Lignin In Rice Straw Research Articles

Multiple hydrolyses of rice straw by domesticated paddy soil microbes for methane production via liquid anaerobic digestion

The aim of this study was to investigate the hydrolysis of rice straw (RS) using domesticated paddy soil microbes (DPSMs) with swine wastewater (SW) as the nitrogen source and the multiple hydrolyses for CH4 production via liquid anaerobic digestion (L-AD). Three hydrolyses of RS with a 45% inoculation ratio (IR) under the conditions of a carbon/nitrogen ratio (C/N ratio) of 40, temperature of 37 °C, inoculum/substrate ratio (I/S ratio) of 2:1, and immersion depth of 6.0 cm were optimal, attaining maximum volatile fatty acids (VFAs) after five days, possibly owing to the synergistic effect of aerobic microbes (Firmicutes and Actinomycetes) and anaerobic microbes (Bacteroidetes and Acidobacteria). After three hydrolyses, the degradation rates of hemicellulose, cellulose, and lignin in RS were 88.45%, 83.19% and 70.09%, respectively. The accumulative CH4 production reached 462.11 mL/g VS after three hydrolyses, and its curve fitted well with the modified Gompertz model (R2 > 0.984).

Integrated hydrothermal and deep eutectic solvent-mediated fractionation of lignocellulosic biocomponents for enhanced accessibility and efficient conversion in anaerobic digestion

Effective fractionation of lignocellulosic biocomponents of lignocellulosic biomass can increase its utilization in anaerobic digestion for high yield biomethane production. A hydrothermal process was optimized and integrated with a deep eutectic solvent (DES) pretreatment to preferentially fractionate hemicellulose, cellulose, and lignin in rice straw. The optimized hydrothermal process resulted in 96% hemicellulose solubilization at moderately low combined pretreatment severity (log S = 2.26), allowing increased hemicellulosic sugar recovery with minimal formation of inhibitory byproducts. Subsequent DES pretreatment resulted in highly bioaccessible cellulosic pulp, removing 81.3% of lignin that can be recovered and converted into value-added products. Anaerobic digestion of hemicellulosic fraction and cellulosic pulp using a microbial methanogenic consortium seed acclimatized to the lignocellulosic inhibitors resulted in a 33.4% higher yield of methane (467.84 mL g−1 VSinitial) than with anaerobic digester sludge seed. This integrated approach can facilitate and maximize the targeted utilization of different biocomponents through sustainable biorefining.

Comparative Evaluation of Adsorption of Major Enzymes in a Cellulase Cocktail Obtained from Trichoderma reesei onto Different Types of Lignin.

Cellulase adsorption onto lignin decreases the productivity of enzymatic hydrolysis of lignocellulosic biomass. Here, adsorption of enzymes onto different types of lignin was investigated, and the five major enzymes—cellobiohydrolases (CBHs), endoglucanase (Cel7B), β-glucosidase (Cel3A), xylanase (XYNIV), and mannanase (Man5A)—in a cellulase cocktail obtained from Trichoderma reesei were individually analyzed through SDS-PAGE and zymogram assay. Lignin was isolated from woody (oak and pine lignin) and herbaceous (rice straw and kenaf lignin) plants. The relative adsorption of CBHs compared to the control was in the range of 14.15–18.61%. The carbohydrate binding motif (CBM) of the CBHs contributed to higher adsorption levels in oak and kenaf lignin, compared to those in pine and rice lignin. The adsorption of endoglucanase (Cel7B) by herbaceous plant lignin was two times higher than that of woody lignin, whereas XYNIV showed the opposite pattern. β-glucosidase (Cel3A) displayed the highest and lowest adsorption ratios on rice straw and kenaf lignin, respectively. Mannanase (Man5A) was found to have the lowest adsorption ratio on pine lignin. Our results showed that the hydrophobic properties of CBM and the enzyme structures are key factors in adsorption onto lignin, whereas the properties of specific lignin types indirectly affect adsorption.

Development of a paddy-based biorefinery approach toward improvement of biomass utilization for more bioproducts

Improvement of biomass utilization productivity following cascading strategy is a priority for the biorefinery-based circular bioeconomy. In recent years, the field of energy research has seen an increasing interest in bio-products from paddy-based biorefinery, but the utilization of the entire value of paddy biomass to guide the commercial viability of its products has not been got feasible outcomes. Here we propose a potential pathway for a conceptual paddy biorefinery framework by addressing wastes for producing more products. The feasibility of the integrated biorefinery was demonstrated by the conversion of wastes into value-added products such as nano-silica and lignin. In particular, this is the first time that silica recovered from bioethanol system was continued to be reused to produce ZSM-5 and Ni/ZSM-5 as catalysts of rice straw lignin depolymerization achieving high conversion of lignin up to 95% and fair yield of phenolic products up to 41%. Material flow of an integrated biorefinery model was reported to give a future outlook for making most of the processing routes of rice residues. We also established a life cycle that follows the circular bioeconomy concept and discussed the relationship between each of potential bioproducts and their market opportunities.

Construction of a fungal consortium for effective degradation of rice straw lignin and potential application in bio-pulping

To improve the lignin degradation efficiency, we established a co-culture consortium (LDFC) consisting of Trametes hirsuta BYL-3, Trametes versicolor BYL-7 and Trametes hirsuta BYL-8. The testing results showed that the constructed consortium showed improved the lignin degradation rate by fungi. The optimal cultivation conditions were mixture at 1:1:1 vol ratio of each fungus, 7% (w/v) of inoculum amount, culture temperature at 26 °C, pH was 6.9 and 10 days of culturing time. Under these conditions, the degradation rate of lignin was 39.7%, which was 9.3% higher than those before optimization (30.4%). Using rice straw for treatment by LDFC to papermaking, the paper tensile strength was 8 N, and the ring pressure index was 2.46 N·m/g, which meets the standards for the production of corrugated paper for packaging. These results indicate that LDFC has potential application value to convert rice straw resources for bio-pulping to make papers.

Comparison of organic acid-based organosolv lignins extracted from the residues of five annual crops

Organosolv lignins were extracted from corn stover, wheat, rice straw, reed straw, and sugarcane bagasse using a mixture of acetic and formic acids, at relatively low temperature and atmospheric pressure. Lignin content, residual carbohydrates, ash levels, proteins, and molecular weights were determined in each extracted lignin. The lignin content of all samples was relatively high, confirming the performance of the pretreatment process. The low molecular weights were in a narrow range, in accordance with the organosolv lignin molar masses. However, some differences between studied lignins were highlighted, in particular in rice straw lignin, which contained the highest silica, calcium, and nitrogen contents. Nuclear magnetic resonance spectroscopies (31P and semi-quantitative Heteronuclear Single Quantum Correlation) underlined the structural similarities and differences between these organosolv lignins. Corn stover and sugarcane bagasse lignins were rich in non-methoxylated (H-Unit) or mono-methoxylated (G-Unit) phenolic units, making them the best promising candidates for production of phenolic resins. Wheat straw lignin was richer in aliphatic OH than in phenolic OH. This is an advantage for use as polyol substitute in polyurethane synthesis. Reed straw lignin was less specific, with a balanced content of OH groups. However, it contained a high concentration of β-O-4 linkages, which is favorable for depolymerization.

Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization.

Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. 31P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (Tg) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low Tg, which is beneficial for its further valorization.

Characteristics and functional bacteria in a microbial consortium for rice straw lignin-degrading

The degradation of lignin is the main rate-limiting step in the bio-pulping of rice straw. A lignin-degrading bacterial consortium LDC, which can efficiently degrade lignin of reed, was screened in the early stage of our laboratory work. In present study, 7-day incubation of LDC can degrade rice straw lignin by 31.18% in mineral salt medium. The communities’ structure of different incubation phases varied greatly, in which high abundance (44.78%) of Anaerocolumna was first found. The expression levels of lignin degradation enzyme class II peroxidase (AA2), vanillyl alcohol oxidase (AA4) and 1,4-benzoquinone reductase (AA6) during peak phase (48 h) were significantly up-regulated than initial phase (24 h), increasing by 112%, 165% and 67%, respectively, and 42.86% AA2 was from Thaurea; 100% AA4 was from Clostridium; 62.5% AA6 was from Pseudomonas. These provide microbial resources and data support for the industrialization of rice straw bio-pulping.

Association mapping identifies quantitative trait loci (QTL) for digestibility in rice straw

BackgroundThe conversion of lignocellulosic biomass from agricultural waste into biofuels and chemicals is considered a promising way to provide sustainable low carbon products without compromising food security. However, the use of lignocellulosic biomass for biofuel and chemical production is limited by the cost-effectiveness of the production process due to its recalcitrance to enzymatic hydrolysis and fermentable sugar release (i.e., saccharification). Rice straw is a particularly attractive feedstock because millions of tons are currently burned in the field each year for disposal. The aim of this study was to explore the underlying natural genetic variation that impacts the recalcitrance of rice (Oryza sativa) straw to enzymatic saccharification. Ultimately, we wanted to investigate whether we could identify genetic markers that could be used in rice breeding to improve commercial cultivars for this trait. Here, we describe the development and characterization of a Vietnamese rice genome-wide association panel, high-throughput analysis of rice straw saccharification and lignin content, and the results from preliminary genome-wide association studies (GWAS) of the combined data sets. We identify both QTL and plausible candidate genes that may have an impact on the saccharification of rice straw.ResultsWe assembled a diversity panel comprising 151 rice genotypes (Indica and Japonica types) from commercial, historical elite cultivars, and traditional landraces grown in Vietnam. The diversity panel was genotyped using genotype by sequencing (GBS) methods yielding a total of 328,915 single nucleotide polymorphisms (SNPs). We collected phenotypic data from stems of these 151 genotypes for biomass saccharification and lignin content. Using GWAS on the indica genotypes over 2 years we identified ten significant QTL for saccharification (digestibility) and seven significant QTL for lignin. One QTL on chromosome 11 occurred in both GWAS for digestibility and for lignin. Seven QTL for digestibility, on CH2, CH6, CH7, CH8, and CH11, were observed in both years of the study. The QTL regions for saccharification include three potential candidate genes that have been previously reported to influence digestibility: OsAT10; OsIRX9; and OsMYB58/63-L.ConclusionsDespite the difficulties associated with multi-phasic analysis of complex traits in novel germplasm, a moderate resolution GWAS successfully identified genetic associations encompassing both known and/or novel genes involved in determining the saccharification potential and lignin content of rice straw. Plausible candidates within QTL regions, in particular those with roles in cell wall biosynthesis, were identified but will require validation to confirm their value for application in rice breeding.

Introduction of a Preconditioning Step Prior to Assisted Single-Step Acid Pretreatment Influences the Structural Integrity of Lignin in Rice Straw

The recalcitrant nature of lignocellulosic biomass is attributed to the presence of cellulose, hemicellulose, and lignin. An effective biomass deconstruction method can overcome this challenge and aid in generating fermentable sugars. In order to improve the efficiency of the previously developed assisted single-step acid pretreatment (ASAP) process, the present study introduced a preconditioning (PreC) step prior to ASAP. Among the different preconditioning methods (viz., hot water, steam, steam in the presence of ASAP catalyst, and xylanases) that were tested on rice straw, an increase in delignification (∼13%) and reactor solids loading (∼50%) were obtained with enzymatic preconditioning. In addition, the characterization of solid and liquid streams arising from all preconditioning and pretreatments revealed the presence of compounds such as polyunsaturated and polysaturated fatty acids as well as organosilanes, which are being reported for the first time in pretreated hydrolysates and solids. Through this study, it is demonstrated that the introduction of a suitable preconditioning method prior to biomass pretreatment can improve bioethanol productivity by ∼50%.

Process development for sodium carbonate pretreatment and enzymatic saccharification of rice straw for bioethanol production

Optimization of pretreatment of rice straw was carried out with sodium carbonate. Initially, sodium carbonate pretreatment of rice straw followed by saccharification using partially purified cellulolytic enzymes of thermophilic mould Myceliophthora thermophila BJTLRMDU3 (20 U/g) at 60 °C and pH 5.0 after 6 h, released about 3-fold more reducing sugars with autoclaving (154.93 mg/g substrate) as compared to room temperature (51.01 mg/g substrate). Further optimization was carried out using statistical tools by response surface methodology (RSM) selecting three variables i.e., sodium carbonate concentration, substrate concentration and autoclaving time. Statistical optimization has resulted in enhanced liberation of reducing sugars i.e., 531.2 mg/g substrate using 5% rice straw, 1.25% sodium carbonate and autoclave time of 30 min after saccharification for 6 h. Furthermore, maximum liberation of reducing sugars (728.45 mg/g substrate) from pretreated rice straw was recorded after 48 h. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) data clearly confirmed the breakdown of cellulose and hemicellulose, removal of lignin and morphological changes in pretreated rice straw. Fermentation of enzymatic hydrolysate (20%) was carried out by Saccharomyces cerevisiae at 30 °C, pH 6.0, 150 rpm that resulted in 18.07 g/L ethanol after 72 h.

Influence of alkaline addition on the composition and yield on the hydrothermal treatment of rice straw

Agricultural waste is abundantly available in Indonesia, including rice straw. The largest components of rice straw are cellulose, hemicellulose, and lignin, making this material good enough as raw material for production of biogas, bioethanol, and other renewable fuels. The bonds in the cellulose and lignin in rice straw are strong and difficult to degrade which consequently will block the microorganisms to degrade them. In this study, a hydrothermal treatment was performed with the addition of NaOH. The purpose of this study was to investigate the effect of alkaline hydrothermal treatment on rice straw delignification, cellulose and hemicellulose solubility, the formation of reducing and furfural sugars, as well as the degrees of cellulose crystallinity. The variables used were NaOH concentration of 3%, 5%, and 7% (w/w total solid) and temperature were 100 ℃, 120 ℃, and 140 ℃. Treatment was performed using an autoclave with water and rice straw ratio of 8:1 with heating time for 2 hours. The results of this study showed that hydrothermal and NaOH treatment can increase rice straw organic degradation as indicated by increasing delignification of rice straw and increased levels of watersoluble sugars. The higher the temperature and the NaOH concentration, the more lignin and soluble hemicellulose content. Meanwhile, the reducing sugar increases with increasing temperature and NaOH concentration. Thermal decomposition rate has also occurred at lower temperature. It was found that the highest organic rice straw degradation occurs at higher temperature and NaOH concentration.

Boron Nitride Quantum Dots Derived from Renewable Lignin

AbstractAlthough numerous attempts have been reported, however, efficient and facile approach about the preparation of boron nitride quantum dots (BNQDs) is yet to be explored. Here we have developed a biomass‐directed suitable strategy from steam exploded rice straw lignin (SERSL) toward mass production of high‐quality BNQDs with quantum yields (QY) as high as 18.2%. Few‐layered BNQDs have a mean lateral size of several nanometers and a thickness ranging from 0.5 nm to 2 nm as confirmed by transmission electron microscopy (TEM) and atomic force microscope (AFM). The BNQDs as‐prepared emit bright and stable blue colors of luminescence under ultraviolet‐light excitation. In addition, the BNQDs also exhibit low cytotoxicity and excellent cellular imaging capability. We believe that these BNQDs probably trigger potentially applications on lightemitting diodes and bioimaging in a green way.

Corrosion inhibition of steel in multiple flow loop under 3.5% NaCl in the presence of rice straw extracts, lignin and ethylene glycol

The investigation of steel corrosion has been done in a multiple flow loop (corrosion test rack) under hydrodynamic condition. Further, the performance of rice straw extracts (RSE), lignin (L) and ethylene glycol (EG) to inhibit the corrosion were studied through weight loss analysis. The data has been tabulated based on the different position of steel specimen in corrosion test rack; middle, elbow and the end of the rack. The initial study was performed at 30 °C of 3.5% NaCl alone and showed slight corrosion damage with the appearance of pitting and oxide growth. The degradation of steel surface was depending on its position in the rack which experienced different flow. A study at 40 °C with inhibitor solution revealed a significant inhibition. NaCl alone and EG exhibited severe corrosion at the end of the rack. In contrast, the use of RSE and lignin inhibitors reduced the corrosion attack significantly at the end of the rack. The effectiveness of the corrosion inhibitors was depending on the chemical constituents, structure, functional groups as well as the composition of the compounds. The order of the best performance of corrosion inhibitor was; RSE > L > EG. Localized pitting corrosion is a primary type of corrosion attack before general and erosion-corrosion take place.

Influence of enhanced ultraviolet-B radiation during rice plant growth on rice straw decomposition with nitrogen deposition

Although straw decomposition is important for ecosystem fertility and carbon balance, influence of ultraviolet-B (UV-B) radiation and nitrogen (N) deposition on this process is unclear. In this study, UV-B-exposed rice straw was decomposed under different N addition treatments for 15 months to investigate the indirect effects of UV-B radiation on straw chemistry and direct effects of N deposition on decomposition. UV-B exposure during rice plant growth changed the rice straw chemical composition, increasing the concentrations of acid-insoluble fraction (AIF), acid-soluble fraction, and UV-B-absorbing compounds. High N content had a negative effect on decomposition of rice straw exposed to enhanced and ambient UV-B radiation. Both AIF concentration and FTIR peak intensities indicated that lignin in rice straw was selectively preserved following N addition and UV-B radiation, reducing straw decomposition rate, which corresponded to lower activities of lignin-degrading enzymes in the later stage of decomposition. Thus, enhanced UV-B radiation during rice plant growth produced more recalcitrant substrates (lignin) and N reacted with lignin to produce more resistant compounds, further decreasing straw decomposition rate. UV-B radiation during plant growth and N deposition inhibit litter decomposition in agroecosystem, and their effects should be considered when establishing biogeochemical models in response to global changes.

Preparation and Characterization of Phenol-Formaldehyde Resins Modified with Alkaline Rice Straw Lignin

Phenol-formaldehyde (PF) is a thermosetting resin that is widely used in many fields. One of its important applications is as an adhesive for wood-based panels manufacturing. In this research work, modified phenol-formaldehyde resins were prepared using hydroxymethylated alkaline rice straw lignin as a substitute for petroleum-based phenol in the range of 20 to 50% by weight. The molar ratios of sodium hydroxide to phenol-modified alkaline lignin and the formaldehyde to phenol-modified alkaline lignin were from 1.0 to 1.4, and 1.8 to 2.6, respectively. The parameters used to characterize the modified phenol-formaldehyde resins were: free-formaldehyde, gel time, viscosity, pH, and solid content. The structural differences and similarities between the prepared resins were determined by FTIR spectroscopy. Results obtained were discussed according to the requirements for adhesives utilization in plywood manufacture, and the optimum operating conditions were selected. Infrared spectra of lignin-based phenol formaldehyde (LPF) resins showed structural similarity with that of PF resin.

Rice straw pretreatment using deep eutectic solvents with different constituents molar ratios: Biomass fractionation, polysaccharides enzymatic digestion and solvent reuse

Lignocellulosic biomass pretreatment with deep eutectic solvents (DESs) is a promising and challenging process for production of biofuels and valuable platform chemicals. In this work, rice straw was mainly fractionated into carbohydrate-rich materials (CRMs) and lignin-rich materials (LRMs) by 90% lactic acid/choline chloride (LC)-water solution with different molar ratio of hydrogen bond donor (HBD, lactic acid) and hydrogen bond acceptor (HBA, choline chloride). It was found that high HBD/HBA molar ratio of DESs was favorable for achieving CRMs and LRMs with high purity, and both HBD and HBA were responsible for effective biomass fractionation possibly due to their synergistic effect on highly efficient breakage of the linkage between hemicellulose and lignin and thus lignin extraction. About 30%-35% of lignin in native rice straw was fractionated as LRMs, and exceeding 70% of xylan were removed and fractionated into the liquid stream as forms of xylose, furfural and humins after pretreatment using aqueous LC (3:1, 5:1) solution. Consequently, polysaccharides enzymatic hydrolysis of the CRMs were significantly enhanced. Moreover, all the DESs could be recovered with high yields of around 90%, and 69% of the LC (3:1) was recovered after 5 cycles reuse at 90°C. Besides, the recycled DES maintained a good pretreatment ability, and glucose yields of 60-70% were achieved in the enzymatic hydrolysis of CRMs obtained in each cycle. The facile process established in present work is promising for large scale production of fermentable sugars and other chemicals.

Adsorption of AuCl 4 − from Acidic Chloride Solution by Chemically Modified Lignin Based on Rice Straw

The chemically modified lignin was synthesized based on rice straw and the adsorption properties of AuCl 4 − were investigated in this paper. The adsorbent was characterized by Fourier transform infrared spectrometer, scanning electronic microscope and thermogravimetric analysis and differential scanning calorimetry. The chemically modified rice straw lignin was of excellent thermal stability and had plenty of primary amines and hydroxyls. Many influence factors such as initial concentration of AuCl 4 − , adsorption time and concentration of hydrochloric acid on AuCl 4 − were optimized. The maximum adsorption capacity was 783.94 mg·g−1. The equilibrium adsorption time was 600 min. The equilibrium isotherm fitted well with the Langmuir model and the pseudo-second-order kinetic model was suitable for describing the adsorption of AuCl 4 − . Low hydrochloric acid concentration could promote the selectivity of adsorption on AuCl 4 − . Combination of ion exchange and reduction was the mechanism. AuCl 4 − was adsorbed by ion exchange first and then reduced from hydrochloric acid medium in the form of Au(0) by phenolic hydroxyl.

Electrocatalytic degradation of rice straw lignin in alkaline solution through oxidation on a Ti/SnO2–Sb2O3/α-PbO2/β-PbO2 anode and reduction on an iron or tin doped titanium cathode

A novel procedure for selective production of biomass-based compounds by electrochemical conversion has been developed in this work.

Synthesis of quaternary ammonium rice straw lignin and its adsorption properties for PtCl62-

ABSTRACTThe quaternary ammonium rice straw lignin (QARSL) with anion exchange functional groups was synthesized based on rice straw through pretreatment, phenolation, polycondensation, chloration and amination reactions and it was characterized by FTIR, SEM and TG-DSC. The effects of adsorption time, initial concentration of and concentration of hydrochloric acid on the adsorption properties of QARSL for were investigated. Furthermore, the kinetic and adsorption isotherm models were explored. The selectivity for in different concentrations of hydrochloric acid solution was also studied. The results showed that QARSL was loose and had excellent thermal stability. The equilibrium time of adsorption was 420 min and the maximum adsorption capacity was 0.54 mol · kg−1. Moreover, the adsorption process could be described by pseudo-second-order kinetic model and adsorption isotherm could be simulated by Langmuir model, which indicated that the process of adsorption was adsorption of chemical single molecule layer. QARSL was of excellent selectivity for when the concentration of hydrochloric acid was 0.5 mol · L−1.