Pretreatment Of Corn Stalk Research Articles

Novel ternary deep eutectic solvents pretreatment of corn stalk to realize high-value utilization

The high-valued utilization of biomass components through pretreatment technology can effectively alleviate the pressure of energy and environment. In this study, a ternary deep eutectic solvent (TDES) was prepared by using glycolic acid (GA) and ethylene glycol (EG) as double hydrogen donors and benzyl trimethyl ammonium chloride (TMBAC) as hydrogen acceptor. The corn stalk was separated by TDES to obtain cellulose-rich solid residue and low-condensed lignin. Moreover, the solid residue was converted into bio-oil by rapid pyrolysis, and the low-condensed lignin was converted into fluorescent lignin by grafting luminol for information encryption. The results showed that under the pretreatment condition of 150℃ for 3 h, TDES with the molar ratio of 1:1:2 had a lignin removal ratio of 90.60 %, and the yield of levoglucosan obtained from solid residue pyrolysis bio-oil reached 36.38 %. Furthermore, TDES prevented lignin from forming a C-C polycondensation structure and endowed it with polyhydroxy properties, which was beneficial to graft luminolto enhance the fluorescence intensity efficiently. The high-intensity fluorescent grafted lignin was used for information encryption of various materials. The mechanism of TDES pretreatment and luminol grafting were explored, and the mass balance of corn stalk during pretreatment was described. This study provides a green, environmentally friendly, and efficient pretreatment process for the high-value utilization of biomass.

Isolation of delignifying bacteria and optimization of microbial pretreatment of biomass for bioenergy.

Microbial pretreatment of lignocellulosic biomass holds significant promise for environmentally friendly biofuel production, offering an alternative to fossil fuels. This study focused on the isolation and characterization of two novel delignifying bacteria, GIET1 and GIET2, to enhance cellulose accessibility by lignin degradation. Molecular characterization confirmed their genetic identities, providing valuable microbial resources for biofuel production. Our results revealed distinct preferences for temperature, pH, and incubation period for the two bacteria. Bacillus haynesii exhibited optimal performance under moderate conditions and shorter incubation period, making it suitable for rice straw and sugarcane bagasse pretreatment. In contrast, Paenibacillus alvei thrived at higher temperatures and slightly alkaline pH, requiring a longer incubation period ideal for corn stalk pretreatment. These strain-specific requirements highlight the importance of tailoring pretreatment conditions to specific feedstocks. Structural, chemical, and morphological analyses demonstrated that microbial pretreatment reduced the amorphous lignin, increasing cellulose crystallinity and accessibility. These findings underscore the potential of microbial pretreatment to enhance biofuel production by modifying the lignocellulosic biomass. Such environmentally friendly bioconversion processes offer sustainable and cleaner energy solutions. Further research to optimize these methods for scalability and broader application is necessary in the pursuit for more efficient and greener biofuel production.

Development of tailored bioprocess for pretreatment and saccharification of corn stalk into bioethanol using hydrolytic enzymes cocktail and fermentative yeasts

Agriculture waste residue (corn stalk), a rich source of reducing sugars explored in the present study for the production of bioethanol using hydrolytic enzymes and fermenting yeast cocktails. Corn stalk pulp was biologically pretreated using hydrolytic enzymes cocktail of ligninase, cellulase and xylanase produced from Bacillus sp. PHS-05, Bacillus subtilis CP-S66 and Bacillus safensis XP-S7 with 2.34 ± 0.28 U/ml, 6.89 ± 0.36 U/ml and 11.9 ± 0.22 U/ml enzyme activities respectively. This biological pretreatment of corn stalk pulp resulted into 51.41 ± 0.34 % removal of lignin and 77.43 ± 2.44 % extraction of reducing sugar (C5 & C6). The changes occur in corn stalk pulp after enzymatic saccharification was confirmed by Fourier-Transform Infrared Spectroscopy (FTIR). Corn stalk sugar hydrolysate was co-fermented into 0.77 ± 0.06 g/g bioethanol with yield of 26.6 ± 0.46 g/kg of biomass, using Kluyveromyces marxianus MTCC 1498 and Saccharomyces cerevisiae. Further, purity (94.27 %) and volumetric productivity (0.20 ± 0.04 g/L/h) of bioethanol was confirmed using Gas Chromatography-Mass Spectrometry (GC-MS). Present findings provide valuable insight to obtain second generation biofuels to solve energy crisis, and environmental problems besides boosting socioeconomic prosperity through sustainable management of agro-residues.

Autohydrolysis pretreatment of corn stalk for improved 5-hydroxymethylfurfural production in molten salt hydrate/acetone

Molten salt hydrate (MSH) is unique in cellulose dissolution and in one-pot conversion of crystalline cellulose into 5-hydroxymethylfurfural (5-HMF). However, low yield of 5-HMF was obtained using raw biomass substrate in MSHs. Herein, we investigated conversion of raw biomass towards HMF using MSHs. We showed that the release of acetic acid from hemicellulose degradation in MSH is a key to influence the yield of 5-HMF. Thus, an autohydrolysis pretreatment method was proposed to remove hemicellulose before conversion of cellulose into 5-HMF. After being pretreated at 180 °C for 40 min, hemicellulose was removed from biomass with 91.8% yield of cellulose remained in solid part. By eliminating the negative effect of acetic acid, 5-HMF yield was significantly improved from 40.9% to 64.6%, together with 9.3% yield of glucose for cellulose conversion in MSH/acetone at 180 °C for 20 min.

Using citric acid to suppress lignin repolymerization in the organosolv pretreatment of corn stalk

The esterification reactions that occur between citric acid (CA) and lignin on hydroxyl groups of side chains can inhibit the formation of reactive intermediates in acid-catalyzed pretreatments. The effects of CA on dilute hydrochloric acid (1.0%) pretreatments of corn stalk in hydrated 1,4–dioxane were investigated with sodium hypophosphite (0.5%) as the catalyst at 95 °C for 3.5 h. The resulting cellulose recovery (62.5–80.9%) and lignin removal (72.5–85.0%) after adding CA were significantly higher than those in the pretreatment without CA. Water content influenced pretreatment and delignification when CA was added into the treatment systems. The highest yield of total reducing sugar (97.1%) was achieved during the enzymatic hydrolysis of cellulose-rich materials obtained from the pretreatment with 11.4% water content. Meanwhile, β–O–4′ in the extracted lignin increased from 22.4/100Ar to 41.2/100Ar with increasing water content from 11.4% to 25.9%. These findings implied that CA as a stabilization agent could inhibit the repolymerization of degraded lignin fragments due to the esterification between CA and lignin and then improved the enzymatic saccharification of cellulose.

Highly efficient one-pot bioethanol production from corn stalk with biocompatible ionic liquids

Efficient utilization of ionic liquids (ILs) for transforming lignocellulose into biofuel and alleviating concerns over shortages of nonrenewable resources is still an urgent issue. Herein, a highly efficient one-pot bioethanol production with biocompatible ILs was designed. XRD, TGA, and DSC analysis showed that pre-treatment of corn stalk with [Ch][Gly] trend to become easier to depolymerize than the untreated sample. Under one-pot process, the efficiency of [Ch][Gly] pretreated method could achieve a 9-fold sugar yield, i.e., 324.7 mg glucose/PU and 131.8 mg xylose/PU (1 PU = 10 g, 3 wt% [Ch][Gly] aqueous). The conditions for the whole process were optimized and the maximum yield% were achieved 80 % for glucose, 79 % for xylose, and 84 % for bioethanol. Besides, we found that increasing surface area and pore size could enhance accessibility for enzymes to attack cellulose and hemicellulose. The proposed study offers an efficient one-pot bioethanol production strategy with sustainable ILs.

Acid and alkali pretreatment of corn stalk for fractal‐like kinetic analysis of enzymatic saccharification

AbstractBACKGROUNDThe conversion of lignocellulose to sugar is part of the process of lignocellulose biorefining and, therefore, is crucial for effective lignocellulose utilization.RESULTSIn this study, alkali and acidic pretreatments were carried out to deconstruct corn stalk (CS) material for efficient subsequent enzymatic saccharification. Most xylan and lignin can be removed from CS material by acid and alkali pretreatments, respectively, as verified by XRD (X‐ray diffractometer) and FT‐IR (Fourier Transform Infrared Spectroscopy) analyses. Fractal‐like kinetics were assessed to analyze the effect of enzyme loading on the glucose and xylose sugar yields from the two pretreated CS materials, with fractal dimension considered as a dominant factor in rate constant decrease. Fractal dimension analysis demonstrated that the alkali pretreated CS was more easily hydrolyzed that the acid pretreated CS. For glucan hydrolysis, the effect of enzyme loading on the rate constant of the alkali pretreated CS was marginally higher than that of the acid pretreated CS. For xylan hydrolysis, enzyme loading was shown to significantly improve the rate constant of the alkali pretreated CS compared to the acid pretreated CS. Furthermore, the developed fractal‐like model exhibits high prediction accuracy for sugar yield at high enzyme loadings.CONCLUSIONThe application of the fractal‐like theory was quite successful for studying enzymatic kinetics. © 2022 Society of Chemical Industry (SCI).

Characterization of lignin streams during ionic liquid/hydrochloric acid/formaldehyde pretreatment of corn stalk

This work investigated the role of formaldehyde (FA) in lignin anti-condensation during corn stalk pretreatment based on 1-butyl-3-methylimidazolium chloride ([C4C1im]Cl)/hydrochloric acid (HCl). As a result of the aldolization reactions between FA and lignin, the condensation of lignin fragments was inhibited, and lignin remained in soluble fragmental molecules. Characterizations on the compositional and structural changes of lignin and its degraded products during pretreatment (80 °C–100 °C, 2–5 h) with FA addition in comparison with those in DO/HCl/FA or [C4C1im]Cl/HCl were conducted. Results revealed that the structural features of lignin were affected by FA addition and solvent type. In the [C4C1im]Cl/HCl/FA system, FA stabilization was unfavorable for the cleavage of β-O-4′ bonds and lignin with low S/G ratio (3.4) and high molecular weight (Mw = 9920 g·mol−1) was extracted. The compositions of degraded products were considerably affected by FA addition.

Effects of formaldehyde on fermentable sugars production in the low-cost pretreatment of corn stalk based on ionic liquids

Low cost processing of lignocellulosic biomass is of great importance for sustainable chemistry and engineering. Herein, a low cost system composed of 1-butyl-3-methylimidazolium chloride ([C 4 C 1 im]Cl), HCl and formaldehyde (FA) was developed for the pretreatment of corn stalk at 80 °C. The efficiency of this technology was compared with that in dioxane system or without FA addition. Due to FA stabilization, the extent of acid-hydrolysis of carbohydrate fraction can be significantly decreased while 70% above of lignin was removed with the pretreatment of [C 4 C 1 im]Cl/HCl/FA system at 80 °C for 2 h. A maximum reducing sugar yield of 93.7% and glucose concentration of 7.0 mg⋅ml −1 were subsequently obtained from enzymatic hydrolysis of the slurry. There were great differences in compositions of small molecule degraded products obtained with FA addition or not. The present [C 4 C 1 im]Cl based system exhibits great potential of substituting volatile organic solvents ( i . e . dioxane) in developing low cost lignocellulosic biomass pretreatment at low temperature. Also, this work would gain insight into understanding on the roles of stabilization methods on the economic improvement of IL based biomass processing.

Macromolecules Evolution in Sequential Acid-Alkali Pretreatment of Corn Stalk

Macromolecules Evolution in Sequential Acid-Alkali Pretreatment of Corn Stalk

Alkali and Intensified Heat Treatment of Corn Stalk for Bioethanol Production

This study investigated combined alkali and heat pretreatment of lignocellulosic biomass for fermentative bioethanol production. Prior to fermentation, alkali pretreatment of corn stalk (CS) was carried out in NaOH solution under varying concentration which was followed by incubation at 100 °C for 1 h. The slurry of alkali-pretreated CS was supplemented with media and incubated at 30 °C, 96 h and pH 5. The 2.0% alkali pretreatment was most effective. Further optimization studies with filtrate and 5% inoculum size produced 43.8 g/L bioethanol. Chemical analysis of CS shows 61.75 and 71.49% degradation of hemicellulose and lignin, respectively, under optimal conditions. Structural changes of CS biomass monitored via scanning electron microscope showed that pretreatment with NaOH induced porosity and surface area disruption when compared to the untreated samples. Pretreated CS showed higher crystallinity index as revealed by X-ray diffraction analysis. The results showed that alkali-pretreated CS can serve as a potential feed stock for bioethanol production to reduce dependency on fossil fuel.

Efficient conversion of cornstalk to bioethanol using dilute H2SO4 pretreatment

Corn stalk (CS) is one of the most abundant agricultural residues containing high polysaccharides for low-cost bioethanol production. In this study, dilute acid along with intensified thermal pretreatment of CS and other parameters were optimized for higher yield of bioethanol. CS samples were pretreated using H2SO4 concentrations of 0.5, 1.0, 1.5, 2.0, and 2.5% at 100 °C for 1 h reaction time. Optimal conditions of 2% acid-pretreated CS, 5% (w/v) of Saccharomyces cerevisiae addition and 48 h fermentation produced highest yield of bioethanol: 32.53 (g/L) which was 1.24-fold increase. Hemicellulose degradation of 75.68% was recorded in the 2% acid-treated substrate. Scanning electron microscope (SEM) images revealed induced porosity and surface area disruption of CS in the treated samples. Crystallinity of the treated samples increased as shown by X-ray diffraction (XRD) analysis. Low concentrated H2SO4 coupled with thermal pretreatment could be a viable method of lignocellulosic biomass utilization for efficient bioethanol production.

Enhancement of converting corn stalk into reducing sugar by ultrasonic-assisted ammonium bicarbonate pretreatment

In order to improve the yield of reducing sugar from corn stalk, ultrasonic-assisted ammonium bicarbonate pretreatment of corn stalk was proposed. Three ultrasonic factors (time (0–30 min), temperature (30–60 °C) and liquid/solid mass ratio (5–20)) were optimized by response surface experiment. The optimal conditions of ultrasonic pretreatment were obtained (liquid/solid mass ratio is 12:1, temperature is 42 °C and time is 11 min). The highest saccharification rate of corn stalk was of 82.61%, which was remarkably increased by 355% compared to the control group.

Study on inhibitors from acid pretreatment of corn stalk on ethanol fermentation by alcohol yeast.

The inhibitory effects of the main inhibitors formed during acid pretreatment of corn stalk were studied through ethanol fermentations of model substrates and hydrolysates from corn stalk by alcohol yeast. Experimental results showed that the tested inhibitors had no significant effect on ethanol fermentations when they were added separately at a concentration according to analysis results from hydrolysate of corn stalk. However, when they were added as a mixture, the inhibitory effects became obvious. With the increase of concentration, there was a delay in ethanol productivity. But complete inhibition was observed at 5.0 g L−1 furfural, 10.0 g L−1 acetic acid, 7.0 g L−1 ferulic acid, and 7.0 g L−1p-coumaric acid, respectively. The inhibitory effect decreased in the order: furfural > acetic acid > ferulic acid > p-coumaric acid > HMF. These results suggest that a high concentration of inhibitor has a strong negative influence on ethanol fermentation, but the inhibiting abilities of various inhibitors are different.

Ammonium bicarbonate pretreatment of corn stalk for improved methane production via anaerobic digestion: Kinetic modeling

This work studied the effects of ammonium carbonate pretreatment on biogas production during sequential anaerobic digestion. The results showed that the addition of ammonium bicarbonate (8%, w/w) obtained the highest biogas production of 14,690 mL with a yield of 222.6 mL g−1, which was 31% higher than that of un-pretreated (control experiment). Interestingly, the COD removal was increased by 100%. Furthermore, it was also helpful in stabilizing the pH of anaerobically digested corn stalk. Based on the results, the modified Gompertz equation fitted the cumulative biogas production curves very well, with high correlation coefficients (>0.994).

Enhanced bio-hydrogen production from cornstalk hydrolysate pretreated by alkaline-enzymolysis with orthogonal design method

Bio-hydrogen (H2) production from renewable biomass has been accepted as a promising method to produce an alternative fuel for the future. In this study, fermentative hydrogen production from cornstalk (CS) hydrolysate pretreated by alkaline-enzymolysis method was investigated. Meanwhile, a five-factor and five-level orthogonal experimental array was designed to study the influences of Ca(OH)2 concentration, alkaline hydrolysis time, alkaline hydrolysis temperature, cellulase and xylanase dosages on cornstalk pretreatment and hydrogen production. A maximum reducing sugar yield of 0.59 g/g-CS was obtained at Ca(OH)2 0.5%, hydrolysis temperature 115 °C, hydrolysis time 1.5 h, cellulase dosage 4000 U/g-CS and xylanase 4000 U/g-CS. Under this same condition, the maximum hydrogen yields of 168.9 mL/g-CS, 357.6 mL/g-CS, and 424.3 mL/g-CS were obtained at dark-fermentation, photo-fermentation, and two-stage fermentation respectively. It's also found that the significance of these five parameters on H2 production followed from high to low order as: Ca(OH)2 concentration, cellulase dosage, xylanase dosage, hydrolysis time, and hydrolysis temperature. By comparing the energy produced with the energy spent, the maximum Energy Sustainability Index (ESI) value of 1.11 was obtained at the two-stage fermentation. The results suggested that two-stage fermentation is a promising and efficient way for hydrogen production from lignocellulosic biomass.

Effect of Alkaline Black Liquor Recycling on Alkali Combined with Ozone Pretreatment of Corn Stalk.

In the early stage, the best conditions for alkali-bound ozone pretreatment were studied. But after treatment, the alkaline black liquor was directly discarded due to the large amount of organic matter, resulting in environmental pollution and waste of resources. In this paper, the alkaline black liquor was recycled under the optimal pretreatment conditions. The results showed that the number of alkaline black liquor cycles had little effect on hemicellulose content, and had a great influence on cellulose content and lignin content. Through structural characterization of corn stover, it was found that the pretreatment caused structural changes of lignin in straw. However, when the alkaline black liquor was recycled for the fourth time, the ether bond in the side chain of lignin and the covalent bond between the components were not sufficiently destroyed, and the damage to the phenolic hydroxyl group was also weakened. It was indicated that when the alkaline black liquor was recycled for the fourth time, the destruction effect of the alkaline black liquor on the straw was significantly inhibited. Therefore, the optimal circulation time of alkaline black liquor was three times, and the cellulolytic conversion rate was 81.53%.

Pretreatment of corn stalk by low concentration tetrabutylammonium hydroxide aqueous solution at low temperature (20–80 °C)

Corn stalk was pretreated by aqueous tetrabutylammonium hydroxide to enhance enzymatic hydrolysis process. The effects of temperature (20–80 °C), concentration of tetrabutylammonium hydroxide (10–40 wt%), time (5–60 min) and ratio of solid to liquid (1:4–1:8, wt/wt) were investigated to find the optimal operational condition, which was determined as 20 °C, 30 wt%, 20 min and 1:5 respectively. This was a quite mild pretreatment condition resulting in 68.17% enzymatic hydrolysis sugar yield and the removal rate of hemicelluloses and lignin were 23.5% and 31.5% respectively. Besides, the microstructure and crystal structure changes of raw material and pretreated samples were analyzed by scanning electron microscope and X-ray diffraction respectively. Finally, a possible mechanism of pretreatment process was put forward based on the comprehensive analysis.

Natural freezing-thawing pretreatment of corn stalk for enhancing anaerobic digestion performance

Natural freezing-thawing (NFT) was proposed as a low energy input and alternative pretreatment method for high biomethane production from corn stalk (CS) by anaerobic digestion (AD). The CS was pretreated by freezing-thawing in winter season using different pretreatment time periods (7d, 14d, 21d and 28d) and solid-to-liquid ratios (1:2, 1:4, 1:6, 1:8 and 1:10). The results showed that CS pretreated for 21d coupled with a solid-to-liquid ratio of 1:6 achieved the best result among all pretreatment conditions. In this case, the biomethane yield and VS removal rate of CS reached the highest values of 253 mL·gvs−1 and 58.6%, respectively, which were 40.5% and 27.4% higher than that of the untreated. It was also found that the predominant bacterial and archaeal at genus level in AD were Clostridium_sensu_stricto_1 (36.1%) and Methanobacterium (54.0%), respectively. This study provided that NFT is a simple pretreatment strategy for efficient AD bioconversion of CS to biomethane.

Furfural wastewater pretreatment of corn stalk for whole slurry anaerobic co-digestion to improve methane production

Previous studies showed that excellent anaerobic digestion performance could be achieved using acid pretreatment, whereas the development of acid pretreatment was limited by high cost of acid consumption and severe operation. The aim of this study consisted in expanding the possibilities of low-cost acid pretreatment method for anaerobic digestion. For this, the feasibility of substituting conventional acid pretreatment with furfural wastewater was verified, and the whole slurry anaerobic digestion was performed to improve the production of methane. The furfural wastewater was used to pretreat crop stalk at different ambient temperatures (20, 35, 50°C) for different time periods (0, 3, 6, 9days). Subsequently, all treated and untreated crop stalk were digested at 35°C for 25days. According to experimental data showed that the dissimilar degradability of compositions for crop stalk was due to furfural wastewater pretreatment, and the reducing sugar content, volatile fatty acid content, pH during pretreatment phase, and their initial maximum & minimum values in anaerobic digestion phase were changed, which made a significant difference in methane production. The highest total methane production of anaerobic digestion (196.68mL/g VS) was achieved by the treatment at 35°C for 6days, which was 59.28% higher than untreated crop stalk (123.48mL/g VS). On the whole, the results showed that furfural wastewater pretreatment followed by the whole slurry anaerobic co-digestion was feasible and could contribute to application value for anaerobic digestion industry while providing an effective way for the treatment of furfural wastewater.