Pre-treated Corn Stalks Research Articles

Preparation of Cellulose Nanofibers from Corn Stalks by Fenton Reaction: A New Insight into the Mechanism by an Experimental and Theoretical Study

Agricultural biomass wastes are an abundant feedstock for biorefineries. However, most of these wastes are not treated in the right way. Here, corn stalks (CSs) were assigned as the raw material to produce cellulose nanofibers (CNFs) via in situ Fenton oxidation treatment. In order to probe the formation mechanism of an in situ Fenton reactor, the bonding interaction of hydrated Fe2+ ions and fiber has been systemically studied based on adsorption experiments, IR spectroscopy, density functional theory (DFT) calculations, and Raman spectroscopy. The results indicate that the coordination of the hydrated Fe2+ ion to the fiber generates a quasi-octahedral-coordinated sphere around the Fe center. The Jahn-Teller distortion effect of the Fe center promotes the Fe-O2H2 bonding interaction via reduction of the energy gap of the dz2 orbital of the Fe center and π2py/π2pz orbitals of the H2O2 molecule. The oxidation treatment of the pretreated CS by the in situ Fenton process shows the formation of a new carboxyl group on the fiber surface. The scanning electron microscopy image shows that the Fenton-treated fiber was scattered into the nanosized CNFs with a diameter of up to 50 nm. Both experimental and theoretical studies show that the pseudo-first-order kinetic reaction could describe the in situ Fenton kinetics well. Moreover, the proposed catalytic cycle shows that the large thermodynamic barrier is the cleavage of the O-O bond of H2O2 to generate the •OH radical, and the whole catalytic cycle is found to be spontaneous at room temperature.

Boosting levoglucosan and furfural production from corn stalks pyrolysis via electro-assisted seawater pretreatment

The seawater electrochemical pretreatment (ECP) was employed to upgrade the bio-oil of corn stalk in the paper. The seawater and its simulants were used as electrolytes without additional reagents. Moreover, the effect of seawater ECP under different conditions on the products distribution of pyrolysis bio-oil of pretreated corn stalks was investigated. The results showed that pretreatment effectively deconstructed the lignin and made cellulose exposed. Especially, under the optimum conditions (3.5 wt% NaCl, 15 V and 4 h), most of lignin was destroyed, and cellulose and hemicellulose were remained in residual solids. Furthermore, the levoglucosan and furfural were enriched in the pyrolysis bio-oil of corn stalk after seawater ECP, reaching 23.22 % and 14.14 %, respectively. Overall, this work presented a novel and green pretreatment process to optimize the components and structure of corn stalks as well as upgrade the bio-oil of corn stalk pyrolysis.

Higher nitrogen removal achieved in constructed wetland with polyethylene fillers and NaOH-heating pre-treated corn stalks for advanced treatment of low C/N sewage.

Advanced processing of low C/N sewage faces the carbon sources shortage, while quantities of agricultural biomass wastes need to be disposed. This study investigated the potential of quantitative modified biomass addition in constructed wetlands (CWs) filled with polyethylene fillers. Results showed that the lignin in NaOH-heating pretreated corn stalks (NH-CSs) was destroyed, and the wrinkles on the stalks increased and became more soft after pretreatment, which was more conducive to the utilization of carbon sources and attachment of microorganisms. Compared with glucose and sodium acetate, the denitrification with mixed carbon source (glucose and NH-CSs) had the highest effective utilization percentage (61.37%) and NH-CSs were expected to become stable and fast-release carbon sources. After adding 30g NH-CSs to the rear unit of CW with polyethylene fillers (CW-A), TN removal efficiency was increased by 18.21%, and the average removal efficiency of COD, NH4+-N, TN, and TP reached 54.83%, 89.95%, 64.11%, and 45.04%, respectively. Compared with the traditional CW (CW-B), CW-A had a significant denitrification advantage (P < 0.05), but the removal efficiency and effluent stability of phosphorus were inferior to CW-B. These results indicate that the biomass carbon sources such as corn stalks and polyethylene fillers have a good potential to improve the denitrification in CWs.

Corn stalk-based activated carbon synthesized by a novel activation method for high-performance adsorption of hexavalent chromium in aqueous solutions

A simple activation method involving treatment with KOH solution was used to synthesize activated carbon (ACs) with micro-meso pores from the agricultural waste of corn stalks. The activation reagent, KOH solution, was easily separated for recycling by centrifugation from the pre-treated corn stalks, and the pollution in the carbonization process was greatly reduced. The morphology and structure of the ACs were characterized by SEM, TEM, N2 adsorption, XRD, FT-IR and Raman analysis. The prepared carbon was applied as an adsorbent for the removal of Cr(VI) in a batch adsorption process. The effect of the concentration of KOH solution on the structure, morphology and Cr(VI) adsorption performance of the synthesized ACs was investigated. The characterization results revealed that some functional groups in the corn stalks were removed by pretreatment with KOH solution and micro-meso porous structures were generated. The ACs showed high adsorption performance for Cr(VI), and the maximum adsorption ability of the ACs prepared by activation with 4% KOH solution reached 89.5 mg g−1 at an adsorbent dosage of 2.5 g·L−1 and pH value of 4.5.

Effects of steam explosion pretreatment on the chemical composition and fiber characteristics of cornstalks

This paper investigated the influence of steam explosion pretreatment with or without acid as the catalyst on the chemical composition and sugar contents of corn stalks. The fiber characteristics of the pretreated corn stalks were analyzed with a scanning electron microscope, a FS-300 automatic fiber analyzer and a fully automatic surface and pore analyzer. The results showed that the steam explosion pretreatment did not change the cellulose content of the corn stalks. However, hemicellulose was degraded and a portion of lignin was solubilized in the steam explosion pretreatment process. When acid was added in the steam explosion process, the fiber surface and cell wall structure of corn stalks were damaged, the specific surface area and pore size increased, and fiber length decreased, all of which were beneficial to subsequent enzymatic hydrolysis with cellulase. However, content of polysaccharides decreased after acid steam explosion pretreatment.

Sustainable biobutanol production using alkali-catalyzed organosolv pretreated cornstalks

Biobutanol is an important alternative fuel source, but current processing methods suffer from low yields. This study aimed to develop and optimize a pretreatment protocol for biobutanol production from cornstalks. Fractionation of cornstalks into carbohydrate (cellulose and hemicellulose) and lignin was performed by alkali-catalyzed organosolv pretreatment (ACOS). After optimization of the process parameters, more than 80% of the total lignin was removed, with minimal hemicellulose degradation, at 110°C, 4% (w/w dry cornstalk) NaOH, 90min reaction time, and 60% (v/v) ethanol. After enzymatic hydrolysis, the maximum recovery of total monosaccharide was 83.7% (85.0% cellulose, 82.0% hemicellulose). In acetone-butanol-ethanol (ABE) fermentation, a slightly higher total ABE concentration (12.8g/L vs. 11.9g/L) was produced from the enzymatic hydrolysate, compared with that from a glucose control. The physical structure and chemical properties of alkali-catalyzed organosolv lignin (ACOSL) showed higher phenolic group content and antioxidant capacity compared with alkali lignin. ACOS pretreatment is an economical method for the production of fermentable monosaccharide and high-value lignin, for use in biofuel production.

Comparing the efficiency of plant material bioconversion processes using biocatalysts based on Trichoderma and Penicillium verruculosum enzyme preparations

A comparative study of the effectiveness of six commercial biocatalysts based on enzyme preparations derived from a fungus of the genus Trichoderma as a producer (Cellic Ctec-1, Cellic Ctec-2, Accelerase 1000, Accelerase 1500, Accelerase XY, Accelerase DUET), and of laboratory biocatalysts based on enzyme preparations derived from the fungus Penicillium verruculosum for the hydrolysis of the four types of plant cellulose material (steam explosion pretreated corn stalks and bagasse, ground pine and aspen), and of microcrystalline cellulose is performed. Biocatalysts activities toward various substrates, and the dependence of the depth of exhaustive hydrolysis of plant material on the dosage of these biocatalysts are determined. It is shown that biocatalysts based on the strains of P. verruculosum are competitive with widely used commercial biocatalysts based on the Trichoderma strain if we scale the biotechnological processes of bioconversion of renewable plant raw materials.

The promoting effect of byproducts from Irpex lacteus on subsequent enzymatic hydrolysis of bio-pretreated cornstalks

BackgroundIrpex lacteus, a versatile lignin-degrading fungus with various extracellular enzymes, has been widely used for biological pretreatment. However, most studies have focused on the change of substrate structure after biological pretreatment, and the effect of these changes on the enzymatic hydrolysis, but the effect of byproducts from biological pretreatment process on subsequent enzymatic hydrolysis is not well understood.MethodsWe developed a biological pretreatment process with I. lacteus that can produce stimulatory byproducts that enhance the enzymatic hydrolysis of cornstalks.ResultsThe maximum hydrolysis yield of glucan (82%) was obtained after pretreatment for 28 days. The maximum reducing sugar yield decreased from 313.5 to 200.1 mg/g raw cornstalks after water-soluble byproducts of biological pretreatment were removed from pretreated cornstalks. The effect of byproducts on enzymatic hydrolysis was also investigated. We found that the hydrolysis efficiency of commercial cellulase preparation on cornstalks could be improved by water extracts from bio-pretreated cornstalks with hydrolytic enzyme activity and iron-reducing activity.ConclusionThe key finding suggested that byproducts from biological pretreatment play important roles in enhancing downstream hydrolysis, which might be attributable to hydrolytic enzymes and iron-reducing compounds produced by I. lacteus.

Microwave Assisted Enzymatic Hydrolysis of Corn Stalks for L-Lactic Acid Production

Glucose production from pretreated corn stalks by cellulose enzymatic hydrolysis with cellulase was investigated and compared with no pretreatment, as a reference. The corn stalks were pretreated with microwave, sulfuric acid hydrolysis and dilute sodium hydroxide solution hydrolysis respectively. The enzymatic hydrolysis experiments were carried out at 50°C, 50 g/l dry matter (DM) solid substrate concentration and 15 filter paper unit (IU)/g DM of a commercial cellulase. Fermentable sugar was able to be produced from all the pretreated corn stalks with an overall yield of 29-58% of the maximum theoretical yield, based on the glucan available in the solid and liquid substrate. The corn stalks pretreated with dilute acid had the best glucose yield as 58.09% followed by the corn stalks pretreated with acid and microwave with an overall yield of 57.02% with 15 IU/g DM of cellulase. Glucose was the main product with enzymatic hydrolysis yield ratio 38.89%in the dilute sulfuric acid pretreated corn stalks, while with enzymatic hydrolysis yield ratio 51.07%in the dilute sodium hydroxide solution and microwave pretreated corn stalks under enzymatic hydrolysis conditions. These advantages, along with their negative price, make these solids a valuable raw material for L-lactic acid production.

Enzymatic hydrolysis of dissolved corn stalk hemicelluloses: reaction kinetics and modeling

AbstractThe enzymatic hydrolysis of hemicelluloses as a filtrate originating from aqueous/steam pretreated corn stalks was carried out using commercial enzyme systems of several activities composed of cellulases and β‐D‐xylosidases from Aspergillus niger. The hydrolysis was conducted using free enzymes in aqueous substrate solution at a temperature of 30 °C and a pH of 5. Saccharification corresponding to 90% of potential simple sugar release was obtained after 10 h using 0.12 activity units (U) of Cellulases_1 complex per mg of dissolved solids present in the filtrate. Synergetic action of Cellulases_1 enzyme complex and β‐D‐xylosidases proved to be effective for the hydrolysis of plant hemicelluloses. A lumped model based on the Michaelis–Menten approach successfully described the fate of the lumped variables describing the hydrolysis of the overall kinetics of corn stalk hemicelluloses. The maximum saccharification rate evolved with the cellulases concentration as $V_{{\max_{i}}}^{{\rm app}} = K \cdot [{Cellulases}]^{n}$. This overall and pseudokinetic tendency was comparable to those reported in the literature for more simple systems employing a defined substrate and a pure hydrolytic enzyme. The n‐value was found to be in the range of 0.1–0.9 depending on the substrate lump involved in the reaction system. Copyright © 2003 Society of Chemical Industry