Lignocellulosic Research Articles

From pollutants to products: Microbial cell factories driving sustainable biomanufacturing and environmental conservation

Microbial cell factories are emerging as powerful tools in addressing pressing environmental challenges and promoting sustainable biomanufacturing. This paper highlights the key role of engineered microorganisms in mitigating pollution, converting waste and pollutants into valuable products, and reducing reliance on fossil fuels. Through advancements in metabolic engineering, gene editing technologies, and synthetic biology, microbial cell factories are being optimized to enhance their efficiency in breaking down pollutants and producing renewable chemicals, such as biofuels, bioplastics, and specialty chemicals. These processes contribute to environmental conservation, waste valorization, and the establishment of a circular economy.The study focuses on overcoming key barriers in microbial biotechnology, such as limited scalability, process inefficiency, and economic viability, by employing strategies like metabolic pathway optimization, enzyme overexpression, and tolerance enhancement. These strategies are applied to various microbial species, demonstrating how their metabolic capabilities can be fine-tuned for industrial applications. Detailed case studies illustrate successful implementations, such as the conversion of lignocellulosic biomass, CO2, and industrial waste into high-value products, underscoring the practical impact of microbial cell factories in diverse sectors, including energy, materials, and chemicals.Furthermore, this research addresses the challenges faced by microbial cell factories in industrial-scale operations, such as maintaining genetic stability and optimizing growth conditions, and offers insight into emerging technological solutions to these obstacles. By providing a comprehensive overview of recent developments and identifying future research directions, this paper offers actionable recommendations for unlocking the full potential of microbial biotechnology. These efforts aim to further integrate microbial processes into industrial systems, contributing to a more sustainable and resilient global economy, with the ultimate goal of fostering a circular bioeconomy.

Catalytic pyrolysis of hydrolyzed lignin using HZSM-5/MCM-41 supported transition-metal to produce monocyclic aromatic hydrocarbons

Hydrolyzed lignin (HL), one kind of organic solid wastes, comes from the production of hydrolysis of lignocellulosic biomass for high-value chemicals, unsuitable treatment of which not only meaning the waste of resources but also resulting environmental pollution. The pyrolysis of HL has the problem of high oxygen-containing compounds and low hydrocarbons in the products. The HZSM-5/MCM-41 (HM) meso-microporous composite catalyst, containing nickel and molybdenum, was synthesized through impregnation to enhance the production of monocyclic aromatic hydrocarbons (MAHs) during the in-situ catalytic pyrolysis of hydrolyzed lignin. Different transition metals loaded on composite molecular sieves were prepared for comparison. The relationship between catalyst structure and pyrolysis efficiency was studied based on characterization techniques including SEM, BET, and XRD. This study investigated the catalytic properties of modified composite molecular sieves with Ni and Mo at different loaded ratios on the pyrolysis of hydrolyzed lignin. Results indicated that HM loaded with different metals had different catalytic pyrolysis selectivity. The relative yield of MAHs on 3 %Ni-HM was the highest, at 27.78 %, while that of phenolic on 5 %Mo-HM was 51.02 %. Thus, by modifying the co-loading ratios between Ni and Mo, the combined catalytic pyrolysis of hydrolyzed lignin was performed, achieving a 39.24 % yield of MAHs on the catalyst Mo1Ni2-HM, markedly surpassing the 17.69 % yield from unaltered HZSM-5/MCM-41. In addition, the improvement of active sites was caused by transition metals loaded and the synergistic effect between bimetals enhanced the catalytic activity and stability. HZSM-5/MCM-41 loaded with metal oxides promoted the depolymerization of macromolecules in the intermediate products of pyrolysis, and thus improved the relative yield of MAHs among pyrolysis products of hydrolyzed lignin.

Investigations on performance of gasifier engine integration using three different biomasses as feedstocks

The integration of a downdraft gasifier with modified internal combustion engines presents a feasible solution for heat and power production, such as off-grid areas. This study conducted an experimental analysis to evaluate combustion in a modified engine. The morphological characteristics of the agricultural residue used in the gasifier were analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM), along with an examination of the slagging inorganic constituents. The engine used in the experiments was a modified single-cylinder design paired with a downdraft gasifier. Three types of biomass feedstocks—eucalyptus, corncob, and pearl millet in pellet form —were tested. The performance of the downdraft gasifier was stabilized, and the engine was run independently on each type of producer gas at a constant speed under different loads to determine the optimum load. Cylinder pressure measurements were taken to estimate the heat release rate.The study found that power generation was lower than typical woody biomasses due to the lower calorific value of the producer gas from the tested feedstocks. Additionally, lower cylinder pressures and heat release rates were recorded, along with longer combustion durations. The varying proportions of producer gas affected combustion stability. Among the studied ashes, pearl millet corncob (PMC) exhibited the highest slagging tendency, followed by corncob (CC). Morphological analysis indicated that the eucalyptus residue's increased porosity was caused by the volatiles changing, forming pores and tube-like structures. An aliphatic C–H peak (3000–2500 cm⁻1) is absent from the residue, indicating that the aliphatic structure was disturbed during thermochemical conversion. During the gasification process, the residue's crystallinity reduced as it split down.

Interactions between soil and other environmental variables modulate forest expansion and ecotone dynamics in humid savannas of Central Africa.

Forest expansion into savanna is a pervasive phenomenon in West and Central Africa, warranting comparative studies under diverse environmental conditions. We collected vegetation data from the woody and grassy components within 73 plots of 0.16 ha distributed along a successional gradient from humid savanna to forest in Central Africa. We associated spatially collocated edaphic parameters and fire frequency derived from remote sensing to investigate their combined influence on the vegetation. Soil texture was more influential in shaping savanna structure and species distribution than soil fertility, with clay-rich soils promoting higher grass productivity and fire frequency. Savanna featuring woody aboveground biomass surpassing 40 Mg ha-1 could escape the grass-fire feedback loop, by depressing grass biomass below 4 Mg ha-1. This thicker woody layer also favoured the establishment of fire-tolerant forest pioneers, which synergically contributed to the expansion of forests. Conversely, savannas below this fire suppression threshold sustained a balance between trees and grasses through the grass-fire feedback mechanism. This hysteresis loop, particularly pronounced on clayey soils, suggests that the contrast between grassy savanna and young forests might represent alternative ecosystem states, although savannas with low woody biomass remained vulnerable to forest edge encroachment.

One-step microwave pyrolysis-H3PO4 activation of woody biomass: Insight into the product characteristics and life cycle assessment

Microwave-assisted pyrolysis coupled with chemical activation was developed to prepare the woody biomass-derived activated carbon (AC) with desirable structural characteristics. In this study, sawdust powder was impregnated with phosphoric acid before being microwave-pyrolyzed to achieve AC. The utilization of microwave greatly enhanced the transformation of volatiles into gaseous components, and the yield of char increased when phosphoric acid accelerated the secondary polymerization of volatile matters. Microwave-induced activation may alter the interaction between activator and sawdust-derived organic species, enriching the categories of oily components. The char originating from microwave-activation treatment has a high graphitization degree, exhibiting superior thermal stability and hydrophilic property. Moreover, one-step microwave-activation approach increased specific surface area (978.2 m2g−1 versus 13.0 m2g−1 in conventional pyrolysis) and improved the formation of porous structure. The life cycle assessment analysis revealed that microwave-activation technique had a low environmental impact due to enhanced heating efficiency and reduced energy consumption.

Mild and efficient approach to aromatic backbone cleavage using copper-lignosulfonate/hydrogen peroxide system

This study investigates the dual role of copper ions in catalysis and complexation during the oxidation of lignosulfonates with hydrogen peroxide (H2O2) under alkaline conditions. The presence of copper ions reduces partial oxidation by 86 % compared to H2O2 treatment alone, enhancing overall conversion efficiency to 63 % under increased oxidative conditions. Analyses reveal that copper-lignosulfonate complexes facilitate redox cycling and hydroxyl radical generation through interactions with H2O2, confirming copper’s dual functions. This mechanism mitigates the hindrance of sulfonic groups on hydroperoxide anions, leading to lignosulfonate degradation into dicarboxylic acids. These findings provide novel insights into the copper-lignosulfonate/H2O2 system, expanding the understanding of oxidative degradation mechanisms beyond traditional Fenton-like reactions. Furthermore, this system offers a simplified and efficient alternative for industrial applications, particularly in integration with the sulfite pretreatment process of woody biomass for producing valuable co-products.

Preparation of CuCo2O4@NFs nanoflower material with abundant VO/VCo: An excellent catalyst for oxidative breakage of the β-O-4 bond of lignin

A hollow nanoflower material CuCo2O4@NFs with abundant oxygen vacancies (VO) and cobalt vacancies (VCo) was prepared by a simple method. The novel material CuCo2O4@NFs showed excellent oxidation activity, cleaving the β-O-4 bond in lignin model compounds. Conversion of the substrate was as high as 99.02%, and the yield of the main product, phenol, reached 49.50%. Structural analysis showed that the petal and cavity form of the material increased its specific surface area, which facilitated its full contact with O2 molecules. Moreover, the VO generated by lattice oxygen detachment during annealing favor the adsorption of O2, and the VCo generated through lattice distortion induced by Cu-metal doping promoted the detachment of oxygen intermediates. The synergy of these two defects improved the rate of the rate-limiting step. Density functional theory calculations revealed that the synergistic effect of VO and VCo narrowed the gap between the Fermi energy levels and the d-band center, thereby enhancing electron mobility. Finally, excellent recyclability of CuCo2O4@NFs was confirmed through cycling experiments. The application of this material provided technical support for the efficient cracking of lignin into high-value-added chemicals and realized the effective utilization of woody biomass resources.

Sustainable Approaches used in Pesticides contaminated Agricultural Waste Water Remediation

With the growing population of our global community and thereby increasing the demand for food has led the farmers to use more and more pesticides. Pesticides are chemical compounds used to kill pests. It is commonly used to control various agricultural pests that destroy crops and ultimately affect our agricultural productivity. Although the use of pesticides is a beneficial approach, but unfortunately it also has some drawbacks in terms of harming the environment and human health. Some pesticides pose significant hazards that ultimately affect human health systems. Contamination of agricultural land and agricultural wastewater by pesticides is a serious environmental problem and has a negative impact on biodiversity. Most synthetic pesticides are not readily biodegradable, they accumulate in the environment and cause soil contamination. To overcome the environmental burden of pesticide-contaminated sites, various sustainable approaches can be effectively used to detoxify contaminants or transform them into harmless secondary compounds. The current review focuses on the role of microorganisms and lignocellulosic biomass and plants in the degradation of agricultural pesticides under sustainable approaches.

Nanocellulose as Sustainable Eco-friendly Nanomaterials: Production, Characterization, and Applications

Nanocellulose is a biodegradable nanomaterial derived from lignocellulosic biomass through mechanical, chemical, or enzymatic defibrillation processes to convert wood fibers into nanofibrils. This material consists of a network of cellulosic fibrils with a wide range of diameters, offering unique properties suitable for various functional applications. Nanocellulose can act as a substrate or coating, serving as an eco-friendly alternative to synthetic plastics. Despite having good barrier properties and strong mechanical strength, nanocellulose films are still not as effective as synthetic plastics. They are used in creating barrier materials, flexible electronics, and coatings for paper products.

Insights into the pelletization behaviors of artificial lignocellulosic biomass based on cellulose, hemicellulose and lignin: A simplex lattice mixture design approach

The use of high quality densified pellet as an alternative to traditional fossil fuels is a promising avenue of research due to their interesting higher density, superior heating values, and enhanced combustion performance. However, little is known about the pelletization behaviors from the aspect of lignocellulosic biomass fundamental components (cellulose, hemicellulose and lignin) and their mixtures. This study presents an artificial biomass developed based on cellulose, hemicellulose and lignin using a simplex lattice design approach, aiming to understand the detailed role of major components and its effects on pellet quality. The correlation between the experimental data obtained from the simplex lattice design and the predicted response parameters were effectively explained by Scheffé's special cubic model, with a coefficient of determination beyond 90 %. Parameter estimates showed a significant synergetic effect of each components for density and Meyer hardness. Results revealed that xylan may be softened like lignin and thereby potentially act as binder. The use of a high cellulose concentration resulted in enhanced pellet strength by acting as a supporting skeleton. Xylan and cellulose played a major role in the thermal degradation of densified pellets. Based on the results obtained, the optimal components composition was determined to be 34.5 % lignin, 36.3 % cellulose, and 29.2 % xylan. Under this, the pellet exhibited the best density and Meyer hardness beyond 1500 kg/m3 and 80 N/mm2, respectively. The results provide a foundation for future efforts to be able to predict pellet properties from the perspective of biomass composition.

Structural and molecular modifications of woody biomass under minimal torrefaction conditions toward making durable pellets

Extensive research has been published on pelletizing severely torrefied biomass with the aid of binders, but limited studies have investigated the structural modifications of biomass during mild torrefaction. This study investigates the effects of several combinations of minimal torrefaction temperatures (230°C and 250°C) and relatively short durations (10, 15, and 30 minutes) on the thermophysical and molecular structure of the model woody biomass loblolly pine (Pinus Taeda) residues. The low severity treated biomass is compared with the untreated biomass and the biomass torrefied at 270°C for 30 minutes. Structural characterization methods include laser diffraction for particle size distribution and Brunauer-Emmett-Teller (BET) analysis to evaluate specific surface area. Additionally, FTIR, XRD, and TGA are used to assess changes in crystallinity and thermochemical composition. The woody residue torrefied at 250°C for 10 minutes exhibited a higher BET surface area (4.7 m²/g) than torrefied at 250°C for 15 minutes (3.5 m²/g). At a constant temperature of 250°C, the crystallinity index increases with the treatment duration, emphasizing the effect of time on retaining more hydroxyl groups that may act as binders for pelletization. This study demonstrates that minimizing the combination of torrefaction time and temperature can help control the degree of biomass molecular structure degradation thus minimizing overall mass loss, offering potential applications in the emerging biocarbon pellet industry.

Unlocking Nature’s Potential: Modelling Acacia melanoxylon as a Renewable Resource for Bio-Oil Production through Thermochemical Liquefaction

This study is focused on the modelling of the production of bio-oil by thermochemical liquefaction. Species Acacia melanoxylon was used as the source of biomass, the standard chemical 2-Ethylhexanol (2-EHEX) was used as solvent, p-Toluenesulfonic acid (pTSA) was used as the catalyst, and acetone was used for the washing process. This procedure consisted of a moderate acid-catalysed liquefaction process and was applied at 3 different temperatures to determine the proper model: 100, 135, and 170 °C, and at 30-, 115-, and 200-min periods with 0.5%, 5.25%, and 10% (m/m) catalyst concentrations of overall mass. Optimized results showed a bio-oil yield of 83.29% and an HHV of 34.31 MJ/kg. A central composite face-centred (CCF) design was applied to the liquefaction reaction optimization. Reaction time, reaction temperature, as well as catalyst concentration, were chosen as independent variables. The resulting model exhibited very good results, with a highly adjusted R-squared (1.000). The liquefied products and biochar samples were characterized by Fourier-transformed infrared (FTIR) and thermogravimetric analysis (TGA); scanning electron microscopy (SEM) was also performed. The results show that invasive species such as acacia may have very good potential to generate biofuels and utilize lignocellulosic biomass in different ways. Additionally, using acacia as feedstock for bio-oil liquefaction will allow the valorisation of woody biomass and prevent forest fires as well. Besides, this process may provide a chance to control the invasive species in the forests, reduce the effect of forest fires, and produce bio-oil as a renewable energy.

Altered Lignin Accumulation in Sorghum Mutated in Silicon Uptake Transporter SbLsi1.

Sorghum [Sorghum bicolor (L.) Moench] has been receiving attention as a feedstock for lignocellulose biomass energy. During the combustion process, the ash containing silicon (Si) can be produced, which causes problems in furnace maintenance. Hence, lowering Si content in the plants is crucial. Nevertheless, limiting Si supply to crops is difficult in practice because Si is abundant in soil. Previously, a Si uptake transporter (SbLsi1) has been identified, and the Si-depleted mutant has also been generated in the model sorghum variety BTx623. In this study, we aim to investigate the change induced by the mutation of SbLsi1 on the accumulation and the structure of lignin in cell walls. Through chemical and NMR analyses, we demonstrated that the lsi1 mutation resulted in a significant increase in lignin accumulation levels as well as a significant reduction in Si content. At least some of the modification was induced by transcriptional changes, as suggested by the upregulation of phenylpropanoid biosynthesis-related genes in the mutant plants. These findings derived from the model variety would be useful for the future development of practical cultivars with high biomass and less Si content for bioenergy applications.

Layer Characteristics on Quartz and Feldspar Bed Particles in an Industrial-Scale Fast Pyrolysis Process of Woody Biomass

Layer Characteristics on Quartz and Feldspar Bed Particles in an Industrial-Scale Fast Pyrolysis Process of Woody Biomass

Quantification of biomass availability for wood harvesting and storage in the continental United States with a carbon cycle model

BackgroundWood Harvesting and Storage (WHS) is a form of Biomass Carbon Removal and Storage (BiCRS) that utilizes a combined natural and engineered process to harvest woody biomass and put it into long term storage, most frequently in the form of subterranean burial. This paper aims to quantify the availability of woody biomass for the purposes of WHS in the continental United States using a carbon cycle modeling approach. Using a regional version of the VEGAS terrestrial carbon cycle model at 10 km resolution, this paper calculates the annual woody net primary production in the continental United States. It then applies a series of constraints to exclude woody biomass that is unavailable for WHS. These constraints include fine woody biomass, current land use, current wood utilization, land conservation, and topographical limitations. These results were then split into state by state and regional totals.ResultsIn total, the model projects the continental United States could produce 1,274 MtCO2e (CO2 equivalent) worth of coarse woody biomass annually in a scenario with no anthropogenic land use or constraints. In a scenario with anthropogenic land use and constraints on wood availability, the model projects that 415 MtCO2e of coarse woody biomass is available for WHS annually. This is enough to offset 8.5% of the United States’ 2020 greenhouse gas emissions. Of this potential, 20 MtCO2e is from the Pacific region, 77 MtCO2e is from the Western Interior, 91 MtCO2e is from the Northeast region, and 228 MtCO2e is from the Southeast region.ConclusionThere is enough coarse woody biomass available in the continental United States to make WHS a viable form of carbon removal and storage in the country. There is coarse woody biomass available across the continental United States. All four primary regions analyzed have enough coarse woody biomass available to justify investment in WHS projects.

Impact of Lentinus sajor-caju on Lignocellulosic Biomass, In Vitro Rumen Digestibility and Antioxidant Properties of Astragalus membranaceus var. mongholicus Stems under Solid-State Fermentation Conditions

Lentinus sajor-caju has shown potential for the bioconversion of lignocellulosic biomass in various substrates. Here, we evaluated whether L. sajor-caju affects the lignocellulosic biomass, in vitro fermentation and antioxidant properties of Astragalus membranaceus var. mongholicus (AMM) stems. The lignocellulosic biomass content and the antioxidant activity of AMM stems were determined by scanning electron microscopy, chemical component analysis, in vitro fermentation and LC-MS metabolomics after 30 days of fermentation by L. sajor-caju at 25 °C. L. sajor-caju significantly altered the rigid structure of the stems. Compared with the control condition, the lignocellulose contents were significantly reduced (p < 0.001) and improved in vitro digestibility and total volatile fatty acids. In total, 624 differential metabolites, including 201 up-regulated and 423 down-regulated, were identified in unfermented and fermented comparison groups. Correlation analysis indicated that there were strongly correlations of the total phenolic content and total antioxidant capacity. Meanwhile, the differential metabolites were primarily associated with antioxidant activity, with 4(3H)-quinazolinone, dihydrocarvyl acetate and jaceoside being the most representative. In summary, L. sajor-caju altered the composition of the cell wall of AMM stems, thereby enhancing their antioxidant activity.

Microbial production of levulinic acid from glucose by engineered Pseudomonas putida KT2440

Levulinic acid(LA) is produced through acid-catalyzed hydrolysis and dehydration of lignocellulosic biomass. It is a key platform chemical used as an intermediate in various industries including biofuels, cosmetics, pharmaceuticals, and polymers. Traditional LA production uses chemical conversion, which requires high temperatures and pressures, strong acids, and produces undesirable side reactions, repolymerization products, and waste problems Therefore, we designed an integrated process to produce LA from glucose through metabolic engineering of Pseudomonas putida KT2440. As a metabolic engineering strategy, codon optimized phospho-2-dehydro-3-deoxyheptonate aldolase (AroG), 3-dehydroshikimate dehydratase (AsbF), and acetoacetate decarboxylase (Adc) were introduced to express genes of the shikimate and β-ketoadipic acid pathways, and the 3-oxoadipate CoA-transferase (pcaIJ) gene was deleted to prevent loss of biosynthetic intermediates. To increase the accumulation of the produced LA, the lva operon encoding levulinyl-CoA synthetase (LvaE) was deleted resulting in the high LA-producing strain P. putida HP203. Culture conditions such as medium, temperature, glucose concentration, and nitrogen source were optimized, and under optimal conditions, P. putida HP203 strain biosynthesized 36.3 mM (4.2 g/L) LA from glucose in a fed-batch fermentation system. When lignocellulosic biomass hydrolysate was used as the substrate, this strain produced 7.31 mM of LA. This is the first report of microbial production of LA from glucose by P. putida. This study suggests the possibility of manipulating biosynthetic pathway to produce biological products from glucose for various applications.

Compositional and structural characterization of eleven types of lignocellulosic biomass and its potential application in obtaining nanopolysaccharides and producing polyhydroxyalkanoates

Compositional and structural characterization of eleven types of lignocellulosic biomass and its potential application in obtaining nanopolysaccharides and producing polyhydroxyalkanoates

VALORIZATION OF LIGNOCELLULOSIC BIOMASS BY DARK FERMENTATION: DEVELOPMENT OF EFFECTIVE CONDITIONS FOR MOLECULAR HYDROGEN BIOSYNTHESIS

Valorization of lignocellulosic biomass (LB) is important to reduce their environmental impact and reduce the risk to human health. Conventional methods for handling secondary raw materials primarily focus on waste disposal, treating lignocellulosic biomass as waste rather than as a source of organic substances for producing value-added products. As an alternative, processes should be developed to add value to waste, producing value-added products with economic and environmental benefits. In this regard, studies have focused on operating parameters, pretreatment, and microbial fermentation to enhance hydrogen yield during dark fermentation. Upper (4%) and lower (20%) concentrations of distillery grain based substrates for biohydrogen synthesis using wild-type E. coli have been established. Conditions for rational formation of reducing sugars by varying feedstock and acid concentrations in distillery grain based substrates have been established. During the study of the effect of acid-hydrothermal treatment of stillage on the total yield of biohydrogen, it was found that the optimal concentration of sulfuric acid is 1,5%, while 10% of the raw material is used. Under these conditions, the maximum yield of molecular hydrogen was achieved, equal to 116 ±1,0 ml/l using wild-type E. coli.

Optimization of Microwave-Assisted Inorganic Salt Pretreatment for Production of Fermentable Sugars from Spent Coffee Ground

Spent coffee ground (SCG) is a solid waste that is generated in the coffee brewing process for coffee beverage production. SCG hold a great potential in reducing sugar production as it consists of high amount of carbohydrates. However, SCG is a lignocellulosic biomass (LCB) which requires pretreatment to degrade the lignocellulosic structure and enhance enzyme accessibility during saccharification process. Hence, this research aims to study the performance of microwave-assisted inorganic salt pretreatment for generation of reducing sugars. Different concentrations of NaCl was applied to determine their effects on reducing sugar produced as well as pH, and solid recovery. Pretreatment with 3% NaCl was found to yield the highest reducing sugar concentration of 43.56 mg/mL, hence it was selected for the subsequent optimization study. Process optimization was designed by using the Response Surface Methodology approach (RSM) with Central Composite Design (CCD), based on three pretreatment parameters; solid to liquid ratio (1:50 - 8:50), microwave power (300W – 800W) and irradiation time (1-10 minutes). The optimized conditions were achieved at solid to liquid of 8:50, microwave power of 800 watt and irradiation time of 10 minutes for a maximum response of 40.89 mg/mL. Moreover, it was observed that microwave-assisted NaCl pretreatment had significantly caused surface morphological changes of the SCG and the removal of functional groups in lignin, resulted in increment of the crystallinity value. In conclusion, microwave pretreatment is a promising green technology for fermentable sugar production from SCG.