Delignification Of Biomass Research Articles

Bacterial endophytes-mediated lignin degradation and co-culture fermentation of ryegrass for bioethanol production

The recalcitrant nature of lignin hinders the lignocellulosic biomass conversion by inhibiting enzymes access to hemicellulose and cellulose. In the present study, the lignin degradation of ryegrass biomass was enhanced via pretreatment by three selected ligninolytic enzyme producing endophyte bacteria. Spectroscopic analyses clearly displayed disruption and decomposition of the biomass structure after the pretreatments. The optimum sugar utilization efficiency was reached at 93.46 % in Bacillus cereus pretreatment, with the highest bioethanol production of 0.51 g/g and 85.78 % bioethanol yield (P ≤ 0.05) after the co-culture anaerobic fermentation. The initial yeast population of 1.65 × 107 cells mL−1 was decreased to 1.56 × 107 cells mL−1 in co-culture of Saccharomyces cerevisiae YPH499 and Pachysolen tannophilus 32691, presenting the significant consumption of yeast cells. The study revealed that bacterial pretreatment could be a viable strategy for delignification of biomass and co-culture fermentation might enhance bioethanol yield from pretreated ryegrass.

Advancing biorefineries with ultrasonically assisted ionic liquid-based delignification: Optimizing biomass processing for enhanced bio-based product yields

Encouraging sustainable business needs utilization of bio-based substrate for green manufacturing of chemicals and fuels to achieve sustainable development goals set by the United Nations. One of the abundantly available bio-based substrates is lignocellulosic (LC) biomass, which requires effective pretreatment to fractionate into its structural biocomponents to maximize biorefinery potential. This study addresses the use of an inexpensive ionic liquid (triethylammonium hydrogen sulfate) [T2220][HSO4] in an ultrasound-assisted process as an environmentally acceptable pretreatment method for the delignification of LC biomass, specifically rice straw (RS). Using ionic liquid (IL)-assisted (IL, acid-IL, and alkali-IL) pretreatment procedures, the effects of IL volume, sonication time, and temperature were methodically examined for RS delignification. To evaluate the compositional changes in pretreated and raw RS, instrumental analyses were carried out. The maximum rates of 47 %, 55 %, and 64 % for the only IL, acid-IL, and alkali-IL treatments demonstrated the effect of temperature, operating time, and IL concentration on the delignification efficiency. The alkali-IL pretreatment was noteworthy for achieving a 64 % delignification rate under optimum values of IL volume (8.65 mL), sonication time (123 min), and temperature (82 °C). Artificial neural networks (ANN) and response surface methodology (RSM) were used for process modeling and optimization. With an accuracy of 0.989 in correlation coefficient, the ANN model outperformed the RSM regression model regarding forecasting delignification performance. Biorefinery of renewable biomass resources ensures the sustainable supply of materials, chemicals, and fuels. The delignification and downstream product recovery technologies are major limiting factors in the commercialization of biomass processing. The suggested [T2220][HSO4]-based ultrasonic approach provides a viable way to boost biomass valorization efficiency, which in turn improves economical and sustainable biorefinery and aids in the shift to green bio-based production.

Optimization of laccase production by Pleurotus pulmonarius through solid substrate fermentation of tender coconut fiber: enhanced laccase production and biomass delignification

Optimization of laccase production by Pleurotus pulmonarius through solid substrate fermentation of tender coconut fiber: enhanced laccase production and biomass delignification

PHYSICO-CHEMICAL AND ELECTROCHEMICAL DELIGNIFICATION AS A PRETREATMENT OF LIGNOCELLULOSIC BIOMASS FOR DIFFERENT APPLICATIONS: A MINI-REVIEW

In recent years, the applications of lignocellulosic biomass (LCB) have substantially increased due to its versatility in different areas of study and interest. Therefore, it is evident that the delignification pretreatment of LCB is fundamental to assure the viability and commercial quality of the final product for different industrial uses. The efficiency of delignification, the obtainment of the desired products, and the required quality depend mainly on the type of pretreatment and the method used. This paper presents a state-of-the-art overview of physical, chemical, organic, biological, hybrid (combination of two or more pretreatments), and other novel pretreatments for the delignification of different lignocellulosic biomass. Additionally, the conditions necessary for the application of the pretreatments, the effect of the variables involved, and the advantages and disadvantages of each method are discussed. Finally, advances in the development of sustainable methods are discussed.

Novel stationary basket reactor for effective biomass delignification with deep eutectic solvent

Biomass pretreatment and conversion are crucial for sustainable development, but lack information on equipment that ensures effective mass transfer and easy biomass separation post-process. This work introduces a novel basket reactor with a stationary bed (StatBioChem) for biomass processing using deep eutectic solvents (DESs). We compared the delignification efficiencies of soft and hard biomass samples processed in the StatBioChem reactor, a stirred tank reactor (STR), and a commercial SpinChem® reactor. The StatBioChem design allowed DES to flow evenly through biomass in the basket, achieving the highest delignification degree, particularly for hard biomass. This effect was not observed in the SpinChem® basket reactor. High delignification led to increased glucose yields in subsequent enzymatic hydrolysis. The StatBioChem effectively combines the simplicity and efficiency of an STR with the ease of solvent recovery typical of basket reactors.

Alcoholysis-induced changes in cell wall surfaces: Structural insights for the effective delignification of lignocellulosic biomass

Alcoholysis (organosolv delignification)-induced changes in cell wall surfaces were investigated to verify whether structural assessments are required for effective delignification. Softwood blocks of Cryptomeria japonica were subjected to alcoholysis at 100–150 °C, which gradually decreased their lignin content. Scanning electron microscopy revealed the emergence of amorphous mesh structures on the intercellular side and their transformation into spherical particles with increasing temperature. In addition, warty layers changed from uneven structures into spherical particles on the lumen side of tracheids. These particles produced in cell walls under harsh alcoholysis conditions, damaging the cell wall layers on both sides. Confocal laser scanning microscopy identified that they were mainly lignin eluted by alcoholysis. Alcoholysis at 130 °C providing the largest specific surface area showed intermediate stages of growth into spherical particles but allowed complete delignification when combined with NaClO2 bleaching. Therefore, the role of the spherical particles, which has so far been debatable, was clarified as causing damage rather than a bleaching accelerant. Focusing only on compositional changes while ignoring structural ones leads to the incorrect identification of optimal conditions that remove lignin but damage the cell walls. Our findings demonstrate that structural considerations are required for effective and noninvasive delignification.

Life cycle assessment of tomato biomass residue anaerobic digestion preceded by ethanol-based organosolv and choline chloride-based deep eutectic solvent

Anaerobic digestion (AD) of lignocellulosic wastes (LW) has garnered substantial interest because of its notable energy and nutrient recovery, along with its potential for reducing greenhouse gas emissions. However, the LW is resistant to degradation, and its hydrolysis typically requires harsh conditions, hence the need for a pretreatment. Conducting a life cycle assessment (LCA) to evaluate the pretreatment of LW is an effective way to assess the environmental impacts associated with various pretreatment methods. This work evaluates and compares three scenarios for handling lignified tomato green waste (TGW), generated in the Greater of Agadir in Morocco, in terms of their environmental impacts and energy demand, using the LCA approach, performed with OpenLCA software. To achieve this aim, the impact of these scenarios on 11 indicators is studied. The analyzed management options include a base case scenario S0 where TGW undergoes a direct anaerobic digestion (AD), organosolv pretreatment of TGW followed by AD of the free-lignin fraction (S1), and choline chloride-based deep eutectic solvent (DES) delignification followed by AD of the free-lignin fraction (S2). The data used for the analysis comes from the Tamelast landfill, laboratory tests, literature, CML-IA baseline and Monte Carlo simulation calculations. The results obtained showed that the introduction of pretreatments in S1 and S2 mitigates significantly the environmental impact in different categories compared to S0. Scenario S2, with its enhanced recovery processes, shows the highest positive environmental contributions, despite its reliance on additional external electricity. S1 and S0 both respect energy circularity. Through this study, it has been demonstrated that chemical pretreatment of LW is energy, water and solvent-intensive and requires a large investment. It opens up perspectives for further works on pretreatment using natural DES technology, its development and its applications in the delignification of ligneous biomass on an industrial scale.

Innovative flow-through reaction system for the sustainable production of phenolic monomers from lignocellulose catalyzed by supported Mo2C.

Molybdenum carbide supported on activated carbon (β-Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow-Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT-RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT-RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13-15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT-RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two-step non-equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs.

Flux decline in crossflow ultrafiltration-based diafiltration process for lignin recovery from a deep eutectic solvent comprised of lactic acid and choline chloride

This study investigates a continuous ultrafiltration (UF)-based diafiltration (DF) method to separate and purify lignin from a deep eutectic solvent (DES) containing lactic acid and choline chloride after biomass delignification. A crossflow setup with a polyether sulfone UF membrane with a molecular weight cut off of 5000 Da was used to evaluate flux decline and fouling in this process. Under different pressure, feed flowrate, lignin, and DES concentrations, lignin rejection is around 0.90. Higher lignin and DES concentrations increase filtration resistance, and thus decrease flux at constant pressure. On the basis of a previously setup model based on dead-end filtration, a modeling approach was further developed to predict the system size required to implement UF-DF on a large scale. The results shows that at a constant pressure, the membrane system's area increases as the cake layer thickness over the membrane's surface increases.

Exploiting Deep Eutectic Solvent-like Mixtures for Fractionation Biomass, and the Mechanism Removal of Lignin: A Review

Green solvents, which include deep eutectic solvent-like mixtures (DES-like mixtures), are categorized as ecological and economical solvents for the pretreatment and fractionation of different types of biomasses. DES-like mixtures represent a group of the most promising green solvents for lignocellulosic pretreatment and are currently used effectively in the biomass pretreatment process. The present work describes the latest applications of DES-like mixtures in biomass delignification processes and, at the same time, summarizes the mechanism of action and influence of DES-like mixture systems on the removal of lignin from different types of biomasses. The results of this review indicate that the physicochemical properties (acidity, hydrogen bond capacity, polarity, viscosity, and water content) of DES-like mixtures have a significant effect on the biomass fractionation process. In addition to the nature of components forming DES-like mixtures, the reaction conditions (temperature, time) influence the efficiency of delignification. Active protons obtained from the hydrogen bond donor facilitate proton-catalyzed bond cleavage during fractionation, where the most significant step is the destruction of the ether and ester bonds between polysaccharides and lignin. DES-like mixtures can depolymerize lignin with subsequent breakdown of the β−O−4 bonds.

Extraction and characterisation of lignin from residues of Mexican Ocote pine (Pinus montezumae Lamb.) for biofuel production

The objective of this research was to extract lignin from residual lignocellulosic biomass of Ocote pine softwood (Pinus montezumae Lamb.) in the south-southwestern region of the Mexican Republic and to determine its potential as raw material to obtain biofuels. The lignin obtained was characterised by Fourier Transform Infrared (FT-IR) spectroscopy, Thermogravimetric Analysis (TGA), Higher Heating Value (HHV) analysis and elemental analysis. The Kraft process was applied for biomass delignification because it is most commonly used in the paper industry worldwide, using sodium hydroxide (NaOH) and sodium sulphide (Na2S) to extract the lignin from the fibres of the forest residues (sawdust and bark) in a 600 mL Parr reactor. The lignin extracted from pine sawdust obtained a better calorific value (28.75 MJ kg−1) than that recovered from the bark (23.61 MJ kg−1). The yield of lignin obtained from 50 g of bark, 5 g, was higher than that obtained from 50 g of sawdust, 2 g. The obtained lignin can be further processed to generate higher value-added products such as liquid biofuels.

Integrated Life Cycle Assessment and Techno-economic Analysis for Ionic Liquids-based Biomass Delignification Process

Ionic liquids (ILs) are a sort of green solvent that possess considerable promise for many industrial applications, such as the delignification of biomass. This study conducted an integrated life cycle assessment (LCA) and techno-economic analysis (TEA) of the utilization of 1 g of ILs for the ionosolv delignification process. [bmim][Cl] was selected as a case study. By using the CML 2001 environmental impact analysis method, 1 g of 1-butyl-3-methylimidazolium chloride [bmim][Cl] utilization for the ionosolv delignification process emitted 3.67 g CO2 eq of GWP100, 0.013 g SO2 eq of acidification potential, 0.015 g PO43- eq of eutrophication potential, and 32.417 g 1,4-DCB eq of HTP 20a.

Selective lignin depolymerization via transfer hydrogenolysis using Pd/hydrotalcite catalysts: model compounds to whole biomass.

Cleavage of lignin ether bonds via transfer hydrogenolysis is a promising route to valorize lignin, thus processes that use mild reaction conditions and exploit renewable hydrogen donor solvents (rather than molecular hydrogen) are economically advantageous. Herein we demonstrate the efficient catalytic transfer hydrogenolysis and tandem decarbonylation of lignin model compounds possessing aromatic ether bonds (α-O-4, β-O-4 and 4-O-5 linkages), over transition metal-modified Pd hydrotalcite catalysts with ethanol as the hydrogen donor and solvent. Quantitative conversions and yields were attained for all model compounds, except for 4-O-5 models, which possess inherently strong sp2 C-O bonds. The latter demonstrates the utility of Pd hydrotalcite catalysts for transfer hydrogenolysis of model compounds. This process was employed to achieve whole pine biomass delignification with 97% yield and a 22% phenolic monomer yield, with 64% selectivity for 4-(3-hydroxypropyl)-2-methoxyphenol.

Application of Aromatic Ring Quaternary Ammonium and Phosphonium Salts–Carboxylic Acids-Based Deep Eutectic Solvent for Enhanced Sugarcane Bagasse Pretreatment, Enzymatic Hydrolysis, and Cellulosic Ethanol Production

Deep eutectic solvents (DESs) with a hydrophobic aromatic ring structure offer a promising pretreatment method for the selective delignification of lignocellulosic biomass, thereby enhancing enzymatic hydrolysis. Further investigation is needed to determine whether the increased presence of aromatic rings in hydrogen bond receptors leads to a more pronounced enhancement of lignin removal. In this study, six DES systems were prepared using lactic acid (LA)/acetic acid (AA)/levulinic acid (LEA) as hydrogen bond donors (HBD), along with two independent hydrogen bond acceptors (HBA) (benzyl triethyl ammonium chloride (TEBAC)/benzyl triphenyl phosphonium chloride (BPP)) to evaluate their ability to break down sugarcane bagasse (SCB). The pretreatment of the SCB (raw material) was carried out with the above DESs at 120 °C for 90 min with a solid–liquid ratio of 1:15. The results indicated that an increase in the number of aromatic rings may result in steric hindrance during DES pretreatment, potentially diminishing the efficacy of delignification. Notably, the use of the TEBAC:LA-based DES under mild operating conditions proved highly efficient in lignin removal, achieving 85.33 ± 0.52% for lignin removal and 98.67 ± 2.84% for cellulose recovery, respectively. The maximum digestibilities of glucan (56.85 ± 0.73%) and xylan (66.41 ± 3.06%) were attained after TEBAC:LA pretreatment. Furthermore, the maximum ethanol concentration and productivity attained from TEBAC:LA-based DES-pretreated SCB were 24.50 g/L and 0.68 g/(L·h), respectively. Finally, the comprehensive structural analyses of SCB, employing X-rays, FT-IR, and SEM techniques, provided valuable insights into the deconstruction process facilitated by different combinations of HBDs and HBAs within the DES pretreatment.

Effect of Delignification on Reducing Sugar Recovery from Crocodile Gourd for Bioethanol Production

A central composite experimental design was used to optimize the key parameters affecting biomass delignification process of crocodile gourd for maximum reducing sugar recovery. The effects of temperature (70 oC to 90 oC), residence time (2 hrs. to 6 hrs.), concentration of sodium chloride (0.05 g/dm3 to 0.1 g/dm3) and volume of acetic acid (0.50 mL to 3 mL) were studied. The result obtained showed that optimum reducing sugar yield for crocodile gourd was achieved at temperature, time, sodium chloride and acetic acid of 70 oC, 6 hrs. 3 g and 3 mL respectively. The results indicate that X3, X4, X1 2 interactions and X2X4 interaction has linear effect on reducing sugar yield for crocodile gourd. The result of the proximate analysis showed moisture content of 6.50+ 0.50 %, Ash Content 11.00+ 0.28 %, Carbohydrate 64.40+0.62 %, Organic carbon 12.95+0.13 (%), Nitrogen 2.10+ 0.02 (%), Carbon/Nitrogen 6.16+0.08 %, Potassium 14100+23 mg/kg, Sodium 228+ 29 mg/kg, and Fixed carbon 7.4+0.80 %. The result of proximate analysis and compositional analysis revealed that the substrate could be utilized for biofuel production.

Changes in various lignocellulose biomasses structure after microwave-assisted hydrotropic pretreatment

Effective pretreatment of lignocellulosic biomass combined with delignification is a condition for effective enzymatic hydrolysis of cellulose, which is of key significance for the efficiency of the process of production of cellulosic ethanol. Becoming aware of the full range of changes in the structure of lignocellulose as a result of biomass pretreatment is important in view of the necessity to optimise the process of technological production of bioethanol. Our research was aimed at a comprehensive analysis of changes in structure of pine chip (softwood), beech chip (hardwood) and wheat straw (non-wood) biomasses resulting from a newly developed pretreatment method combining the use of hydrotrope in the form of sodium cumene sulfonate and microwave radiation. The performed analyses of the biomass composition indicate a high effectiveness of the proposed pretreatment method in the area of biomass delignification and hemicellulose removal. An effective removal of amorphous substances, i.e. lignin and hemicellulose, led to an increase in the crystallinity of pine chip biomass to 55%, and beech chips and wheat straw biomasses to 61%.

Chemical and Biological Delignification of Biomass: A Review

Chemical and Biological Delignification of Biomass: A Review

H8[PV5Mo7O40] (HPA-5) - a unique polyoxometalate for acid and RedOx catalysis: synthesis, characterization, and modern applications in green chemical processes.

Polyoxometalates (POMs) are a fascinating group of anionic metal-oxide clusters with a broad variety of structural properties and several catalytic applications, especially in the conversion of bio-derived platform chemicals. H8[PV5Mo7O40] (HPA-5) is a unique POM catalyst that ideally links numerous fascinating research fields for the following reasons: a) HPA-5 can be synthesized by rational design approaches; b) HPA-5 can be well characterised using multiple analytical tools explaining its catalytic properties; and c) HPA-5 is suitable for multiple important catalytic transformations of bio-based feedstocks. This review combines the fields of synthesis, spectroscopic, electrochemical and crystallographic characterization of HPA-5 with those of sustainable catalysis and green chemistry. Selected catalytic applications include esterification, dehydration and delignification of biomass as well as selective oxidation and fractionation of bio-based feedstock. We are fascinated from this unique POM and hope that the reader can get deeper insights into the chemistry of HPA-5 and its broad scope for biomass valorisation.

Chemomechanical pretreatment for efficient delignification and saccharification of corn stover biomass

The development of multifunctional pretreatments for effective and economical fractionation of lignocellulosic biomass (LCB), while targeting entirely lignocellulose-oriented valorization can pave the cutting-edge innovation in biorefinery. Herein, a promising high-solid chemomechanical pretreatment (CMP) based on ball milling (BM) coupled with ethylenediamine (EDA) pretreatment was designed to maximize the output of corn stover (CS) biomass under the mild temperature (≤120 °C) and active stabilization. The synergistic effects of EDA/BM configuration brought about desirable characteristics that eventually intensify delignification and saccharification at the expense of less solvent load and energy consumption up to 3.0 MJ kg−1 compare with EDA pretreatment (7.3 MJ kg−1). Importantly, CMP generated aminated and uncondensed lignin up to 85 % at 400 rpm for 1 h, with a high content of β-O-4 linkages (44.7/100Ar), which render it competently suitable for valorization into nitrogen-containing aromatic chemicals and lignin-based fluorescent materials. CMP led to 97 % conversion of glucan, and 94 % of xylan in 72 h at enzymatic loading of 1 and 0.5 %w. w-1 of Cellic CTec3 and xylanase, respectively. This lignin-first and entirely lignocellulose-oriented pretreatment could overcome the hampering of solid-state conversion and contribute to the sustainable LCB-based economy.

Optimization of pretreatment in delignification of hyacinth biomass for ethanol production

Water hyacinth ( Eichhornia crassipes ) is one of the potential feedstocks for bioethanol production due to their higher cellulose content. It needs the optimization of pretreatment to remove lignin and release cellulose and hemicellulose from lignocellulosic complex. Pretreatment was done using sulfuric acid, sodium hydroxide, and calcium hypochlorite as soaking agents. Experiment was carried out at 121 °C for 15 minutes. Pretreatment with 1% sulfuric acid decreased lignin by 6.74%, 4.0% sodium hydroxide reduced lignin content by 11.23%, whereas pretreatment with 0.3% calcium hypochlorite removed lignin by 8.30% from original lignin content lignocellulosic substrate. Therefore, sodium hydroxide pretreatment showed highest efficacy in delignification processes, followed by calcium hypochlorite, and sulfuric acid pretreatments. Keywords: Lignin reduction; Lignocellulose; Pretreatment; Water hyacinth