Hydrolysis Of Wheat Straw Research Articles

A CRISPR activation and interference toolkit for industrial Saccharomyces cerevisiae strain KE6-12

Recent advances in CRISPR/Cas9 based genome editing have considerably advanced genetic engineering of industrial yeast strains. In this study, we report the construction and characterization of a toolkit for CRISPR activation and interference (CRISPRa/i) for a polyploid industrial yeast strain. In the CRISPRa/i plasmids that are available in high and low copy variants, dCas9 is expressed alone, or as a fusion with an activation or repression domain; VP64, VPR or Mxi1. The sgRNA is introduced to the CRISPRa/i plasmids from a double stranded oligonucleotide by in vivo homology-directed repair, allowing rapid transcriptional modulation of new target genes without cloning. The CRISPRa/i toolkit was characterized by alteration of expression of fluorescent protein-encoding genes under two different promoters allowing expression alterations up to ~ 2.5-fold. Furthermore, we demonstrated the usability of the CRISPRa/i toolkit by improving the tolerance towards wheat straw hydrolysate of our industrial production strain. We anticipate that our CRISPRa/i toolkit can be widely used to assess novel targets for strain improvement and thus accelerate the design-build-test cycle for developing various industrial production strains.

Исследование кинетики выхода редуцирующих веществ и рН гидролизатов пшеничной соломы

In low-acid hydrolysis, the temperature, pH, pressure, and the type of hydrolyzed material can have a significant effect on the yield of reducing sugars. The active acidity of the medium can undergo significant changes under the influence of the reaction products. The processes of hydrolytic decomposition can be facilitated by acetic acid, which is formed during the deacetylation of hemicelluloses, as well as the ability of natural biomass to neutralize acids. The level of neutralization potential (buffer capacity) depends on the type of biomass. The influence of the pH on the yield of reducing substances in the process of hydrolysis of wheat straw with dilute sulfurous acid in a wide temperature range is envistigated. The choice of optimal conditions for the release of reducing sugars is complicated by the need to compare the hydrolysis regimes with several interrelated parameters. In order to analyze the influence of different factors, a comparative assessment of the process conditions was carried out, under which the maximum yield of reducing substances was achieved in each series of experiments. The studies have shown that the initial stage of the process is characterized by a decrease in the actual pH level in hydrolysates, and the greatest change is observed in liquid autohydrolysis products. The pH of hydrolysates, depending on the process mode, varies in the range from 1.26 to 4.1, but the highest yield of reducing substances corresponds to pH values of about 2. It is shown that dimensionless values of the maximum concentrations of reducing substances graphically correspond to the given values of the medium.

Nutrient-supplemented propagation of Saccharomyces cerevisiae improves its lignocellulose fermentation ability

Propagation conditions have been shown to be of considerable importance for the fermentation ability of Saccharomyces cerevisiae. The limited tolerance of yeast to inhibitors present in lignocellulosic hydrolysates is a major challenge in second-generation bioethanol production. We have investigated the hypothesis that the addition of nutrients during propagation leads to yeast cultures with improved ability to subsequently ferment lignocellulosic materials. This hypothesis was tested with and without short-term adaptation to wheat straw or corn stover hydrolysates during propagation of the yeast. The study was performed using the industrial xylose-fermenting S. cerevisiae strain CR01. Adding a mixture of pyridoxine, thiamine, and biotin to unadapted propagation cultures improved cell growth and ethanol yields during fermentation in wheat straw hydrolysate from 0.04 g g−1 to 0.19 g g−1 and in corn stover hydrolysate from 0.02 g g−1 to 0.08 g g−1. The combination of short–term adaptation and supplementation with the vitamin mixture during propagation led to ethanol yields of 0.43 g g−1 in wheat straw hydrolysate fermentation and 0.41 g g−1 in corn stover hydrolysate fermentation. These ethanol yields were improved compared to ethanol yields from cultures that were solely short-term adapted (0.37 and 0.33 g g−1). Supplementing the propagation medium with nutrients in combination with short-term adaptation was thus demonstrated to be a promising strategy to improve the efficiency of industrial lignocellulosic fermentation.

Small scale screening of yeast strains enables high-throughput evaluation of performance in lignocellulose hydrolysates

Second generation biorefineries demand efficient lignocellulosic hydrolysate fermenting strains and recent advances in strain isolation and engineering have progressed the bottleneck in developing production hosts from generation of strains into testing these under relevant conditions. In this paper, we introduce a methodology for high-throughput analysis of yeast strains directly in lignocellulosic hydrolysates. The Biolector platform was used to assess aerobic and anaerobic growth of 12 Saccharomyces cerevisiae strains and their ΔPdr12 mutants in wheat straw hydrolysate. The strains evaluated included lab, industrial and wild type strains and the screening could capture significant differences in growth and ethanol production among the strains. The methodology was also demonstrated with corn stover hydrolysate and the results were in line with shake flask cultures. Our study demonstrates that growth in lignocellulosic hydrolysates could be rapidly monitored using 1 ml cultures and that measuring growth and product formation under relevant conditions are crucial for evaluating strain performance.

Optimization of pH as a strategy to improve enzymatic saccharification of wheat straw for enhancing bioethanol production

In this work, wheat straw (WS) was used as a lignocellulosic substrate to investigate the influence of pH on enzymatic saccharification. The optimum enzymatic hydrolysis occurred at pH range 5.8–6.0, instead of 4.8–5.0 as has been widely reported in research. Two enzymes cocktails, Celluclast® 1.5 L with Novozymes 188, Cellic® CTec2 and endo-1,4-β-xylanase, were used for the pH investigation over a pH range of 3.0–7.0. The highest concentration of total reduced sugar was found at pH 6.0 for all the different enzymes used in this study. The total reduced sugar produced from the enzymatic saccharification at pH 6.0 was found to be 7.0, 7.4, and 10.8 (g L−1) for Celluclast® 1.5 L with Novozymes 188, endo-1,4-β-xylanase and Cellic® CTec2, respectively. By increasing the pH from 4.8 to 6.0, the total reduced sugar yield increased by 25% for Celluclast® 1.5 L with Novozymes 188 and endo-1 4-β-xylanase and 21% for Cellic® CTec2. The results from this study indicate that WS hydrolysis can be improved significantly by elevating the pH at which the reaction occurs to the range of 5.8 to 6.0.

Effects of hydrothermal pretreatment on the mono- and co-digestion of waste activated sludge and wheat straw

The refractory properties of waste activated sludge and wheat straw inhibit their bioenergy recovery by anaerobic digestion. This paper attempted to estimate the digestive performance, energy conversion efficiency and economic feasibility of wheat straw mono-digestion and its co-digestion with sludge by hydrothermal pretreatment at different temperature gradients (125, 150 and 175 °C). The results illustrated that the hydrolysis of both wheat straw and sludge were improved with the temperature increasing. It is noted that after pretreatment at 175 °C, wheat straw mono-digestion obtained the cumulative specific methane yield of 168.8 mL/g·VS, 6.9% reduction compared to the unpretreated straw (181.4 mL/g·VS) due to the inhibition by by-products (furfural and 5-hydroxymethylfurfural, 5-HMF) formed at high temperatures. The highest cumulative specific methane yield of 225.7 mL/g·VS was achieved by the co-digestion of pretreated wheat straw and pretreated sludge under 175 °C, indicating that the participation of sludge in co-digestion improved the buffer capacity of the system to relieve the inhibition. In addition, the co-digestion of sludge and wheat straw both pretreated at 175 °C obtained the maximum energy production of 7901.1 MJ/t, 52% promotion compared to the mono-digestion without pretreatment. The results of economic analysis showed that the mono-digestion of wheat straw obtained relatively low net profits and the mono-digestion of sludge pretreated at 175 °C achieved the highest net profit of 31.44 US$/t. These results suggest that the co-digestion of both pretreated wheat straw and sludge can achieve the highest biogas production and energy conversion efficiency.

Extended fed-batch fermentation of a C5/C6 optimised yeast strain on wheat straw hydrolysate using an online refractive index sensor to measure the relative fermentation rate

In the production of 2nd generation ethanol, using Saccharomyces cerevisiae, the highest productivity obtained using C5/C6 fermenting yeast is in the co-fermentation phase, in which xylose and glucose are fermented simultaneously. Extending this phase in a fed-batch process increases the yield, rate and additionally reduces needed yeast amount for pitching. Extending this phase, as long as possible, would further enhance yield and economy of the process. To realise the concept a fermentation monitoring technique was developed and applied. Based on online measured refractive index an optimal residual sugar concentration could be maintained in the primary fermentor during the feed phase, requiring little knowledge of the nature of the substrate. The system was able to run stably for at least five fermentor volumes giving an ethanol yield >90% throughout the run. This was achieved with addition of only urea to the wheat straw hydrolysate and with an initial yeast pitch of 0.2 g/L total of finished broth. It has the potential to improve the fermentation technology used in fuel ethanol plants, which could help to meet the growing demand for more sustainable fuels.

Coproduction of hydrogen, ethanol and 2,3-butanediol from agro-industrial residues by the Antarctic psychrophilic GA0F bacterium

In this study, the simultaneous production of hydrogen, ethanol, and 2,3-butanediol was assessed using three agro-industrial residues: cheese whey powder (CWP), wheat straw hydrolysate (WSH) and sugarcane molasses (SCM), by the Antarctic psychrophilic GA0F bacterium [EU636050], which is closely related to Pseudomonas antarctica [KX186936.1]. The main soluble metabolites produced in all the fermentations were ethanol and 2,3-butanediol. CWP demonstrated to be the most effective carbon source, since fermentation of this substrate resulted in the highest yields of H2 (73.5 ± 10 cm3 g−1), ethanol (0.24 ± 0.03 g g−1) and 2,3-butanediol (0.42 ± 0.04 g g−1), followed by the use of SCM, whereas WSH showed to have an inhibitory effect during the fermentation process, showing the lowest production values. Our results demonstrated the ability of the Antarctic psychrophilic GA0F bacterium to produce valuable products using low-cost substrates at room temperature conditions.

Wheat straw hydrolysis by using co-cultures of Trichoderma reesei and Monascus purpureus toward enhanced biodegradation of the lignocellulosic biomass in bioethanol biorefinery

Wheat straw (Triticum aestivum) is one of the lignocellulosic materials largely available worldwide and could be potentially used for biofuel production. Aiming the cost-effective utilization of wheat straw in the sugar-based biorefineries, co-cultures of Trichoderma reesei and Monascus purpureus were used for the enzymatic hydrolysis of the wheat straw biomass. The enzymatic breakdown of the dual-fungi-treated wheat straw was chemically analyzed through different enzyme/compositional assays, and the structural modifications were studied through scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). For hydrolytic enzyme assays, the co-culture treatments resulted in significantly higher values (carboxymethyl cellulase (212.3 U/ml; p = 0.0173*), total cellulase (202 U/ml; p < 0.0001****), and xylanase (96.7 U/ml; p < 0.0001****) when compared with the readings of pure cultures. This hydrolytic activity resulted in the enhanced breakdown of wheat straw exhibiting a significant loss of 45.2% in lignin, 19.18% in cellulase, and 21.84% in hemicellulose contents. Furthermore, SEM and FTIR analysis of the co-culture treatments verified the improved biodegradation of wheat straw. Accumulatively, these results suggest a better approach for the effective use of dual-fungi for the lignocellulosic biomass breakdown and may have applications in bioethanol biorefineries using wheat straw as a sugar feedstock.

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.

Concentration-driven reverse membrane bioreactor for the fermentation of highly inhibitory lignocellulosic hydrolysate

Optimal production of lignocellulosic bioethanol is hindered due to commonly faced issues with the presence of inhibitory compounds and sequentially consumed sugars in the lignocellulosic hydrolysate. Therefore, in order to find a robust fermentation approach, this study aimed at enhancing simultaneous co-assimilation of sugars, and inhibitor tolerance and detoxification. Therefore, fermentation of toxic wheat straw hydrolysate containing up to 20 g/l furfural, using the concentration-driven diffusion-based technique of reverse membrane bioreactor (rMBR) was studied. The rMBR fermentation of the hydrolysate led to complete furfural detoxification and the conversion of 87 % of sugars into ethanol at a yield of 0.48 g/g. Moreover, when the toxicity level of the hydrolysate was increased to 9 g/l of initial furfural, the system responded exceptionally by reducing 89 % of the inhibitor while only experiencing about 25 % drop in the ethanol yield. In addition, using this diffusion-based set-up in extremely inhibitory conditions (16 g/l furfural), cells could detoxify 40 % of the furfural at a high initial furfural to cell ratio of 9.5:1. The rMBR set-up applied proved that by properly synchronizing the medium condition, membrane area, and inhibitor to cell ratio, some of the shortcomings with conventional lignocellulosic fermentation can be tackled, guaranteeing a robust fermentation.

Screening of cellulolytic bacteria from rotten wood of Qinling (China) for biomass degradation and cloning of cellulases from Bacillus methylotrophicus

BackgroundCellulosic biomass degradation still needs to be paid more attentions as bioenergy is the most likely to replace fossil energy in the future, and more evaluable cellulolytic bacteria isolation will lay a foundation for this filed. Qinling Mountains have unique biodiversity, acting as promising source of cellulose-degrading bacteria exhibiting noteworthy properties. Therefore, the aim of this work was to find potential cellulolytic bacteria and verify the possibility of the cloning of cellulases from the selected powerful bacteria.ResultsIn present study, 55 potential cellulolytic bacteria were screened and identified from the rotten wood of Qinling Mountains. Based on the investigation of cellulase activities and degradation effect on different cellulose substrates, Bacillus methylotrophicus 1EJ7, Bacillus subtilis 1AJ3 and Bacillus subtilis 3BJ4 were further applied to hydrolyze wheat straw, corn stover and switchgrass, and the results suggested that B. methylotrophicus 1EJ7 was the most preponderant bacterium, and which also indicated that Bacillus was the main cellulolytic bacteria in rotten wood. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction analysis of micromorphology and crystallinity of wheat straw also verified the significant hydrolyzation. With ascertaining the target sequence of cellulase β-glucosidase (243 aa) and endoglucanase (499 aa) were successfully heterogeneously cloned and expressed from B. methylotrophicus 1EJ7, and which performed a good effect on cellulose degradation with enzyme activity of 1670.15 ± 18.94 U/mL and 0.130 ± 0.002 U/mL, respectively. In addition, based on analysis of amino acid sequence, it found that β-glucosidase were belonged to GH16 family, and endoglucanase was composed of GH5 family catalytic domain and a carbohydrate-binding module of CBM3 family.ConclusionsBased on the screening, identification and cellulose degradation effect evaluation of cellulolytic bacteria from rotten wood of Qinling Mountains, it found that Bacillus were the predominant species among the isolated strains, and B. methylotrophicus 1EJ7 performed best on cellulose degradation. Meanwhile, the β-glucosidase and endoglucanase were successfully cloned and expressed from B. methylotrophicus for the first time, which provided new materials of both strain and the recombinant enzymes for the study of cellulose degradation and its application in industry.

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.

Efficient itaconic acid production by Aspergillus terreus: Overcoming the strong inhibitory effect of manganese.

Itaconic acid (IA), a building block platform chemical, is produced industrially by Aspergillus terreus utilizing glucose. Lignocellulosic biomass can serve as a low cost source of sugars for IA production. However, the fungus could not produce IA from dilute acid pretreated and enzymatically saccharified wheat straw hydrolyzate even at 100-fold dilution. Furfural, hydroxymethyl furfural and acetic acid were inhibitory, as is typical, but Mn2+ was particularly problematic for IA production. It was present in the hydrolyzate at a level that was 230 times over the inhibitory limit (50 ppb). Recently, it was found that PO43- limitation decreased the inhibitory effect of Mn2+ on IA production. In the present study, a novel medium was developed for production of IA by varying PO43- , Fe3+ and Cu2+ concentrations using response surface methodology, which alleviated the strong inhibitory effect of Mn2+ . The new medium contained 0.08 g KH2 PO4 , 3 g NH4 NO3 , 1 g MgSO4 ·7H2 O, 5 g CaCl2 ·2 H2 O, 0.83 mg FeCl3 ·6H2 O, 8 mg ZnSO4 ·7H2 O, and 45 mg CuSO4 ·5H2 O per liter. The fungus was able to produce IA very well in the presence of Mn2+ up to 100 ppm in the medium. This medium will be extremely useful for IA production in the presence of Mn2+ . This is the first report on the development of Mn2+ tolerant medium for IA production by A. terreus.

Lipid and carotenoid production from wheat straw hydrolysates by different oleaginous yeasts

This work aimed to support the development of a new process for the production of lipids and carotenoids by oleaginous yeasts using both cellulosic and hemicellulosic fractions of biomass as feedstock for fermentation. The hypothesis behind this idea is that this strategy could lead to a sustainable pathway to produce these valuable components with potential to reduce the production costs. For the experiments, six oleaginous yeasts were initially cultivated in synthetic media containing glucose or xylose as carbon sources and different carbon to nitrogen ratios in order to identify the top producers. Rhodosporidium toruloides NRRL Y-1091 and Lipomyces starkeyi NRRL Y-1389 produced the highest amount of carotenoids and lipids, respectively. Then, the performance of these two strains when cultivated in wheat straw cellulosic and hemicellulosic hydrolysates was assessed. Detoxification of the cellulosic and hemicellulosic hydrolysates with activated charcoal removed 87.80% and 77.17% of inhibitors, respectively, and significantly improved the performance of the two yeasts. The highest concentration of lipids, 3.99 ± 0.35 g/L, was obtained by cultivating L. starkeyi in washed cellulosic hydrolysate; while the highest production of carotenoids, 24.58 ± 1.88 mg/L, was obtained by cultivating R. toruloides in decolorized cellulosic hydrolysate. Increasing the tolerance of oleaginous yeasts to inhibitors resulting from biomass pretreatment and/or using cost-effective detoxification methods were identified as key parameters for further development of this process at commercial scale.

Enhanced Enzymatic Hydrolysis and Lignin Extraction of Wheat Straw by Triethylbenzyl Ammonium Chloride/Lactic Acid-Based Deep Eutectic Solvent Pretreatment.

Efficient and feasible pretreatment of lignocellulosic biomass waste is an important prerequisite step to promote subsequent enzymatic hydrolysis and enhance the economics of biofuels production. This study focuses on the pretreatment of wheat straw (WS) with triethylbenzyl ammonium chloride/lactic acid (TEBAC/LA)-based deep eutectic solvents to enhance biomass fractionation and lignin extraction. Effects of pretreatment time, temperature, and TEBAC/LA molar ratio on pretreatment were evaluated systematically. Results suggested that 89.06 ± 1.05% of cellulose and 71.00 ± 1.03% of xylan were hydrolyzed with enzyme loadings of 35 FPU cellulase and 82 CBU β-glucosidase (per gram of dry biomass) after pretreatment by TEBAC/LA (1:9) at 373 K for 10 h. A total monosaccharide yield of 0.550 g/g WS (91.27% of the theoretical yield) was achieved with 79.73 ± 0.93% of lignin removal. Furthermore, the 1H–13C two-dimensional heteronuclear single quantum correlation (2D-HSQC) NMR spectroscopy showed that the regenerated lignin (75.69 ± 1.32% purity) was mainly composed of the syringyl units and the guaiacyl units. Overall, the results in this study provide an effective and facile pretreatment method for lignocellulosic biomass waste to enhance enzymatic hydrolysis saccharification.

The residue from the acidic concentrated lithium bromide treated crop residue as biochar to remove Cr (VI)

In this work, the hydrolysis residue produced from the acidic concentrated lithium bromide hydrolysis (ALBH) of wheat straw, corn stover and elephant grass were characterized as biochar. The ALBH biochar as the black power had high content of carbon (49.65–55 wt%), specific surface areas (4.53–7.79 m2/g), porous structures (micropores, mesopores and macropores) and abundant oxygen functional groups (hydroxy, carbonyl, ester and ketone groups). These properties made ALBH biochar as a potential adsorbent for environmental remediation, with relatively high removal efficiency for a variety of heavy metal ions, especially hexavalent chromium (Cr(VI)). Therefore, ALBH technology may be an efficient strategy for synthesis of bio-char along with fermentable sugars, which met the concern of sustainability and green chemistry.

Optimization of an artificial cellulase cocktail for high-solids enzymatic hydrolysis of cellulosic materials with different pretreatment methods

Optimization of the composition of cellulase mixtures is an effective strategy to improve their hydrolytic efficiency and reduce protein demand during enzymatic degradation of lignocelluloses. In this study, the mixture design method was used to optimize the ratios of endoglucanase II (EG II), cellobiohydrolase I (CBH I) and β-glucosidase I (BG I) from Penicillium oxalicum in an artificial cellulase mixture for the hydrolysis of six different cellulosic materials. The optimal composition of enzyme mixture was distinctly different among not only cellulosic materials with different pretreatment methods but hydrolyses at different solids concentrations. CBH I was most critical for the hydrolysis of two acid-pretreated materials, probably due to its strong adsorption on lignin. A higher proportion of EG II was needed for the hydrolysis of ammonium sulfite pretreated wheat straw. The requirements of specific cellulase components were more pronounced at high solids concentrations, highlighting the importance of considering solids loading when optimizing cellulase cocktails.

Aqueous phase reforming of sugar-based biorefinery streams: from the simplicity of model compounds to the complexity of real feeds

Abstract Glucose, xylose and corresponding sugar alcohols (sorbitol and xylitol) have been subjected to aqueous phase reforming for the production of hydrogen as representative compounds of hemicellulose. The aim of the investigation was to explore new valorization pathways for pentoses sugars, nowadays still not effectively exploited. A developmental platinum-based catalyst supported on carbon was used to perform the reaction in a batch system. The influence of temperature and carbon concentration were investigated in the 230–270 °C and 0.3–1.8 wt.% range, respectively. Moving towards the exploitation of a biorefinery side-stream, wheat straw hydrolysate was subjected to the same reaction conditions. A hydrogenation step was used as pre-treatment to selectively convert the sugars to their corresponding sugar alcohols, and a net hydrogen production was obtained. Deactivation phenomena were investigated during the APR of sugars reusing the catalyst after the reaction. The characterization of the spent catalysts through TGA-IR allowed to confirm the presence of superficial organic deposits responsible for the lack of the catalyst stability.

Isolation of Lignocelluloses via Acidification of Hydrolysates Induced from Different Straws

Hydrolysis has been commercially practiced for isolating hemicelluloses from wood chips. Acidification has also been reported as means to isolate lignocelluloses from hydrolysate. However, the performance of hydrolysis and subsequently acidification of induced hydrolysate on non-wood species is unclear. In this work, the hot water hydrolysis of wheat straw, rice straw and maize straw and the acidification of the generated hydrolysates were investigated. The hot water hydrolysis process of wheat, rice and maize straws were optimized. The effect of acidification on separating lignin from hydrolysates was also evaluated as a means to generate lignin. The properties of the collected lignocelluloses were determined to identify a potential application for them. The optimal conditions of the hydrolysis for straws were liquid/solid ratio of 12/1 (wt/wt), temperature of 170 °C and time of 60 min, which yielded rice straw hydrolysate containing more sugars than did the hydrolysates of wheat and maize straws. Acidification to pH 1.5 led to 27.49%, 29.17% and 23.38% lignin removals from the hydrolysates of wheat, rice and maize straws, respectively. Acidification decreased the furfural concentration of hydrolysates and increased the acetic acid concentration. The precipitates generated via acidification of hydrolysates had different heating values, thermal stability and ash content, and the precipitates of acidified rice straw hydrolysate had a higher heating value and thermal stability, but lower ash, than did those of acidified wheat and maize straws. The hot water hydrolysis of different straws could be conducted under the same conditions, but the acidification of hydrolysates would generate lignin with varied properties that may be suitable for altered applications. These results provide evidence for the impact of straw type on the thermal properties of extracted lignin of straw and thus its potential applications.