Hemicellulose Degradation Research Articles

COMPARISON OF TWO METHOD FOR ISOLATION OF FIBRILLATED CELLULOSE FROM LIGNOCELLULOSIC BIOMASS

Fibrillated cellulose from distillery refuse based on maize starch was prepared by two different procedures. The effect of sonification was evaluated atacid-alkali extractionas well as the type of used acid. The results from the alkali-acid procedure were compared with these obtained by method of steam explosion at different temperatures. The acid-alkali method brings a better result regarding degradation of hemicellulose and lignin as well as cellulose. Lignin/hemicellulose were only released from lignocellulose network using steam explosion at 120-180°C. At higher temperature, the results were comparable with those obtained by acid-alkali method. Similarly pore size distribution of filter paper decreased more significantly when fibrillated cellulose from acid-alkali treatment was applied. After steam explosion, higher extend of longer still fibres remains.

Solid-state fermentation of corn wet distiller grains and wheat bran with Trichoderma reesei and Candida utilis for improving feed value.

Solid-state fermentation is one of the most effective methods for the high-value utilization of agro-industrial by-products. Co-fermentation of wet distiller grains and agricultural waste is an effective way to mitigate the feed shortage caused by corn consumption for bioethanol. It is still challenging to convert wet distiller grains and wheat bran to easily accessible carbon sources and adjust the balanced proportion of amino acids together by fermentation. Fermentation time, strain ratio, and the addition of ammonium sulfate have been verified to be the important factors influencing the symbiosis of Trichoderma reesei (T. reesei) and Candida utilis (C. utilis) in a mixed system of wet distiller grains and wheat bran. The optimum conditions were fermentation for 8 days, 2:1 (T. reesei: C. utilis) strain ratio, and addition of 4% ammonium sulfate. After fermentation, the cellulose degradation proportion reached 39.1%, and the hemicellulose degradation proportion was 13.1%. The protein content improved by 29.6%. The lysine content increased by 126%, reaching 11.3 g·kg-1. The threonine content increased from 6.10 to 10.3 g·kg-1. The phytate content was decreased to 3.97 g·kg-1. The in vitro digestibility of dry matter and protein increased to 62.8% and 76.1%, respectively. These results indicated the feasibility of improving the feeding value of wet distiller grains and wheat bran by the symbiosis of T. reesei and C. utilis. © 2024 Society of Chemical Industry.

Long-read sequencing sheds light on key bacteria contributing to deadwood decomposition processes

BackgroundDeadwood decomposition is an essential ecological process in forest ecosystems, playing a key role in nutrient cycling and carbon sequestration by enriching soils with organic matter. This process is driven by diverse microbial communities encompassing specialized functions in breaking down organic matter, but the specific roles of individual microorganisms in this process are still not fully understood.ResultsHere, we characterized the deadwood microbiome in a natural mixed temperate forest in Central Europe using PacBio HiFi long-read sequencing and a genome-resolved transcriptomics approach in order to uncover key microbial contributors to wood decomposition. We obtained high quality assemblies, which allowed attribution of complex microbial functions such as nitrogen fixation to individual microbial taxa and enabled the recovery of metagenome-assembled genomes (MAGs) from both abundant and rare deadwood bacteria. We successfully assembled 69 MAGs (including 14 high-quality and 7 single-contig genomes) from 4 samples, representing most of the abundant bacterial phyla in deadwood. The MAGs exhibited a rich diversity of carbohydrate-active enzymes (CAZymes), with Myxococcota encoding the highest number of CAZymes and the full complement of enzymes required for cellulose decomposition. For the first time we observed active nitrogen fixation by Steroidobacteraceae, as well as hemicellulose degradation and chitin recycling by Patescibacteria. Furthermore, PacBio HiFi sequencing identified over 1000 biosynthetic gene clusters, highlighting a vast potential for secondary metabolite production in deadwood, particularly in Pseudomonadota and Myxococcota.ConclusionsPacBio HiFi long-read sequencing offers comprehensive insights into deadwood decomposition processes by advancing the identification of functional features involving multiple genes. It represents a robust tool for unraveling novel microbial genomes in complex ecosystems and allows the identification of key microorganisms contributing to deadwood decomposition.

Lanthanum and cerium added to soil influence microbial carbon and nitrogen cycling genes

The soil microbiome plays an important role in carbon (C) and nitrogen (N) processing and storage and is influenced by rare earth elements (REEs), which can have both direct and indirect effects on plant metabolic processes. Using conventional physicochemical methods and metagenomic-based analyses, we investigated REEs effects on soil respiration, soil mineral N, soil microbial community structure and functional genes related to C and N metabolism. High doses of cerium (0.16 and 0.32 mmol kg−1 soil) increased CO2 net production rate by 59 and 42%, and N2O net production rate by 255 and 609%, respectively, compared to no REEs. Similarly, high doses of lanthanum (0.16 and 0.32 mmol kg−1 soil) increased CO2 net production rate by 47 and 39%, and N2O net production rate by 105 and 187%, respectively. Increased soil respiration from altered relative abundances of key soil microorganisms associated with soil N cycling and organic matter degradation and functional genes encoding enzymes involved in C and N metabolism, accelerated N mineralization. Elevated REEs levels substantially increased the relative abundances of functional genes related to cellulose, chitin, glucans, hemicellulose, lignin, and peptidoglycan degradation. REEs also influenced multiple functional genes associated with the N cycle. The abundance of genes responsible for organic N degradation and synthesis, such as asnB, gdh_K15371, glsA, and gs, increased with elevated cerium and lanthanum concentrations. Similarly, the abundances of denitrification genes, including narl, narJ, narZ, and nosZ, also rose with increasing amounts of cerium and lanthanum. However, the decrease in narB and nirB gene abundance with increasing REE concentrations was attributed to the reduction of nitrate to amino groups. Our findings highlight the influence of REEs on key soil microorganisms associated with soil N cycling and organic matter degradation and key functional genes in soil C and N metabolism, with implications for agriculture, environmental protection, and human health.

Enhancing the water resistance properties of bamboo particleboard by reconstructing lignocellulose through carbonization treatment

Bamboo particleboards are recognized as a highly promising alternative to traditional wood particleboards owing to their short growth cycle, abundant availability, and exceptional mechanical properties. However, bamboo particleboards frequently exhibit undesirable hygroscopicity, which limits their broader applications. This study introduces a straightforward and inhibitor-free carbonization treatment method to enhance the water resistance properties of bamboo particleboards. During the carbonization process, the degradation of hemicelluloses and amorphous cellulose, combined with the condensation reactions among lignin molecules, leads to a significant reduction in the hydrophilic hydroxyl and carbonyl group content, resulting in a more compact micro-fibril structure. Concurrently, the degradation of specific macromolecules within the cell wall facilitates the crushing of bamboo during particleboard pressing, thereby reducing the macroscopic pore size between the particles in the board. When compared to the original bamboo particleboard, the moisture absorption, 24-h water absorption (at a relative humidity of 50 %), 24-h thickness swelling, and bound water content of the deep carbon bamboo particleboard decreased by 32.28 %, 81.57 %, 67.16 %, and 66.7 %, respectively, while the water contact angle increased by 88.89 %.

VvARF19 represses VvLBD13-mediated cell wall degradation to delay softening of grape berries

Abstract The fruit softening directly impacts its storage life, transportability, and customer acceptance. Auxin plays a key role during fruit ripening, but the underlying mechanisms of how auxin regulates fruit softening remain unclear. In this study, we investigated the regulatory roles of auxin on berry cell wall degradation during grape (Vitis vinifera L.) softening. During grape berry development, berry firmness and auxin content are both firstly increasing and then decreasing, and peaks occur at 4-6 WAFB (weeks after full blooming). Exogenous NAA (α-naphthalene acetic acid, a synthetic auxin) treatment inhibits berry softening by delaying propectin, cellulose and hemicellulose degradation, which maintains cell wall integrity in the grape flesh. Weighted gene co-expression network analysis (WGCNA) shows that VvLBD13 correlated with VvARF19 could be a key gene in this delaying of berry softening, which involved in auxin signal transduction and cell wall degradation metabolism. Over-expression and transient over-expression of VvLBD13 in tomato or in grape berry indicate that VvLBD13 accelerates hemicellulose degradation by binding the promoters of VvXTH10 (the xyloglucan endotransglucosylase/hydrolase 10) and VvEXPLA1 (expansion-like A1), which results in rapid softening after veraison. Collectively, this research furnishes an exhaustive understanding of the auxin- driven regulatory mechanisms of grape berry softening.

Effects of Inoculation of Thermotolerant Bacillus Strains on Lignocellulose Degradation

Thise study investigated the effect of three lignocellulolytic thermophilic Bacillus strains (F11, Q1, and FP4) on lignocellulose degradation, enzymatic activities, and microbial community structure in composting. The lignin degradation rate reached 36% in the presence of the inoculant, the hemicellulose degradation rate ranged from 43% (F11) to 51% (Q1), and cellulose degradation rates reached 57% in F11 and in FP4, which were significantly higher than the control (CK). The inoculation treatment could explain 28% of the lignin degradation for all three strains. The contribution of FP4 to hemicellulose and cellulose degradation was 30% and 20%, respectively. Compared to CK, lignin peroxidase activity in the water extract of the compost had increased by 66~145% for inoculation treatments, and manganese peroxidase and laccase activity increased by 114% and 78% for Q1. The inoculation stimulated the growth of indigenous bacteria with stronger lignocellulolytic enzyme-producing ability; such shifts in microbial communities were most likely responsible for the improved lignocellulose degradation.

Unraveling the impact of intervention strategies and oxygen disparity in humification during domestic waste composting

This study constructs three different photovoltaic assisted composting systems to treat rural domestic waste, and explores the interaction pathways between biomacromolecules and other factors under oxygen disparity at gradient heights of the compost. The optimized mode of regular turning and ventilation-dehydration significantly reduced the moisture content by 53.6% and increased the seed germination index by 35.6%. The oxygen content at different heights under the optimized mode significantly affects the physicochemical properties of the compost, and the degradation of cellulose, hemicellulose, and protein in the middle is higher than other parts. The structural equation model shows that the physicochemical properties at the bottom are affected by biomacromolecules, which may be related to volatile fatty acids(VFAs) produced under low oxygen conditions.The research results show that using manual turning and ventilation-dehydration as the optimized process can promote compost maturity, and oxygen concentration has an important impact on the humification process of the compost.

Rapid production of high-performance unilaterally surface-densified wood through integrating mechanical compression and thermochemical modification

Enhancing the mechanical performance and dimensional stability of fast-growing wood in an efficient and eco-friendly manner remains a challenge. This study introduces a straightforward and highly efficient technique for fabricating unilaterally surface-densified (USD) wood from fast-growing poplar wood. This process involves a pre-drying treatment, high-temperature compression at 250 ℃, and subsequent cooling, all completed within a total compression time of 300 s. The produced USD wood exhibits outstanding physical and mechanical properties, along with excellent dimensional stability. Notably, the USD wood achieved a hardness of 4.3 kN, a modulus of rupture of 117.0 MPa, and a modulus of elasticity of 12.2 GPa, representing increases of 104.7 %, 72.0 %, and 38.6 %, respectively, compared to untreated wood, aligning with the properties of several premium hardwoods. Furthermore, the USD wood showed superior impact resistance and bending stiffness, alongside minimal irreversible thickness swelling (2.29 %) under humid and high-temperature conditions, evidencing its robust mechanical and dimensional stability. These improved performances are attributed to the formation of a densified layer with an intact cell wall structure, which benefits from the favorable effects of high temperature-induced plasticization of cell walls and thermal degradation of hemicellulose. The efficacy of this high-temperature compression technique highlights its significant potential for the mass production of high-performance wood from fast-growing species. Consequently, the resulting USD wood is ideally suited for value-added applications in the furniture and construction industries, offering a pathway towards sustainable and eco-friendly manufacturing solutions.

Thermal Decomposition and Kinetic Analysis of Amazonian Woods: A Comparative Study of Goupia glabra and Manilkara huberi

This study presents a detailed analysis of the thermal degradation and kinetic behavior of two Amazonian wood species, Goupia glabra (cupiúba) and Manilkara huberi (maçaranduba), using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR-ATR), and direct infusion mass spectrometry (DIMS). Wood samples were subjected to controlled heating rates of 20, 40, and 60 °C/min from 25 to 800 °C under an argon atmosphere. TGA revealed moisture evaporation below 120 °C, with hemicellulose degradation occurring between 220 and 315 °C, cellulose decomposition between 315 and 400 °C, and lignin breakdown over a broader range from 180 to 900 °C. The highest rate of mass loss occurred at 363.99 °C for G. glabra and 360.27 °C for M. huberi at a heating rate of 20 °C/min, with shifts to higher temperatures at faster heating rates. Activation energies were calculated using Arrhenius and Kissinger models, yielding values between 53.46–61.45 kJ/mol for G. glabra and 58.18–62.77 kJ/mol for M. huberi, confirming their stable thermal profiles. DSC analysis identified a significant endothermic peak related to moisture evaporation below 100 °C, followed by two exothermic peaks. For G. glabra, the first exothermic peak appeared at 331.45 °C and the second at 466.08 °C, while for M. huberi, these occurred at 366.41 °C and 466.08 °C, indicating the decomposition of hemicellulose, cellulose, and lignin. Enthalpy values for G. glabra were 12,633.37 mJ and 18,652.66 mJ for the first and second peaks, respectively, while M. huberi showed lower enthalpies of 9648.04 mJ and 14,417.68 mJ, suggesting a higher energy release in G. glabra. FTIR-ATR analysis highlighted the presence of key functional groups in both species, with strong absorption bands in the 3330–3500 cm−1 region corresponding to O-H stretching vibrations, indicative of hydroxyl groups in cellulose and hemicellulose. The 1500–1600 cm−1 region, representing aromatic C=C vibrations, confirmed the presence of lignin. Quantitatively, these results suggest a high content of cellulose and lignin in both species. DIMS analysis further identified polyphenolic compounds and triterpenoids in M. huberi, with major ions at m/z 289 and 409, while G. glabra showed steroidal and polyphenolic compounds with a base peak at m/z 395. These findings indicate the significant presence of bioactive compounds, contributing to the wood’s resistance to microbial degradation. This comprehensive thermal and chemical characterization suggests that both species have potential industrial applications in environments requiring high thermal stability.

Ethylene-Induced Postharvest Changes in Five Chinese Bayberry Cultivars Affecting the Fruit Ripening and Shelf Life

Ethylene is an essential indicator of fruit ripening and climacteric or non-climacteric nature. This study investigated the postharvest behavior of five Chinese bayberry cultivars ‘Biqi’, ‘Dongkui’, ‘Fenhong’, ‘Xiazhihong’, and ‘Shuijing’. The fruits were harvested mature and stored at room temperature (25 °C) and under cold storage conditions (4 °C) to investigate the dynamics of ethylene production, firmness, anthocyanin content, and cell wall polysaccharide composition, as well as basic fruit physicochemical characteristics. The results show that Chinese bayberry is a climacteric fruit with ethylene production peaking shortly after harvest, especially at room temperature. Fruit color intensified over time due to anthocyanin accumulation, particularly in the flesh core. Darker cultivars produced more ethylene, which correlated with higher anthocyanin levels. At room temperature, ‘Biqi’ (black) had the highest ethylene production (4.03 µL·kg−1·h−1) and anthocyanin content (0.91 mg/g FW), while ‘Shuijing’, the white cultivar, had the lowest ethylene levels (1.9 µL·kg−1·h−1) and anthocyanin content (0.03 mg/g FW). Firmness significantly decreased at room temperature due to the degradation of hemicellulose and insoluble pectin, whereas cold storage mitigates this effect. After 3 days at room temperature, the average of firmness decreased by 23.7% in the five cultivars, compared to 12.7% under cold storage. Total soluble solids increase during storage, enhancing sweetness, especially at room temperature, with ‘Biqi’ increasing from 9.2 to 10.9% at 4 °C. Titratable acidity slightly decreased over time: the value for ‘Biqi’ decreased from 1.2% to 0.95% at room temperature and 1.1% at 4 °C. Citric, malic, and tartaric acid generally declined at room temperature but stabilized under cold storage. Sucrose, fructose, and glucose increased or remained stable, with significant varietal differences. Our results indicate that storing Chinese bayberry at 4 °C effectively preserves its quality and extends postharvest life. These findings underscore ethylene’s key role in regulating ripening, postharvest quality, and shelf life by influencing fruit color, firmness, and overall consumer appeal.

Thermal modification of Lantana camara stalks and its characterization

Abstract This paper deals with value addition and utilization of Lantana camara, an invasive species with unprecedented rate of growth, by thermal modification. Lantana camara stalks were thermally modified using vacuum heat treatment (VHT), oil heat treatment (OHT), and steam heat treatment (SHT) at 180 °C and 200 °C and subsequently changes in physical, chemical and mechanical properties were studied. Weight loss was observed in vacuum and steam heat treated samples due to thermal degradation while oil heat treated samples showed weight gain due to oil uptake. SHT exhibited the highest (19 %) weight loss at 200 °C. The color of the modified lantana attained uniform dark colour, OHT exhibited the most intense effect on colour changes. Fourier transform infrared (FTIR) and Fourier transform near infrared (FTNIR) spectroscopic analyses indicated degradation of hemicellulose and change in cellulose crystallinity due to heat treatment. Dimensional stability of thermally modified Lantana stalks improved across treatments, with SHT achieving the highest anti-swelling efficiency of 67.3 % at 200 °C and lowest water absorption (43 %) after 72 h of water soaking. The dynamic modulus of elasticity of thermally modified Lantana remained constant in all the treatment processes. Overall, the results indicate that thermal modification can increase utilization potential of L. camara.

Seasonal stability of the rumen microbiome contributes to the adaptation patterns to extreme environmental conditions in grazing yak and cattle

BackgroundThe rumen microbiome plays an essential role in maintaining ruminants’ growth and performance even under extreme environmental conditions, however, which factors influence rumen microbiome stability when ruminants are reared in such habitats throughout the year is unclear. Hence, the rumen microbiome of yak (less domesticated) and cattle (domesticated) reared on the Qinghai-Tibetan Plateau through the year were assessed to evaluate temporal changes in their composition, function, and stability.ResultsRumen fermentation characteristics and pH significantly shifted across seasons in both cattle and yak, but the patterns differed between the two ruminant species. Ruminal enzyme activity varied with season, and production of xylanase and cellulase was greater in yak compared to cattle in both fall and winter. The rumen bacterial community varied with season in both yak and cattle, with higher alpha diversity and similarity (beta diversity) in yak than cattle. The diversity indices of eukaryotic community did not change with season in both ruminant species, but higher similarity was observed in yak. In addition, the similarity of rumen microbiome functional community was higher in yak than cattle across seasons. Moreover, yak rumen microbiome encoded more genes (GH2 and GH3) related to cellulose and hemicellulose degradation compared to cattle, and a new enzyme family (GH160) gene involved in oligosaccharides was uniquely detected in yak rumen. The season affected microbiome attenuation and buffering values (stability), with higher buffering value in yak rumen microbiome than cattle. Positive correlations between antimicrobial resistance gene (dfrF) and CAZyme family (GH113) and microbiome stability were identified in yak, but such relationship was negatively correlated in cattle.ConclusionsThe findings of the potential of cellulose degradation, the relationship between rumen microbial stability and the abundance of functional genes varied differently across seasons and between yak and cattle provide insight into the mechanisms that may underpin their divergent adaptation patterns to the harsh climate of the Qinghai-Tibetan Plateau. These results lay a solid foundation for developing strategies to maintain and improve rumen microbiome stability and dig out the potential candidates for manufacturing lignocellulolytic enzymes in the yak rumen to enhance ruminants’ performance under extreme environmental conditions.

Impact of Trichoderma spiralis Treatment on the Photothermal Water Evaporation Capacity of Poplar

In recent years, research on interfacial photothermal water evaporation has been thriving. Due to its inherent porosity, exceptional hydrophilicity, and renewable characteristics, wood has garnered significant attention as a material for interfacial photothermal evaporation absorbers. In order to enhance the cellular channels of poplar and improve its water migration capacity, Trichoderma spiralis was selected to inoculate and culture poplar specimens from different sections for 3, 5, and 7 weeks. Simultaneously, a solar radiation intensity of 1 kW·m⁻2 was simulated to perform photothermal evaporation tests on the specimens. This validated the water migration capabilities of different sections of poplar treated with Trichoderma spiralis under light and heat exposure. The characteristic changes were analyzed using electron microscope scanning, infrared spectrum analysis, X-ray photoelectron spectroscopy analysis, surface infiltration performance, and automatic specific surface porosity. The results suggested that the moderate degradation of cellulose and hemicellulose in poplar by Trichoderma spiralis could dredge the cell channels and improve the permeability of poplar, particularly with regard to lateral permeability. The maximum photothermal evaporation rate of the poplar specimen reached 1.18 kg m⁻2 h⁻1, while the evaporation efficiency increased to 72.2%.

The combined nitrogen and phosphorus fertilizer application reduced soil multifunctionality in Qinghai-Tibet plateau grasslands, China

The impact of nitrogen (N) and phosphorus (P) fertilizer inputs on soil nutrient cycling and ecological function processes has garnered significant attention. Soil multifunctionality primarily refers to the soil's ability to perform multiple functions simultaneously, particularly the functions related to the genes involved in carbon (C), nitrogen (N), and phosphorus (P) cycles, which are critical for ecosystem sustainability. Despite this, the effects of N and P fertilizers on the expression of genes involved in soil carbon (C), nitrogen (N), and phosphorus (P) cycles, and their consequent influence on soil multifunctionality, remain unclear. To investigate this, we conducted a long-term nine-year experiment. The experimental site was fenced to prevent grazing and included four treatments: Control (no fertilizer), N (10 g N m−2 y−1, urea), P (5 g P m−2 y−1, Ca(H2PO4)2), and NP (10 g N and 5 g P m−2 y−1, urea and Ca(H2PO4)2). We examined the effects of these treatments on soil microbial functional gene abundance and multifunctionality. Our findings revealed that N addition altered the composition of soil microbial functional genes but did not affect functional diversity. Both N and P inputs, as well as their combination, negatively impacted soil carbon fixation and the genes encoding enzymes for the degradation of starch, hemicellulose, cellulose, and chitin. N input also disrupted soil nitrogen and phosphorus cycling by inhibiting the expression of soil denitrification genes (nirS and nosZ), phytate hydrolase gene (cphy), and a phosphatase gene (phoD). Additionally, P input significantly inhibited functional genes involved in soil nitrification, denitrification, ammonification, nitrogen fixation, and ammonia oxidation processes. It also adversely affected phytate synthesis and degradation. The combined N and P inputs had a substantial negative impact on soil nitrification (hao), denitrification (narG, nirK, nirS, and norZ), ammonification (gdh), nitrogen fixation, annamox, and nitrogen reduction, and inhibited the expression of soil phosphorus cycle genes. Long-term phosphorus application was found to have a more detrimental effect on soil multifunctionality compared to nitrogen application. Furthermore, our study showed that vegetation diversity and abundance are crucial drivers of soil carbon, nitrogen, and phosphorus cycling functional genes and multifunctionality. We concluded that N and P inputs alter soil multifunctionality by influencing vegetation diversity; therefore, maintaining vegetation diversity is essential for sustaining soil multifunctionality.

Effects of different accelerated aging modes on the mechanical properties, color and microstructure of wood

This research experimentally investigated the mechanical properties, color and microstructure of wood materials based on three accelerated aging modes. The moisture content, density, tension properties, compression properties, bending properties, shear properties, color, chemical composition and microstructure of the aged woods were studied. The density was reduced by 24–29 % within accelerated aging. The shear properties decreased the most (nearly 50 %), followed by the tensile and compressive properties, and the bending properties decreased the least (20–30 %). Lightness changed significantly during accelerated aging, which was the main reason affecting the color differences. The degradation of hemicellulose was the most (23–33 %), followed by lignin, while that of the cellulose was the least (about 5 %). Accelerated aging modes primarily influenced the degrees of the crystallinity, rather than altering the crystalline structures. The swelling of the wood particles and the degradation of the cellulose microfibril revealed by the microstructure characterized the reductions in mechanical properties. The CSA 2-h boil mode can be used as the accelerated aging mode for wood materials, while the other two accelerated aging modes had a similar aging effect with a slight extent.

Unveiling the Hidden Responses: Metagenomic Insights into Dwarf Bamboo (Fargesia denudata) Rhizosphere under Drought and Nitrogen Challenges.

Dwarf bamboo (Fargesia denudata) is a crucial food source for the giant pandas. With its shallow root system and rapid growth, dwarf bamboo is highly sensitive to drought stress and nitrogen deposition, both major concerns of global climate change affecting plant growth and rhizosphere environments. However, few reports address the response mechanisms of the dwarf bamboo rhizosphere environment to these two factors. Therefore, this study investigated the effects of drought stress and nitrogen deposition on the physicochemical properties and microbial community composition of the arrow bamboo rhizosphere soil, using metagenomic sequencing to analyze functional genes involved in carbon and nitrogen cycles. Both drought stress and nitrogen deposition significantly altered the soil nutrient content, but their combination had no significant impact on these indicators. Nitrogen deposition increased the relative abundance of the microbial functional gene nrfA, while decreasing the abundances of nirK, nosZ, norB, and nifH. Drought stress inhibited the functional genes of key microbial enzymes involved in starch and sucrose metabolism, but promoted those involved in galactose metabolism, inositol phosphate metabolism, and hemicellulose degradation. NO3--N showed the highest correlation with N-cycling functional genes (p < 0.01). Total C and total N had the greatest impact on the relative abundance of key enzyme functional genes involved in carbon degradation. This research provides theoretical and technical references for the sustainable management and conservation of dwarf bamboo forests in giant panda habitats under global climate change.

Effects of peracetic acid delignification on hemicellulose extraction by dimethyl sulfoxide

Extracting high-purity and structurally intact hemicelluloses from lignocellulosic fibers is a prerequisite to reveal their structures and realize high-value utilization. Delignification is usually performed before hemicellulose extraction to break the covalent bonds between hemicelluloses and lignin for effective separations, but usually leads to toxic by-products and hemicellulose degradation. Peracetic acid (PAA) is an environmentally friendly oxidizing agent, which is more selective for delignification and has less effect on the primary structure of hemicelluloses. However, the yields and chemical structures of hemicelluloses extracted at different PAA delignification conditions are not clear, which greatly hinders its research and application. Consequently, the response surface methodology (RSM) was used in this study to optimize the process parameters of PAA delignification. With the increase of temperature or time, the yield of holocellulose decreases, and the hemicellulose yield increases first and then decreases. With the increase of delignification degree, the hemicellulose yield increases significantly. The degree of PAA delignification also has a significant effect on the chemical structures of extracted hemicelluloses; hemicellulose samples extracted from highly delignified holocelluloses have a higher xylose unit content, molecular weight (MW) and degree of substitution by acetyl groups (DSAc). The tert-butanol solvent exchange or ball milling treatments on holocelluloses significantly increase the hemicellulose yields, by avoiding the hornification and improving the accessibility of holocellulose. This study will provide theoretical and technical support for the efficient separation of hemicelluloses.

Integrated approach for improving mechanical and high-temperature properties of fast-growing poplar wood using lignin-controlled treatment combined with densification

Previous studies on the modification of fast-growing wood have extensively examined the effects of density and lignin content on the strength and high-temperature properties of modified wood. However, a comprehensive quantitative analysis of their effects on high-temperature performance remains insufficient. To address this knowledge gap, we applied alkali treatment and compression densification to fast-growing poplar, resulting in modified specimens with varying densities and lignin levels. The quantitative effects of density and lignin content on high-temperature properties were meticulously evaluated. Chemical changes were analyzed using Fourier transform infrared spectroscopy (FT-IR), while the mechanical and high-temperature properties were comprehensively assessed. Delignification was found to be positively correlated with treatment duration, with hemicellulose degradation also detected via FT-IR analysis. Significant enhancements were recorded in flexural strength, tensile strength, and modulus of elasticity, accompanied by improvements in ductility ratio and compressive strength. The modified poplar wood exhibited increased thermal stability at elevated temperatures. Furthermore, density and lignin content were identified as significant factors affecting high-temperature performance, establishing minimum density thresholds for various lignin contents in modified poplar wood to ensure optimal performance. This study enhances to the understanding of the intricate relationships among wood properties, modification techniques, and high-temperature performance.

Improving hydrolysis and acidification by regulating the oxygen status and solid content of lignocellulosic waste: Emphasis on the unsealed environment and harnessing the potential of microbial communities

The recalcitrant nature of lignocellulosic raw materials poses a challenge for current biogas plant operations, where hydrolysis and acidification (HA) are the rate-determining steps. To explore the HA balance and microbial mechanisms according to oxygen status and in conditions with relatively high solid content, we made a simple change to build an unsealed reactor. We found that the hemicellulose degradation rate increased by 149.3 % under unsealed conditions. Under microaerobic conditions (Mi), HA with more than 10 % total solid (TS) content exhibited a carbon loss rate of < 10 % in the first 7 days. In the 15 % TS Mi treatment, the organic acid conversion coefficient was 0.04, and the concentration increased to 7.4 g/L within 2 days. A high solid content was the key factor for ensuring efficient organic acid production in the early stage, whereas Mi affected the middle stage. Multiple methods revealed that abundant Prevotella and Clostridium, as well as rare Bifidobacterium, Sporacetigenium, and specific bacteria, had substantial effects on efficient organic acid production and HA balance. The correlation with Mi was 0.57–0.83. The abundance of hemicellulase genes increased by 18.41 %, and the abundance of pyruvate kinase in Mi increased by 15.55 % compared with the sealed condition, demonstrating that Mi can provide complementary advantages in the HA process. The findings in this study improved the operational quality of conventional HA and anaerobic digestion.