Selective hydrolysis of hemicellulose from wheat straw by a nanoscale solid acid catalyst

Simultaneous saccharification of hemicellulose and cellulose of corncob in a one-pot system using catalysis of carbon based solid acid from lignosulfonate

The drive towards sustainable chemistry has inspired the development of active solid acids as catalysts and ionic liquids as solvents for an efficient release of sugars from lignocellulosic biomass for future biorefinery practices. Carbon-based solid acid (SI-C-S-H2O2) prepared from sodium lignosulfonate, a waste of the paper industry, was used with water or ionic liquid to hydrolyze corncob in this study. The effects of various reaction parameters were investigated in different solvent systems. The highest xylose yield of 83.4% and hemicellulose removal rate of 90.6% were obtained in an aqueous system at 130 °C for 14 h. After the pretreatment, cellulase was used for the hydrolysis of residue and the enzymatic digestibility of 92.6% was obtained. Following these two hydrolysis steps in the aqueous systems, the highest yield of total reducing sugar (TRS) was obtained at 88.1%. Further, one-step depolymerization and saccharification of corncob hemicellulose and cellulose to reducing sugars in an IL-water system catalyzed by SI-C-S-H2O2 was conducted at 130 °C for 10 h, with a high TRS yield of 75.1% obtained directly. After recycling five times, the solid acid catalyst still showed a high catalytic activity for sugar yield in different systems, providing a green and effective method for lignocellulose degradation.

Construction of an enzymatic shuttling compartment based on reverse micellar for bamboo biomass hydrolysis in ionic liquids

The enzymatic saccharification of regenerated lignocellulose must occur separately due to the toxicity of ionic liquids to cellulase. Therefore, it is important to develop a biocompatible IL-cellulase system which effectively achieves activation and saccharification of lignocellulose. For this purpose, a dual-phase "enzyme-shuttling compartment" was constructed in this study. Tween 80 was found to form reverse micelles in the isooctane-IL two-liquid phase, acting as a microenvironment that maintains the energetic conformation of the reactive cellulase. The activated bamboo biomass was enzymatically hydrolyzed in 20% (w/v) 1-ethyl-3-methylimidazolium dimethyl phosphate and 50 mM citrate buffer at 50 °C, achieving a high total reducing sugar yield of 71.2% and maintaining an enzymatic activity of 91.2% after 24 h. Thus, an efficient system with the simultaneous activation and saccharification of natural biomass was successfully developed in a one-pot procedure at low temperatures, ensuring large-scale biomass conversion into biofuels and biological products.

One-pot conversion of wheat straw into biobased chemicals in methanol/water medium using cheap mixed acid catalyst

BACKGROUND

Environmental concerns and the diminishing availability of unrenewable resources have spurred research into the use of agricultural waste as a feedstock for industrial applications. Efficient conversion of wheat straw into biobased chemicals is an important way to realize the potential value of renewable agricultural biomass. This study investigated one-pot conversion of wheat straw into two notable platform chemicals, levulinic acid (LA) and methyl levulinate (ML).

RESULTS

A mixed acid catalyst system, including 1% H₂ SO₄ and 0.015 mol L^-1 Al₂ (SO₄ )₃ , was an efficient catalyst for the conversion of wheat straw due to the combination of Brønsted acid and Lewis acid. A ratio of wheat straw to methanol of 5 g/50 mL was identified as the preferred solid/liquid ratio, and a methanol/H₂ O medium with 25% water content aided the simultaneous production of LA and ML from wheat straw. Under optimum conditions, the maximum total yield of LA and ML reached 23.01% at 220 °C and 3 h. The kinetics of biobased chemical formation and the reaction pathways in methanol/water were investigated.

CONCLUSION

The presence of water in the methanol/H₂ O medium affected the distribution of products and promoted hydrolysis reactions. The methanol/H₂ O medium not only inhibited the side reactions but also promoted the degradation of wheat straw and increased the total yield of LA and ML. This study provides a feasible method for the conversion of wheat straw to prepare biobased chemicals. © 2021 Society of Chemical Industry.

Combination of Autohydrolysis and Catalytic Hydrolysis of Biomass for the Production of Hemicellulose Oligosaccharides and Sugars

Three different types of biomass sourced from forestry waste (eucalyptus residues), agricultural waste (wheat straw), and energy crop (miscanthus) were used as starting materials to produce hemicellulosic sugars, furans (furfural and hydroxymethylfurfural), and oligosaccharides. A two-step hybrid process was implemented; biomass was first autohydrolysed without any additive to extract hemicelluloses and dissolve it in water. Then, the hydrolysate was treated with a solid acid catalyst, TiO2-WOx, in order to achieve hydrolysis and produce monomeric sugars and furans. This article investigates the role of the biomass type, autohydrolysis experimental conditions, polymerisation degree and composition of hemicelluloses on the performance of the process coupling autohydrolysis and catalytic hydrolysis. The highest global yields of both oligosaccharides and monomeric sugars were obtained from Eucalyptus (37% and 18%, respectively).

The Kinetics Studies on Hydrolysis of Hemicellulose

The kinetics studies is of great importance for the understanding of the mechanism of hemicellulose pyrolysis and expanding the applications of hemicellulose. In the past years, rapid progress has been paid on the kinetics studies of hemicellulose hydrolysis. In this article, we first introduced the hydrolysis of hemicelluloses via various strategies such as autohydrolysis, dilute acid hydrolysis, catalytic hydrolysis, and enzymatic hydrolysis. Then, the history of kinetic models during hemicellulose hydrolysis was summarized. Special attention was paid to the oligosaccharides as intermediates or substrates, acid as catalyst, and thermogravimetric as analyzer method during the hemicellulose hydrolysis. Furthermore, the problems and suggestions of kinetic models during hemicellulose hydrolysis was provided. It expected that this article will favor the understanding of the mechanism of hemicellulose pyrolysis.

Recent Developments and Applications of Hemicellulose From Wheat Straw: A Review

Hemicellulose is an important component of plant cell walls, which is mainly used in biofuels and bioproducts. The hemicellulose extracted from different plant sources and plant locations has different microstructure and molecule. Wheat straw is an important biomass raw material for the extraction of hemicellulose. The aims of this review are to summary the recent developments and various applications of hemicellulose from wheat straw. The microstructure and molecule of hemicellulose extracted by different methods are comparably discussed. The hemicellulose-based derivatives and composites are also reviewed. Special attention was paid to the applications of hemicellulose such as biofuel production, packaging field, and adsorbent. The problems and developing direction were given based on our knowledge. We expect that this review will put forward to the development and high-value applications of hemicellulose from wheat straw.

A two-step process for pre-hydrolysis of hemicellulose in pulp-impregnated effluent with high alkali concentration to improve xylose production

The viscose fiber production process is accompanied by the accumulation of pulp-impregnated effluent (PIE), including hemicellulose and large amounts of alkali, and discharge of PIE will cause environment pollution. This paper aims to relieve the inhibition of high concentration of alkali on xylose production from hydrolysis of hemicellulose in PIE. Based on the fact that solid acid uses H⁺ at the acid sites to exchange with cations in PIE and can be recycled, a two-step method including an extra pretreatment process before pre-hydrolysis (SPP) is proposed. After the alkali was removed by the H⁺ dissociated from solid acid in the extra pretreatment process, the pH of PIE dropped from 14 to 4, and the content of Na⁺ and proteins was reduced by 99.13 % and 78.51 %, respectively. After SPP, the polymerization degree of the hemicellulose decreased by 73.4 %, and the subsequent enzymatic hydrolysis process was promoted. Finally, the xylose yield of SPP followed by enzymatic hydrolysis reached 57.15 g/L, which was 145.38 % more than that of enzymatic hydrolysis alone. The load of a downstream ion purification procedure was relieved compared to that of inorganic acid hydrolysis. The development of SPP contributes to the resource utilization of high alkali concentration wastewater.

Efficient and Selective Catalytic Conversion of Hemicellulose in Rice Straw by Metal Catalyst under Mild Conditions

Rice straw is an abundant material with the potential to be converted into a sustainable energy resource. Transition-metal catalysis activated the C–O bond in the hemicellulose of raw rice straw, cleaving it to form monosaccharides. The mechanism of rice straw catalytic conversion had a synergistic effect due to in situ acid catalysis and metal catalysis. The conditions for the hydrogenation of hemicellulose from rice straw were optimized: catalyst to rice straw solid/solid ratio of 3:10, stirring speed of 600 r/min, temperature of 160 °C, time of 3 h, solid/liquid ratio of 1:15, and H2 gas pressure of 1.5 MPa. An excellent hemicellulose conversion of 97.3% with the yields of xylose and arabinose at 53.0% and 17.3%, respectively, were obtained. The results from FTIR and SEM experiments also confirmed the destruction of the rigidity and reticulate structure of rice straw after the catalytic reaction.

Hydrolysis of Corncob Hemicellulose by Solid Acid Sulfated Zirconia and Its Evaluation in Xylitol Production

Corncob is an abundant agricultural residue containing high content of hemicellulose. In this paper, the hemicellulosic hydrolysate was prepared from the hydrolysis of corncob using the solid acid sulfated zirconia as a catalyst. According to response surface analysis experiments, the optimum conditions for preparing hemicellulosic hydrolysate catalyzed by sulfated zirconia were determined as follows: solid (sulfated zirconia)-solid (corncob) ratio was 0.33, solid (corncob)-liquid (water) ratio was 0.09, temperature was 153 °C, and time was 5.3 h. Under the optimized conditions, the soluble sugar concentration was 30.12 g/L with a yield of 033 g/g corncob. Subsequently, xylitol production from the resulting hemicellulosic hydrolysate was demonstrated by Candida tropicalis, and results showed that the yield of xylitol from the hemicellulosic hydrolysate could be significantly improved on a basis of decolorization and detoxification before fermentation. The maximum yield of xylitol from the hemicellulosic hydrolysate fermented by C. tropicalis was 0.76 g/g. This study provides a new attempt for xylitol production from the hemicellulosic hydrolysate.

Effect of β-mannanase domain from Trichoderma reesei on its biochemical characters and synergistic hydrolysis of sugarcane bagasse

BACKGROUND

β-mannanase is a key enzyme for hydrolyzing mannan, a major constituent of hemicellulose, which is the second most abundant polysaccharide in nature. Different structural domains greatly affect its biochemical characters and catalytic efficiency. However, the effects of linker and carbohydrate-binding module (CBM) on β-mannanase from Trichoderma reesei (Man1) have not yet been fully described. The present study aimed to determine the influence of different domains on the expression efficiency, biochemical characteristics and hemicellulosic deconstruction of Man1.

RESULTS

The expression efficiency was improved after truncating CBM. Activities of Man1 and Man1ΔCBM (CBM) in the culture supernatant after 168 h of induction were 34.5 and 42.9 IU mL^-1 , although a value of only 0.36 IU mL^-1 was detected for Man1ΔLCBM (lacking CBM and linker). Man1 showed higher thermostability than Man1ΔCBM at low temperature, whereas Man1ΔCBM had a higher specificity for galactomannan (K_m  = 2.5 mg mL^-1 ) than Man1 (K_m  = 4.0 mg mL^-1 ). Both Man1 and Man1ΔCBM could synergistically improve the hydrolysis of cellulose, galactomannan and pretreated sugarcane bagasse, with a 10-30% improvement of the reducing sugar yield.

CONCLUSION

Linker and CBM domains were vital for mannanase activity and expression efficiency. CBM affected the thermostability and adsorption ability of Man1. The results obtained in the present study should help guide the rational design and directional modification of Man with respect to improving its catalytic efficiency. © 2017 Society of Chemical Industry.

Preparation and investigation of highly selective solid acid catalysts with sodium lignosulfonate for hydrolysis of hemicellulose in corncob

Saccharification of lignocellulose is a necessary procedure for deconstructing the complex structure for building a sugar platform that can be used for producing biofuel and high-value chemicals. In this study, a carbon-based solid acid catalyst derived from sodium lignosulfonate, a waste by-product from the paper industry, was successfully prepared and used for the hydrolysis of hemicellulose in corncob. The optimum preparation conditions for the catalyst were determined to be carbonization at 250 °C for 6 h, followed by sulfonation with concentrated H₂SO₄ (98%) and oxidation with 10% H₂O₂ (solid–liquid ratio of 1 : 75 g mL⁻¹) at 50 °C for 90 min. SEM, XRD, FT-IR, elemental analysis and acid–base titration were used for the characterization of the catalysts. It was found that 0.68 mmol g⁻¹ SO₃H and 4.78 mmol g⁻¹ total acid were loaded onto the catalyst. When corncob was hydrolyzed by this catalyst at 130 °C for 12 h, the catalyst exhibited high selectivity and produced a relatively high xylose yield of up to 84.2% (w/w) with a few by-products. Under these conditions, the retention rate of cellulose was 82.5%, and the selectivity reached 86.75%. After 5 cycles of reuse, the catalyst still showed high catalytic activity, with slightly decreased yields of xylose from 84.2% to 70.7%.

A novel carbon-based catalyst with high catalytic ability and xylose selectivity was prepared from sodium lignosulfonate.

Maximization of monomeric C5 sugars from wheat bran by using mesoporous ordered silica catalysts

The hydrolysis process of a real fraction of arabinoxylans derived from wheat bran was studied. The influence of catalyst type and loading, reaction time and different metal cations were discussed in terms of the hydrolysis yield of arabinose and xylose oligomers as well as the formation of furfural as degradation product. A high yield of arabinoxylans into the corresponding monomeric sugars (96 and 94% from arabino- and xylo-oligosaccharides, respectively) was obtained at relatively high temperatures (180°C) and short reaction times (15min) with a catalyst loading of 4.8g of RuCl₃/Al-MCM-48 per g of initial carbon in hemicelluloses.

Enhanced hydrolysis of bamboo biomass by chitosan based solid acid catalyst with surfactant addition in ionic liquid

Surfactants were used for the hydrolysis of bamboo biomass to enhance lignocellulose hydrolysis. Tween 80, polyethylene glycol 4000 (PEG 4000), and sodium dodecyl sulfate (SDS) were tested as surfactants for improving the bamboo hydrolysis with a novel sulfonated cross-linked chitosan solid acid catalyst (SCCAC) in ionic liquid (IL). Compared to the use of only SCCAC in 1-Butyl-3-methylimidazolium chloride ([BMIM]Cl), the surfactants facilitated hydrolysis and improved the yield of total reducing sugar (TRS) under the same conditions. Tween 80 was the most effective surfactant, with a TRS yield of 68.01% achieved at 120°C after 24h. Surfactants broke the lignocellulose structure, promoted lignin removal, and increased positive interactions between cellulose and the catalyst, which were favorable for hydrolysis. This novel surfactant-assisted hydrolysis strategy with SCCAC and IL as the solvent demonstrated a promise for the large-scale transformation of biomass into biofuels and bioproducts.

Valorization of exhausted sugar beet cossettes by successive hydrolysis and two fermentations for the production of bio-products

Exhausted sugar beet cossettes (ESBC) show an enormous potential as a source of sugars for the production of bio-products. Enzyme hydrolysis with the combined effect of mainly cellulases, xylanases and pectinases, turned out to be very efficient, obtaining almost double the concentration of sugars measured with the sole action of Celluclast® and β-glucosidase, and increasing 5 times the hydrolysis rate. As the sole pretreatment, ESBC soaked in the hydrolysis buffer were autoclaved, avoiding the application of severe conventional biomass pretreatments. Moreover, a promising alternative for the complete utilization of glucose, xylose, arabinose, mannose and maltose contained in ESBC is proposed in this paper. It consists of sequential fermentation of sugars released in the hydrolysis step to produce bioethanol and lactic acid as main bio-products. Compared to separate fermentations, with this strategy glucose and hemicellulose derived sugars were completely consumed and the 44% of pectin derived sugars.

Bioconversion of lignocellulosic biomass to xylitol: An overview

Lignocellulosic wastes include agricultural and forest residues which are most promising alternative energy sources and serve as potential low cost raw materials that can be exploited to produce xylitol. The strong physical and chemical construction of lignocelluloses is a major constraint for the recovery of xylose. The large scale production of xylitol is attained by nickel catalyzed chemical process that is based on xylose hydrogenation, that requires purified xylose as raw substrate and the process requires high temperature and pressure that remains to be cost intensive and energy consuming. Therefore, there is a necessity to develop an integrated process for biotechnological conversion of lignocelluloses to xylitol and make the process economical. The present review confers about the pretreatment strategies that facilitate cellulose and hemicellulose acquiescent for hydrolysis. There is also an emphasis on various detoxification and fermentation methodologies including genetic engineering strategies for the efficient conversion of xylose to xylitol.