Enhancement Of Enzymatic Hydrolysis Research Articles

Enhancing Enzymatic Hydrolysis of Rice Straw by Acid-Assisted Mechanocatalytic Depolymerization Pretreatment

The inherent complexity of cellulose, hemicellulose, and lignin contributes to the recalcitrance of lignocellulosic biomass, resulting in a low conversion efficiency and high cost of bioethanol conversion. Pretreatment methods that disrupt the plant cell structure of lignocellulose, such as straw, can significantly enhance the conversion efficiency. In this study, we utilized an acid-assisted mechanocatalytic depolymerization technique to pretreat rice straw, and the results demonstrated a significant disruption of the cellulose structure of the straw. Compared to the untreated straw, the particle size of pretreated straw reduced from 279 μm to 11.8 μm, the crystallinity of cellulose decreased from 43.05% to 22.71%, the specific surface area increased by 177%, and the surface oxygen-to-carbon ratio (O/C) ratio was enhanced by 75%. The changes in microstructure enabled the pretreated straw to achieve a total sugar yield of over 95% within 12 h of enzymatic hydrolysis, significantly superior to the 36.24% yield from untreated straw, the 45.20% yield from acid impregnated straw, and the 73.25% yield from ball milled straw. Consequently, acid-assisted mechanocatalytic depolymerization emerges as a highly effective pretreatment strategy to enhance both the enzymatic hydrolysis and the overall conversion efficiency of rice straw.

Synergism of jet milling and deep eutectic solvent pretreatment on grapevine lignin fractionation and enhancing enzymatic hydrolysis

Herein, we investigated the synergistic effects of jet milling (JM) and deep eutectic solvent (DES) pretreatment on the fractionation of grapevine lignin and the consequent enhancement of enzymatic hydrolysis. Grapevine, a substantial byproduct of the wine industry, was subjected to JM pretreatment to produce finely powdered particles (median diameter D50 = 98.90), which were then further treated with acidic ChCl-LA and alkaline K2CO3-EG DESs. The results revealed that the combined JM + ChCl-LA pretreatment significantly increased the cellulose preservation under optimal conditions (110 °C, 4 h, and 20 % water content), achieving removal rates of 74.18 % xylan and 66.05 % lignin, respectively. The pretreatment temperature and inhibitor production were reduced, resulting in a remarkable threefold increase in glucose yield compared to untreated samples. Moreover, the structural analysis of the pretreated lignin indicated an enrichment of phenolic units, leading to enhanced antioxidant and antibacterial activities, particularly in the JM pretreated samples. These findings underscore the promising potential of the synergistic JM and DES pretreatment in facilitating the efficient utilization of grapevine lignocellulosic biomass for sustainable biorefinery technologies.

Catalytic action of hydronium-ion in rice straw pretreatment and enhancement of enzymatic hydrolysis and ethanol production

The present investigation will focus on the catalytic effect of hydronium ion during liquid-water/ dilute sulfuric acid/ferric chloride pretreatment (LWP/ SAP/ FCP) on the hydrolysate and pretreated rice straw. The overall pretreatment process has been represented as a sequential catalytic reactions. The temperature range of pretreatment is varied in the range of 140–180 °C and the concentration of dilute sulfuric acid and ferric chloride is 0.1 M. The first order rate constants of xylan and glucan degradation have been determined for LWP/ SAP/ FCP. The maximum xylan and glucan conversion of 96.8% w/wand 31.4%w/w respectively are achieved for FCP at 180 °C. Xylose, glucose, furfural, 5-hydroxymethyl furfural, acetic acid and formic acid appear as the main products for all pretreatments. Only in case of FCP levulinic acid also appears as a hydrolysis product. The thermal characteristics, functional groups, crystallinity, surface morphology of untreated and pretreated rice straw have been evaluated. Among all pretreatment processes under study, the highest values of glucose yield of 78.96% (w/w) using enzymatic hydrolysis and 83.79% of theoretical yield of ethanol using Saccharomyces cerevisiae have been achieved for ferric chloride pretreatment.

Enhancing Enzymatic Hydrolysis and Delignification of Sugarcane Bagasse Using Different Concentrations of Sodium Alkaline Pretreatment

Lignin, being highly resistant, needs to be eliminated in the process of extraction of soluble reducing sugar and bioethanol production from lignocellulosic biomass. In the present work, pretreatment of sugarcane bagasse (SCB) was performed using NaOH of various concentrations (1-5%) to facilitate delignification. The hydrolysis efficiency of pretreated SCB was evaluated at different reaction times by the production of reducing sugar using the Cellic CTec2 enzyme. The maximum cellulose content of 57.6% and lignin removal of 62.04% were observed with 2% sodium hydroxide at 121°C autoclaved for 60 min. The hemicellulose content decreased with increasing NaOH concentration with the maximum decrease of 13.6% from native bagasse having 26.5% xylan content. The microstructure, morphology, and chemical composition of SCB were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform InfraRed (FTIR), and XRD. The hydrolysis with 10 FPU.g-1 of enzyme at 48 h of reaction time shows a maximum yield of 12.34 g.L-1 corresponding to 55.53 ± 0.45% at 2% NaOH pretreated SCB. This study claims that lignin components exhibited the highest susceptibility to NaOH pretreatment, which directly affects enzymatic hydrolysis.

Enhancing enzymatic hydrolysis of industrial hemp hurds (Cannabis sativa L.) by combination of soaking in dilute acid and steam pretreatment

Enhancing enzymatic hydrolysis of industrial hemp hurds (Cannabis sativa L.) by combination of soaking in dilute acid and steam pretreatment

Enhancing enzymatic hydrolysis of waste sunflower straw by clean hydrothermal pretreatment

Hydrothermal pretreatment is an effective way to change the lignocellulose structure and improve its saccharification. An efficient hydrothermal pretreatment of sunflower straw was conducted when the severity factor (LogR0) was 4.1. 58.8% of xylan and 33.5% of lignin were removed at 180 °C for 120 min with a solid-to-liquid ratio of 1:15. A series of characterizations (such as X-ray diffraction, Fourier Transform infrared spectroscopy, scanning electron microscopy, chemical component analysis, cellulase accessibility) proved that hydrothermal pretreatment destroyed sunflower straw surface structure, enlarged its pores, and enhanced the accessibility to cellulase (371.2 mg/g). After the enzymatic saccharification of treated sunflower straw for 72 h, 68.0% yield of reducing sugar and 61.8% yield of glucose were achieved, and 3.2 g/L xylo-oligosaccharide was obtained in the filtrate. Overall, this easy-to-operate and green hydrothermal pretreatment could effectively destroy the surface barrier of lignocellulose, help remove lignin and xylan, and increase the enzymatic hydrolysis efficiency.

Lignin-grafted quaternary ammonium phosphate with temperature and pH responsive behavior for improved enzymatic hydrolysis and cellulase recovery

The cost of lignocellulosic enzymatic hydrolysis was reduced by enhancing enzymatic hydrolysis and recycling cellulase. Lignin-grafted quaternary ammonium phosphate (LQAP) with sensitive temperature and pH response, was obtained by grafting quaternary ammonium phosphate (QAP) onto enzymatic hydrolysis lignin (EHL). LQAP dissolved under the hydrolysis condition (pH 5.0, 50 °C) and enhanced the hydrolysis. After hydrolysis, LQAP and cellulase co-precipitated by the hydrophobic binding and electrostatic attraction, when lowering pH to 3.2, and cooling to 25 °C. LQAP had significant performances of pH-UCST response, enzymatic hydrolysis enhancement and cellulase recovery at the same time. When 3.0 g/L LQAP-100 was added to the system of corncob residue, SED@48 h increased from 62.6 % to 84.4 %, and 50 % of amount of cellulase was saved. Precipitation of LQAP at low temperature was mainly attributed to the salt formation of positive and negative ions in QAP; LQAP enhanced the hydrolysis for its ability to decrease the ineffective adsorption of cellulase by forming a hydration film on lignin and through the electrostatic repulsion. In this work, a lignin amphoteric surfactant with temperature response, was used to enhance hydrolysis and recover cellulase. This work will provide a new idea for reducing the cost of lignocellulose-based sugar platform technology, and high-value utilization of industrial lignin.

Enhancing enzymatic hydrolysis of Chinese fir sawdust by using the synergistic effect of dilute sulfuric acid and sodium chlorite pretreatment

Enhancing enzymatic hydrolysis of Chinese fir sawdust by using the synergistic effect of dilute sulfuric acid and sodium chlorite pretreatment

Mild pretreatment with Brønsted acidic deep eutectic solvents for fractionating β–O–4 linkage-rich lignin with high sunscreen performance and evaluation of enzymatic saccharification synergism

Herein, a mild fractionation method by employing polyol-based Brønsted acidic DESs (BDESs) was proposed to extract lignin with well-preserved β–O–4 substructures and to enhance fermentable sugar yields simultaneously. For ethylene glycol-oxalic acid (EG-OA), more than 53 % of lignin was obtained and superb carbohydrate digestibility (i.e., glucose and xylose yields were reached to 94.6 % and 87.7 %, respectively) was achieved after pretreatment. Remarkably, detailed structural studies revealed that the polyol was incorporated into lignin, which stabilized reactive carbocation intermediates formed during BDESs treatment and prevented undesired recondensation reactions. This lignin protection mechanism was shown to play a key role in enzymatic hydrolysis enhancement and lignin valorization. The resultant β–O–4 linkage-rich lignin fractions were attractive for natural sunscreen applications due to their lighter color and excellent UV-blocking performance. Overall, this work proposed a sustainable and economically practical lignin-first biorefinery approach that is beneficial for achieving comprehensive valorization of lignocellulose.

Additives Enhancing Enzymatic Hydrolysis of Wheat Straw to Obtain Fermentable Sugar.

In order to explore the effect of additives on enzymatic hydrolysis of lignocellulose biomass, the effect of two different additives, Triton X-100 (TX-100) and Bovine serum albumin (BSA), enzyme dosages, and additive concentrations on enzymatic hydrolysis to obtain fermentable sugar using cellulose extracted from wheat straw (WS) as the substrate was investigated in this study. An enzymatic hydrolysis kinetic model was used to successfully describe the enzymatic hydrolysis in a heterogeneous system. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were used to determine the effect of extraction and enzymatic hydrolysis on the composition and structure of the samples. The results showed that the total reducing sugar concentration of the raw was 1.535g/L at 120h, but that of the extracted cellulose (EC) increased to 5.087g/L at 120h, indicating that EC from WS is more conducive to enzymatic hydrolysis compared with the raw. The total reducing sugar concentration with the addition of the TX-100 was 6.737g/L at 120h, which was greater than that with the addition of the BSA (5.728g/L at 120h), indicating that the addition of two additives improved the enzymatic hydrolysis efficiency, especially TX-100. The kinetic studies showed that the initial enzymatic hydrolysis reaction rate (Km) of the EC was more than four times greater than that of the raw. The Km of the EC added with TX-100 and BSA were increased by 29.50% and 22.89% compared with that of the EC without the addition of additive. The addition of additives is an effective method for enhancing enzymatic hydrolysis efficiency and fermentable sugar production from lignocellulosic biomass.

Enhancing enzymatic hydrolysis efficiency of crop straws via tetrahydrofuran/water co-solvent pretreatment

Pretreatment and enzymatic hydrolysis are critical steps in bio-ethanol production from lignocellulose. The enhancement of enzymatic hydrolysis of several typical crop straws and the particle size adaptability of sorghum straw by tetrahydrofuran/water co-solvent pretreatment were studied. Efficient cellulose conversions (>83.2%) and adequate hemicellulose conversion (>40.7%) were obtained from pretreated rice straw, sorghum straw, wheat straw and corn stover in enzymatic hydrolysis, and the highest glucose yield and xylose yield were 274.0 and 26.3 mg/g dry solid, respectively. Glucose production of 140.4 mg/mL was obtained when the pretreated sorghum straw with mixed particle sizes was employed in enzymatic hydrolysis at 20% solid loading (8 FPU/g cellulose). When the enzyme loading reduced to 4 FPU/g cellulose, 221.7 mg/g dry solid glucose yield and 68.6% enzymatic hydrolysis efficiency could be still obtained with 15% solid loading, exhibiting high potential for bio-ethanol production.

One-Pot Pretreatment for Furfural Production and Enhancing Enzymatic Hydrolysis by Des-Based Biphasic System: Chemical, Topochemical, and Morphological Changes

One-Pot Pretreatment for Furfural Production and Enhancing Enzymatic Hydrolysis by Des-Based Biphasic System: Chemical, Topochemical, and Morphological Changes

Alkaline deep eutectic solvents as novel and effective pretreatment media for hemicellulose dissociation and enzymatic hydrolysis enhancement

In recent years, deep eutectic solvents (DESs) are used for enhancing the enzymatic digestibility and lignin fractionation in pretreatment, while hemicellulosic fraction receives scant attention. Herein, we report a novel approach of applying alkaline deep eutectic solvents (ADESs) for dissociating hemicelluloses from woody biomass. Among these ADESs, choline chloride-monoethanolamine (C-M) was the most efficacious medium for deconstructing the recalcitrant structure of poplar and 63.3% of hemicelluloses was obtained at 80 °C. Structure analysis showed that the ADESs-extracted hemicelluloses retained partial of O-acetyl groups. Different ADESs could be used to obtain hemicelluloses with various degrees of branching. Furthermore, the enzymatic digestibility of cellulose was significantly increased by 6.6 times compared to that of the untreated poplar under the optimum conditions (C-M, 140 °C). This work provides a view on the dissociation behavior of hemicelluloses during ADESs pretreatment, which would be beneficial for devising DESs toward effective fractionation and comprehensive utilization of biomass.

Characterization of glycoside hydrolase family 11 xylanase from Streptomyces sp. strain J103; its synergetic effect with acetyl xylan esterase and enhancement of enzymatic hydrolysis of lignocellulosic biomass

BackgroundXylanase-containing enzyme cocktails are used on an industrial scale to convert xylan into value-added products, as they hydrolyse the β-1,4-glycosidic linkages between xylopyranosyl residues. In the present study, we focused on xynS1, the glycoside hydrolase (GH) 11 xylanase gene derived from the Streptomyces sp. strain J103, which can mediate XynS1 protein synthesis and lignocellulosic material hydrolysis.ResultsxynS1 has an open reading frame with 693 base pairs that encodes a protein with 230 amino acids. The predicted molecular weight and isoelectric point of the protein were 24.47 kDa and 7.92, respectively. The gene was cloned into the pET-11a expression vector and expressed in Escherichia coli BL21(DE3). Recombinant XynS1 (rXynS1) was purified via His-tag affinity column chromatography. rXynS1 exhibited optimal activity at a pH of 5.0 and temperature of 55 °C. Thermal stability was in the temperature range of 50–55 °C. The estimated Km and Vmax values were 51.4 mg/mL and 898.2 U/mg, respectively. One millimolar of Mn2+ and Na+ ions stimulated the activity of rXynS1 by up to 209% and 122.4%, respectively, and 1 mM Co2+ and Ni2+ acted as inhibitors of the enzyme. The mixture of rXynS1, originates from Streptomyces sp. strain J103 and acetyl xylan esterase (AXE), originating from the marine bacterium Ochrovirga pacifica, enhanced the xylan degradation by 2.27-fold, compared to the activity of rXynS1 alone when Mn2+ was used in the reaction mixture; this reflected the ability of both enzymes to hydrolyse the xylan structure. The use of an enzyme cocktail of rXynS1, AXE, and commercial cellulase (Celluclast® 1.5 L) for the hydrolysis of lignocellulosic biomass was more effective than that of commercial cellulase alone, thereby increasing the relative activity 2.3 fold.ConclusionThe supplementation of rXynS1 with AXE enhanced the xylan degradation process via the de-esterification of acetyl groups in the xylan structure. Synergetic action of rXynS1 with commercial cellulase improved the hydrolysis of pre-treated lignocellulosic biomass; thus, rXynS1 could potentially be used in several industrial applications.

Synergistic Effect of Moderate Steam Explosion Pretreatment and Bovine Serum Albumin Addition for Enhancing Enzymatic Hydrolysis of Poplar

Steam explosion (SE) pretreatment is a widely adopted method for enhancing enzymatic hydrolysis of lignocellulosic biomass in biorefinery. In this work, moderate SE pretreatment was employed to overcome the recalcitrance of cell wall through systematically assessing physicochemical and structural modifications. The hydrolysis yield of pretreated poplar by SE pretreatment (up to 69.7%) was higher than untreated poplar (26.8%). With increasing SE severity from 3.5 to 4.5, the contents of hemicellulose and lignin were reduced from 15.7 to 5.3% and 25.4 to 20.7%, respectively. Furthermore, it was observed that the cell wall structure became rough and collapsed. Meanwhile, channels emerged in the internal cell wall primarily due to the removal of hemicellulose and lignin along with the migration of lignin from inside to the out surface of cell wall. These results induced more exposure of cellulose to enzyme attacking, thus improved accessibility to cellulolytic enzymes. Addition of bovine serum albumin (BSA) obtained equal hydrolysis efficiency of 70.1% with a 33% reduction of enzyme loading, which was advantageous for enzyme costs effective.

Enhancement of enzyme hydrolysis by increasing the zeta potential to reduce non-productive cellulase adsorption on sugarcane bagasse treated with liquid hot water

The enhancement of enzymatic hydrolysis is important for the biorefinery industry of lignocellulose. Changing the pH of hydrolysis is a simple and direct way to improve hydrolysis efficiencies. In this study, the enzymatic hydrolysis efficiencies of sugarcane bagasse (SCB) treated with liquid hot water (LHW) were 56.7% and 65.5% at pHs of 4.8 and 5.5, respectively. The result of cellulase adsorption on the LHW treated SCB showed that the non-productive adsorption was smaller at pH 5.5, which might tend to enhance hydrolysis. The surface hydrophobicity of lignin was larger at pH 5.5. This suggested that the hydrophobic interaction was not dominant because a strong hydrophobicity force can cause more non-productive adsorption of cellulase with lignin. At pH 5.5, the surface negative charges of lignin and cellulase increased. Therefore, the electrostatic repulsive force between lignin and cellulase increased, leading to less of the non-productive adsorption of cellulase on lignin. In addition, the cellulase desorption from the LHW treated SCB also increased at pH 5.5. This was beneficial in increasing the possibility of cellulase re-adsorption in new binding sites on cellulose and promoting enzyme hydrolysis efficiency.

Heterologous Expression of Laccase From Lentinula edodes in Pichia pastoris and Its Application in Degrading Rape Straw.

Rape straw cannot be efficiently degraded and utilized by ruminants due to its severe lignification and complex cross-linked structure between fiber and lignin. The laccases can catalyze the inter-unit bond cleavage in lignin substrates. Therefore, this study investigated the recombinant laccase from Lentinula edodes (LeLac) and its application in degrading rape straw. The LeLac was expressed using Pichia pastoris. It had the maximum activity at 60°C and pH 3.0 using ABTS as substrate and at 50°C and pH 4.0 using o-tolidine as substrate. The LeLac exhibited preferential oxidation of ABTS and featured resistance to high temperature, but relatively poor thermal stability. The LeLac activity could be strengthened by Cu2+ in dose-dependent manners. The LeLac could tolerate 15% of ethanol and methanol. The optimal pH for the lignin degradation of rape straw acid detergent fiber (ADF) by LeLac was 4.0. The LeLac could improve the cellulose enzymolysis of rape straw ADF by degrading its lignin. Relatively fewer lignin but more soluble phenols from original rape straw were removed by LeLac. The enhancement of enzymatic hydrolysis in original rape straw should be a combined result of polyphenols removal and lignin degradation caused by LeLac. This study demonstrated that the LeLac could improve the utilization of rape straw by degrading its lignin, meanwhile it’s worth noting that removing the soluble phenols by LeLac might also play an important role.

Enhancing enzymatic hydrolysis and fermentation efficiency of rice straw by pretreatment of sodium perborate

In this study, we proposed a simple and effective sodium perborate (SPB) pretreatment method to enhance the enzymatic hydrolysis efficiency of rice straw (RS). The lignin removal rate reached 45.76% under the optimum pretreatment conditions of 8% SPB and 80 °C for 4 h, and the enzymatic hydrolysis efficiency of pretreated RS was 84% at a cellulase loading of 20 FPU/g RS. Through simultaneous saccharification and co-fermentation (SScF) of the pretreated RS solid with Saccharomyces cerevisiae SHY07-1, the maximum ethanol concentration was 15.29 g/L at 72 h, with a fermentation efficiency as high as 91.96%. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) analyses revealed that the RS structure was destroyed by SPB pretreatment, and lignin was effectively removed. The overall data of this study indicate that SPB pretreatment is a promising method to improve enzymatic hydrolysis and bioethanol production from RS by inoculating Saccharomyces cerevisiae SHY07-1.

Enhancing enzymatic hydrolysis of corn stover by twin-screw extrusion pretreatment

Efficient and cost-effective hydrolysis of cellulose and hemicellulose into monosaccharide is the crucial and challengeable step for corn stover utilization. In this study, twin-screw extrusion pretreatment changed the particle size distribution and spatial structure of corn stover samples, but had basically no effects on their chemical structure. Cellulose content of CS-DW and CS-DW-GNa increased, but hemicellulose content and crystalline index decreased with extrusion pretreatment. Glucose yield of CS-DW increased from 25 g/L of CS with 48 h hydrolysis time to 34 g/L by 36 h of hydrolysis time, and glucose yield of CS-DW-GNa increased to 45 g/L with 24 h hydrolysis time. Meanwhile, xylose yield of CS-DW and CS-DW-GNa increased from 19 g/L of CS (48 h) to 27 g/L (36 h) and 40 g/L (24 h), respectively. These results provide good guidance for improving the conversation of lignocelluloses to monosaccharide for further utilization.

Enhancing enzymatic hydrolysis yield of sweet sorghum straw polysaccharides by heavy ion beams irradiation pretreatment

A deeper understanding of the pretreatment process of lignocellulosic biomass could enhance the production efficiency of biofuels. Sweet sorghum straws (SSS) were subjected to heavy ion beams irradiation (HIBI) pretreatment and then hydrolyzed with 2.4 FPU of cellulase. Notably, the pretreatment has been proved to increase enzymatic digestibility of SSS. The reducing sugar yield and hydrolysis yield of SSS pretreated by 600 Gray (Gy) of HIBI reached to 7.23 mg/mL and 34.43% for 36 h, respectively, which was significantly higher than that of the untreated SSS (4.93 mg/mL of reducing sugar and 23.47% of hydrolysis yield). Additionally, the analysis of pretreated SSS showed that the destruction of amorphous region and surface ultrastructure as well as the transformation of polymorphs (Iα →Iβ) of cellulose I were major effects on SSS by HIBI pretreatment. The results demonstrated that HIBI could be chosen as an effective physical pretreatment process for enhancing enzymatic hydrolysis yield of lignocellulosic biomass.