Conversion Of Lignocellulose Research Articles

Increasing PHB production with an industrially scalable hardwood hydrolysate as a carbon source

In this study, we report an industrially feasible conversion of wood hydrolysate from a pilot-scale forest biorefinery. The wood hydrolysate was compared to a synthetic hydrolysate with a similar content of carbon sources (glucose, xylose, and acetate). To maximize the PHB concentration, high-cell density cultivations were conducted in bioreactors for 52 h using the bacterium Paraburkholderia sacchari IPT 101 LMG 19450. The conversion of wood hydrolysate yielded a maximum PHB concentration of 34.5 g/L, which is among the highest reported for lignocellulose hydrolysates. In comparison, the use of a synthetic hydrolysate resulted in substantially lower PHB concentration (22.0 g/L). This could be attributed to a higher maximum specific growth rate of 0.36 vs. 0.33 per h for cells grown in wood hydrolysate vs. synthetic hydrolysate. For the wood hydrolysate, the final PHB content per cell mass reached 58 % g/g and a maximum PHB productivity of 0.72 g/(Lh), while the synthetic hydrolysate reached 55 % g/g and 0.46 g/(Lh) respectively. Given the increase in bacterial growth and PHB productivity when using the wood hydrolysate, the chosen lignocellulose conversion process is beneficial for subsequent biotechnological conversion to key bioproducts.

Conversion of lignocellulose into biochar and furfural through boron complexation and esterification reactions

The aim of this work was to study the conversion of lignocellulose into biochar and furfural through boron complexation and esterification reaction. Boric acid was used to modify lignocellulose to obtain a high biochar yield boron-lignocellulosic material through complexation and esterification reactions. Furthermore, clean furfural was obtained as the gas products of boron-lignocellulosic materials pyrolysis. The structures of the boron-lignocellulosic materials were characterized, and their compound principle was revealed. Boric acid treatments increased the initial thermal degradation temperature of lignocellulose and promoted the formation of biochar and furfural. The biochar yield rate increased by 135.7% from 18.6 to 42.9% at 600 ℃ after 5% boric acid solution treatment. Compared with pure lignocellulose, cleaner and higher quantities of furfural were obtained from boron-lignocellulose pyrolysis. Finally, the possible chemical decomposition pathways of boron-lignocellulosic materials were identified. This study provides a new perspective on the thermochemical conversion of lignocellulose to furfural and biochar.

Extraction and intensive conversion of lignocellulose from oil palm solid waste into lignin monomer by the combination of hydrothermal pretreatment and biological treatment

Empty fruit bunches from palm oil production contain lignin, which can be a source of valuable aromatic chemicals such as protocatechuic acid. In this study, empty fruit bunches were utilized in the hydrothermal pretreatment at different temperatures (100–200 °C) to produce liquid fractions containing depolymerized lignin such as single aromatic chemicals. The liquid fractions then underwent microbial processing by a mutant, ∆pcaHG Rhodococcus jostii RHA1 for six days to produce protocatechuic acid. Hydrothermal pretreatment temperature influenced the types of single aromatic chemicals produced and the sum of area of the single aromatic chemicals in both ethyl acetate extracts and TMS derivatives. The single aromatic chemicals obtained at 160 °C, 180 °C, and 200 °C act as precursors to accumulate protocatechuic acid by ∆pcaHG Rhodococcus jostii RHA1 on the third day of incubation. The role of single aromatic chemicals that acted as either precursors or inhibitors of protocatechuic acid was discussed.

Enhanced Biomass Yield of and Saccharification in Transgenic Tobacco Over-Expressing β-Glucosidase.

Here, we report an increase in biomass yield and saccharification in transgenic tobacco plants (Nicotiana tabacum L.) overexpressing thermostable β-glucosidase from Thermotoga maritima, BglB, targeted to the chloroplasts and vacuoles. The transgenic tobacco plants showed phenotypic characteristics that were significantly different from those of the wild-type plants. The biomass yield and life cycle (from germination to flowering and harvest) of the transgenic tobacco plants overexpressing BglB were 52% higher and 36% shorter than those of the wild-type tobacco plants, respectively, indicating a change in the genome transcription levels in the transgenic tobacco plants. Saccharification in biomass samples from the transgenic tobacco plants was 92% higher than that in biomass samples from the wild-type tobacco plants. The transgenic tobacco plants required a total investment (US$/year) corresponding to 52.9% of that required for the wild-type tobacco plants, but the total biomass yield (kg/year) of the transgenic tobacco plants was 43% higher than that of the wild-type tobacco plants. This approach could be applied to other plants to increase biomass yields and overproduce β-glucosidase for lignocellulose conversion.

Combined sodium percarbonate and glycerol pretreatment of sugarcane bagasse for enhanced enzymatic hydrolysis

Pretreatment is an important process for breaking the internal structure of lignocellulose to utilize waste biomass efficiently and transforming it into valuable products. In this study, combination of sodium percarbonate and glycerol (SPG) was employed to pretreat sugarcane bagasse (SCB). The pretreatment conditions including sodium percarbonate (SP) concentration, temperature and pretreatment time were further optimized. Under the optimal conditions (12% SP, 121 °C, 40 min), total reducing sugar (TRS), total enzymatic efficiency (TEE) and the lignin removal rate were found to be 16.67 g/L, 91.06% and 81.14%, respectively. The results exhibited that the SPG pretreatment could improve the enzymatic efficiency significantly as compared to the sodium percarbonate or glycerol pretreatment alone. Physical and chemical methods were used to analyze the structural changes of pretreated and raw SCB, further confirming that the SPG pretreatment could be an effective method for lignocellulose conversion.

Conversion of waste lignocellulose to furfural using sulfonated carbon microspheres as catalyst

Catalytic conversion of xylose and the hemicellulose fraction of waste biomass to furfural is important for the valorization of waste lignocellulose. Here, a clean and efficient catalytic system consisting of sulfonated carbon microspheres catalysts and γ-valerolactone was developed for the upgrading of xylose and waste lignocellulose to the furfural in one-pot. Sulfonated carbon microspheres (CCoS) with Brønsted and Lewis acid sites were prepared to yield furfural. The mesoporous structures were facilitated by introduction of Co element in xylose hydrothermal process, and the density of Brønsted acid sites were improved by the sulfonation. The furfural yield from xylose reached 75.12% using CCoS as catalyst at 170 °C for 30 min in a γ-valerolactone/water (17/3 v/v) solvent. As typical Brønsted acid, the SO3H groups on the surface of CCoS catalyst is essential for catalytic dehydration xylose to furfural. Additionally, the mesoporous structures of CCoS improved the mass transfer in the furfural production process. The catalytic system was applied in the conversion of real biomass (including corncob, corn straw and Eucalyptus sawdust) to evaluate the possibility of application. These three biomass species all reached excellent furfural yields, which were more than 70%. This work provided a catalytic strategy for effective conversion of xylose and biomass to furfural.

Micro-assay method for enzymatic saccharification of industrially relevant lignocellulose substrates

The development of micro-assays suitable for automation systems represents a helpful alternative by which many enzymes and factors can be studied simultaneously for the conversion of lignocellulose. The purpose of the present study was to evaluate a micro-assay method, based on hand-sheets, to reproducibly aliquot-pretreated lignocellulosic biomass at milligramme scale with minimal impact on the digestibility of the material. To favour representative sampling and handling for enzymatic conversion at milligramme scale, the solid fractions from steam-pretreated sweet sorghum bagasse (SSB) and triticale straw (TS) were subjected to homogenisation steps in sequential disintegrator and liquidiser at different severities prior to hand-sheet making (TAPPI). In the case of SSB, the disintegrator treatment (37,500 rpm) was sufficient to obtain the required fibre lengths, while the combined treatment with liquidiser (6250 rpm) and disintegrator (31,250 rpm) was needed for TS. The selected steps were able to improve homogenisation and fibre size distribution in the hand-sheets, attaining the required fibre lengths (less than 8 mm), with minimal influence on glucan conversion when using a conventional enzyme cocktail. The combined treatment and hand-sheet making had a more pronounced effect on the conversion of the xylan, with reduced xylose yields compared to small scale. The carbohydrate conversion in micro-assay was susceptible to more efficient enzyme combinations depending on the structural properties of the pretreated materials, presence and concentration of inhibitors as well as the enzyme dosage used. Nevertheless, the micro-assay method could distinguish between the different enzyme combinations, identifying those resulting in higher sugar yields from different lignocellulose materials pretreated under relatively mild conditions.

The conversion of lignocellulosic biomass to bioethanol: pretreatment technology comparison

The barrier to realising the potential of lignocellulosic bioethanol is the recalcitrance of cellulosic biomass. Overcoming this biomass recalcitrance is the key challenge to large scale production of lignocellulosic bioethanol. Pretreatment is an important and critical step that enables enzyme hydrolysis of lignocellulose conversion to ethanol. Finding a pretreatment method for reducing the high recalcitrance via cost-effective pretreatment methods would therefore be of great benefit. This study aims at investigating the effect of pretreatment on delignification process of sugarcane bagasse and oil palm trunk. Two methods of pretreatment were compared i.e. alkaline hydrogen peroxide pretreatment (1% and 5% H2O2) and subcritical water pretreatment (170°C, 2.2 MPa) for the effectiveness of reducing the lignin content. Scanning Electron Microscopy (SEM) analysis was also performed to investigate the effect of pretreatment on surface of lignocellulosic biomass. It was observed that alkaline hydrogen peroxide pretreatment gave better results than subcritical water pretreatment based on the lignin content for both lignocellulosic biomass. Pretreated sugarcane bagasse presented lower lignin content than pretreated oil palm trunk. Lignin was successfully removed until 56.99% under the best condition of 5% of alkaline hydrogen peroxide, at 28°C for 72 hours incubation. This study confirmed that alkaline pretreatment was found to have a better method for the conversion of lignocellulosic materials. Furthermore, sugarcane bagasse has a greater potential as basic raw materials used for the bioethanol production than oil palm trunk because it has lower content of lignin with higher content of cellulose.

Quantitative structures and thermal properties of Miscanthus × giganteus lignin after alcoholamine-based ionic liquid pretreatment

Alcoholamine-based ionic liquid (IL) pretreatment has been potential due to low cost (∼$1.0/kg) and efficient delignification. However, valuable exploration of lignin during this pretreatment has not been systematically studied and this hinders its further commercialized application. In this study, the effects of mild and efficient ethanolamine acetate [EOA][OAc] pretreatment on the structural and thermal feature of Miscanthus × giganteus (M×g) lignin were evaluated in detail. The ionic liquid lignin (ILL), and residual-enzymatic hydrolysis-mild acidolysis lignin (R-EMAL) were compared with the original-enzymatic hydrolysis-mild acidolysis lignin (O-EMAL). Results determined that Guaiacyl (G) was the predominant unit in all the lignins. As compared to O-EMAL, ILL had higher yield, high purity, less β-O-4 ether linkages, and more COOH contents as well as a higher thermal stability owing to formation of slightly condensed structures. Additionally, depolymerization of the lignin occurred as the reduction of the molecular weight, and cleavage of β-O-4 ether linkages. Furthermore, R-EMAL was similar to O-EMAL as approximative β-O-4 ether linkages, molecular weight and thermal stability. The structural elucidation of M×g lignin could provide a good theoretical basis for economic improvement of the alcoholamine-based biorefinery and efficient conversion of lignocellulose to high value-added lignin-based products.

The Roles of H2O/Tetrahydrofuran System in Lignocellulose Valorization.

Lignocellulosic biomass as a potential alternative to fossil resource for the production of valuable chemicals and fuels has attracted substantial attention, while reducing the recalcitrance of lignocellulosic biomass is still challenging due to the complex and cross-linking structure of biomass. Solvent system plays important roles in the pretreatment of lignocellulose, enabling the transformation of solid biomass to liquid fluid with better mass and heat transfer, as well as in the selective formation of target products. In particular, H2O/tetrahydrofuran (H2O/THF) system has recently been widely applied in lignocellulose valorization, which has been proved to exhibit outstanding efficiency for the conversion of lignocellulose, solubilization of the intermediates and products, and shifting reaction equilibrium, thereby significantly improving the yield and selectivity of target products, as well as the full utilization of lignocellulose. In addition, THF shows low toxicity, and is known as a renewable solvent which can be produced from bio-derived chemicals. Herein, this review concentrates on the advances of H2O/THF system in lignocellulose valorization in recent years. Several aspects relative to the roles of H2O/THF system are discussed as follows: the pretreatment of lignin, conversion of hemicellulose and cellulose components in lignocelluloses, and the promoting formation of valuable chemicals like furfural, 5-hydroxymethyl furfural (HMF), levulinic acid, and so on, as well as the inhibiting role in humins formation. This review might provide useful information for the design of effective solvent system in full utilization of lignocellulosic biomass.

Optimization of mixed enzymolysis of acid-exploded poplar wood residues for directional bioconversion

Enzymolysis is a key bioconversion process of lignocellulosic biomass. The optimization of enzymolysis is important for its efficiency and accuracy. There is potential to solve the problem of low reducing sugar in the conversion of lignocellulose to bioethanol. In this study, mixed cellulases (cellulase and β-glucosidase) were used in the enzymolysis of acid-exploded poplar wood residues. The mixed enzymolysis process was optimized by response surface area test, and its kinetics model was established based on the Michaelis-Menten equation. The optimal parameters of the mixed enzymolysis were: initial, pH 5.2; temperature, 46 °C; and cellulase to β-glucosidase ratio, 1.62. These parameters resulted in enzymatic saccharification efficiency 1.3 times as high as that of the control (conducted with un-optimized parameters). The modeling revealed that there was a strong correlation (R2 = 0.97) between substrate concentration and reaction rate. Multiple simultaneous saccharification and cofermentation (MSSCF) developed in the laboratory was also employed to verify the optimal parameters. The mixed enzymolysis process carried out with the optimal parameters achieved an ethanol concentration of 30.09 ± 0.49 g/L, which was 1.64 times higher than that conducted with un-optimized parameters. The fermentation time was also reduced by 24 h. Overall, the optimization of mixed enzymolysis process could enhance the efficiency of lignocellulosic directional conversion to bioethanol.

Complete Genome Sequence of Rhodococcus ruber R1, a Novel Strain Showing a Broad Catabolic Potential toward Lignin-Derived Aromatics.

Rhodococcus ruber R1 was isolated from a pulp mill wastewater treatment plant because of its ability to use methoxylated aromatics as growth substrates. We report the 5.56-Mb genome sequence of strain R1, which can provide insights into the biodegradation of lignin-derived phenolic monomers and potentially support processes for lignocellulose conversion.

Sensitivity analysis of xylose production process using aspen plus

Xylose production has become one of the most studied process over the year due to the significant application as a raw material for the production of a variety of specialty chemicals, mainly xylitol. The most promising raw material is lignocellulosic biomass because of its widely available and cheap. There are several type of pretreatment process has been studied to depolymerized the lignocellulosic compounds into fermentable sugars. Among all, dilute acid hydrolysis is the most promising process to produce high xylose. However, disadvantage of this pretreatment process is production of byproduct that can slowdown the fermentation step. Understanding the effect of pretreatment processing parameters on lignocellulosic depolymerization could possibly result in minimization of degradation compounds. Therefore, the aim of this work is to carry out the sensitivity analysis of the acid hydrolysis process used for the production of fermentable sugars with the aid of Aspen Plus by considering the concentration of xylose, glucose, furfural and acetic acid obtained at the outlet of reactor as the output variable. Sensitivity analysis were apply at temperature (160 °C, 170 °C and 180 °C) and residence time (0-160 min). The results indicate that the developed process model is possible to improve lignocellulosic conversion efficiency while minimizing degradation product generation with the highest xylose produce is 18.26 g/L at 180 °C during 20 min reaction time.

Enhanced ethanol production by Saccharomyces cerevisiae fermentation post acidic and alkali chemical pretreatments of cotton stalk lignocellulose

Direct conversion of lignocellulose to biofuel without pretreatment always results in a low-ethanol yield owing to its highly rigid structure. The current study was performed to improve the effectiveness of two different chemical pretreatments, alkaline and acidic, prior to the enzymatic hydrolysis of cotton stalk, and the yeast fermentation process for ethanol production. Alkaline pretreatments used alkaline hydrogen peroxide (AHP) and sodium hydroxide (NaOH), while acidic pretreatments used sulfuric acid (H2SO4) and phosphoric acid (H3PO4) at concentrations of 1.0%, 3.0%, 5.0%, and 7.0%. The highest bioethanol production (3.956 g/L) was observed in the 1.0% AHP pretreated sample, while the reducing sugar yield after enzymatic hydrolysis was 178 mg/g. The highest reducing sugar yield after enzymatic hydrolysis was obtained from the samples pretreated with 7.0% NaOH and 7.0% AHP, which yielded 241 mg/g and 238 mg/g, respectively, and provided 3.798 g/L and 3.739 g/L of ethanol, respectively. Scanning electron microscopy and Fourier-transform infrared analyses of the biomass showed that the structure of the alkali-treated cotton stalk was more disrupted and distorted than the acid-treated cotton stalk. Therefore, alkaline chemical pretreatment is more effective for breaking down lignocellulose and enhancing the yield of reducing sugars and bioethanol production from cotton stalk.

Fuels and Chemicals from lignocelluloses: A Short Overview

This paper looked at the potential and available alternative conversion paths for fuels and chemicals production away from the conventional conversion processes of fossil based fuels. Lignocellulosic biomasses are abundant, renewable, and domestically available energy resources. Though with its own attendant challenges, there are achievements and prospects that have been made in developing environmentally friendly processes for small and large scale conversion of lignocelluloses to different fuels and chemicals. With the continuous reliance on fossil fuels, there is the ever increasing climate change caused by the increasing greenhouse gas emissions such as carbon dioxide. Biomass from marine, trees, plants, animal wastes, food and non- food crops, grains, and wood based can produce fuels such as ethanol, butanol, and other chemicals through some promising technologies. Therefore, identifying ways to improving production efficiency of fuels and chemicals during biomass conversion processes to a sustainable level is very crucial.

Comparative study of the effectiveness of protic and aprotic ionic liquids in microwave-irradiated catalytic conversion of lignocellulosic June grass to biofuel precursors

This work compares the effectiveness of protic (PIL) and aprotic (APIL) ionic liquids in microwave-irradiated transition metal-catalysed one-pot conversion of a cellulose-rich non-edible lignocellulose, namely, June grass – composed of cellulose (82.3%), hemicelluloses (1.3%), with crystallinity index of 54% – to biofuel precursors such as glucose, hydroxymethylfurfural (HMF), levulinic (LA) and formic (FA) acids. Reaction parameters such as catalyst-substrate loading, IL-substrate loading, water concentration, temperature, and time are optimized to target specific biofuel precursor molecules and regulate the product distribution. The APIL ([BMIM]Cl) gives a maximum glucose yield of 88.2% at 180 °C and 40% water concentration, while the PIL ([Et3NH][HSO4]) produces a maximum HMF yield of 34.8% at 180 °C with no added water, and maximum LA and FA yields of 19.2% and 7.6%, respectively, at 200 °C. The PIL-based conversion targeting HMF as the biofuel precursor molecule, with glucose, LA, and FA as co-products, gives a product: reactant cost ratio 194.

Novel process to obtain aguamiel by directed fermentation

The functioning of a novel auxiliary enzyme, TgSWO from Trichoderma guizhouense NJAU4742, was investigated based on the proteomic analysis of wild-type (WT), knockout (KO) and overexpression (OE) treatments. The results showed that the cellulase and hemicellulase activities of OE and WT were significantly higher than those of KO. Simultaneously, tandem mass tag (TMT) analysis results indicated that cellulases and hemicellulases were significantly upregulated in OE, especially hydrophobin (HFB, A1A105805.1) and endo-β-1,4-glucanases (A1A101831.1), with ratios of 43.73 and 9.88, respectively, compared with WT. The synergistic effect of TgSWO on cellulases increased the reducing sugar content by 1.45 times in KO + TgSWO (1.8 mg) compared with KO, and there was no significant difference between KO + TgSWO (1.2 mg) and WT. This study elucidated the function of TgSWO in promoting the lignocellulose degradation capacity of NAJU4742, which provides new insights into the efficient conversion of lignocellulose.

Lignocellulosic conversion into value-added products: A review

Abstract In the present context of energy crisis, exploration of lignocellulosic biomass has emerged as potential substitute to maintain environmental sustainability. However, the conversion of biomass into value-added products still faces challenges to find a suitable unit operation. The stubborn dependency on the cost intensive enzymatic system, limits an effective saccharification to hydrolyze the biomass. India has been one of the top most agriculturally enriched countries with broad scope of utilizing waste residue that remains as an unused biomass at harvested locations. Hence, in the present script, an overview on the latest R&D initiatives taken by Government of India are briefed to highlight the projects based on biofuels and in addition, global scenario of biofuel production is comprehensively discussed. Further, critical analysis on the advancement of different pretreatment operations are highlighted through latest inventions. Thereafter, biochemistry of cellulase enzyme with essential factors were explored to understand the mechanistic interactions involved during saccharification of biomass. An insight on the latest accomplishments of various fermentation process provides an in depth understanding of metabolic engineering based on the genetic studies of fermentative microorganisms. Finally, the article is concluded with brief discussions on fate of the derivatives obtained from macromolecules such as cellulose and lignin.

Microwave-assisted direct transformation of lignocellulose into methyl glycopyranoside in ionic liquid

Abstract Recently, conversion of lignocellulose into useful substances has attracted increasing attention. In our previous investigations, microcrystalline cellulose was successfully converted to methyl glucopyranosides (MeGlc) by the combined use of ionic liquid (IL) and microwave irradiation under moderate reaction conditions. In this study, lignocelluloses, including softwood, hardwood, and rice straw, were directly converted to methyl glycopyranosides (MG), including MeGlc, methyl mannopyranosides (MeMan), and methyl xylopyranosides (MeXyl) using acid-catalyzed methanolysis under microwave irradiation in ILs. Lignocellulose ball-milling was quite effective as a crucial process of increasing the yield of MG. Under the optimized reaction conditions, the molar yield of MeGlc reached 40% from softwood, which was a comparable yield from microcrystalline cellulose. MeXyl was also obtained in a 48% yield. These results showed that the combination of the dissolution of ball-milled lignocellulose in IL and the microwave-assisted methanolysis was an effective method of converting lignocellulose into a high-value-added substance.

C-O Bond Hydrogenolysis of Aqueous Mixtures of Sugar Polyols and Sugars over ReOx-Rh/ZrO2 Catalyst: Application to an Hemicelluloses Extracted Liquor

The recovery and upgrade of hemicelluloses, a family of heteropolysaccharides in wood, is a key step to making lignocellulosic biomass conversion a cost-effective sustainable process in biorefinery. The comparative selective catalytic C-O bond hydrogenolysis of C5-C6 polyols, sugars, and their mixtures for the production of valuable C6 and C5 deoxygenated products was studied at 200 °C under 80 bar H2 over ReOx-Rh/ZrO2 catalysts. The sugars were rapidly converted to the polyols or converted into their hydrogenolysis products. Regardless of the reactants, C-O bond cleavage occurred significantly via multiple consecutive deoxygenation steps and led to the formation of linear deoxygenated C6 or C5 polyols. The distribution of products depended on the nature of the substrate and C-C bond scission was more important from monosaccharides. In addition, we demonstrated effective hydrogenolysis of a hemicellulose-extracted liquor from delignified maritime pine containing monosaccharides and low MW oligomers. Compared with the sugar-derived polyols, the mono- and oligosaccharides in the liquor were more rapidly converted to hexanediols or pentanediols. C-O bond scission was significant, giving a yield of desired deoxygenated products as high as 65%, higher than in the reaction of the synthetic mixture of glucose/xylose of the same C6/C5 sugar ratio (yield of 30%).