Enzymatic Hydrolysis Of Wheat Straw Research Articles

Application of natural fungi in bioconversion of lignocellulosic waste to second-generation ethanol

The second generation (2G) or cellulosic ethanol can help with diversification of the use of fossil energy sources. However, as bioconversion of plant waste into 2G bioethanol requires expensive additional steps of pre-treatment/hydrolysis of lignocellulosic materials, and this technology has not yet reached the technological readiness level which would allow it to be scaled-up, this process needs more interdisciplinary and comprehensive studies. This work was aimed at experimental study of a full cycle of successive processes of pre-treatment/saccharification using cellulolytic enzymes of filamentous fungi and fermentation of obtained syrups by xylose-fermenting yeast, using selected natural microorganisms for the fungal-based bioconversion of lignocellulosic agricultural waste to 2G ethanol. Using the Plackett-Burman and Box-Behnken methods of mathematical statistics, the optimal conditions for pre-treatment and enzymatic hydrolysis of wheat straw by a hemi- and cellulolytic multi-enzyme complex of the selected fungal strain Talaromyces funiculosus UCM F-16795 were established: microwave-assisted alkali pre-treatment with sodium hydroxide (NaOH) solutions (concentration range 4.6–4.8%), and saccharification conditions of medium pH 4, temperature 40 °С, hydrolysis duration 18 hours, and dilution of culture liquid with a buffer solution 1:1. The total energy of microwave irradiation 1.2 kJ and the ratio of substrate/enzyme solution 100 mg/1 mL were used. Under optimized conditions, wheat straw hydrolysates contained 5.0–7.5 g/L of reducing sugars, which, according to HPLC assessment, contained 0.7–1.0 g/L of glucose, 2.2–2.9 g/L of xylose and 0.7–0.8 g/L cellobiose. We used the selected strain of xylose-fermenting yeast in fermentation of mixtures of the most important monosaccharides in hydrolysates, xylose and glucose, in the concentration range relevant for syrups obtained by us during the optimized saccharification of lignocellulosic substrates with T. funiculosus enzymes. Based on sequencing and phylogenetic analysis, strain UCM Y-2810 was confirmed as Scheffersomyces stipitis; its nucleotide sequences of ITS region and 28S gene rDNA were deposited in GenBank under the accession numbers OP931914 and OP931915, respectively. The ethanologenic process for S. stipitis UCM Y-2810 was studied according to Box-Behnken design, assessing ethanol concentration by gas chromatography-mass spectrometry. Yeast fermentation under static microaerophilic conditions showed a 1.5 times higher rate of bioethanol production and 1.7 times greater efficiency of ethanologenesis per yeast biomass than for submerged cultivation. Optimization of the process of ethanologenesis resulted in the maximum rate of fermentation mixture of sugars, being 11.30 ± 0.36 g/L of ethanol, with optimal values of factors: 30 g/L of xylose, 5.5 g/L of glucose and cultivation for 5.5 days. It was revealed that the tested glucose concentrations did not significantly affect the process of xylose-fermentation by yeast, and non-competitive inhibition of xylose transport by glucose into yeast cells did not occur. This study demonstrated the potential of a full cycle bioconversion of lignocellulosic waste to 2G ethanol based on use of natural fungal strains and optimization of conditions for all steps.

Optimization of potassium hydroxide combined urea pretreatment and enzymatic hydrolysis of wheat straw using response surface methodology for improving sugar production

To improve sugar yields from wheat straw (WS), response surface methodology (RSM) was adopted to optimize potassium hydroxide combined urea pretreatment and enzymatic hydrolysis of WS. Glucose and xylose yields from the pretreated WS were used as responses during the whole optimization. Potassium hydroxide concentration, time and temperature during pretreatment were found to have significant effects on sugar yields. Sugar yields could be enhanced while WS was pretreated using 45 g/L potassium hydroxide solution containing 15 g/L urea with solid to liquid ratio of 1:5 (g/mL) at 74.0 °C for 50 min. Cellulose recovery, hemicellulose recovery, and lignin removal after optimization were 98.1%, 72.6%, and 75.8%, respectively. In addition, enzyme loading, biomass loading, and reaction time during enzymatic hydrolysis also had significant effects on sugar yields. Maximal yields of glucose (610.25 mg/gds, miligram per gram dry substrate) and xylose (221.26 mg/gds) could be achieved while hydrolysis was carried out at 50 °C for 32.8 h with 141 g/L of biomass loading, 8.1 FPU/gds (filter paper activity unit per gram dry substrate) of enzyme loading and 0.4% (w/v) of polysorbate 80. The corresponding cellulose conversion and hemicellulose conversion were 97.2% and 90.4%, respectively.

Optimization of Alkaline Hydrogen Peroxide Pretreatment and Enzymatic Hydrolysis of Wheat Straw for Enhancing Sugar Yields

Optimization of alkaline hydrogen peroxide (AHP) pretreatment and enzymatic hydrolysis of wheat straw (WS) was carried out to enhance fermentable sugar yields with the use of glucose and xylose yields from the pretreated WS as responses. In the first step, variables including temperature, hydrogen peroxide concentration and time during pretreatment were detected to have significant effects on the sugar yields. The results indicate that maximal sugar yields could be obtained while the WS was pretreated using 71 g/L hydrogen peroxide solution with 200 g/L of solid loading at 50 °C for 7.6 h. The corresponding cellulose recovery, hemicellulose recovery and lignin removal were 97.5%, 84.3% and 75.0%, respectively. In the second step, enzymatic hydrolysis of the pretreated WS was optimized. The results show that the reaction time, enzyme loading and biomass loading during enzymatic hydrolysis also had significant effects on the sugar yields. The final maximum yields of glucose (552.7 mg/gds (mg/g dry substrate)) and xylose (223.6 mg/gds) could be obtained while enzymatic hydrolysis was carried out at 50 °C for 37.0 h using 10.8 FPU/gds (filter paper activity unit per gram dry substrate) of enzyme loading, 88 g/L of biomass loading and 0.3% (w/v) of Tween-80. The corresponding cellulose conversion and hemicellulose conversion were 94.0% and 83.5%, respectively.

Comparative study on the mild pretreatment processes for enzymatic hydrolysis of wheat straw with high-solid loading

Comparative study on the mild pretreatment processes for enzymatic hydrolysis of wheat straw with high-solid loading

Enhanced Enzymatic Hydrolysis of Wheat Straw to Improve Reducing Sugar Yield by Novel Method under Mild Conditions

Wheat straw is a suitable source material for bioethanol production. Removing lignin and hemicellulose in wheat straw to improve enzymatic hydrolysis efficiency is essential because of its complex structure. Deep eutectic solvents (DESs) have become substitutes for ionic liquids (ILs), with the characteristics of good biocompatibility, simple synthesis procedure and low cost. However, the process of removing lignin and hemicellulose using present DESs requires a high operation temperature or long operation time. Therefore, we studied a novel method under mild conditions for screening a series of novel DESs based on an inorganic base to remove lignin and hemicellulose in wheat straw. In this work, the effect of DES type, the pH of the DESs, the operation temperature and operation time for enhancing enzymatic hydrolysis, and the crystal structure and the chemical structure and surface morphology of wheat straw were investigated. In particular, Na:EG exhibited the most excellent solubility for wheat straw under mild conditions, removing 80.6% lignin and 78.5% hemicellulose, while reserving 87.4% cellulose at 90 °C for 5 h, resulting in 81.6% reducing sugar produced during hydrolysis for 72 h. Furthermore, XRD, FT-IR and SEM analysis verified the lignin and hemicellulose removal. Hence, DESs based on an inorganic base used for removing lignin and hemicellulose will enhance enzymatic hydrolysis, and thus promote the industrial application of wheat straw to produce bioethanol.

Multi-efficient endoglucanase from Aspergillus niger MPS25 and its potential applications in saccharification of wheat straw and waste paper deinking

The deinking in the paper industry is in great demand, and microbial enzymes are key players. In the present study, the endoglucanase production from newly isolated fungi Aspergillus niger MPS25 is reported. The optimization of endoglucanase production was carried out using one factor at a time approach resulting in endoglucanase activity (2.37 IU/ml) at 45 °C and pH 8 in submerged fermentation (SmF), which shows optimum enzyme activity at 60 °C. Interestingly, the metal ions viz. Co2+ stimulated the endoglucanase activity, whereas Mn2+ reduced the enzyme activity, which shows that this enzyme can be used for effluent treatment released through deinking. The enzymatic hydrolysis of wheat straw produced 26.96 ± 0.108 mg/g of reducing sugars, indicating its potential in saccharification and the biofuel industry. Furthermore, the validation of the deinking efficiency of this enzyme resulted in improved deinking of mixed office waste and old newspapers by 31.5% and 20.4%, respectively. The strength properties, viz. burst factor and tear index, breaking length, and tensile index of the handmade paper sheets, were also improved which were analyzed by the scanning electron micrographs. The FTIR and XRD analysis of pulp provided insights into the changes in functional groups and cellulose crystallinity, respectively. These results indicate that multi-efficient endoglucanase from Aspergillus niger MPS25 is suitable for enzyme-based eco-friendly deinking for waste paper recycling and lignocellulosic biomass saccharification.

Optimization of ultrasound pretreatment and enzymatic hydrolysis of wheat straw: From lab to semi-industrial scale

In this paper, the dominance of the physical effects of ultrasound (US) pretreatment in improving the delignification of wheat straw at a 1:20 solid/liquid (biomass/water) ratio is reported showing low-frequency/high power (25 kHz, 2 or 3 kW) as preferred conditions. The sonochemical pretreatment with alkali was identified as an optimal method to make the cellulose more susceptible to further enzymatic hydrolysis, thereby increasing the yield of soluble sugars. Previous bench-scale studies have shown that US pretreatment has a positive effect on delignification, nevertheless this has not yet been demonstrated on a larger scale. The objective of this study was to demonstrate the effectiveness of US pretreatment for wheat straw delignification from lab to semi-industrial scale (40 kg biomass) in terms of sugar yield and energy efficiency. A 59.2% of lignin removal was recorded after the cavitational treatment of wheat straw with a subsequent 68 ± 5.7% yield in terms of enzymatic hydrolysis (52.6% glucose, 42.9% xylose and 4.5% arabinose).It was demonstrated that the positive effect of US alkali pretreatment of wheat straw on sugar yield was due to a combination of factors, including (i) an easier accessibility of the biomass carbohydrate network to enzymes due to the increased wheat straw porosity, (ii) the partial removal of lignin, which increases the relative proportion of carbohydrates in the treated biomass, and (iii) the disordering (amorphization) of the cellulose structure, which promotes carbohydrate hydrolysis as well as saponification of the acetyl groups in the hemicellulose. With respect to the Life Cycle Assessment (LCA) and the Cost Benefit Analysis the US pretreatment process herein reported was compared to an alternative Steam Explosion pretreatment. The results of the LCA analysis showed, that for all five environmental categories (energy consumption, global warming potential, water and fossil depletion, and the land occupation) the US pretreatment has advantages in comparison with the standard industrial Steam Explosion pretreatment.

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.

A bio-inspired flexible squeezing reactor for efficient enzymatic hydrolysis of lignocellulosic biomass for bioenergy production

Wheat straw is a promising source that can be used to obtain clean energy through its bioconversion into biofuel. Enzymatic hydrolysis is considered as a key step in biofuel production. However, the poor mixing of enzymes and lignocellulosic substrates caused by the high viscosity of biomass slurry significantly astricts such a process. In this study, a novel bio-inspired flexible tube reactor was developed for enhancing mass transfer through squeezing at different parts to imitate the intestinal peristalsis. The results of the visualization experiment showed that the apparent vertical diffusion velocity at different position were about 1.4–4.2 times faster than the control without squeezing, when the concentration of model solution (carboxymethyl cellulose solution) was 5 g/L. More importantly, the apparent vertical diffusion velocity increased by 5.2 times as the concentration of model solution increased to 20 g/L at squeezing mode. When the total solid (TS) concentration of lignocellulosic slurry was increased to 7.5%, the bionic reactor showed an excellent performance on the enzymatic hydrolysis of wheat straw. The highest reducing sugar yield achieved 20.2 g/L with 71.8% of carbohydrate conversion after 170 min at 40 rpm, which was 2.1 times higher than the control without squeezing.

Enhanced efficiency of enzymatic hydrolysis of wheat straw via freeze–thaw pretreatment

This research investigated enhancing the efficiency of enzymatic hydrolysis of wheat straw via freeze-thaw pretreatment and assessed the physicochemical structural changes after this pretreatment. The enzymatic hydrolysis efficiency of cellulose and hemicellulose was enhanced, and hemicellulose was more susceptible to pretreatment. The highest enzymatic hydrolysis efficiency of cellulose and hemicellulose was 57.06 and 70.66%, respectively, at - 80 ℃ for 24h and - 10 ℃ for 24h, respectively, which were 2.23 and 3.13-fold higher than the control levels, respectively. Scanning electron microscopy images indicated that transverse cracks appeared before longitudinal cracks with stronger pretreatment conditions, and holes were found in every sample after this pretreatment. Fourier transform infrared spectroscopy and X-ray diffraction analysis indicated that freeze-thaw pretreatment affected both the crystalline and amorphous regions and disrupted the hydrogen bonds within them. This study provides a physical pretreatment method to improve the efficiency of enzymatic hydrolysis of wheat straw.

Impact of mixed lignocellulosic substrate and fungal consortia to enhance cellulase production and its application in NiFe2O4 nanoparticles mediated enzymatic hydrolysis of wheat straw

Economic biowaste to biofuels production technology suffers from issues including high production cost of cellulase enzyme and its low efficiency. In this study five lignocellulosic biomass based on their high cellulosic contents are employed in 1:1 ratio with mixed fungal consortia to achieve enhance cellulase production via solid state fermentation. Under the optimum condition total 41 IU/gds FP activity was achieved in 120 h at 40 °C and pH 6.0. Further, crude cellulase was evaluated to improve thermal and pH stability under the influence of 2.0 mg/L NiFe2O4 nanoparticles, showed stability at 70 °C and pH 6.0 up to 8 h. Consequently, NiFe2O4 nanoparticles treated cellulase was used for the enzymatic hydrolysis of alkali treated wheat straw, and total 53 g/L reducing sugars could be produced in 18 h at 65 °C and pH 6.0. Thus, nanoparticles mediated enzymatic hydrolysis exhibited ∼ 29% and ∼ 28% higher sugar yield and productivity as compared to control after 18 h.

Optimisation of enzymatic saccharification of wheat straw pre-treated with sodium hydroxide

To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis. The enzymatic hydrolysis was based on the cellulase from Trichoderma reesi ATCC 26921, the optimum NaOH pre-treatment conditions were an NaOH concentration of 1.0% (w/w), a solid content of 5.0% (w/v) and a pre-treatment time of 60 min. Various parameters that affect the enzymatic hydrolysis of wheat straw, including the solid content, enzyme loading, pH and hydrolysis time, were investigated and optimized through a Box–Behnken design and response surface methodology. The predicted optimum conditions for enzymatic hydrolysis were a solid content of 8.0% (w/v), an enzyme loading of 35 FPU/g substrate, a temperature of 50 °C, a pH of 5.3 and a hydrolysis time of 96 h. The experimental result showed that the maximum reducing sugar yield was 60.73% (53.35% higher than the wheat straw without NaOH pre-treatment), which is in accordance with the predicted conditions.

Comparison of sulfomethylated lignin from poplar and masson pine on cellulase adsorption and the enzymatic hydrolysis of wheat straw

In this work, effects of sulfomethylated lignins (SLs) prepared from masson pine (SLM) and poplar (SLP) on enzymatic hydrolysis and cellulase-lignin interaction were comparatively investigated. The results showed that both SLM and SLP significantly promoted the substrate enzymatic digestibility. The total sugar yield increased from 38.6% to 74.4% and ∼ 100%, respectively at 10 FPU/g-cellulose of cellulase dosage. The protein content in hydrolysate linearly increased with the addition of SL (0 – 1.6 g/g-substrate lignin), which suggested the competitive adsorption of cellulase may occur to substrate lignin and SLs. Further structural analysis of lignin revealed the high S/(V + H) ratio was directly related to the high enzymatic saccharification efficiency. The strong interaction between SL and cellulase decreased the nonproductive adsorption of cellulase onto substrate lignin and increased the accessibility of cellulase to carbohydrate, which was considered to be the key factor for the improvement of substrate enzymatic digestibility.

Lignin – Derived antioxidants as value-added products obtained under cavitation treatments of the wheat straw processing for sugar production

Most of biorefinery technologies are focused on the utilization of plant polysaccharides into chemicals, whereas lignin, the second most abundant natural polymer, is commonly used as a resource to generate power. This is the first report on flavones-bound lignin obtained by wheat straw (WS) pretreatment under low-frequency ultrasound (US) and hydrodynamic cavitation (HC) in sugar production processing. US and HC procedures carried out in aqueous 0.2–0.4% NaOH solutions and various liquid/biomass ratios strongly decreased the lignin content in the solid fraction by 30–45% and 25%, respectively, compared to non-treated WS. Moreover, НС pretreatment increased (approximately tenfold) the portion of ordered cellulose in residual biomass that could hinder the further enzymatic hydrolysis of WS. By means of sequential HC and US pretreatment the ordered cellulose content in solid fraction significantly decreased, compared to the HC alone. Furthermore, it was demonstrated that, after US pretreatment, hemicelluloses and oligomeric fragments of lignin and ligno-carbohydrate complexes were transferred into the liquid phase. In particular, tricin derivatives were detected in liquid fractions with a concentration of 30–35% on o.v.d. ash free sample, and more than 50 compounds associated with low-molecular-weight lignin fragments. These compounds were tentatively identified using high-resolution mass spectrometry (HR-MS) based fragmentation (sequencing) and a self-made database, showing that 16 out of 50 identified compounds belonged to the fragments of model lignin structural units. Tricin and low molecular weight lignin derivatives may find applications as strong antioxidants (i.e. lipidic systems). These findings proved that waste lignin streams obtained after cavitational processes could be a source of value-added products from WS conversion.

Enzymatic hydrolysis of lignocellulosic biomass using native cellulase produced by Aspergillus niger ITV02 under liquid state fermentation.

The objective of this work was to evaluate the biochemical characteristics of an enzymatic extract obtained from autochthonous fungus Aspergillus niger ITV02 and its application in the enzymatic hydrolysis of wheat straw and corn stubble pretreated by steam explosion. The enzymatic extract was obtained by submerged fermentation using delignified sweet sorghum bagasse as a carbon source. The results obtained showed that the enzymatic extract had β-glucosidase and endoglucanase activities. The effects of pH and temperature on cellulase activity were evaluated and its thermostability was determined. The optimal parameters of the β-glucosidase and endoglucanase activities obtained were pH 5 and 70°C. The enzymatic extract of A. niger ITV02 was used to hydrolyze wheat straw and corn stubble, and the hydrolysis yields were compared with those obtained by a commercial cellulase (Celluclast 1.5L NS 50013) and CellicCTec3. The results showed that with the use the mixture of Celluclast 1.5L-A. niger ITV02 and CellicCTec3-A. niger ITV02 in the hydrolysis, conversions of 86.36% and 67.8% were obtained, respectively. Glucose production for the mixture extract increased 2.15 times more than when the enzyme was used independently alone. The present work shows that A. niger ITV02 has a potential as an enzyme producer for lignocellulosic hydrolysis.

Towards upscaling the valorization of wheat straw residues: alkaline pretreatment using sodium hydroxide, enzymatic hydrolysis and biogas production.

Lignocellulosic biomass is considered as a recalcitrant substrate for anaerobic digestion due to its complex nature that limits its biological degradation. Therefore, suitable preprocessing for the improvement of the performance of conventional anaerobic digestion remains a challenge in the development of anaerobic digestion technology. The physical and chemical characteristics of wheat straw (WS), as a representative lignocellulosic biomass, have a significant impact on the anaerobic digestion process in terms of quantity and quality of the produced biogas. This study aimed at investigating the enzymatic saccharification and detoxification of straw prior to anaerobic digestion with the final objective of enhancing the performance of conventional anaerobic systems of recalcitrant fractions of agricultural waste. The experimental activity was performed in lab and pilot scale treating WS. Alkaline delignification of straw using sodium hydroxide (NaOH) was studied prior to enzymatic hydrolysis for the production of easily biodegradable sugars. After defining the optimum conditions for the pretreatment scheme, the anaerobic digestability of the effluents produced was measured. Finally, the final liquid effluents were fed to a pilot scale anaerobic digester of 0.5m3 volume, applying an increasing organic loading rate (OLR) regime (in terms of chemical oxygen demand (COD) from 0.2 to 15kg COD/m3/day). The optimum conditions for the delignification and enzymatic hydrolysis of WS were defined as 0.5M NaOH at 50°C for 3-5h and 15μL Cellic CTec2/g pretreated straw at 50°C. It was proven that the resulting liquid effluents could be fed to an anaerobic digester in the ratio that they are produced with satisfactory COD removal efficiencies (over 70%) for OLRs up to 10kg COD/m3/day. This value is correspondent to a hydraulic retention time of around 7.5days, much lower than the respective one for untreated straw (over 12days).

Bioconversión sostenible de residuos agrícolas sacarificados en bioetanol por Wickerhamomyces anomalus

Snowballing levels of greenhouse gas emissions and concerns about climate change has led to an ongoing exploration of biofuels. Bioethanol can be obtained from wheat straw and can be readily available as clean fuel for combustion engines. Therefore, Wickerhamomyces anomalus yeast strain IHZ-26 was used to produce bioethanol from sugar solution obtained from enzymatic hydrolysis of wheat straw. Nineteen different fermentation media were used for this purpose in which carbon source employed was sugar solution obtained from enzymatic hydrolysis of wheat straw. Out of which, maximum bioethanol yield (1.09 g/L; p <0.05) was observed in ‘C1 Yeast extract, peptone, glucose’ medium. After optimization of different cultural parameters, surface culture fermentation for 5 days at 25℃ gave maximum results using 2, 1.5 and 2 g of glucose, xylose and ammonium dihydrogen phosphate, respectively. Four hours old inoculum of yeast in a concentration of 3.5% was optimized for maximum bioethanol yield. These optimized parameters resulted in augmented bioethanol production (5.0g/L) by 5.02 folds. This study revelas that W. anomalus IHZ-26 employed was able to covert pentose and hexose sugars simultaneously with efficient ethanol yield.

Effect of alkaline pretreatments on the enzymatic hydrolysis of wheat straw.

Lignocellulosic materials are mainly consisted of lignin, cellulose, and hemicellulose. Lignin is recognized as the main obstacle for the enzymatic saccharification of cellulose towards the fermentable sugars' production. Hence, the removal of lignin from the lignocellulosic feedstock is beneficial for reducing the recalcitrance of lignocellulose for enzymatic attack. For this purpose, various different alkaline pretreatments were examined in order to study their effect on the enzymatic saccharification of wheat straw, as a typical lignocellulosic material. Results revealed that the alkaline pretreatments promoted delignification reactions. Regarding the removal of lignin, the most efficient pretreatments were alkaline treatment with hydrogen peroxide 10% and NaOH 2% autoclave with delignification efficiencies of 89.60% and 84.86% respectively. X-ray diffraction analysis was performed to enlighten the structural changes of raw and pretreated materials. The higher the delignification of the raw material, the higher the conversion of cellulose during enzymatic saccharification. In all cases after enzymatic saccharification, the cellulosic conversion was much higher (32-77%) than the untreated wheat straw (8.6%). After undergoing alkaline peroxide 10% pretreatment and cellulase treatment, 99% of the initial raw straw was eventually solubilized. Thus, wheat straw could be considered as an ideal material for the production of glucose with proper pretreatments and effective enzymatic hydrolysis.

Enhanced enzymatic hydrolysis of wheat straw via a combination of alkaline hydrogen peroxide and lithium chloride/N,N-dimethylacetamide pretreatment

The aim of this work was to enhance enzymatic hydrolysis of wheat straw (WS) via a combination of alkaline hydrogen peroxide (AHP) and lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) pretreatment. The physicochemical structural changes of pretreated WS were systematically characterized. Furthermore, the hydrolytic efficiency and synergistic action between xylanase and cellulase in the enzymatic hydrolysis of pretreated WS were investigated. Results suggested that AHP-LiCl/DMAc pretreatment enhanced the enzymatic hydrolysis efficiency dramatically by effective delignification and completely deconstructing the crystalline structure of cellulose in WS. The maximum cellulose and xylan enzymatic hydrolysis efficiencies of AHP-LiCl/DMAc treated WS reached up to 97.49% and 87.80%, respectively, by adding cellulase and xylanase simultaneously. The disruption of hydrogen bond in cellulose and xylan reduced the synergistic effect between xylanase and cellulase during enzymatic hydrolysis of AHP-LiCl/DMAc pretreated WS, especially for cellulose hydrolysis. The hydrogen bond present in cellulose and xylan is one of the key factors on determining the synergistic action of xylanase and cellulase, which also plays an important role in enzymatic saccharification process. Overall, this study provides a promising pretreatment strategy for the efficient enzymatic hydrolysis of WS into fermentable sugars.

The effects of exogenous ash on the autohydrolysis and enzymatic hydrolysis of wheat straw

The effects of exogenous ash (EA) from harvest wheat straw and its internal components on wheat straw autohydrolysis efficiency and subsequent enzymatic hydrolysis were investigated. Results showed that when EA and its insoluble mineral components were included in the autohydrolysis, the enzymatic efficiencies of pretreated residues were significantly reduced from 84.9% to 66.3% and 58.4%, respectively. This was found to be largely attributable to the buffering of free H+ in the pretreatment medium which took place due to the ash. Specifically, the insoluble mineral fraction of said ash exerted strongest buffering capacity in EA. Furthermore, this decrease was found to linearly correlate with decreases to substrate enzymatic accessibility and hydrophobicity. These results demonstrate that the penalties of ash upon autohydrolysis are borne of specific fractions comprising the ash, making the case for ash removal processes or supplementation of processes with additives that will counter the negative effects of ash.