Hydrolysis Of Straw Research Articles

Kinetics of producing vanillin and 4-hydroxy benzaldehyde from the hydrolysis residue of rice straw by photocatalysis

Alkali soluble lignin present in rice straw hydrolysis residue (RSHR) is subjected to photocatalytic treatment to study its degradation rates and production of different value-added oxygenated organic compounds. TiO2 and ZnO are used as photocatalysts. ZnO could degrade lignin faster than TiO2 in pseudo-first order photocatalytic degradation. The maximum observed photocatalytic lignin degradation is 83.4% using 2 g/L ZnO dose with pseudo-first order rate constant 0.1386 h−1. Vanillin and 4-hydroxy benzaldehyde are the two important value-added products formed during photocatalysis. Both these compounds, themselves, are susceptible to photocatalytic degradation. Vanillin degradation followed pseudo-first order kinetics and the highest rate constant of 0.1415 h−1 is achieved using 2 g/L ZnO as photocatalyst. While the degradation kinetics of 4-hydroxy benzaldehyde is pseudo-first order with TiO2 and ZnO as a photocatalyst. Higher catalyst doses increased the reaction rate constant. With multiple reactions in operation, the concentration of both vanillin and 4-hydroxy benzaldehyde in the reaction mixture first increased, attained their maxima, and thereafter decreased. With 1 g/L TiO2 as a photocatalyst, the maximum attained vanillin concentration is 22.4 mg/L after 7 h photocatalysis. Maximum attained vanillin concentration, after 8 h photocatalysis, is significantly higher at 51.2 mg/L when 2 g/L ZnO is used as a catalyst. 4-Hydroxy benzaldehyde is produced in lesser amounts. Its maximum observed concentration in the reaction mixture is 20.4 mg/L, obtained with 1.5 g/L TiO2 after 10 h photocatalysis.

Effects of LAT on chemical structure and enzymatic hydrolysis of crop straw

Objective This study aims to investigate the effects of liquid ammonia treatment (LAT) pretreatment on the hydrolysis resistance of biomass and the enzymatic hydrolysis rate of lignocellulosic biomass. Method Four different types of lignocelluloses biomass, namely wheat straw (Triticum aestivum), alfalfa (Lotus corniculatus), sorghum straw (Sorghum bicolor), and their mixture (mass ratio 1∶1∶1), were pretreated by LAT method, and the effect of LAT on their chemical structure changes was studied by using thermo gravimetric analysis (TGA), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), and scanning electron microscope (SEM). Then, the effect of pretreatment temperature and enzymatic hydrolysis time on the enzymatic hydrolysis conversion rates of glucan and xylan in the four raw materials was investigated. Result LAT had a significant effect on the chemical structure of biomass materials. After this pretreatment, the relative content of glucan, xylan, and arabinan in four types of lignocelluloses biomass slightly decreased. The relative content of O and H decreased because some functional groups containing O and H dropped off. The crystallinity decreased slightly, while the surface pore structure significantly increased, and the availability of enzymes in the chemical structure of biomass increased. The optimum pretreatment temperature of wheat straw and mixture was 90 ℃, while that of alfalfa and sorghum straw was 110 ℃. The enzymatic hydrolysis rates of glucan and xylan increased with the increase of enzymatic hydrolysis time. Among the four types of lignocelluloses biomass, the highest enzymatic hydrolysis rate of glucan obtained at the optimal enzymatic hydrolysis condition was wheat straw, followed by the mixture, sorghum straw, and alfalfa. The enzymatic hydrolysis rate of xylan ranging from large to small was sorghum straw, wheat straw, the mixture, and alfalfa. Conclusion LAT can improve the enzymatic hydrolysis efficiency of lignocellulosic biomass, especially that of wheat straw and sorghum straw. [Ch, 8 fig. 2 tab. 24 ref.]

Optimization of cello-oligosaccharides production by enzymatic hydrolysis of hydrothermally pretreated sugarcane straw using cellulolytic and oxidative enzymes

Enzymatic hydrolysis of lignocellulosic biomass accounts for 20–30% of the total cost of second-generation bioethanol production and many efforts have been made in recent years to overcome the high cost of enzymes. Using cello-oligosaccharides (COS), intermediates in cellulose conversion to glucose, may provide advantages over monomeric glucose fermentation, such as lower risk of growth of process contaminants, shorter fermentation time and limited process inhibition by high concentrations of glucose. In addition, COS are also useful as functional oligosaccharides in the food and feed sectors. This study aimed to optimize COS production for further industrial applications. To the best of our knowledge, this is the first study that has used a design of experiments approach to analyze the synergism between endoglucanases, lytic polysaccharide monooxygenase (LPMO), cellobiose dehydrogenase (CDH) and different additives during the hydrolysis of a pretreated sugarcane straw for COS production. After optimization of enzymatic hydrolysis, a combination of the endoglucanases CaCel and CcCel9m, the LPMO TrCel61A, the CDH NcCDHIIa, with lactose and copper as additives, produced 60.49 mg of COS per g of pretreated sugarcane straw, 1.8–2.7-fold more than the commercial enzyme cocktails Cellic® Ctec2 and Celluclast® 1.5 L. The COS/glucose ratio achieved was 298.31, an increase of 3314 and 2294-fold over the commercial enzymatic cocktails, respectively. These results open a new perspective regarding COS production and its industrial application.

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.

Biobutanol production from lignocellulosic biomass using immobilized Clostridium acetobutylicum

Biobutanol produced by acetone-biobutanol-ethanol (ABE) fermentation process has been revisited in the light of its use as “drop in” liquid biofuel to be blended with gasoline. In this study, renewable feedstock like rice straw, sugarcane bagasse and microalgal hydrolysate were used in ABE fermentation via separate hydrolysis and fermentation. Clostridium acetobutylicum ATCC 824 was used as the fermenting organism. Alkali pretreatment followed by enzymatic hydrolysis was used for rice straw and sugarcane bagasse. In batch fermentation, a biobutanol titer and yield of 9.10 g/L and 0.42 mol/mol glucose (0.17 g biobutanol/g glucose), respectively was obtained from rice straw, while sugarcane bagasse achieved a biobutanol titer and yield of 8.40 g/L and 0.40 mol/mol glucose (0.16 g biobutanol/g glucose), respectively. Higher microalgal biomass loading with 3% acid pretreatment severely inhibited fermentation performance. Unhydrolyzed microalgal biomass at a loading of 180 g/L in ABE fermentation resulted in 4.32 g/L biobutanol and 0.09 g biobutanol/g microalgae as yield. C. acetobutylicum was immobilized in polyvinyl alcohol (PVA) for improving the cell loading in fermentation and protect the cells from biobutanol toxicity. With rice straw hydrolysate as a feedstock and in the absence of yeast extract, a biobutanol titer, yield and productivity of 13.80 g/L, 0.90 g/L/h, and 0.58 mol biobutanol/mol glucose (0.23 g biobutanol/g glucose), respectively were obtained. Hence, rice straw is a potential feedstock for biobutanol production for fuel use.

Optimization of peroxide-alkaline pretreatment and enzymatic hydrolysis of barley straw (Hordeum vulgare L.) to produce fermentable sugars using a Box–Behnken design

In recent years, interest has increased in the use of agro-industrial wastes for use as raw materials in the production of second-generation biofuels and other products of industrial interest. A pretreatment is necessary, followed by an enzymatic hydrolysis to obtain high yields of fermentable sugars. In the present study, the best conditions were established both for peroxide-alkaline pretreatment and for enzymatic hydrolysis of the Mexican barley straw (Hordeum vulgare L.) variety Dona Josefa in order to maximize lignin removal and improve enzyme conversion. Response surface methodology based on a Box–Behnken experimental design was used to optimize pretreatment conditions (concentration of hydrogen peroxide [H2O2], reaction time, and liquid–solid ratio (LSR)), and enzymatic hydrolysis (cellulase and xylanase concentrations and reaction time). Samples obtained from residual bagasse at each process stage were analyzed by means of scanning electron microscopy (SEM) and infrared spectrometry (FTIR) to evaluate the changes in the structure of the material after treatments. In pretreatment optimization, it was possible to obtain 60% delignification at a 6% peroxide concentration and a 12:1 LSR in 24 h. In saccharification, a maximum 82% conversion of cellulose to glucose using 6% cellulase (Cellic® CTec III), and 4% xylanase (Cellic® HTec III) in 20 h of hydrolysis, was used in obtaining a maximum sugar concentration of 70 g/L. Peroxide-alkaline pretreatment together with state-of-the-art enzyme saccharification makes barley straw an excellent alternative for fermentable sugar production that can be used for various biotech industries.

Production of cellulolytic enzymes by Myceliophthora thermophila and their applicability in saccharification of rice straw

Optimization of cellulase production by Myceliophthora thermophila BJTLRMDU3 was studied in solid state fermentation. Sequential use of Plackett-Burman and response surface methodology (RSM) resulted in the production of 98.81, 243.19, and 316.48 U/g dry moldy residue (DMR) of FPase, CMCase, and β-glucosidase, respectively. Statistical optimization has resulted in more than 4.0-fold increase in the production of cellulases. Optimization of saccharification of untreated and pretreated rice straw was carried out by cellulolytic enzymes of thermophilic mold M. thermophila. The liberation of reducing sugars was higher using fungal cellulases in ammonia-pretreated rice straw as compared with untreated biomass. Maximum liberation of reducing sugars was attained at 60 °C (224.24 mg/g substrate) and pH 5.0 (246.33 mg/g substrate) after an incubation time of 24 h (345.61 mg/g substrate) using enzyme dose of 20 U/g in ammonia-pretreated rice straw. Supplementation of xylanase further enhanced the saccharification (488.78 mg/g substrate) of pretreated rice straw. Analysis using high-performance liquid chromatography (HPLC) indicated the presence of various monomeric and oligomeric sugars in the enzymatic hydrolysate of pretreated rice straw. Both, Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) revealed the structural changes in rice straw after ammonia pretreatment.

Enhanced Enzymatic Saccharification of Wheat Flour Arabinoxylan and Barley Straw Using Recombinant Hemicellulases

Enzymatic hydrolysis of hemicelluloses in biomass feedstocks requires multiple enzymes for sacchari-fication to fermentable monosaccharides. Considering the high cost of enzymes, the need for enzymes in the cocktail for maximum saccharification can be minimized using a statistically significant experimental design. In the present study, response surface methodology was used to optimize the saccharification of wheat arabinoxylan and pretreatment of barley straw. A hemicellulase enzyme mixture consisting of recombinant xylanase (rPcXynC), arabinanase (rPcAra), and bifunctional β-xylosidase/L-arabinofuranosidase (rPcXyl) was used. A central composite design was used to evaluate and confirm the effectiveness and interactions of these enzymes along with reaction time. A 100% sacchari-fication of 1 g of wheat arabinoxylan was achieved using 21.85 U, 6.025 U, and 182 U of rPcXynC, rPcAra, and rPcXyl, respectively, for 11.46 h. Subsequently, using pretreated barley straw as a substrate, a maximum saccharification of 42% was achieved in 12 h using an enzyme cocktail of 25 U rPcXynC, 5 U rPcAra, and 200 U rPcXyl. The total hydrolysis of pretreated barley straw was increased to 1.71% by the addition of acetyl xylan esterase as a pretreatment factor followed by optimization of enzyme cocktail. The experimental values under the optimum conditions were consistent with the predicted values and a minimum cocktail was involved for a synergistic effect of the enzymes.

Microbial lipid production from rice straw hydrolysates and recycled pretreated glycerol

Microbial lipids were produced by both rice straw hydrolysates and recycled pretreated glycerol. First, lipid fermentation of glucose via Cryptococcus curvatus was optimized by response surface methodology. Variables were selected by Plackett–Burman design, and optimized by central composite design, achieving 4.9 g/L total lipid and 0.16 g/g lipid yield, and increased further as glucose increased from 30 to 50 g/L. Secondly, after pretreatment, 72% lignin of rice straw was removed with glucose yield increased by 2.4 times to 74% at 20% substrate and 3 FPU/g. Subsequently, its hydrolysates produced high total lipid (8.8 g/L) and lipid yield (0.17 g/g). Finally, recycled glycerol reached the maximum total lipid of 7.2 g/L and high lipid yield of 0.16 g/g. Based on the calculation, 2.9 g total lipid would be produced from 1 g rice straw and the recycled glycerol, with a similar composition to soybean oil.

Distinct mechanisms of enzymatic saccharification and bioethanol conversion enhancement by three surfactants under steam explosion and mild chemical pretreatments in bioenergy Miscanthus

Miscanthus is a leading bioenergy crop that represents an enormous lignocellulose resource for biofuels and bioproducts. However, as lignocellulose recalcitrance leads to financially inviable bioethanol production and the potential of secondary wastes into the environment, it becomes crucial to explore green-like and cost-effective biomass processing technologies. To address these issues, low doses of chemical surfactants have been added to enhance biomass enzymatic hydrolysis and bioethanol conversion, but much remains unknown about the mechanism of enhancement. For first time, in this study, a novel chemical surfactant (1% Silwet L-77) was applied to enhance the enzymatic hydrolysis of raw Miscanthus straw, and 40% cellulose digestion was achieved, which is 1.2- and 4.5-fold higher than that of two well-known surfactants (PEG-4000 and Tween-80), respectively. Using lignocellulose substrates obtained from Miscanthus biomass samples that were pretreated by green-like steam explosion followed by mild chemical (NaOH or H2SO4) pretreatments, supplementation with the three surfactants led to significantly enhanced enzymatic saccharification. The 2% Tween-80 supply resulted in a hexose yield of 99% (% cellulose) from enzymatic hydrolysis, followed by 95% with 0.5% PEG-4000 and 71% with 1% Silwet L-77. Despite the slightly lower hexose yield, Silwet L-77 resulted in consistently higher sugar-ethanol conversion rates in all lignocellulose substrates examined. Furthermore, based on the enzyme profiling of mixed cellulase adsorption on lignocellulose and the chemical analysis of wall polymer features and lignocellulose accessibility, this study proposed multiple hypothetical models to interpret the distinct enhancement roles of three surfactants in the enzymatic hydrolyses of diverse lignocellulose substrates. These models also provide a powerful strategy for low-cost bioethanol production with the potential for high-value bioproducts by using desirable surfactants in Miscanthus and other bioenergy crops.

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.

Optimization of microwave-assisted alkali pretreatment followed by acid hydrolysis of sugarcane straw for production of acetone-butanol-ethanol

ABSTRACT The production of acetone-butanol-ethanol (ABE) calls for effective pretreatment and hydrolysis techniques to maximize reducing sugar yields. In this study, optimized microwave-assisted alkali (MAA) pretreatment followed by acid hydrolysis was assessed for the production of reducing sugars from sugarcane straw (SCS). To evaluate effects of MAA pretreatment on SCS composition, response surface methodology (RSM) was employed upon subjecting SCS to 320, 640, and 960 W microwave power, using 1–3% (w/v) NaOH, and residence time of 5, 15, and 25 min. The pretreated SCS was made to undergo acid hydrolysis at 121 °C temperature and reaction time of 10–60 min to release reducing sugars. ABE was produced by anaerobic fermentation of reducing sugars using Clostridium beijerinkii. After pretreatment, maximum responses of 76.3% lignin removal, 21.1% hemicellulose, and 71.9% cellulose were achieved at 640 W microwave power, 2.8% NaOH concentration, and 19 min. The maximum reducing sugar concentration was 46.2 g/L while 18.7 g/L of ABE was produced. The results revealed that optimized MAA pretreatment followed by acid hydrolysis can enhance the yield of reducing sugars for ABE production with no need for costly enzymes.

Efficient production of L-lactic acid from corn straw hydrolysate

In this study, L-lactic acid was produced from corn straw hydrolysate by the strain Lactobacillus sp. L47, the fermentation conditions such as nitrogen sources, mineral salts, metal ions, incubation periods, pH values and temperatures were investigated, and the optimal incubation conditions were obtained: corn straw hydrolysate of 243.1 ml/l, (NH4)2SO4 10 g/l, yeast extract 10 g/l, KH2PO4 0.5 g/l, ZnSO4 • 7H2O 0.3 g/l, MgSO4• 7H2O 0.1 g/l, MnSO4• H2O 0.01 g/l, CaCO3 60 g/l, initial medium pH 6.0, controlled fermentation pH 6.0, 20 ml of seed, incubation temperatrure 46 °C. Under the optimal fermentation conditions, the highest L-lactic acid production was 99.8 g/l in 40 h.

Valorization of xylose-rich hydrolysate from rice straw, an agroresidue, through biosurfactant production by the soil bacterium Serratia nematodiphila

Biosurfactants, amphiphilic compounds that reduce interfacial tension in oil-aqueous mixtures, are used in the petroleum, pharmaceutical, food, and agriculture industries. Fermentative production of biosurfactants requires expensive sugar or lipid substrates. Lignocellulosic biomass is a relatively cheap and abundant agricultural residue that can be used as an alternative substrate. Currently, several million tonnes of rice and wheat straw are generated globally as agricultural residues, most of which is disposed by open-field burning thereby leading to severe environmental pollution. This study aimed to produce biosurfactants in xylose-rich hydrolysates generated from rice straw. The hydrolysate is also a byproduct of 2G biofuel processes that often goes underutilized. A soil bacterium capable of growing and producing biosurfactants in rice straw hydrolysates, which typically contain growth-inhibitory compounds such as furfural and hydroxymethyl furfural, was isolated. Interestingly, the organism, identified as Serratia nematodiphila, exhibited higher glycolipid formation (4.5 ± 0.6 gL−1) in xylose-rich hydrolysate than in glucose-rich enzymatic hydrolysate (3.1 ± 0.2 gL−1) despite the higher bacterial cell density observed with the latter. The biosurfactants were thermostable and possessed promising emulsifying property and anti-microbial activity against bacteria and yeast. Further optimization of C:N resulted in a 2.8-fold increase in glycolipid production from xylose-rich hydrolysates. This study demonstrates the production of glycolipid biosurfactants from lignocellulosic biomass, a low-cost substrate and offers a plausible strategy for the management of these residues. Further, it also provides insights into the generation of additional high-value compounds in a bioethanol biorefinery to improve its commercial feasibility.

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.

Effect of periodic high-frequency vibration with rigid spheres added on high solids enzymatic hydrolysis of steam-exploded corn straw

The periodic low-frequency force can improve mixing efficiency and reduce water constraint, thus intensifying the high solids enzymatic hydrolysis. However, the availability of intensification methods for the periodic force with different frequencies needs to be studied. The periodic high-frequency vibration with rigid spheres added as another intensification method was proposed to shorten the time of water constraint and improve efficiency. Within this study, glucan and xylan conversions in periodic high-frequency vibration with rigid spheres added enzymatic hydrolysis (PVEH) increased by 8.3%-35% and 5.0%-33.5%, respectively, with solid loading increasing from 15% to 25%, compared with those in static state enzymatic hydrolysis (SEH). The physical properties variations of substrate indirectly proved the higher efficiency of PVEH. Based on the change regularity of constrained water release, PVEH was divided into three stages. The effects of micromixing and macromixing in three stages were analyzed. Additionally, the efficiency of high solids enzymatic hydrolysis can be enhanced by using proper intensification methods in different stages.

Construction and characterization of a chimeric enzyme of swollenin and xylanase to improve soybean straw hydrolysis

A study was carried out to produce a fusion protein (Swo-Xyn) using the Trichoderma reesei swollenin and Lentinula edodes xylanase and to investigate its characteristics and application in degrading soybean straw. In parallel, L. edodes xylanase (Xyn) alone was used as a control protein in application tests. The Swo-Xyn was recombined, expressed and produced by Pichia pastoris and had the maximum activity at 40 °C and pH 3.0 using xylan as substrate. The Swo-Xyn exhibited preferential hydrolysis of Xylan. The Swo-Xyn had slight low Km value (23.90 vs. 25.36 mg/ml) but significantly low Vmax value (162.4 vs. 227.2 μmol/mg·min) and specific activity (18.82 vs. 38.97 U/mg) relative to the Xyn. The Swo-Xyn activity was enhanced by Zn2+ in dose dependent manners with the peak activity at 30 mM of Zn2+. The Swo-Xyn could tolerate 15% of methanol, ethanol, aceton, and DMSO with >60% residual activity. The Swo-Xyn had the greater tolerance to SDS, EDTA, 2-ME than the Xyn and could be activated by DTT, Triton X-100, and Tween 20. Compared with the Xyn, the hydrolysis and sequent cellulose enzymolysis of soybean straw could be better improved by the Swo-Xyn. The Swo-Xyn should be more useful for improving the utilization of soybean straw.

Acid-base properties of aluminosilicates from rice husk and straw

We obtained aluminosilicates of sodium and potassium from alkaline hydrolysate of rice straw and husk. Chemical, phase composition of the samples was determined, and nature of the functional groups was studied. We presented results of studying acid-base properties of aluminosilicates’ surface by pH-metry and Hammett methods. We built distribution curves of a number of acid-base centers of the samples from pКa indicators. It was found that the surface of the as-prepared aluminosilicates is characterized by a wider spectrum of Bronsted acid centers (pKa + 2.5; + 3.46; + 6.4), presence of Lewis acid centers (pKa + 16.8) and main Bronsted centers (pKa + 9.45). The largest number of Lewis acid centers was recorded on the surface of sodium aluminosilicates with a narrow ratio of Al2O3:SiO2 = 1:2, the smallest—on the surface of potassium aluminosilicate with a wide ratio of Al2O3:SiO2 = 1:5. The maximum number of Bronsted acid centers was present on the surface of sodium aluminosilicates from rice straw, the minimum—on the surface of potassium aluminosilicate with the amount of SiO2 equal to 41%.

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.

Bio-pretreatment promote hydrolysis and acidification of oilseed rape straw: Roles of fermentation broth and micro-oxygen

Oilseed rape straw (ORS) is capable of producing renewable energy. However, cellulose, hemicellulose and lignin are intertwined together in ORS, which makes it difficult for anaerobic digestion (AD). Hence, pretreatment is the key factor in reducing the rate-limiting step of AD. This study reports that the pretreatment combined fermentation broth and micro-oxygen could enhance the degradation of ORS. The maximum biodegradation ratios of cellulose, hemicellulose, and lignin (CHL) were 20.6%, 18.1%, and 24.7%, respectively, at 120 mL/gVS/d oxygen load. The maximum volatile fatty acids and soluble chemical oxygen demand of hydrolysis and acidification of the pretreated groups were significantly higher than that of the control groups. Microorganisms in the fermentation broth at micro-aerobic conditions led to the reduction of CHL content, and altered the structure of ORS. The fermentation broth bio-pretreatment could effectively decrease the functional groups related to lignin.