provide our perspectives on the future development about the basic biology and engineering biology of this strain. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the changes occurring in the wood cellulose of the fast-growing poplar (Populus deltoides × maximowiczii) under the influence of steam explosion (SE) pretreatment. Cellulose from native wood and after pretreatment at 160 and 205 °C was isolated. Cellulose polymerization degree by size exclusion chromatography (SEC) and cellulose crystallinity index by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) were determined. The profiles of sugars in the native wood and in the solid fraction after pretreatment (using the acid hydrolysis method) were also determined. In addition, the profile of monosaccharides in the liquid fraction obtained after steam explosion and in the liquid fraction after acid hydrolysis of the oligosaccharides were investigated using high-performance liquid chromatography (HPLC). This allowed to determine the change in the yield of hexoses and pentoses in the studied material. The behavior of cellulose in wood subjected to steam explosion at 160 and 205 °C and isolated by the Kürschner–Hoffer method was studied by determining the absorption bands of FTIR-ATR spectra. The lateral order index (LOI) of cellulose was calculated from the ratio of the intensity of the corresponding absorption bands A1422/A896 cm−1. Total crystallinity index (TCI) of cellulose was calculated from the ratio of the intensity of absorption bands A1372/A2900 cm−1. TCI of Kürschner-Hoffer cellulose isolated from wood subjected to steam explosion at 160 and 205 °C decreased by 5.6 and 5.0%, respectively, with regard to the applied temperature. LOI increased in cellulose isolated from wood subjected to steam explosion at 160 °C (by 0.7%) and at 205 °C (by 19.2%) in relation to the index of cellulose isolated from native wood. Kürschner–Hoffer cellulose isolated from wood subjected to steam explosion at 160 and 205 °C exhibited, respectively, a reduced degree of polymerization of about 11% and about 8%. Polydispersity index in Kürschner–Hoffer cellulose was 1% lower after both pretreatments than native sample. [ABSTRACT FROM AUTHOR]